Encountering difficulty in establishing a global variable within the subscribe function

Question

Encountering difficulty in establishing a global variable within the subscribe function

I am looking to store the service response in a variable for use in my view. The TypeScript file I am working with is shown below:

The MenuService is a custom service that includes a function called getMenus() to fetch all menus from the database.

import { Component, OnInit } from '@angular/core';
import { TranslateService } from '@ngx-translate/core';
import { MenusService } from '../menus.service'; 

@Component({
  selector: 'app-header1',
  templateUrl: './header1.component.html',
  styleUrls: ['./header1.component.css'],
  providers:[MenusService]
})
export class Header1Component implements OnInit {

  menus=['Login','Register','Subscribe'];
  primeryMenus:any; 
  //menus1=['Home','Matches','Players','Teams','Tournaments','Contact Us','About Us'];
   constructor(private translate: TranslateService,private _ser:MenusService) {
    translate.setDefaultLang('en');
  }

  ngOnInit(){
    this.getMenu();
  }
  getMenu(){
    this._ser.getMenus().subscribe(res=>{
      this.primeryMenus = res;
      console.log(this.primeryMenus) // output is json object ( getting correct output )
    });
    console.log(this.primeryMenus) // output is undefined

  }

  switchLanguage(language: string) {
    this.translate.use(language);
  }


}

I need help on how to assign the response data to the `primeryMenus` variable within the subscribe method of the observable.

angular typescript

Answer 1

Answer №1

Your code

this._ser.getMenus().subscribe(res=>{
  this.primeryMenus = res;
  console.log(this.primeryMenus) // the output is a JSON object (getting the correct output)
});
console.log(this.primeryMenus) // the output is undefined

This is the core principle of using subscribe. The callback function is executed after all synchronous code is completed.

Solution

Access the value only after the subscribe method is called.

Answer 2

Your code

this._ser.getMenus().subscribe(res=>{
  this.primeryMenus = res;
  console.log(this.primeryMenus) // the output is a JSON object (getting the correct output)
});
console.log(this.primeryMenus) // the output is undefined

This is the core principle of using subscribe. The callback function is executed after all synchronous code is completed.

Solution

Access the value only after the subscribe method is called.

Answer 3

Answer №2

Observables operate asynchronously. Make sure to place the second console.log() outside of the subscription function to ensure it is processed after the Observable returns a value. Follow this pattern:

getMenu(){
    this._ser.getMenus().subscribe(res=>{
          this.primeryMenus = res;
          console.log(this.primeryMenus) // output is json object ( getting correct output )
});

// Avoid placing a console(log) here if you want to view the value returned by the observable above, as it will be processed before the Observable returns a value.

Answer 4

Observables operate asynchronously. Make sure to place the second console.log() outside of the subscription function to ensure it is processed after the Observable returns a value. Follow this pattern:

getMenu(){
    this._ser.getMenus().subscribe(res=>{
          this.primeryMenus = res;
          console.log(this.primeryMenus) // output is json object ( getting correct output )
});

// Avoid placing a console(log) here if you want to view the value returned by the observable above, as it will be processed before the Observable returns a value.

Answer 5

Answer №3

It appears that the response you are receiving from the service is only available after the outer console log execution, hence showing as undefined. To ensure that you can do or display something only when the response is received, it is advisable to call a function within the subscribe method.

  getMenu(){
    this._ser.getMenus().subscribe(res=>{
          this.primeryMenus = res;
          this.doSomething();
});

doSomething() {
   console.log(this.primeryMenus);
  // Implement some action here
}

Answer 6

It appears that the response you are receiving from the service is only available after the outer console log execution, hence showing as undefined. To ensure that you can do or display something only when the response is received, it is advisable to call a function within the subscribe method.

  getMenu(){
    this._ser.getMenus().subscribe(res=>{
          this.primeryMenus = res;
          this.doSomething();
});

doSomething() {
   console.log(this.primeryMenus);
  // Implement some action here
}

Answer 7

Answer №4

Within the MenusService component

/**
     * Function used for fetching data
     * 
     */
    getMenus():  Observable<any> {
        this.requestURL = `url`;
        return this.http.get(this.requestURL);
    }

Inside the Header1Component:

getMenu(){
    this._ser.getMenus().subscribe((res: any)=> {
      this.primeryMenus = res;
      console.log(this.primeryMenus);
    });
    console.log(this.primeryMenus) ;
  }

Answer 8

Within the MenusService component

/**
     * Function used for fetching data
     * 
     */
    getMenus():  Observable<any> {
        this.requestURL = `url`;
        return this.http.get(this.requestURL);
    }

Inside the Header1Component:

getMenu(){
    this._ser.getMenus().subscribe((res: any)=> {
      this.primeryMenus = res;
      console.log(this.primeryMenus);
    });
    console.log(this.primeryMenus) ;
  }

Encountering difficulty in establishing a global variable within the subscribe function

Answer №1

Solution

Answer №2

Answer №3

Answer №4

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