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Alias directive for Angular
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| import { Component } from '@angular/core'; | |
| import { TestBed } from '@angular/core/testing'; | |
| import { By } from '@angular/platform-browser'; | |
| import { AliasDirective } from './alias.directive'; | |
| describe('Alias directive', () => { | |
| beforeEach(() => | |
| TestBed.configureTestingModule({ | |
| declarations: [AliasDirective, DoubleComponent, TripleComponent], | |
| })); | |
| it('should respond to changes in the host', () => { | |
| const fixture = TestBed.createComponent(DoubleComponent); | |
| fixture.detectChanges(); | |
| expect(fixture.debugElement.query(By.css('h1')).nativeElement.textContent).toEqual('4'); | |
| fixture.componentInstance.value = 10; | |
| fixture.detectChanges(); | |
| expect(fixture.debugElement.query(By.css('h1')).nativeElement.textContent).toEqual('20'); | |
| }); | |
| it('should support the "as" notation', () => { | |
| const fixture = TestBed.createComponent(TripleComponent); | |
| fixture.detectChanges(); | |
| expect(fixture.debugElement.query(By.css('h1')).nativeElement.textContent).toEqual('6'); | |
| }); | |
| }); | |
| @Component({ | |
| template: `<h1 *alias="double(value); let doubled">{{ doubled }}</h1>`, | |
| }) | |
| class DoubleComponent { | |
| value = 2; | |
| double(value: number): number { | |
| return value * 2; | |
| } | |
| } | |
| @Component({ | |
| template: `<h1 *alias="triple(value) as tripled">{{ tripled }}</h1>`, | |
| }) | |
| class TripleComponent { | |
| value = 2; | |
| triple(value: number): number { | |
| return value * 3; | |
| } | |
| } |
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| import { Directive, EmbeddedViewRef, Input, TemplateRef, ViewContainerRef } from '@angular/core'; | |
| @Directive({ | |
| selector: '[alias]', | |
| }) | |
| export class AliasDirective { | |
| private context: AliasContext = { $implicit: null, alias: null }; | |
| private viewRef: EmbeddedViewRef<AliasContext> = null; | |
| constructor(private viewContainer: ViewContainerRef, private templateRef: TemplateRef<AliasContext>) {} | |
| @Input() | |
| set alias(source: any) { | |
| this.context.$implicit = this.context.alias = source; | |
| if (!this.viewRef) { | |
| this.viewContainer.clear(); | |
| this.viewRef = this.viewContainer.createEmbeddedView(this.templateRef, this.context); | |
| } else { | |
| this.viewRef.markForCheck(); | |
| } | |
| } | |
| } | |
| interface AliasContext { | |
| $implicit: any; | |
| alias: any; | |
| } |
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