Alert the parent angular component of any changes in the object

Question

Alert the parent angular component of any changes in the object

I am working with a large object in my component, where the properties of the object are connected to various components and inputs within the template:

  constructor() {
    this.data = {
      identifier: null,
      isRequired: true,
      title: 'Untitled',
      type: this.fileTypes[0].name,
      description: '',
      //more code here
}

<app-text-input [(model)]="data.title" label="Title" type="text" variant="white">

Due to all properties in data being bound to different input elements, the values within the object remain up to date. Additionally, this component acts as a child component to another.

In order for the parent component to access the data object when an event triggers (such as a button click), I am unsure of the best approach. While I am familiar with using @Outputs, the events are occurring on the parent rather than the child. Furthermore, I have not yet implemented any FormControl classes - should I incorporate these to achieve the desired result?

angular typescript

Answer 1

Answer №1

There are several approaches to accomplish this task.

1. Implement a `BehaviorSubject`.

This method is recommended when working with Reactive Forms instead of using ngModel:

Child Component:

@Input()
data: BehaviorSubject<T>;

form = new FormGroup({
  title: new FormControl()
});

ngOnInit() {
  this.form.valueChanges.subscribe(formData => {
    this.data.next({
      ...this.data.value,
      ...formData
    });
  });
}

<div [formGroup]="form">
  <input [formControlName]="title">
</div>

Parent Component:

<child [data]="data"></child>

data: BehaviorSubject<T>;

buttonClicked() {
  // access this.data.value
}

2. Opt for two-way binding.

This approach still utilizes ngModel, but you will need to customize the two-way bindings on form elements to trigger updates:

Child Component:

@Input()
data: T;

@Output()
dataChange: EventEmitter<T>;

<input [model]="data.title" (modelChange)="data.title = $event; dataChange.next(data)">

Parent Component:

<child [(data)]="data"></child>

data: T;

buttonClicked() {
  // utilize this.data
}

You can also combine these methods, such as utilizing two-way data binding on ngModel like in option 2, while passing a BehaviorSubject from parent to child as described in option 1.

Answer 2

There are several approaches to accomplish this task.

1. Implement a `BehaviorSubject`.

This method is recommended when working with Reactive Forms instead of using ngModel:

Child Component:

@Input()
data: BehaviorSubject<T>;

form = new FormGroup({
  title: new FormControl()
});

ngOnInit() {
  this.form.valueChanges.subscribe(formData => {
    this.data.next({
      ...this.data.value,
      ...formData
    });
  });
}

<div [formGroup]="form">
  <input [formControlName]="title">
</div>

Parent Component:

<child [data]="data"></child>

data: BehaviorSubject<T>;

buttonClicked() {
  // access this.data.value
}

2. Opt for two-way binding.

This approach still utilizes ngModel, but you will need to customize the two-way bindings on form elements to trigger updates:

Child Component:

@Input()
data: T;

@Output()
dataChange: EventEmitter<T>;

<input [model]="data.title" (modelChange)="data.title = $event; dataChange.next(data)">

Parent Component:

<child [(data)]="data"></child>

data: T;

buttonClicked() {
  // utilize this.data
}

You can also combine these methods, such as utilizing two-way data binding on ngModel like in option 2, while passing a BehaviorSubject from parent to child as described in option 1.

Answer 3

Answer №2

To implement this functionality using event emitter, you must subscribe to it in the child component so that any changes or emitted data can be captured and displayed in the child component or any other component.

Check out this Stackblitz example on event emitters

Shared Service Implementation:

// Shared Service
Subject: Subject<Object>;

// Parent Component
constructor(DataService: DataService)
this.DataService.event.next(data);

// Child Component
constructor(DataService: DataService)
this.DataService.event.subscribe((data)=>{
   // receive emitted event with updated data here
});

By emitting data from the parent using the next method, you can capture and act upon it in the child or any other related component.

Answer 4

To implement this functionality using event emitter, you must subscribe to it in the child component so that any changes or emitted data can be captured and displayed in the child component or any other component.

Check out this Stackblitz example on event emitters

Shared Service Implementation:

// Shared Service
Subject: Subject<Object>;

// Parent Component
constructor(DataService: DataService)
this.DataService.event.next(data);

// Child Component
constructor(DataService: DataService)
this.DataService.event.subscribe((data)=>{
   // receive emitted event with updated data here
});

By emitting data from the parent using the next method, you can capture and act upon it in the child or any other related component.

Alert the parent angular component of any changes in the object

Answer №1

1. Implement a `BehaviorSubject`.

2. Opt for two-way binding.

Answer №2

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Alert the parent angular component of any changes in the object

Answer №1

1. Implement a BehaviorSubject.

2. Opt for two-way binding.

Answer №2

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1. Implement a `BehaviorSubject`.