StackBlitz
Here is my FormArray (variants):
this.productGroup = this.fb.group({
name: '',
variants: this.fb.array([
this.fb.group({
type: '',
options: ''
})
])
})
I'm using MatChips to store a string array. This array needs to be passed to options:
<div formArrayName="variants" *ngFor="let item of productGroup.controls['variants'].controls; let i = index;">
<div [formGroupName]="i">
<div class="row">
<mat-form-field class="col-12">
<input formControlName="type">
</mat-form-field>
</div>
<div class="row">
<mat-form-field class="col-12">
<mat-chip-list #chipList>
<mat-chip *ngFor="let opt of typesOptions" [selectable]="true"
[removable]="true" (removed)="removeOpt(opt)">
{{opt}}
<mat-icon matChipRemove>cancel</mat-icon>
</mat-chip>
<input placeholder="Conjunto de opções deste Tipo"
formControlName="options"
[matChipInputFor]="chipList"
[matChipInputSeparatorKeyCodes]="separatorKeysCodes"
[matChipInputAddOnBlur]="true"
(matChipInputTokenEnd)="addOpt($event)">
</mat-chip-list>
</mat-form-field>
</div>
</div>
<div class="row">
Add Variants
Remove Variants
</div>
</div>
Here is the methods:
// Dynamic Methods
addItem(): void {
this.variantsArray = this.productGroup.get('variants') as FormArray;
this.variantsArray.push(this.fb.group({
type: '',
options: ''
}));
}
removeItem(index: number) {
this.variantsArray.removeAt(index);
}
// MatChip Methods
addOpt(item: number, event: MatChipInputEvent): void {
const input = event.input;
const value = event.value;
// Add our fruit
if ((value || '').trim()) {
this.typesOptions.push(value.trim());
}
// Reset the input value
if (input) {
input.value = '';
}
}
removeOpt(opt: string): void {
const index = this.typesOptions.indexOf(opt);
if (index >= 0) {
this.typesOptions.splice(index, 1);
}
I'm successfully adding dynamic fields to my variants formArray. However MatChipList is the same for every dynamic field. I need to make MatChipList dynamic as well. Is there a way to achieve this? Like changing <mat-chip-list #chipList+i> or something like that.
EDIT: StackBlitz
I'm not sure the dom reference variable #chiplist is the issue. It looks like the matChipList is backed by the typesOptions array, but you only have one array. So every time you add a matChipList component it is still being backed by the same array as all the others. You need to have an array of typesOptions, an array of arrays. Then when you addItem, you also push a new sub array to typesOptions (and similarly remove one for removeItem).
I haven't coded this up, just a suggestion from looking at the code.
Edit - coded up a solution based on James's stackblitz.
https://stackblitz.com/edit/angular-3od6rd-jkidxf
Note I haven't looked in detail at how the delete variant holds together, ideally I'd probably like to use a key/value pair to track the variant options using the dom input element id as the key (which is in the MatChipInputEvent), instead of relying on the outer loop index.
Some code from the stackblitz:
export class ChipsOverviewExample {
productGroup: FormGroup;
variantsArray: FormArray;
typesOptionsArray: string[][] = [];
readonly separatorKeysCodes: number[] = [ENTER, COMMA];
constructor(private fb: FormBuilder) {}
ngOnInit() {
this.productGroup = this.fb.group({
name: '',
variants: this.fb.array([
this.fb.group({
type: '',
options: ''
})
]),
});
this.typesOptionsArray.push([]);
}
saveProduct(form: FormGroup) {
console.log(form);
}
// Add new item to FormArray
addItem(): void {
this.variantsArray = this.productGroup.get('variants') as FormArray;
this.variantsArray.push(this.fb.group({
type: '',
options: ''
}));
this.typesOptionsArray.push([]);
}
removeItem(index: number) {
this.variantsArray.removeAt(index);
}
addOpt(event: MatChipInputEvent, index: number): void {
const input = event.input;
const value = event.value;
// Add our fruit
if ((value || '').trim()) {
this.typesOptionsArray[index].push(value.trim());
}
// Reset the input value
if (input) {
input.value = '';
}
}
removeOpt(opt: string, index: number): void {
const optIndex = this.typesOptionsArray[index].indexOf(opt);
if (optIndex >= 0) {
this.typesOptionsArray[index].splice(optIndex, 1);
}
}
}
try to make the formGroup as a new component and input formGroup to it(not formGroupName).
