docs: edit $any() section and add example in Template Syntax (#28157)
PR Close #28157
This commit is contained in:
Kapunahele Wong
Matias Niemelä
parent
a9020a028f
commit
c0ad9e104d
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'use strict'; // necessary for es6 output in node
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import { browser, element, by } from 'protractor';
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describe('Built Template Functions Example', function () {
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beforeAll(function () {
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browser.get('');
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});
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it('should have title Built-in Template Functions', function () {
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let title = element.all(by.css('h1')).get(0);
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expect(title.getText()).toEqual('Built-in Template Functions');
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});
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it('should display $any( ) in h2', function () {
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let header = element(by.css('h2'));
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expect(header.getText()).toContain('$any( )');
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});
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});
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<h1>{{title}}</h1>
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<h2><code>$any( )</code> type cast function and an undeclared member</h2>
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<p>There is no such member as <code>bestByDate</code> in the following two examples, so nothing renders:</p>
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<!-- #docregion any-type-cast-function-1 -->
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<p>The item's undeclared best by date is: {{$any(item).bestByDate}}</p>
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<!-- #enddocregion any-type-cast-function-1 -->
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<h2>using <code>this</code></h2>
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<!-- #docregion any-type-cast-function-2 -->
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<p>The item's undeclared best by date is: {{$any(this).bestByDate}}</p>
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<!-- #enddocregion any-type-cast-function-2 -->
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import { TestBed, async } from '@angular/core/testing';
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import { AppComponent } from './app.component';
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describe('AppComponent', () => {
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beforeEach(async(() => {
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TestBed.configureTestingModule({
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declarations: [
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AppComponent
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],
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}).compileComponents();
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}));
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it('should create the app', async(() => {
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const fixture = TestBed.createComponent(AppComponent);
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const app = fixture.debugElement.componentInstance;
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expect(app).toBeTruthy();
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}));
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});
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import { Component } from '@angular/core';
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@Component({
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selector: 'app-root',
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templateUrl: './app.component.html',
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styleUrls: ['./app.component.css']
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})
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export class AppComponent {
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title = 'Built-in Template Functions';
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item = {
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name : 'Telephone',
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origin : 'Sweden',
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price: 98
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};
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}
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import { BrowserModule } from '@angular/platform-browser';
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import { NgModule } from '@angular/core';
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import { AppComponent } from './app.component';
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@NgModule({
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declarations: [
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AppComponent
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],
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imports: [
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BrowserModule
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],
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providers: [],
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bootstrap: [AppComponent]
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})
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export class AppModule { }
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<!doctype html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Built-in Template Functions Example</title>
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<base href="/">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<link rel="icon" type="image/x-icon" href="favicon.ico">
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</head>
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<body>
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<app-root>Loading...</app-root>
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</body>
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</html>
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import { enableProdMode } from '@angular/core';
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import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
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import { AppModule } from './app/app.module';
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import { environment } from './environments/environment';
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if (environment.production) {
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enableProdMode();
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}
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platformBrowserDynamic().bootstrapModule(AppModule);
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{
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"description": "Built-in Template Functions",
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"files": [
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"!**/*.d.ts",
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"!**/*.js",
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"!**/*.[1,2].*"
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],
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"file": "src/app/app.component.ts",
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"tags": ["Built-in Template Functions"]
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}
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@ -13,15 +13,4 @@ describe('AppComponent', () => {
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const app = fixture.debugElement.componentInstance;
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expect(app).toBeTruthy();
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}));
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it(`should have as title 'Featured product:'`, async(() => {
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const fixture = TestBed.createComponent(AppComponent);
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const app = fixture.debugElement.componentInstance;
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expect(app.title).toEqual('Featured product:');
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}));
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it('should render title in a p tag', async(() => {
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const fixture = TestBed.createComponent(AppComponent);
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fixture.detectChanges();
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const compiled = fixture.debugElement.nativeElement;
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expect(compiled.querySelector('p').textContent).toContain('Featured product:');
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}));
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});
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@ -1997,29 +1997,29 @@ You'll need this template operator when you turn on strict null checks. It's opt
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<hr/>
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{@a built-in-template-functions}
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## Built-in template functions
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{@a any-type-cast-function}
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## The `$any` type cast function (`$any( <expression> )`)
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### The `$any()` type cast function
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Sometimes a binding expression will be reported as a type error and it is not possible or difficult
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to fully specify the type. To silence the error, you can use the `$any` cast function to cast
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the expression to [the `any` type](http://www.typescriptlang.org/docs/handbook/basic-types.html#any).
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Sometimes a binding expression triggers a type error during [AOT compilation](guide/aot-compiler) and it is not possible or difficult
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to fully specify the type. To silence the error, you can use the `$any()` cast function to cast
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the expression to [the `any` type](http://www.typescriptlang.org/docs/handbook/basic-types.html#any) as in the following example:
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<code-example path="template-syntax/src/app/app.component.html" region="any-type-cast-function-1" header="src/app/app.component.html" linenums="false">
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<code-example path="built-in-template-functions/src/app/app.component.html" region="any-type-cast-function-1" header="src/app/app.component.html" linenums="false">
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</code-example>
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In this example, when the Angular compiler turns your template into TypeScript code,
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it prevents TypeScript from reporting that `marker` is not a member of the `Hero`
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interface.
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When the Angular compiler turns this template into TypeScript code,
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it prevents TypeScript from reporting that `bestByDate` is not a member of the `item`
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object when it runs type checking on the template.
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The `$any` cast function can be used in conjunction with `this` to allow access to undeclared members of
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The `$any()` cast function also works with `this` to allow access to undeclared members of
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the component.
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<code-example path="template-syntax/src/app/app.component.html" region="any-type-cast-function-2" header="src/app/app.component.html" linenums="false">
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<code-example path="built-in-template-functions/src/app/app.component.html" region="any-type-cast-function-2" header="src/app/app.component.html" linenums="false">
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</code-example>
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The `$any` cast function can be used anywhere in a binding expression where a method call is valid.
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## Summary
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You've completed this survey of template syntax.
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Now it's time to put that knowledge to work on your own components and directives.
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The `$any()` cast function works anywhere in a binding expression where a method call is valid.
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