Here is an template example:
<span count="{{currentCount}}"></span>
<span [count]="currentCount"></span>
Here both of them does the same thing. Which one is preferred and why?
[]
is for binding from a value in the parent component to an @Input()
in the child component. It allows to pass objects.
{{}}
is for binding strings in properties and HTML like
<div somePropOrAttr="{{xxx}}">abc {{xxx}} yz</div>
where the binding can be part of a string.
()
is for binding an event handler to be called when a DOM event is fired or an EventEmitter
on the child component emits an event
@Component({
selector: 'child-comp',
template: `
<h1>{{title}}</h1>
<button (click)="notifyParent()">notify</button>
`,
})
export class ChildComponent {
@Output() notify = new EventEmitter();
@Input() title;
notifyParent() {
this.notify.emit('Some notification');
}
}
@Component({
selector: 'my-app',
directives: [ChildComponent]
template: `
<h1>Hello</h1>
<child-comp [title]="childTitle" (notify)="onNotification($event)"></child-comp>
<div>note from child: {{notification}}</div>
`,
})
export class AppComponent {
childTitle = "I'm the child";
onNotification(event) {
this.notification = event;
}
}
Plunker example
More details in https://angular.io/docs/ts/latest/guide/template-syntax.html#!#binding-syntax
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