<div formArrayName="variants" *ngFor="let item of productGroup.controls['variants'].controls; let i = index;">
<variant [varientGroup]="item"><varient>
<div class="row">
Add Variants
Remove Variants
</div>
</div>
varient component.html
<div [formGroup]="varientGroup">
<div class="row">
<mat-form-field class="col-12">
<input formControlName="type">
</mat-form-field>
</div>
<div class="row">
<mat-form-field class="col-12">
<mat-chip-list #chipList>
<mat-chip *ngFor="let opt of typesOptions" [selectable]="true"
[removable]="true" (removed)="removeOpt(opt)">
{{opt}}
<mat-icon matChipRemove>cancel</mat-icon>
</mat-chip>
<input placeholder="Conjunto de opções deste Tipo"
[matChipInputFor]="chipList"
[matChipInputSeparatorKeyCodes]="separatorKeysCodes"
[matChipInputAddOnBlur]="true"
(matChipInputTokenEnd)="addOpt($event)">
</mat-chip-list>
</mat-form-field>
</div>
</div>
in varient.component.ts
#Input()varientGroup: FormGroup
This is my object:
const ELEMENT_DATA: Element[] = [
{id: 1, name: 'Hydrogen', symbol: 'H'},
{id: 2, name: 'Hydrogen', symbol: 'H1'},
{id: 3, name: 'Helium', symbol: 'He'}
];
which is displayed in datatable with Edit buttons, like so:
When I click Edit (for example I clicked Hydrogen) it should populate with
name: 'Hydrogen', symbol: 'H'.
But now I am getting the Symbol List dropdown empty.
Demo
When I click the Add button, a pop up will come with two dropdowns: Element List and Symbol List. Based on the Element name Symbol List will come.
Now when I click the Edit button in datatable, that should populate that particular row in the popup. How can I do this?
html
<form [formGroup]="addTaskForm" (ngSubmit)="save()" >
<mat-form-field>
<mat-select formControlName="name" placeholder="Element List" (selectionChange)="elementSelectionChange($event)">
<mat-option *ngFor="let element of Elements" [value]="element.name">
{{ element.name }}
</mat-option>
</mat-select>
</mat-form-field>
<mat-form-field>
<mat-select formControlName="symbol" placeholder="Symbol List">
<mat-option *ngFor="let element of selectedElementSymbol" [value]="element.symbol">
{{ element.symbol }}
</mat-option>
</mat-select>
</mat-form-field>
<div mat-dialog-actions>
<button mat-button (click)="onNoClick()">Cancel</button>
<button type="submit" mat-button cdkFocusInitial>Add</button>
</div>
</form>
You shoule update datasource after each value added from the dialog, change your save() function like this:
save() {
const data = this.data.originalform.dataSource.data;
this.addTaskForm.value["id"]=data.length+1
data.push(this.addTaskForm.value);
this.data.originalform.dataSource=new MatTableDataSource<Element>(data);
console.log('working');
console.log(this.addTaskForm.value);
}
And to not forget to add a referer to the parent object originalform from this:
let dialogRef = this.dialog.open(DialogOverviewExampleDialog, {
width: '250px',
data: { element: element,originalform:this }
});
Hope this helps:)
Edit:
By call of this comment, i updated the fiddle in the following to fit the paginating in.
Adding paginator figures as following:
this.data.originalform.dataSource.paginator=this.data.originalform.paginator;
The symbol list is initialized in the method elementSelectionChange, but
you are calling elementSelectionChange($event) only when the Element list selection changes.
<mat-select formControlName="name" placeholder="Element List" (selectionChange)="elementSelectionChange($event)">
One way you can do it is,
elementSelectionChange(event) {
this.loadSymbols(event.value);
}
loadSymbols(name) {
let value = this.Elements.find(e => e.name === name);
this.selectedElementSymbol = this.Symbols.filter(e => e.id === value.id);
console.log(this.selectedElementSymbol);
}
and then call loadSymbols in the constructor
constructor() {
if (data.element) {
this.name = data.element.name;
this.symbol = data.element.symbol;
this.loadSymbols(this.name);
}
}
StackBlitz
Given a list of checkboxes bound to the same formControlName, how can I produce an array of checkbox values bound to the formControl, rather than simply true/false?
Example:
<form [formGroup]="checkboxGroup">
<input type="checkbox" id="checkbox-1" value="value-1" formControlName="myValues" />
<input type="checkbox" id="checkbox-2" value="value-2" formControlName="myValues" />
<input type="checkbox" id="checkbox-3" value="value-2" formControlName="myValues" />
</form>
checkboxGroup.controls['myValues'].value currently produces:
true or false
What I want it to produce:
['value-1', 'value-2', ...]
With the help of silentsod answer, I wrote a solution to get values instead of states in my formBuilder.
