Getting JavaScript result in Angular - javascript

I'm using a third party JS I'm calling from Angular:
import { Component } from '#angular/core';
declare var SomeApi: any;
#Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent {
firstName: string;
onStartTest() {
SomeApi.runTest();
function onTestCompleted(testResult) {
//Can get testResult.FirstName
this.firstName = testResult.FirstName;
}
}
}
I can successfully run the SomeApi.runTest() in Angular and when it finished I can get the testResult and its properties like FirstName and display to HTML. But the problem is I can't pass this to the local Angular variable which is firstName: string in this case. The component I think finishes up as the .runTest() runs in async.
I also tried running a service inside the function so that I can pass the data to a service after onTestCompleted():
constructor(private dataService: DataService) {}
function onTestCompleted(testResult) {
//Can get testResult.FirstName
this.firstName = testResult.FirstName;
this.dataService.writeResult(testResult.FirstName);
}
But the problem is that an error comes out saying that .writeResult() is not known. I think it's because the life of the Component has ended?
I just want to ask for help on how I would get the testResult object and its properties outside function()?

I think third party API that compatible with Angular 2 support observable,
try using subscribe instead of waiting the test to finish and then passing the result value to a function, like this:
SomeApi.runTest().subscribe(testResult => {
this.firstName = testResult.FirstName;
...
});
or you can use promise as well, like this:
var dataPromise = SomeApi.runTest();
dataPromise.then(function(result) {
// this is only run after runTest() resolves
this.firstName = testResult.FirstName;
...
});

Related

get undefined for data assigned in service in angular 6

I don't want to call the service in the .ts file. It will cause a lot of time. So I just want to assigned this as a global value that I can use, but I keep get undefined
Here is my service file
#Injectable({
providedIn: 'root'
})
export class DeService {
data:any;
constructor(private http: HttpClient){}
getData(id:any):Observable<any>{
this.http.get(Url.getDetails+"id="+id).pipe(first()).subscribe(res=>{
this.data = res;
console.log(this.data) //Here I got the data
}
return this.http.get(Url.getDetails+"id="+id)
}
}
the ts file
export class text implements OnInit{
constructor(public de:DeService){}
ngOnInIt(){
console.log(this.de.data); //here it returns undefind
}
}
You cannot access the observable like that, you need to call the method and subscribe to the method as follows,
getData(id:any):Observable<any>{
return this.http.get(Url.getDetails+"id="+id);
}
and in component,
ngOnInIt(){
this.de.getData(id).subscribe((data)=>{
console.log(data);
});
}
Since you are using Observable, and Observable works with async data, your data:any; is not initialized therefore it logs undefined.
This is happening
export class text implements OnInit{
constructor(public de:DeService){}
ngOnInIt(){
console.log(this.de.data); //here it returns undefind
}
}
Before this:
getData(id:any):Observable<any>{
this.http.get(Url.getDetails+"id="+id).pipe(first()).subscribe(res=>{
this.data = res;
console.log(this.data) //Here I got the data
}
return this.http.get(Url.getDetails+"id="+id)
}
To fix this you must set the data:any to some value or use #Sajeetharan solution ofcourse.

Why we need to inject service through constructor in angular2?

