angular-cn/modules/@angular/compiler/src/pipe_resolver.ts

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/**
* @license
* Copyright Google Inc. All Rights Reserved.
*
* Use of this source code is governed by an MIT-style license that can be
* found in the LICENSE file at https://angular.io/license
*/
import {Pipe, Type, resolveForwardRef} from '@angular/core';
import {ListWrapper} from './facade/collection';
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import {stringify} from './facade/lang';
import {CompilerInjectable} from './injectable';
import {ReflectorReader, reflector} from './private_import_core';
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function _isPipeMetadata(type: any): boolean {
return type instanceof Pipe;
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}
/**
* Resolve a `Type` for {@link Pipe}.
*
* This interface can be overridden by the application developer to create custom behavior.
*
* See {@link Compiler}
*/
@CompilerInjectable()
export class PipeResolver {
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constructor(private _reflector: ReflectorReader = reflector) {}
isPipe(type: Type<any>) {
const typeMetadata = this._reflector.annotations(resolveForwardRef(type));
return typeMetadata && typeMetadata.some(_isPipeMetadata);
}
/**
* Return {@link Pipe} for a given `Type`.
*/
resolve(type: Type<any>, throwIfNotFound = true): Pipe {
const metas = this._reflector.annotations(resolveForwardRef(type));
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if (metas) {
const annotation = ListWrapper.findLast(metas, _isPipeMetadata);
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if (annotation) {
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return annotation;
}
}
if (throwIfNotFound) {
throw new Error(`No Pipe decorator found on ${stringify(type)}`);
}
return null;
}
}