12

I want to return a boolean value ,but the variable in the "if" condition is undefined. 

function() {
    this.menuDataService.getMenu()
      .subscribe(res => {
       this.mainMenus = res.MainMenus;
       console.log(this.mainMenus);
    });

    console.log(this.mainMenus);

    if(this.mainMenus == 1){
       return true;
    }
    else {
      return false;
    }
}
Willi Mentzel
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kzrfaisal
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3 Answers3

4

Once you start using observables you have to work within the chained set of methods off of the observable. In your case you could do something like this:

function InnerFunc(){
  return this.menuDataService.getMenu()
  .map(res => {
    if (res.mainMenus == 1) {
      return true;
    } else {
      return false;
    }
  )
}

function OuterFunc() {
  InnerFunc()
  .subscribe(result => {
    // will be either true or false
    console.log(result);
  });    
}
Maxie Berkmann
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seescode
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3

seescode's answer helped me but I can't comment it.

I just wanted to say that with RxJS 6, their way to chain Observable operators changed, and we now have to use the pipe(...) method. (see RxJS 6 - What Changed? What's New?)

Here is what his InnerFunc would look like updated to RxJS 6 :

function InnerFunc(){
  return this.menuDataService.getMenu().pipe(
    map(res => {
      if(res.mainMenus == 1){
       return true;
      }
      else{
       return false;
      }
    )
  )
}
icoum
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2

You could have finally event over observable, so that subscription got called.

this.menuDataService.getMenu()
.finally( () => { console.log(this.mainMenus) });
.subscribe(res =>{
   this.mainMenus = res.MainMenus;
   console.log(this.mainMenus);
});
Pankaj Parkar
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    why not use the third callback of `subscribe` ? – Dhyey Jul 06 '17 at 13:38
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    in finally ..it's coming undefined – kzrfaisal Jul 06 '17 at 13:42
  • Actually I want to work on the data recieved in subscribe ,based on that data i want to return a boolean value, I can't do this whole code in subscribe beacause value will not be reflected from subscribe – kzrfaisal Jul 06 '17 at 13:46
  • @MohdFaisalAnsari finally well get called after each stream event gets received/rejected, what exactly you needed? – Pankaj Parkar Jul 06 '17 at 15:18
  • @Dhyey I assumed `finally` and `3rd` subscribe callback does the same thing, so using `finally` make it more readable IMO;) – Pankaj Parkar Jul 06 '17 at 16:36
  • @PankajParker shouldn't you use fat arrow functions as value of `this` will change when a function is defined with `function` keyword. @MohdFaisalAnsari u should try `finally(() => console.log(this.mainMenus) ) ` – Dhyey Jul 07 '17 at 02:33