I'm learning Angular 2. And got confused over constructor.
Consider the below code :
import { Component, OnInit } from '#angular/core';
import { FormGroup,FormsModule,FormControl } from '#angular/forms';
import { WeatherService } from '../weather.service';
import { WeatherItem } from '../weather-item';
#Component({
selector: 'app-weather-search',
templateUrl: './weather-search.component.html',
styleUrls: ['../../assets/app.css'],
//providers: [WeatherService]
})
export class WeatherSearchComponent implements OnInit {
constructor(private _weatherService : WeatherService) { }
onSubmit(form : FormGroup){
//alert(form.value.location);
this._weatherService.searchWeatherData(form.value.location)
.subscribe(
data => {
const weatherItem = new WeatherItem(data.data.request["0"].query,data.data.weather["0"].maxtempC,data.data.weather["0"].maxtempC);
this._weatherService.addWeatherItems(weatherItem);
console.log(form);
})
}
ngOnInit() {
}
}
Here we are injecting 'WeatherService' in constructor. Can't we do the same outside constructor ? What constructor is doing here actually? Do we really need it here?
The constructor itself is not doing actual work.
Angular creates a new WeatherSearchComponent executing
new WeatherSearchComponent(weatherService);
and this causes the constructor in WeatherSearchComponent to receive the weatherService value.
The constructor
constructor(private _weatherService : WeatherService)
causes an instance field _weatherService to be created and initialized with the value passed from DI.
The constructor is the only place where it is easy to know when the injected service is available and when not.
If the service would passed to a field, setter or method, code in the constructor could not access it because the constructor is executed before outside code has a change to set a field or call a method.
Also for code outside the constructor it is not safe to assume the service is available because this code could be called from the constructor before a field could be set from the outside.
For dependency injection passing dependencies to the constructor is the only way to avoid a lot of complexity.
Dependency Injection in constructor is always better option and while the component is getting created it will get the weatherService as a parameter. To make it clear, below is the transpiled code for your snippet.
var WeatherSearchComponent = (function () {
function WeatherSearchComponent(_weatherService) {
this._weatherService = _weatherService;
}
WeatherSearchComponent.prototype.onSubmit = function (form) {
var _this = this;
//alert(form.value.location);
this._weatherService.searchWeatherData(form.value.location)
.subscribe(function (data) {
var weatherItem = new weather_item_1.WeatherItem(data.data.request["0"].query, data.data.weather["0"].maxtempC, data.data.weather["0"].maxtempC);
_this._weatherService.addWeatherItems(weatherItem);
console.log(form);
});
};
WeatherSearchComponent.prototype.ngOnInit = function () {
};
WeatherSearchComponent = __decorate([
core_1.Component({
selector: 'app-weather-search',
templateUrl: './weather-search.component.html',
styleUrls: ['../../assets/app.css'],
})
], WeatherSearchComponent);
return WeatherSearchComponent;
}());
exports.WeatherSearchComponent = WeatherSearchComponent;
As you can see in turn the javascript code has weatherService Instance being passed on to the function weatherSearchComponent.

How to transform an AngularJS 1 service into an Angular 2 service?

I am trying to reuse some working code from AngularJS 1 services written in plain JavaScript in an Angular 2 environment.
The services look, for instance, like the following example:
(function () {
angular.module('myapp.mysubmodule').factory('myappMysubmoduleNormalService', ['someOtherService',
function (someOtherService) {
var internalState = {
someNumber: 0
};
var service = {};
service.someFunction = function () {
internalState.someNumber++;
};
someOtherService.getValues().forEach(function (v) {
service[v] = function () {
console.log(v + internalState.someNumber);
};
});
return service;
}]);
})();
I have found various examples of how to convert AngularJS 1 services to Angular 2 services (such as this one), all of which have in common that instead of the service factory, I have to export a class.
This should look roughly as follows:
import { Injectable } from '#angular/core';
#Injectable()
export class myappMysubmoduleNormalService {
someFunction: function () {
// ?
}
}
Now, the question is how to incorporate the internal state and the dynamically added properties.
Is it really the way to go to do all that in the constructor, i.e. fill each instance of the class upon initialization, like so:
import { Injectable } from '#angular/core';
#Injectable()
export class myappMysubmoduleNormalService {
constructor() {
var internalState = {
someNumber: 0
};
var service = {};
this.someFunction = function () {
internalState.someNumber++;
};
this.getValues().forEach(function (v) {
service[v] = function () {
console.log(v + internalState.someNumber);
};
});
}
}
Or is there any other way? The above probably works (save for the missing dependency injection, that I still have to find out about how to do in Angular 2). However, i am wondering whether it is a good way because I have not come across any samples that did much of a member initialization in their constructor.
You can use just the same approach in Angular with factory providers:
export function someServiceFactory(someOtherService) {
var internalState = {
someNumber: 0
};
var service = {};
service.someFunction = function () {
internalState.someNumber++;
};
someOtherService.getValues().forEach(function (v) {
service[v] = function () {
console.log(v + internalState.someNumber);
};
});
return service;
};
#NgModule({
providers: [
{
token: 'myappMysubmoduleNormalService',
useFactory: someServiceFactory,
deps: ['someOtherService']
}
]
})
Both in Angular and AngularJS the value returned by the factory function is cached.
A service is just a class that you can inject into components. It will create a singleton in the scope where it is named a provider.
import { Injectable. OnInit } from '#angular/core';
#Injectable()
export class myappMysubmoduleNormalService implements OnInit {
internalState: number;
constructor() {}
ngOnInit(){
this.internalState = 0;
}
incrementSomeNumber() {
this.internalState++;
console.log(this.internalState};
}
}
I realize this is not logging a distinct internal state for multiple functions but you get the idea.
Register this as a provider in the app.module (if you want a singleton for app scope)
When you import into a component and then inject in the constructor
constructor(private _myservice : myappMysubmoduleNormalService) {}
you can now use the _myservice methods
myNumber : number = 0 ;
componentFunction() {
_myservice.incrementSomeNumber();
this.myNumber = _myservice.internalState;
}
Of course you could have the service method return the incremented number (or data or a promise of data)
This is rough but gives you the idea. Very little code belongs in the constructor. A service should be injected. what is shown in component constructor is shorthand to a get private variable referencing the service. The service will be a singleton for the scope in which it is provided. (can be overridden within the scope but that seems a code smell to me)
To pass back a value :
In service
incrementSomeNumber(): number {
this._internalState++;
console.log(this._internalState};
return this._internalState;
}
In component:
mynumber: number;
componentFunction() {
this.mynumber = _myservice.incrementSomeNumber();
}
Not sure what you're trying to accomplish but just wanted to show example of getting information from services. Most common use of services for me is a dataservice, so the code would be a little more complex as it is asynch.