I use a method to add or remove values in the formArray. It may be a bad approch, but it works !
component.html
<div *ngFor="let choice of checks; let i=index" class="col-md-2">
<label>
<input type="checkbox" [value]="choice.value" (change)="onCheckChange($event)">
{{choice.description}}
</label>
</div>
component.ts
// For example, an array of choices
public checks: Array<ChoiceClass> = [
{description: 'descr1', value: 'value1'},
{description: "descr2", value: 'value2'},
{description: "descr3", value: 'value3'}
];
initModelForm(): FormGroup{
return this._fb.group({
otherControls: [''],
// The formArray, empty
myChoices: new FormArray([]),
}
}
onCheckChange(event) {
const formArray: FormArray = this.myForm.get('myChoices') as FormArray;
/* Selected */
if(event.target.checked){
// Add a new control in the arrayForm
formArray.push(new FormControl(event.target.value));
}
/* unselected */
else{
// find the unselected element
let i: number = 0;
formArray.controls.forEach((ctrl: FormControl) => {
if(ctrl.value == event.target.value) {
// Remove the unselected element from the arrayForm
formArray.removeAt(i);
return;
}
i++;
});
}
}
When I submit my form, for example my model looks like:
otherControls : "foo",
myChoices : ['value1', 'value2']
Only one thing is missing, a function to fill the formArray if your model already has checked values.
Here's a good place to use the FormArray https://angular.io/docs/ts/latest/api/forms/index/FormArray-class.html
To start we'll build up our array of controls either with a FormBuilder or newing up a FormArray
FormBuilder
this.checkboxGroup = _fb.group({
myValues: _fb.array([true, false, true])
});
new FormArray
let checkboxArray = new FormArray([
new FormControl(true),
new FormControl(false),
new FormControl(true)]);
this.checkboxGroup = _fb.group({
myValues: checkboxArray
});
Easy enough to do, but then we're going to change our template and let the templating engine handle how we bind to our controls:
template.html
<form [formGroup]="checkboxGroup">
<input *ngFor="let control of checkboxGroup.controls['myValues'].controls"
type="checkbox" id="checkbox-1" value="value-1" [formControl]="control" />
</form>
Here we're iterating over our set of FormControls in our myValues FormArray and for each control we're binding [formControl] to that control instead of to the FormArray control and <div>{{checkboxGroup.controls['myValues'].value}}</div> produces true,false,true while also making your template syntax a little less manual.
You can use this example: http://plnkr.co/edit/a9OdMAq2YIwQFo7gixbj?p=preview to poke around
It's significantly easier to do this in Angular 6 than it was in previous versions, even when the checkbox information is populated asynchronously from an API.
The first thing to realise is that thanks to Angular 6's keyvalue pipe we don't need to have to use FormArray anymore, and can instead nest a FormGroup.
First, pass FormBuilder into the constructor
constructor(
private _formBuilder: FormBuilder,
) { }
Then initialise our form.
ngOnInit() {
this.form = this._formBuilder.group({
'checkboxes': this._formBuilder.group({}),
});
}
When our checkbox options data is available, iterate it and we can push it directly into the nested FormGroup as a named FormControl, without having to rely on number indexed lookup arrays.
const checkboxes = <FormGroup>this.form.get('checkboxes');
options.forEach((option: any) => {
checkboxes.addControl(option.title, new FormControl(true));
});
Finally, in the template we just need to iterate the keyvalue of the checkboxes: no additional let index = i, and the checkboxes will automatically be in alphabetical order: much cleaner.
<form [formGroup]="form">
<h3>Options</h3>
<div formGroupName="checkboxes">
<ul>
<li *ngFor="let item of form.get('checkboxes').value | keyvalue">
<label>
<input type="checkbox" [formControlName]="item.key" [value]="item.value" /> {{ item.key }}
</label>
</li>
</ul>
</div>
</form>
I don't see a solution here that completely answers the question using reactive forms to its fullest extent so here's my solution for the same.
Summary
Here's the pith of the detailed explanation along with a StackBlitz example.
Use FormArray for the checkboxes and initialize the form.
The valueChanges observable is perfect for when you want the form to display something but store something else in the component. Map the true/false values to the desired values here.
Filter out the false values at the time of submission.
Unsubscribe from valueChanges observable.
StackBlitz example
Detailed explanation
Use FormArray to define the form
As already mentioned in the answer marked as correct. FormArray is the way to go in such cases where you would prefer to get the data in an array. So the first thing you need to do is create the form.
checkboxGroup: FormGroup;
checkboxes = [{
name: 'Value 1',
value: 'value-1'
}, {
name: 'Value 2',
value: 'value-2'
}];
this.checkboxGroup = this.fb.group({
checkboxes: this.fb.array(this.checkboxes.map(x => false))
});
This will just set the initial value of all the checkboxes to false.
