角度:未检测到管道变化 [英] Angular: Change in Pipe not detected

问题描述

我有这个管道，它将 input 值乘以从服务检索到的另一个值:

I have this pipe which multiplies the input value by an other value retrieved from a service:

@Pipe({
    name: 'multiply'
})
export class MultiplyPipe implements PipeTransform {
    constructor(private service: StateService) { }

    transform(value: any, args?: any): any {
        return value * this.service.multiplier;
    }
}

用法:

{{ value | multiply }}

演示

这很好用，但是当服务中的multiply值被更改时，它不会触发任何更改检测，因此

This works fine, but when the multiply value from the service is changed, it doesn't trigger any change detection, and thus

 {{ value | multiply }}

不会再次运行，将旧值保留在屏幕上.有什么建议可以解决吗?

is not run again, leaving the old value on the screen. Any suggestion how this can be fixed?

推荐答案

如 Angular文档，如此stackblitz 所示，这是强制实施的一种方法要调用的管道是不纯的:

As discussed in Angular documentation, and as shown in this stackblitz, one way to force the pipe to be called is to make it impure:

@Pipe({
  name: 'multiply',
  pure: false
})

有关纯净管道和不纯净管道的更多详细信息，请参见

For more details about pure and impure pipes, you can see this article.

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