Set global variable of class from inside a promise Angular 2

I am facing a weird issue in assigning response to a class's global variable from inside a observable. So my program logic is as follows:
Get latest playlists ID's from elastic search (i use elastic search from a type definition file). This returns me a PromiseLike to which i hook a then operator.
Inside the promise resolution, i make another http get call (i.e an observable)
In Observable subscription, i assign my global array with the response from the server.
Code is working correctly, I am getting responses as they should be but i cant assign the variable to the global one.
Here is my code:
import {Component, OnInit} from '#angular/core';
import {PlaylistService} from '../api/services'
#Component({
selector: 'app-playlists',
templateUrl: './playlists.component.html',
styleUrls: ['./playlists.component.css']
})
export class PlaylistsComponent implements OnInit {
public playlists: any[] = [];
constructor(private playlistService: PlaylistService) {
}
ngOnInit() {
let that = this;
this.playlistService.listIds().then((val) => { // <-- promise resolution
return this.playlistService.getByIds(val).toPromise(); // <-- http get call which i then convert to promise for simplicity
}).then((res) => { // <-- resolution of the http get call
console.log(this.playlists); <-- in this log, i get my desired results
// here is my problem, this assignment doesn't happens
this.playlists = res.data;
});
}
}
The listIds function is as follows:
listIds() {
return this.api.listing('playlist').then((body) => {
let hits = body.hits.hits;
return _.keys(_.groupBy(hits, '_id'));
});
}
and here is my api.listing function (elastic search client)
listing(type: string) {
let es = this.prepareES();
return es.search({
index: 'test',
_source: ["_id"],
type: type
});
}
The return type of es.search is
search(params: SearchParams): PromiseLike>;
Any ideas why i am not being able to assign value to global variable?
It looks like the promise returned by this.playlistservice.listIds() doesn't run inside Angulars zone. This is why Angular2 doesn't run change detection and doesn't recognize the change.
You can invoke change detection explicitly after the change:
constructor(private playlistService: PlaylistService, private cdRef:ChangeDetectorRef) {
...
ngOnInit() {
let that = this;
this.playlistService.listIds().then((val) => { // <-- promise resolution
return this.playlistService.getByIds(val).toPromise(); // <-- http get call which i then convert to promise for simplicity
}).then((res) => { // <-- resolution of the http get call
console.log(this.playlists); <-- in this log, i get my desired results
// here is my problem, this assignment doesn't happens
this.playlists = res.data;
this.cdRef.detectChanges();
});
}
Can you try passing
this.playlistService.listIds()
call inside your
return this.playlistService.getByIds(val)
replace val with first service call and see if your view gets updated. Just for testing purpose like
return this.playlistService.getByIds(this.playlistService.listIds())
.then((results)=>{/*rest of logic here*/});

How can I call a class method inside a promise in Angular 2?

If I have an Angular 2 component and I get data from a service that returns an async promise or observable how can I then call a method in the component to display that data?
#Component({
moduleId: module.id,
selector: 'charts',
templateUrl: 'charts.component.html',
providers: [DataService]
})
export class ChartsComponent implements OnInit {
constructor(private dataService:DataService)
ngOnInit() {
this.getData();
}
getData(){
this.dataService.getData().then(function (data) {
this.drawChart(data);
});
}
drawChart(){
//implement drawing chart
}
}
The problem is that inside a promise "this" in "this.drawChart()" no longer refers to the ChartsComponent class. How can I call a class method post promise?
Also, I cant put drawChart() inside the promise because it needs to use other class properties.
When you use Arrow functions, the this is kept:
getData(){
this.dataService.getData().then((data) => { // <-- changed here
this.drawChart(data);
});
}
There are 2 solutions:
1) using "self":
var self = this;
ngOnInit() {
self.getData();
}
getData(){
self.dataService.getData().then(function (data) {
self.drawChart(data);
});
}
2) using "bind method" (or something like that):
.then(function (data) {
this.drawChart(data);
}).bind(this)
you can find so much information about this method, for example: Use of the JavaScript 'bind' method
I prefer first solution, because it helps make code more transparent.

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