Issue with Angular: Child component not receiving data after successful parent component call

I'm currently working with a parent and child component setup.

Within the child component, I have a button configured like this:

//child.component.html

<button mat-raised-button  [disabled]="!form.valid || submitButtonDisable" type = 'Submit' color='primary'  >
{{generateButton}}
</button>


//child.component.ts
@Output() onGenerateReport: EventEmitter<any> = new EventEmitter<any>();
@Input() generateButton: String;

OnSubmit() {
  this.onGenerateReport.emit(this.parameterRequest);  // sending data to parent after button click
  this.submitButtonDisable = true;
  this.generateButton = 'Generating...'
  }

Let's take a look at the parent component below:

  // parent component.html

  <child-component
      (onGenerateReport)="handleGenerateReport($event)"
      [generateButton] = "generateButton | async">
  </child-component>

    //parent.component.ts
 generateButton: Observable<String >;

   handleGenerateReport($event: ParameterRequest) {  // event listener

        this.store.dispatch(new fromStore.SendRequest($event));

    this.store.select(fromStore.isDataLoaded).pipe(take(1)).subscribe(data => {
    if(data) {
    this.generateButton = of('Generate');   // trying to pass this data back to child
   }
 })
}

The goal is to update the label of the button in the child component once the request is successful.

However, there seems to be an issue with ngrx select where data is not being passed to the child component. Is there something that I might be overlooking?

Answer №1

To detect changes from the parent in a child component, you should utilize ngOnChanges. Below is the code snippet that you can use in your child component:

import { OnChanges, SimpleChanges } from '@angular/core';
class ChildComponent implements OnChanges, OnInit, AfterViewInit {
//child.component.ts
@Output() onGenerateReport: EventEmitter<any> = new EventEmitter<any>();
@Input() generateButton: String;

ngOnChanges(changes: SimpleChanges): void {
  if (changes != null) {
    console.log(changes); // Here, the changes object will provide the updated value of input variables like generateButton
  }
}

onSubmit() {
   this.onGenerateReport.emit(this.parameterRequest); // Passing data to parent after button click
   this.submitButtonDisable = true;
   this.generateButton = 'Generating...';
}}

Answer №2

Follow these simple steps to get started:

  • Begin by importing the necessary
    import { Input, OnChanges, SimpleChanges } from '@angular/core';
    package.
  • Next, implement the interface by using
    export class ComponentName implements OnChanges
  • Finally, create a function as follows:
    ngOnChanges(changes: SimpleChanges){
      // Access changes to your input properties (including both old and new values)
      // This is where you can track all @Input property changes.
    }

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