Tobias Bosch
f5c8e0989d
## Inheritance Semantics:
Decorators:
1) list the decorators of the class and its parents in the ancestor first order
2) only use the last decorator of each kind (e.g. @Component / ...)
Constructor parameters:
If a class inherits from a parent class and does not declare
a constructor, it inherits the parent class constructor,
and with it the parameter metadata of that parent class.
Lifecycle hooks:
Follow the normal class inheritance model,
i.e. lifecycle hooks of parent classes will be called
even if the method is not overwritten in the child class.
## Example
E.g. the following is a valid use of inheritance and it will
also inherit all metadata:
```
@Directive({selector: 'someDir'})
class ParentDirective {
constructor(someDep: SomeDep) {}
ngOnInit() {}
}
class ChildDirective extends ParentDirective {}
```
Closes #11606
Closes #12892
52 lines
1.4 KiB
TypeScript
52 lines
1.4 KiB
TypeScript
/**
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* @license
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* Copyright Google Inc. All Rights Reserved.
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*
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* Use of this source code is governed by an MIT-style license that can be
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* found in the LICENSE file at https://angular.io/license
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*/
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import {Injectable, Pipe, Type, resolveForwardRef} from '@angular/core';
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import {ListWrapper} from './facade/collection';
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import {isPresent, stringify} from './facade/lang';
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import {ReflectorReader, reflector} from './private_import_core';
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function _isPipeMetadata(type: any): boolean {
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return type instanceof Pipe;
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}
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/**
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* Resolve a `Type` for {@link Pipe}.
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*
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* This interface can be overridden by the application developer to create custom behavior.
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*
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* See {@link Compiler}
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*/
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@Injectable()
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export class PipeResolver {
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constructor(private _reflector: ReflectorReader = reflector) {}
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isPipe(type: Type<any>) {
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const typeMetadata = this._reflector.annotations(resolveForwardRef(type));
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return typeMetadata && typeMetadata.some(_isPipeMetadata);
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}
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/**
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* Return {@link Pipe} for a given `Type`.
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*/
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resolve(type: Type<any>, throwIfNotFound = true): Pipe {
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const metas = this._reflector.annotations(resolveForwardRef(type));
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if (isPresent(metas)) {
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const annotation = ListWrapper.findLast(metas, _isPipeMetadata);
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if (isPresent(annotation)) {
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return annotation;
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}
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}
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if (throwIfNotFound) {
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throw new Error(`No Pipe decorator found on ${stringify(type)}`);
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}
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return null;
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}
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}
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