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docs(ivy): clean up class binding docs and update to v9 behavior (#35066) 

PR Close #35066
This commit is contained in:
Kara Erickson 2020-01-29 17:31:09 -08:00 committed by Misko Hevery
parent 4fc2678438
commit a08f6d9795
3 changed files with 42 additions and 37 deletions
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32
aio/content/examples/attribute-binding/src/app/app.component.html
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@ -29,26 +29,24 @@
<h2>Class binding</h2>
<!-- #docregion is-special -->
<h3>toggle the "special" class on/off with a property:</h3>
<div [class.special]="isSpecial">The class binding is special.</div>
<h3>binding to class.special overrides the class attribute:</h3>
<div class="special" [class.special]="!isSpecial">This one is not so special.</div>
<h3>Using the bind- syntax:</h3>
<div bind-class.special="isSpecial">This class binding is special too.</div>
<!-- #enddocregion is-special -->
<!-- #docregion add-class -->
<h3>Add a class:</h3>
<div class="item clearance special" [class.item-clearance]="itemClearance">Add another class</div>
<h3>Bind to a specific class</h3>
<div class="item clearance" [class.special]="isSpecial">This class binding is special.</div>
<!-- #enddocregion add-class -->
<!-- #docregion class-override -->
<h3>Overwrite all existing classes with a new class:</h3>
<div class="item clearance special" [attr.class]="resetClasses">Reset all classes at once</div>
<!-- #enddocregion class-override -->
<!-- #docregion bind-syntax -->
<h3>Using the bind- syntax:</h3>
<div bind-class.special="isSpecial">This class binding is special too.</div>
<!-- #enddocregion bind-syntax -->
<!-- #docregion direct-class-binding -->
<h3>Bind to multiple classes</h3>
<div [class]="someClasses">Add multiple classes</div>
<!-- #enddocregion direct-class-binding -->
<hr />

7
aio/content/examples/attribute-binding/src/app/app.component.ts
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@ -8,8 +8,9 @@ import { Component } from '@angular/core';
export class AppComponent {
actionName = 'Go for it';
isSpecial = true;
itemClearance = true;
resetClasses = 'new-class';
canSave = true;
someClasses = 'foo bar';
classExpr = 'special foo';
styleExpr = 'color: red';
color = 'blue';
}

38
aio/content/guide/template-syntax.md
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@ -895,7 +895,7 @@ Instead, you'd use property binding and write it like this:
Add and remove CSS class names from an element's `class` attribute with
a **class binding**.
Here's how to set the attribute without binding in plain HTML:
Here's how to set the attribute without a binding in plain HTML:
```html
<!-- standard class attribute setting -->
@ -904,26 +904,32 @@ Here's how to set the attribute without binding in plain HTML:
Class binding syntax resembles property binding, but instead of an element property between brackets, start with the prefix `class`,
optionally followed by a dot (`.`) and the name of a CSS class: `[class.class-name]`.
You can replace that with a binding to a string of the desired class names; this is an all-or-nothing, replacement binding.
<code-example path="attribute-binding/src/app/app.component.html" region="class-override" header="src/app/app.component.html"></code-example>
You can also add a class to an element without overwriting the classes already on the element:
<code-example path="attribute-binding/src/app/app.component.html" region="add-class" header="src/app/app.component.html"></code-example>
Finally, you can bind to a specific class name.
Angular adds the class when the template expression evaluates to truthy.
It removes the class when the expression is falsy.
<code-example path="attribute-binding/src/app/app.component.html" region="is-special" header="src/app/app.component.html"></code-example>
Binding to a specific class is additive, so it won't overwrite other class bindings or static classes unless the class names are duplicated.
While this technique is suitable for toggling a single class name,
consider the [`NgClass`](guide/template-syntax#ngClass) directive when
managing multiple class names at the same time.
In the example below, the final class list for the `<div>` will be `"item clearance special"` if `isSpecial` is truthy, and only `"item clearance"` if it is falsy.
<code-example path="attribute-binding/src/app/app.component.html" region="add-class" header="src/app/app.component.html"></code-example>
You can also use the alternative class binding syntax that replaces square brackets with the `bind-` keyword:
<code-example path="attribute-binding/src/app/app.component.html" region="bind-syntax" header="src/app/app.component.html"></code-example>
If there are multiple classes you'd like to toggle, you can bind to the `[class]` property directly.
Binding to `[class]` is additive, so it shouldn't overwrite other class bindings or static classes unless the class names are duplicated*.
<code-example path="attribute-binding/src/app/app.component.html" region="direct-class-binding" header="src/app/app.component.html"></code-example>
The expression attached to the `[class]` binding is most often a string list of class names like `"clearance special"`.
You can also format the expression as an object with class names as the keys and truthy/falsy expressions as the values, like `{clearance: true, special: false}`.
In this case, Angular will add a class only if its associated value is truthy.
It's important to note that with object format, the identity of the object must change for the class list to be updated.
Updating the property without changing object identity will have no effect.
*This is true for Angular version 9 and later. For Angular version 8, see <a href="http://v8.angular.io/guide/template-syntax#class-binding">v8.angular.io</a>
<hr/>