Next, we need to register these form variables in the template and iterate over the checkboxes array (NOT the FormArray but the checkbox data) to display them in the template.
<form [formGroup]="checkboxGroup">
<ng-container *ngFor="let checkbox of checkboxes; let i = index" formArrayName="checkboxes">
<input type="checkbox" [formControlName]="i" />{{checkbox.name}}
</ng-container>
</form>
Make use of the valueChanges observable
Here's the part I don't see mentioned in any answer given here. In situations such as this, where we would like to display said data but store it as something else, the valueChanges observable is very helpful. Using valueChanges, we can observe the changes in the checkboxes and then map the true/false values received from the FormArray to the desired data. Note that this will not change the selection of the checkboxes as any truthy value passed to the checkbox will mark it as checked and vice-versa.
subscription: Subscription;
const checkboxControl = (this.checkboxGroup.controls.checkboxes as FormArray);
this.subscription = checkboxControl.valueChanges.subscribe(checkbox => {
checkboxControl.setValue(
checkboxControl.value.map((value, i) => value ? this.checkboxes[i].value : false),
{ emitEvent: false }
);
});
This basically maps the FormArray values to the original checkboxes array and returns the value in case the checkbox is marked as true, else it returns false. The emitEvent: false is important here since setting the FormArray value without it will cause valueChanges to emit an event creating an endless loop. By setting emitEvent to false, we are making sure the valueChanges observable does not emit when we set the value here.
Filter out the false values
We cannot directly filter the false values in the FormArray because doing so will mess up the template since they are bound to the checkboxes. So the best possible solution is to filter out the false values during submission. Use the spread operator to do this.
submit() {
const checkboxControl = (this.checkboxGroup.controls.checkboxes as FormArray);
const formValue = {
...this.checkboxGroup.value,
checkboxes: checkboxControl.value.filter(value => !!value)
}
// Submit formValue here instead of this.checkboxGroup.value as it contains the filtered data
}
This basically filters out the falsy values from the checkboxes.
Unsubscribe from valueChanges
Lastly, don't forget to unsubscribe from valueChanges
ngOnDestroy() {
this.subscription.unsubscribe();
}
Note: There is a special case where a value cannot be set to the FormArray in valueChanges, i.e if the checkbox value is set to the number 0. This will make it look like the checkbox cannot be selected since selecting the checkbox will set the FormControl as the number 0 (a falsy value) and hence keep it unchecked. It would be preferred not to use the number 0 as a value but if it is required, you have to conditionally set 0 to some truthy value, say string '0' or just plain true and then on submitting, convert it back to the number 0.
StackBlitz example
The StackBlitz also has code for when you want to pass default values to the checkboxes so they get marked as checked in the UI.
TL;DR
I prefer to use FormGroup to populate the list of checkbox
Write a custom validator to check at least one checkbox was selected
Working example https://stackblitz.com/edit/angular-validate-at-least-one-checkbox-was-selected
This also struck me sometimes so I did try both FormArray and FormGroup approaches.
Most of the time, the list of checkboxes was populated on the server and I received it through API. But sometimes you will have a static set of checkboxes with your predefined value. With each use case, the corresponding FormArray or FormGroup will be used.
Basically FormArray is a variant of FormGroup. The key difference is that its data gets serialized as an array (as opposed to being serialized as an object in case of FormGroup). This might be especially useful when you don’t know how many controls will be present within the group, like dynamic forms.
For the sake of simplicity, imagine you have a simple create product form with
One required product name textbox.
A list of categories to select from, required at least one to be checked. Assume the list will be retrieved from the server.
First, I set up a form with only the product name formControl. It is a required field.
this.form = this.formBuilder.group({
name: ["", Validators.required]
});
Since the category is dynamically rendering, I will have to add these data into the form later after the data was ready.
this.getCategories().subscribe(categories => {
this.form.addControl("categoriesFormArr", this.buildCategoryFormArr(categories));
this.form.addControl("categoriesFormGroup", this.buildCategoryFormGroup(categories));
})
There are two approaches to build up the category list.
1. Form Array
buildCategoryFormArr(categories: ProductCategory[], selectedCategoryIds: string[] = []): FormArray {
const controlArr = categories.map(category => {
let isSelected = selectedCategoryIds.some(id => id === category.id);
return this.formBuilder.control(isSelected);
})
return this.formBuilder.array(controlArr, atLeastOneCheckboxCheckedValidator())
}
<div *ngFor="let control of categoriesFormArr?.controls; let i = index" class="checkbox">
<label><input type="checkbox" [formControl]="control" />
{{ categories[i]?.title }}
</label>
</div>
This buildCategoryFormGroup will return me a FormArray. It also takes a list of selected values as an argument so If you want to reuse the form for editing data, it could be helpful. For the purpose of creating a new product form, it is not applicable yet.
