docs(attribute-directives): copy tweaks (#3284)
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<!-- #docregion -->
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<h1>My First Attribute Directive</h1>
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<!-- #docregion applied -->
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<p myHighlight>Highlight me!</p>
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<!-- #enddocregion applied -->
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<!-- #enddocregion -->
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<!-- #docregion color-1 -->
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@ -24,13 +24,13 @@ a#directive-overview
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## Directives overview
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There are three kinds of directives in Angular:
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1. Components — directives with a template.
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1. Structural directives — change the DOM layout by adding and removing DOM elements.
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1. Attribute directives — change the appearance or behavior of an element, component, or another directive.
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1. Components—directives with a template.
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1. Structural directives—change the DOM layout by adding and removing DOM elements.
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1. Attribute directives—change the appearance or behavior of an element, component, or another directive.
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*Components* are the most common of the three directives.
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You saw a component for the first time in the [QuickStart](../quickstart.html) example.
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You saw a component for the first time in the [QuickStart](../quickstart.html) guide.
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*Structural Directives* change the structure of the view.
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Two examples are [NgFor](template-syntax.html#ngFor) and [NgIf](template-syntax.html#ngIf).
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@ -49,29 +49,19 @@ a#write-directive
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the attribute.
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The controller class implements the desired directive behavior.
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This page demonstrates building a simple attribute
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This page demonstrates building a simple _myHighlight_ attribute
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directive to set an element's background color
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when the user hovers over that element.
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.l-sub-section
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:marked
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Technically, a directive isn't necessary to simply set the background color. Style binding can set styles as follows:
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+makeExample('attribute-directives/ts/src/app/app.component.1.html','p-style-background')
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:marked
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Read more about [style binding](template-syntax.html#style-binding) on the [Template Syntax](template-syntax.html) page.
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For a simple example, though, this will demonstrate how attribute directives work.
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when the user hovers over that element. You can apply it like this:
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+makeExample('attribute-directives/ts/src/app/app.component.1.html','applied')
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:marked
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### Write the directive code
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Follow the [setup](setup.html) instructions for creating a new project
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Follow the [setup](setup.html) instructions for creating a new local project
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named <span ngio-ex>attribute-directives</span>.
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:marked
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Create the following source file in the indicated folder with the following code:
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Create the following source file in `src/app` with the following code:
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+makeExample('src/app/highlight.directive.1.ts')
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block highlight-directive-1
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@ -91,14 +81,14 @@ block highlight-directive-1
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The [CSS selector for an attribute](https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors)
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is the attribute name in square brackets.
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Here, the directive's selector is `[myHighlight]`.
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Angular will locate all elements in the template that have an attribute named `myHighlight`.
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Angular locates all elements in the template that have an attribute named `myHighlight`.
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.l-sub-section
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:marked
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### Why not call it "highlight"?
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Though *highlight* is a more concise name than *myHighlight* and would work,
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a best practice is to prefix selector names to ensure
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they don't conflict with standard HTML attributes.
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This also reduces the risk colliding with third-party directive names.
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This also reduces the risk of colliding with third-party directive names.
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Make sure you do **not** prefix the `highlight` directive name with **`ng`** because
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that prefix is reserved for Angular and using it could cause bugs that are difficult to diagnose. For a simple demo, the short prefix, `my`, helps distinguish your custom directive.
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@ -120,7 +110,7 @@ a#apply-directive
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## Apply the attribute directive
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To use the new `HighlightDirective`, create a template that
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applies the directive as an attribute to a paragraph (`<p>`) element.
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In Angular terms, the `<p>` element will be the attribute **host**.
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In Angular terms, the `<p>` element is the attribute **host**.
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p
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| Put the template in its own
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code #[+adjExPath('app.component.html')]
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@ -210,7 +200,7 @@ a#bindings
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## Pass values into the directive with an _@Input_ data binding
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Currently the highlight color is hard-coded _within_ the directive. That's inflexible.
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Let the user of the directive set the color in the template with a binding.
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In this section, you give the developer the power to set the highlight color while applying the directive.
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Start by adding a `highlightColor` property to the directive class like this:
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+makeExample('attribute-directives/ts/src/app/highlight.directive.2.ts','color', 'src/app/highlight.directive.ts')
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@ -300,8 +290,9 @@ a#second-property
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## Bind to a second property
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This highlight directive has a single customizable property. In a real app, it may need more.
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At the moment, the default color — the color that prevails until the user picks a highlight color —
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is hard-coded as "red". Let the template developer set the default color.
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At the moment, the default color—the color that prevails until
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the user picks a highlight color—is hard-coded as "red".
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Let the template developer set the default color.
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Add a second **input** property to `HighlightDirective` called `defaultColor`:
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+makeExcerpt('attribute-directives/ts/src/app/highlight.directive.ts', 'defaultColor','src/app/highlight.directive.ts (defaultColor)')
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