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docs: remove invalid style binding example (#40334) 

Providing an array to `[style]` bindings is not supported and the behavior
of the rendered style attribute is not as one might expect.

This commit removes that array example from the table to discourage its
use.

Fixes #40147

PR Close #40334
This commit is contained in:
Pete Bacon Darwin 2021-01-07 09:49:54 +00:00 committed by atscott
parent 34d2988d14
commit 3acbec8532
1 changed files with 20 additions and 13 deletions
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29
aio/content/guide/attribute-binding.md
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@ -91,8 +91,13 @@ See [styling delegation](guide/style-precedence#styling-delegation) for more inf
### Binding to multiple CSS classes
To bind to multiple classes, use `[class]` set to an expression—for example, `[class]="classExpression"`.
The expression can be a space-delimited string of class names, or an object with class names as the keys and truthy or falsy expressions as the values.
With an object format, Angular adds a class only if its associated value is truthy.
The expression can be one of:
* A space-delimited string of class names.
* An object with class names as the keys and truthy or falsy expressions as the values.
* An array of class names.
With the object format, Angular adds a class only if its associated value is truthy.
<div class="alert is-important">
@ -178,13 +183,16 @@ You can write a style property name in either [dash-case](guide/glossary#dash-ca
### Binding to multiple styles
To toggle multiple styles, bind to the `[style]` attribute&mdash;for example, `[style]="styleExpression"`.
The expression is often a string list of styles such as `"width: 100px; height: 100px;"`.
The `styleExpression` can be one of:
You can also format the expression as an object with style names as the keys and style values as the values, such as `{width: '100px', height: '100px'}`.
* A string list of styles such as `"width: 100px; height: 100px;"`.
* An object with style names as the keys and style values as the values, such as `{width: '100px', height: '100px'}`.
Note that binding an array to `[style]` is not supported.
<div class="alert is-important">
With any object-like expression&mdash;such as `object`, `Array`, `Map`, or `Set`&mdash;the identity of the object must change for Angular to update the class list.
When binding `[style]` to an object expression, the identity of the object must change for Angular to update the class list.
Updating the property without changing object identity has no effect.
</div>
@ -234,8 +242,8 @@ The following table summarizes style binding syntax.
<td><code>100</code></td>
</tr>
<tr>
<td rowspan=3>Multi-style binding</td>
<td rowspan=3><code>[style]="styleExpression"</code></td>
<td rowspan=2>Multi-style binding</td>
<td rowspan=2><code>[style]="styleExpression"</code></td>
<td><code>string</code></td>
<td><code>"width: 100px; height: 100px"</code></td>
</tr>
@ -243,15 +251,14 @@ The following table summarizes style binding syntax.
<td><code>{[key: string]: string | undefined | null}</code></td>
<td><code>{width: '100px', height: '100px'}</code></td>
</tr>
<tr>
<td><code>Array</code><<code>string</code>></td>
<td><code>['width', '100px']</code></td>
</tr>
</table>
<div class="alert is-helpful">
The [NgStyle](guide/built-in-directives/#ngstyle) directive can be used as an alternative to direct `[style]` bindings.
However, using the above style binding syntax without `NgStyle` is preferred because due to improvements in style binding in Angular, `NgStyle` no longer provides significant value, and might eventually be removed in the future.
</div>
<hr/>