Noted that when you try to access the formArray values. It will looks like [false, true, true]. To get a list of selected id, it required a bit more work to check from the list but based on the array index. Doesn't sound good to me but it works.
get categoriesFormArraySelectedIds(): string[] {
return this.categories
.filter((cat, catIdx) => this.categoriesFormArr.controls.some((control, controlIdx) => catIdx === controlIdx && control.value))
.map(cat => cat.id);
}
That's why I came up using FormGroup for that matter
2. Form Group
formGroup will store the form data as the object, which required a key map to a form control. So it is a good idea to set the key as the categoryId and then we can retrieve it later.
buildCategoryFormGroup(categories: ProductCategory[], selectedCategoryIds: string[] = []): FormGroup {
let group = this.formBuilder.group({}, {
validators: atLeastOneCheckboxCheckedValidator()
});
categories.forEach(category => {
let isSelected = selectedCategoryIds.some(id => id === category.id);
group.addControl(category.id, this.formBuilder.control(isSelected));
})
return group;
}
<div *ngFor="let item of categories; let i = index" class="checkbox">
<label><input type="checkbox" [formControl]="categoriesFormGroup?.controls[item.id]" /> {{ categories[i]?.title }}
</label>
</div>
The value of the form group will look like this:
{
"category1": false,
"category2": true,
"category3": true,
}
But most often we want to get only the list of categoryIds as ["category2", "category3"]. I also have to write a get to take these data. I like this approach better compared to the formArray, because I could actually take the value from the form itself.
get categoriesFormGroupSelectedIds(): string[] {
let ids: string[] = [];
for (var key in this.categoriesFormGroup.controls) {
if (this.categoriesFormGroup.controls[key].value) {
ids.push(key);
}
else {
ids = ids.filter(id => id !== key);
}
}
return ids;
}
3. Custom validator to check at least one checkbox was selected
I made the validator check at least X checkbox was selected, by default it will check against one checkbox only.
export function atLeastOneCheckboxCheckedValidator(minRequired = 1): ValidatorFn {
return function validate(formGroup: FormGroup) {
let checked = 0;
Object.keys(formGroup.controls).forEach(key => {
const control = formGroup.controls[key];
if (control.value) {
checked++;
}
});
if (checked < minRequired) {
return {
requireCheckboxToBeChecked: true,
};
}
return null;
};
}
If you are looking for checkbox values in JSON format
{ "name": "", "countries": [ { "US": true }, { "Germany": true }, { "France": true } ] }
Full example here.
I apologise for using Country Names as checkbox values instead of those in the question. Further explannation -
Create a FormGroup for the form
createForm() {
//Form Group for a Hero Form
this.heroForm = this.fb.group({
name: '',
countries: this.fb.array([])
});
let countries=['US','Germany','France'];
this.setCountries(countries);}
}
Let each checkbox be a FormGroup built from an object whose only property is the checkbox's value.
setCountries(countries:string[]) {
//One Form Group for one country
const countriesFGs = countries.map(country =>{
let obj={};obj[country]=true;
return this.fb.group(obj)
});
const countryFormArray = this.fb.array(countriesFGs);
this.heroForm.setControl('countries', countryFormArray);
}
The array of FormGroups for the checkboxes is used to set the control for the 'countries' in the parent Form.
get countries(): FormArray {
return this.heroForm.get('countries') as FormArray;
};
In the template, use a pipe to get the name for the checkbox control
<div formArrayName="countries" class="well well-lg">
<div *ngFor="let country of countries.controls; let i=index" [formGroupName]="i" >
<div *ngFor="let key of country.controls | mapToKeys" >
<input type="checkbox" formControlName="{{key.key}}">{{key.key}}
</div>
</div>
</div>
If you want to use an Angular reactive form (https://angular.io/guide/reactive-forms).
