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Angular - Using custom directive to load several components is returning undefined

I am developing an app and for now, I have a dynamic grid generator which divides the space in the screen to fit several components dynamically. So, the component encharged of this must render the components after angular has rendered the page. In order to achieve that I've followed the angular dynamic component loader guide (https://angular.io/guide/dynamic-component-loader).
So I am in a point where I do have the component where the other components must be rendered, I have my custom directive to render the components.
The directive
#Directive({
selector: '[componentLoader]'
})
export class ComponentLoaderDirective {
constructor (
public ViewContainerRef: ViewContainerRef
) {}
}
Now the component ( grid component )
grid.component.ts
// ... Stuff above
export class GridComponent implements OnInit {
#Input() public items: gridItem[] = [];
#ViewChild(ComponentLoaderDirective) componentLoader: ComponentLoaderDirective | undefined;
constructor(
private sanitizer: DomSanitizer,
private componentFactoryResolver: ComponentFactoryResolver
) {}
ngOnInit(): void { this.processRow(this.items) }
processRow( row: gridItem[] ) {
// Some grid related stuff ...
for ( let item of row ) {
// Stuff performed over every item in each grid row
this.renderComponentIfNeeded(item)
}
}
renderComponentIfNeeded( item: gridItem ):void {
if ( item.components ) {
let componentFactory = this.componentFactoryResolver.resolveComponentFactory(component);
let viewContainerRef = this.componentLoader.ViewContainerRef;
viewContainerRef.clear();
let componentRef = viewContainerRef.createComponent<any>(componentFactory);
componentRef.instance.data = item;
console.log('Directive ', this.componentLoader, 'ComponentRef: ', componentRef);
}
}
And the HTML of the component:
<!-- Dynamic grid generation using ng-template and ng-content. This is generated several times using the *ngFor, for every item in the items array we will have a componentLoader -->
<ng-template componentLoader>
</ng-template>
There is a lot more content in these files but for simplicity I will only post this, If you need more code just tell me.
Okay, so my problem is that when I access to this.contentLoader the returned value is just undefined, so this.componentLoader.viewContainerRef causes an error because componentLoader is undefined.
I've tried adding the exportAs property to the directive's decorator and it is giving exacly the same error.
I've also tried to add the directive in the module declarations without success, and changed the <ng-template componentLoader> to <ng-template #loader=componentLoader> which causes a different error ( No directive has 'componentLoader' exportAs or something like this )
PS: In the ´´´this.componentFacotryResolver.resolveComponentFactory(component)``` I successfully have each component that has been given to the grid.
I prefer you not to solve my issue but to point me in the right direction and help me see what am I doing wrong in order to improve myself.
Any help will be much appreciated :)

I've managed to solve this issue in a very simple way.
I was trying to do too many things inside the grid component so I removed to code related to the component loader and moved it into a single component, called ComponentLoaderComponent.
Inside the component I've setted up all the logic in the same way than I did in the grid component. So now I have a new ts file like this:
import { Component, ComponentFactoryResolver, Input, OnInit, ViewChild } from '#angular/core';
import { ComponentLoaderDirective } from 'src/app/shared/directives/componentLoader.directive';
#Component({
selector: 'component-loader',
templateUrl: './component-loader.component.html',
styleUrls: ['./component-loader.component.css']
})
export class ComponentLoaderComponent implements OnInit {
#Input() public component: any;
#ViewChild(ComponentLoaderDirective, { static: true }) componentLoader!: ComponentLoaderDirective;
constructor(
private componentFactoryResolver: ComponentFactoryResolver
) { }
ngOnInit(): void {
this.loadComponent();
}
loadComponent():void {
if (this.component) {
let componentFactory = this.componentFactoryResolver.resolveComponentFactory(this.component);
let viewContainerRef = this.componentLoader.viewContainerRef;
viewContainerRef.clear();
let componentRef = viewContainerRef.createComponent<any>(componentFactory);
}
}
And an HTML like this:
<ng-template componentLoader>
</ng-template>
Now from the grid component I only have to call the ComponentLoader for every component I want to add to the grid, so the grid html will look like this:
<div
*ngIf=" gridItem.components && gridItem.components.length > 0"
class="component-container"
>
<component-loader
*ngFor="let component of gridItem.components"
[component]="component">
</component-loader>
</div >
Now the components are getting loaded correclty, anyways I still don't know what I was missing in before.

Angular functions are performed twice when called in the html file

I tried to start an angular project, I've created a simple component and started a console.log in it but I have Confusing problem. when I calling a function in html file from ts file its run twice
TS:
import { Component, OnInit } from '#angular/core';
#Component({
selector: 'app-hello',
templateUrl: './hello.component.html',
styleUrls: ['./hello.component.less']
})
export class HelloComponent implements OnInit {
constructor() { }
ngOnInit(): void {
}
log(val)
{
console.log(val);
}
test() {
let time = new Date()
console.log(time.getSeconds());
}
}
html :
hello works!
{{log('test')}}
{{test()}}
image log:
enter image description here

Where and how often do you call your component?
Can you produce a simple example on stackblitz?
Without any further info, we can just guess what it is.
You propably have called your component via '' twice.
Each instance will call all your template and hence its calling functions.

