Angular provides a convenient way to call an API on key press. Let's delve

Question

Angular provides a convenient way to call an API on key press. Let's delve

How can I trigger an API call in Angular when a user clicks on a textbox during a keypress event? I am encountering an error with the debounce method that says

Cannot read property 'valueChanges' of undefined

app.component.ts

ngOnInit() {

    this.searchField.valueChanges

        .pipe(
            debounceTime(500),
            distinctUntilChanged(),
            map((val) => {
                this.http.post<any>('http://localhost:3000/articles/articleslistData', { pubid: '3', pubdate: this.dateChanged }).subscribe({
                    next: data => {
                        console.log(data);
                    },
                    error: error => {
                        this.errorMessage = error.message;
                        console.error('There was an error!', error);
                    }
                })
            })
        )
        .subscribe();
}

app.component.html

<div class="form-field col-lg-12">
<label class="label" for="message">Headline</label>
<input id="message" class="input-text js-input" type="text" required [formControl]="searchField">
</div>

angular typescript rxjs

Answer 1

Answer №1

Additionally, utilizing switchMap (switchMap "replaces" one observable with another) would look something like this:

this.searchField.valueChanges.pipe(
    debounceTime(500),
    distinctUntilChanged(),
    switchMap ((val) => {
          //we cannot return the "val" directly, instead
          //we need to use it in the HTTP POST request
          return this.http.post<any>('http://localhost:3000/articles/articleslistData', { pubid: '3', pubdate: this.dateChanged })
    })
).subscribe(data => {
   console.log(data);
},
error => {
  this.errorMessage = error.message;
  console.error('There was an error!', error);
}
);

Notice that there is only one subscription in this implementation.

Answer 2

Additionally, utilizing switchMap (switchMap "replaces" one observable with another) would look something like this:

this.searchField.valueChanges.pipe(
    debounceTime(500),
    distinctUntilChanged(),
    switchMap ((val) => {
          //we cannot return the "val" directly, instead
          //we need to use it in the HTTP POST request
          return this.http.post<any>('http://localhost:3000/articles/articleslistData', { pubid: '3', pubdate: this.dateChanged })
    })
).subscribe(data => {
   console.log(data);
},
error => {
  this.errorMessage = error.message;
  console.error('There was an error!', error);
}
);

Notice that there is only one subscription in this implementation.

Answer 3

Answer №2

To properly set up your form control, it is recommended to initialize it either in the ngOnInit function or in the property declaration.

export class MyComponent {
  // Option 1
  public formControl = new FormControl({});
  ngOnInit() {
      // Option 2
      this.formControl = new FormControl({});
      // Add your code here
  }
}

Alternatively, you can utilize the FormBuild class for initializing form controls.

For additional information, please refer to: https://angular.io/api/forms/FormControl#initializing-form-controls

Answer 4

To properly set up your form control, it is recommended to initialize it either in the ngOnInit function or in the property declaration.

export class MyComponent {
  // Option 1
  public formControl = new FormControl({});
  ngOnInit() {
      // Option 2
      this.formControl = new FormControl({});
      // Add your code here
  }
}

Alternatively, you can utilize the FormBuild class for initializing form controls.

For additional information, please refer to: https://angular.io/api/forms/FormControl#initializing-form-controls

Angular provides a convenient way to call an API on key press. Let's delve

Answer №1

Answer №2

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