Angular 2 Pipe under condition

问题:

Is it possible in Angular 2 to apply a pipe under condition? I would like to do something like:

{{ variable.text | (variable.value ? SomePipe : OtherPipe) }}

If not, what is the preferred way to achieve this effect?

回答1:

You need to change the syntax a bit:

{{variable.value ? (variable.text | SomePipe) : (variable.text | pipe2)}}

Plunker example

回答2:

Since such syntax isn't supported, I think that the only way to do that is to implement another pipe to handle the condition:

@Pipe({
  name: 'condition'
})
export class ConditionPipe {
  transform(val,conditions) {
    let condition = conditions[0];
    let conditionValue = conditions[1];

    if (condition===conditionValue) {
      return new Pipe1().transform(val);
    } else {
      return new Pipe2().transform(val);
    }
  }
}

And use it this way:

@Component({
  selector: 'app'
  template: `
    <div>
      {{val | condition:cond:1}}<br/>
    </div>
  `,
  pipes: [ Pipe1, Pipe2, ConditionPipe ]
})
export class App {
  val:string = 'test';
  cond:number = 1;
}

See this plunkr: https://plnkr.co/edit/KPIA5ly515xZk4QZx4lp?p=preview.