You can use one form control to manage the outputted value of the group of checkboxes.
component
import { Component } from '#angular/core';
import { FormGroup, FormControl } from '#angular/forms';
import { flow } from 'lodash';
import { flatMap, filter } from 'lodash/fp';
#Component({
selector: 'multi-checkbox',
templateUrl: './multi-checkbox.layout.html',
})
export class MultiChecboxComponent {
checklistState = [
{
label: 'Frodo Baggins',
value: 'frodo_baggins',
checked: false
},
{
label: 'Samwise Gamgee',
value: 'samwise_gamgee',
checked: true,
},
{
label: 'Merry Brandybuck',
value: 'merry_brandybuck',
checked: false
}
];
form = new FormGroup({
checklist : new FormControl(this.flattenValues(this.checklistState)),
});
checklist = this.form.get('checklist');
onChecklistChange(checked, checkbox) {
checkbox.checked = checked;
this.checklist.setValue(this.flattenValues(this.checklistState));
}
flattenValues(checkboxes) {
const flattenedValues = flow([
filter(checkbox => checkbox.checked),
flatMap(checkbox => checkbox.value )
])(checkboxes)
return flattenedValues.join(',');
}
}
html
<form [formGroup]="form">
<label *ngFor="let checkbox of checklistState" class="checkbox-control">
<input type="checkbox" (change)="onChecklistChange($event.target.checked, checkbox)" [checked]="checkbox.checked" [value]="checkbox.value" /> {{ checkbox.label }}
</label>
</form>
checklistState
Manages the model/state of the checklist inputs. This model allows you to map the current state to whatever value format you need.
Model:
{
label: 'Value 1',
value: 'value_1',
checked: false
},
{
label: 'Samwise Gamgee',
value: 'samwise_gamgee',
checked: true,
},
{
label: 'Merry Brandybuck',
value: 'merry_brandybuck',
checked: false
}
checklist Form Control
This control stores the value would like to save as e.g
value output: "value_1,value_2"
See demo at https://stackblitz.com/edit/angular-multi-checklist
Make an event when it's clicked and then manually change the value of true to the name of what the check box represents, then the name or true will evaluate the same and you can get all the values instead of a list of true/false. Ex:
component.html
<form [formGroup]="customForm" (ngSubmit)="onSubmit()">
<div class="form-group" *ngFor="let parameter of parameters"> <!--I iterate here to list all my checkboxes -->
<label class="control-label" for="{{parameter.Title}}"> {{parameter.Title}} </label>
<div class="checkbox">
<input
type="checkbox"
id="{{parameter.Title}}"
formControlName="{{parameter.Title}}"
(change)="onCheckboxChange($event)"
> <!-- ^^THIS^^ is the important part -->
</div>
</div>
</form>
component.ts
onCheckboxChange(event) {
//We want to get back what the name of the checkbox represents, so I'm intercepting the event and
//manually changing the value from true to the name of what is being checked.
//check if the value is true first, if it is then change it to the name of the value
//this way when it's set to false it will skip over this and make it false, thus unchecking
//the box
if(this.customForm.get(event.target.id).value) {
this.customForm.patchValue({[event.target.id] : event.target.id}); //make sure to have the square brackets
}
}
This catches the event after it was already changed to true or false by Angular Forms, if it's true I change the name to the name of what the checkbox represents, which if needed will also evaluate to true if it's being checked for true/false as well.
Apparently, this is a very common problem and no one has a "perfect" solution. I believe I was able to come with a pretty elegant solution, using object orientation to extend the capabilities of FormGroup.
Desired API
In a single object I want to be able to have:
The form control for each checkbox
The label and value for each checkbox
The values of all selected checkbox
So the HTML structure can be simple as this:
<div *ngFor="let item of checkboxGroup.items">
<input type="checkbox" [id]="item.value" [formControl]="item.control">
<label [for]="item.value">{{ item.label }}</label>
</div>
And the typescript part can be simple as this:
checkboxGroup.value; // return the list of selected item values
checkboxGroup.control.valid; // return if there's at least one checked value
Solution
As you can see in the HTML part, the checkboxGroup needs to be a class with at least three properties:
items (each item is a checkbox with a value, label and a FormControl)
value (gets all selected items)
control (gets the FormArray control)
So the class will be like:
// # This represents a single checkbox item
class CheckboxItemControl {
label: string; // value to be shown in the UI
value: string; // value to be saved in backend
control: FormControl;
constructor({ label, value, defaultValue = false }: { label: string; value: string; defaultValue?: boolean }) {
this.label = label;
this.value = value;
this.control = new FormControl(defaultValue || false);
}
get selected(): boolean {
return Boolean(this.control.value);
}
}
// # This represents a checkbox group, with several items
class CheckboxGroupControl {
name?: string; // name of the checkbox group
items: CheckboxItemControl[];
control: FormArray;
constructor(name: string, items: CheckboxItemControl[]) {
this.name = name;
this.items = items;
this.control = new FormArray(this.getAllItemsControls(), CheckboxGroupControl.emptyArrayFormValidator);
}
get value(): string[] {
return this.selectedItems.map(item => item.value);
}
private get selectedItems(): CheckboxItemControl[] {
return this.items.filter(item => item.selected);
}
private getAllItemsControls(): FormControl[] {
return this.items.map(item => item.control);
}
private static emptyArrayFormValidator(control: FormControl) {
const valid = (control.value as boolean[]).some(Boolean);
// #todo improve error message
return valid ? null : {
error: 'empty'
};
}
}
You can see how each class exposes a simple API (object.value and object.control) which allows you to easily get all that you need.