function variable dynamic setting

This question related to Syntactically anonymous/Arrow Function/add-hoc/factory DP functions:
I have a component which is embedded in the Html.
The component has a click event which is binded to a function. This function content depend on another component which has a reference to this component.
This is the component with the click event:
HTML:
<div (click)="doSomething()">Content.....</div> \\ Should it be with a brackets ?
In the component I just want to define the function signature:
#Component({
selector: 'app-embedded'
})
export class className
{
constructor() { }
ngOnInit() { }
doSomething:(booleanparams: boolean) => any; //The function get a boolean parameter as input and return void or any
}
Now this is where the component is embedded:
<div >
<app-embedded #emb></app-embedded>
</div>
This is the component of the container of the embedded component, which has a reference to the embedded component:
#Component({
selector: 'app-container',
})
export class container
{
#ViewChild('emb') private emb: ElementRef;
booleanParam : booelan;
constructor()
{
emb.doSomething = containerFunction(true);
}
containerFunction(booleanParam : boolean)
{
// do something in this context
}
}
The idea is that this embedded component is embedded in many other containers and whenever the click event triggered a function that was set in the doSomething function variable should be executed.
What changes in the code I need to do in order to accomplish this ?

The best way i see of doing this would be to simply use an event emitter and capture the event on the other side? so embedded would have this:
#Component({
selector: 'app-embedded'
})
export class className
{
#Output()
public something: EventEmitter<boolean> = new EventEmitter<boolean>();
constructor() { }
ngOnInit() { }
doSomething:(booleanparams: boolean) {
this.something.emit(booleanparams);
}; //The function get a boolean parameter as input and return void or any
}
Then where it is called:
<div >
<app-embedded #emb (something)="doSomething($event)"></app-embedded>
</div>
Other solution that would allow a return
#Component({
selector: 'app-embedded'
})
export class className
{
#Input()
public somethingFunc: (boolean)=>any;
constructor() { }
ngOnInit() { }
doSomething:(booleanparams: boolean) {
let w_potato = this.somethingFunc(booleanparams);
//Do whatever you want with w_potato
}; //The function get a boolean parameter as input and return void or any
}
in this case the view would be
<div >
<app-embedded #emb [somethingFunc]="doSomething"></app-embedded>
</div>
I hope this helps! Passing the function or emitting an event will be much more angular than trying to modify an instance of a component. On top of that, a constructor is only called once when Angular starts up so #emb at that time will not be defined to be anything. If you wanted to do it that way you would have to bind yourself in something ngAfterViewInit.
But again, I think that passing it through attributes will be much more angular looking.
Good Luck let me know if this doesn't suit your answer.

Angular 2+ Dynamic HTML template

Following what is documented here: Dynamic Component Loader.
I want to know how is it possible to handle the data inside this HeroJobAdComponent class:
import { Component, Input } from '#angular/core';
import { AdComponent } from './ad.component';
#Component({
template: `
<div class="job-ad">
<h4>{{data.headline}}</h4>
{{data.body}}
</div>
`
})
export class HeroJobAdComponent implements AdComponent {
#Input() data: any;
}
As you can see, data is the object holding the data received. I want to be able to define a constructor for my HeroJobAdComponent class but if I do, the object data is undefined inside my constructor. I tried using ngOnChange instead which supposedly executes once input is changed from undefined to defined but it also did not execute at all.
Can someone please explain first why is the object undefined even though the data is defined in my main component calling it, and what's the workaround for this issue?
This is the constructor I am using:
constructor()
{
this.values = this.data.values;
this.spec_name = this.data.spec_name;
}

if you want to use any operation when you receive data in your component , you can use setter
export class HeroJobAdComponent implements AdComponent {
_data;
#Input() set data (data: any){
//operation on data goes here
this._data=data
};
get data() {
return this._data;
}
}

how can i call a function when a template loads in angular2?

I am new to angular2. I have a requirement to call a function when a template loads/initializes. I know how to do this in angular1.x., but I am not able to find out how it can be done in angular-2.
This is how I tried in angular1.x
In html
<div ng-init="getItems()">
//some logic to get my items
</div>
In controller
getItems = function(){
console.log('in the getitems function call');
//logic to get my items from db/localStorage
}
This is how I used ng-init in angular1.x, but there is no ng-init in angular-2?Please help me on this issue.

#Component({
...
})
class MyComponent {
constructor() {
// when component class instance is created
}
ngOnChanges(...) {
// when inputs are updated
}
ngOnInit() {
// after `ngOnChanges()` was called the first time
}
ngAfterViewInit() {
// after the view was created
}
ngAfterContentInit() {
// after content was projected
}
}
See also https://angular.io/docs/ts/latest/guide/lifecycle-hooks.html#!#hooks-overview for the full list

Check lifecycle events of a component https://angular.io/docs/ts/latest/guide/lifecycle-hooks.html . From what you are saying you probably needs ngAfterViewInit

In angular2 you can use component phase ngOnInit it is equal to on-init in angularJS. Here is more information about lifecycle in angular.
Example:
export class PeekABoo implements OnInit {
constructor(private logger: LoggerService) { }
// implement OnInit's `ngOnInit` method
ngOnInit() {
this.logIt(`OnInit`);
}
protected logIt(msg: string) {
this.logger.log(`#${nextId++} ${msg}`);
}
}