What is causing this object to become populated only after the second call?

Here is a method that I have crafted:

fetchUser(endpoint: string, email: string) { 
  const url = this.envConfigurationService.baseEndpoint + '/' + conf.apiPrefix + '/' + endpoint + email; 
  this.loadingService.loadingOn(); 
  return this.http.get(url).pipe( 
    finalize(() => this.loadingService.loadingOff()), 
    catchError((err) => { 
      this.handleError(err); 
      return throwError(err); 
    }), 
    tap(() => this.toastrService.success('OK')), 
 ); 
}

and this is how I invoke it in the component.ts file:

searchUser() { 
    this.backendIntegrationService.fetchUser('user?code=', encodeURIComponent(this.form.value.email)).subscribe({ 
      next: (res) => { 
        if (res['result'] === 'OK') { 
            this.userdata = res['body']; 
            this.message = res['message'] 
        } 
        else { 
          this.errorMessage = res; 
        } 
      }, 
      error: err => { 
        this.errorMessage = err; 
      } 
    }); 
    console.log(this.userdata) 
    this.entityConfiguration.inputFields.forEach(field => { 
      console.log(this.userData) 
      let value = null; 
       
      value = this.userData[field.name]; 
      if (field.disabled) { 
        this.formControls[field.name] = this.fb.control({value: value, disabled: true}); 
      } else { 
        this.formControls[field.name] = this.fb.control(value); 
      } 
    }); 
    this.form = this.fb.group(this.formControls); 
  }

I am encountering an issue where the object this.userdata only gets populated on the second call (when I press the search user button for the second time), even though I receive the values from the backend on the first attempt.

What could be the mistake here?

Answer №1

When dealing with async operations, it's important to consider the timing of variable assignments. Your service call may set a variable inside a `subscribe` block after your code has already moved on to another part of the function. This can result in the variable being undefined when you try to access it, leading to unexpected behavior such as printing out an undefined value.

To avoid this issue, make sure to wait for the async call to complete before processing the response in your `next` block. This ensures that any variables set by the call are available for use at the right time.

It's worth noting that while the variable may be defined the second time around, it likely holds the response from the initial call rather than the expected data.

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