Usage
So let's see in practice how it'll work:
HTML
<div *ngFor="let item of checkboxGroup.items">
<input type="checkbox" [id]="item.value" [formControl]="item.control">
<label [for]="item.value">{{ item.label }}</label>
</div>
Typescript
checkboxGroup;
ngOnInit() {
this.createFormInputs();
}
private createFormInputs() {
const checkboxItems = [
new CheckboxItemControl({ value: 'checkbox-1', label: 'Checkbox 1' }),
new CheckboxItemControl({ value: 'checkbox-2', label: 'Checkbox 2' }),
new CheckboxItemControl({ value: 'checkbox-3', label: 'Checkbox 3', defaultValue: true })
];
this.checkboxGroup = new CheckboxGroupControl('name_of_group', checkboxItems);
this.form = new FormGroup({
checkbox: this.checkboxGroup.control
});
// this.checkboxGroup.value returns ['checkbox-1', ...] for the selected checkboxes
// this.checkboxGroup.valid returns if there's any checkbox selected
// this.form.valid returns if the whole form is valid. Which is useful if you include others checkbox groups
}
Other resources
This article sparks the light for me to come up with this solution.
My solution - solved it for Angular 5 with Material View
The connection is through the
formArrayName="notification"
(change)="updateChkbxArray(n.id, $event.checked, 'notification')"
This way it can work for multiple checkboxes arrays in one form.
Just set the name of the controls array to connect each time.
constructor(
private fb: FormBuilder,
private http: Http,
private codeTableService: CodeTablesService) {
this.codeTableService.getnotifications().subscribe(response => {
this.notifications = response;
})
...
}
createForm() {
this.form = this.fb.group({
notification: this.fb.array([])...
});
}
ngOnInit() {
this.createForm();
}
updateChkbxArray(id, isChecked, key) {
const chkArray = < FormArray > this.form.get(key);
if (isChecked) {
chkArray.push(new FormControl(id));
} else {
let idx = chkArray.controls.findIndex(x => x.value == id);
chkArray.removeAt(idx);
}
}
<div class="col-md-12">
<section class="checkbox-section text-center" *ngIf="notifications && notifications.length > 0">
<label class="example-margin">Notifications to send:</label>
<p *ngFor="let n of notifications; let i = index" formArrayName="notification">
<mat-checkbox class="checkbox-margin" (change)="updateChkbxArray(n.id, $event.checked, 'notification')" value="n.id">{{n.description}}</mat-checkbox>
</p>
</section>
</div>
At the end you are getting to save the form with array of original records id's to save/update.
Will be happy to have any remarks for improvement.
Component:
formGroup: FormGroup;
games = [
{ keyword: 'hots', score: 9 },
{ keyword: 'xcom', score: 9 },
{ keyword: 'fallout', score: 8 }
];
constructor(private fb: FormBuilder) {}
ngOnInit() {
this.formGroup = this.fb.group(
this.games.reduce((obj, game) => {
obj[game.keyword] = [false];
return obj;
}, {})
);
const enabledGames$ = this.formGroup.valueChanges.pipe(
map(value =>
Object.entries(value)
.filter(([key, enabled]) => enabled)
.map(([key]) =>
this.games.find(({ keyword }) => keyword === key)
)
)
);
}
Template:
<form [formGroup]="formGroup">
<div *ngFor="let control of formGroup.controls | keyvalue">
<input
type="checkbox"
[formControlName]="control.key">
<label>
{{ control.key }}
</label>
</div>
</form>
I was able to accomplish this using a FormArray of FormGroups. The FormGroup consists of two controls. One for the data and one to store the checked boolean.
TS
options: options[] = [{id: 1, text: option1}, {id: 2, text: option2}];
this.fb.group({
options: this.fb.array([])
})
populateFormArray() {
this.options.forEach(option => {
let checked = ***is checked logic here***;
this.checkboxGroup.get('options').push(this.createOptionGroup(option, checked))
});
}
createOptionGroup(option: Option, checked: boolean) {
return this.fb.group({
option: this.fb.control(option),
checked: this.fb.control(checked)
});
}
HTML
This allows you to loop through the options and bind to the corresponding checked control.
