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docs(PipeTransform): added pure parameter #4667

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7 changes: 4 additions & 3 deletions modules/angular2/src/core/change_detection/pipe_transform.ts
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Expand Up @@ -33,22 +33,23 @@
export interface PipeTransform { transform(value: any, args: any[]): any; }

/**
* To create a stateful Pipe, you should implement this interface.
* To create a stateful Pipe, you should implement this interface and set the `pure`
* parameter to `false` in the {@link PipeMetadata}.
*
* A stateful pipe may produce different output, given the same input. It is
* likely that a stateful pipe may contain state that should be cleaned up when
* a binding is destroyed. For example, a subscription to a stream of data may need to
* be disposed, or an interval may need to be cleared.
*
* ### Example ([live demo](http://plnkr.co/edit/hlaejwQAmWayxwc5YXQE?p=preview))
* ### Example ([live demo](http://plnkr.co/edit/i8pm5brO4sPaLxBx56MR?p=preview))

@ocombe ocombe Oct 13, 2015

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Feel free to make one that I'll link here :)

*
* In this example, a pipe is created to countdown its input value, updating it every
* 50ms. Because it maintains an internal interval, it automatically clears
* the interval when the binding is destroyed or the countdown completes.
*
* ```
* import {Pipe, PipeTransform} from 'angular2/angular2'
* @Pipe({name: 'countdown'})
* @Pipe({name: 'countdown', pure: false})
* class CountDown implements PipeTransform, PipeOnDestroy {
* remainingTime:Number;
* interval:SetInterval;
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