angular-cn/packages/compiler/src/pipe_resolver.ts

46 lines
1.3 KiB
TypeScript

/**
* @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 {CompileReflector} from './compile_reflector';
import {Pipe, Type, createPipe} from './core';
import {findLast} from './directive_resolver';
import {resolveForwardRef, stringify} from './util';
/**
* Resolve a `Type` for {@link Pipe}.
*
* This interface can be overridden by the application developer to create custom behavior.
*
* See {@link Compiler}
*/
export class PipeResolver {
constructor(private _reflector: CompileReflector) {}
isPipe(type: Type) {
const typeMetadata = this._reflector.annotations(resolveForwardRef(type));
return typeMetadata && typeMetadata.some(createPipe.isTypeOf);
}
/**
* Return {@link Pipe} for a given `Type`.
*/
resolve(type: Type, throwIfNotFound = true): Pipe|null {
const metas = this._reflector.annotations(resolveForwardRef(type));
if (metas) {
const annotation = findLast(metas, createPipe.isTypeOf);
if (annotation) {
return annotation;
}
}
if (throwIfNotFound) {
throw new Error(`No Pipe decorator found on ${stringify(type)}`);
}
return null;
}
}