<form [formGroup]="checkboxGroup">
<div formArrayName="options" *ngFor="let option of options; index as i">
<div [formGroupName]="i">
<input type="checkbox" formControlName="checked" />
{{ option.text }}
</div>
</div>
</form>
Output
The form returns data in the form {option: Option, checked: boolean}[].
You can get a list of checked options using the below code
this.checkboxGroup.get('options').value.filter(el => el.checked).map(el => el.option);
With two way binding
my.component.html
<form [formGroup]="formGroup" (ngSubmit)="onSubmit()">
<div formGroupName="options">
<mat-checkbox formControlName="myVal1">My Value 1</mat-checkbox>
<mat-checkbox formControlName="myVal2">My Value 2</mat-checkbox>
</div>
<button type="submit">Submit</button>
</form>
my.component.ts
export class ClientStatementReportComponent implements OnInit {
formGroup: FormGroup;
ngOnInit(): void {
this.formGroup = new FormGroup({
options: new FormGroup({
myVal1: new FormControl(false),
myVal2: new FormControl(false)
}),
});
}
onSubmit() {
const options = this.formGroup.value.options;
const result = Object.keys(options).filter(key => options[key])
// is array of checked elements e.g. ["myVal1"]
}
}
With one way binding (to form state)
my.component.html
<form [formGroup]="formGroup">
<mat-checkbox value="val-1" (change)="selectOption($event)">Value 1</mat-checkbox>
<mat-checkbox value="val-2" (change)="selectOption($event)">Value 2</mat-checkbox>
</form>
my.component.ts
export class MyComponent implements OnInit {
formGroup: FormGroup;
ngOnInit(): void {
this.formGroup = new FormGroup({
options: new FormControl([]),
});
}
selectOption($event: MatCheckboxChange) {
const value = $event.source.value;
const optionControl = this.formGroup.controls['options']
const options = optionControl.value as [];
if(checked){
optionControl.setValue([...options, value])
} else {
optionControl.setValue(options.filter(option => option !== value))
}
}
}
TEMPLATE PART:-
<div class="form-group">
<label for="options">Options:</label>
<div *ngFor="let option of options">
<label>
<input type="checkbox"
name="options"
value="{{option.value}}"
[(ngModel)]="option.checked"
/>
{{option.name}}
</label>
</div>
<br/>
<button (click)="getselectedOptions()" >Get Selected Items</button>
</div>
CONTROLLER PART:-
export class Angular2NgFor {
constructor() {
this.options = [
{name:'OptionA', value:'first_opt', checked:true},
{name:'OptionB', value:'second_opt', checked:false},
{name:'OptionC', value:'third_opt', checked:true}
];
this.getselectedOptions = function() {
alert(this.options
.filter(opt => opt.checked)
.map(opt => opt.value));
}
}
}
Add my 5 cents)
My question model
{
name: "what_is_it",
options:[
{
label: 'Option name',
value: '1'
},
{
label: 'Option name 2',
value: '2'
}
]
}
template.html
<div class="question" formGroupName="{{ question.name }}">
<div *ngFor="let opt of question.options; index as i" class="question__answer" >
<input
type="checkbox" id="{{question.name}}_{{i}}"
[name]="question.name" class="hidden question__input"
[value]="opt.value"
[formControlName]="opt.label"
>
<label for="{{question.name}}_{{i}}" class="question__label question__label_checkbox">
{{opt.label}}
</label>
</div>
component.ts
onSubmit() {
let formModel = {};
for (let key in this.form.value) {
if (typeof this.form.value[key] !== 'object') {
formModel[key] = this.form.value[key]
} else { //if formgroup item
formModel[key] = '';
for (let k in this.form.value[key]) {
if (this.form.value[key][k])
formModel[key] = formModel[key] + k + ';'; //create string with ';' separators like 'a;b;c'
}
}
}
console.log(formModel)
}
Template
<div>
<input name="fruits" type="checkbox" value="orange" (change)="change($event)">
<input name="fruits" type="checkbox" value="apple" (change)="change($event)">
<input name="fruits" type="checkbox" value="banana" (change)="change($event)">
</div>
Component
formGroup = this.formBuilder.group(
{
fruits: [[]] //["Orange","Banana",...]
})
change(event: Event) {
let target = (event.target as HTMLInputElement);
let array = (this.formGroup.get(target.name)?.value as Array);
if (target.checked && !array.find(element => {
return (element === target.value);
})) {
array.push(target.value)// element not exists, push (check)
}
else {
array.splice(array.findIndex(element => {
return (element === target.value);//delete element (uncheck)
}), 1)
}
}
This is how I would do it, although I always use Angular Material List
https://material.angular.io/components/list/overview
Everything comes from the factory for these tasks