2016-05-10 00:51:23 -07:00
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block includes
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include ../_util-fns
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2016-04-05 09:27:10 +03:00
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:marked
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Angular 2 applications are styled with regular CSS. That means we can apply
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everything we know about CSS stylesheets, selectors, rules, and media queries
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to our Angular applications directly.
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On top of this, Angular has the ability to bundle *component styles*
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with our components enabling a more modular design than regular stylesheets.
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2016-04-18 11:32:46 +03:00
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In this chapter we learn how to load and apply these *component styles*.
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2016-04-05 09:27:10 +03:00
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# Table Of Contents
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* [Using Component Styles](#using-component-styles)
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* [Special selectors](#special-selectors)
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2016-05-10 00:51:23 -07:00
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* [Loading Styles into Components](#loading-styles)
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* [Controlling View Encapsulation: Emulated, Native, and None](#view-encapsulation)
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2016-04-05 09:27:10 +03:00
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* [Appendix 1: Inspecting the generated runtime component styles](#inspect-generated-css)
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* [Appendix 2: Loading Styles with Relative URLs](#relative-urls)
|
2016-05-20 16:18:58 -07:00
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|
2016-07-03 17:11:17 -07:00
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Run the <live-example></live-example> of the code shown in this chapter.
|
2016-04-05 09:27:10 +03:00
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.l-main-section
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:marked
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## Using Component Styles
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For every Angular 2 component we write, we may define not only an HTML template,
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but also the CSS styles that go with that template,
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specifying any selectors, rules, and media queries that we need.
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One way to do this is to set the `styles` property in the component metadata.
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2016-05-31 15:25:59 -07:00
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The `styles` property takes #{_an} #{_array} of strings that contain CSS code.
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2016-04-05 09:27:10 +03:00
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Usually we give it one string as in this example:
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+makeExample('component-styles/ts/app/hero-app.component.ts')(format='.')
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:marked
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Component styles differ from traditional, global styles in a couple of ways.
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2016-05-08 17:39:50 -04:00
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Firstly, the selectors we put into a component's styles *only apply within the template
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2016-05-10 00:51:23 -07:00
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of that component*. The `h1` selector in the example above only applies to the `<h1>` tag
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2016-04-05 09:27:10 +03:00
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in the template of `HeroAppComponent`. Any `<h1>` elements elsewhere in
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the application are unaffected.
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This is a big improvement in modularity compared to how CSS traditionally works:
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1. We can use the CSS class names and selectors that make the most sense in the context of each component.
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1. Class names and selectors are local to the component and won't collide with
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classes and selectors used elsewhere in the application.
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1. Our component's styles *cannot* be changed by changes to styles elsewhere in the application.
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1. We can co-locate the CSS code of each component with the TypeScript and HTML code of the component,
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which leads to a neat and tidy project structure.
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1. We can change or remove component CSS code in the future without trawling through the
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whole application to see where else it may have been used. We just look at the component we're in.
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a(id="special-selectors")
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.l-main-section
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:marked
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## Special selectors
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Component styles have a few special *selectors* from the world of
|
2016-05-10 00:51:23 -07:00
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[shadow DOM style scoping](https://www.w3.org/TR/css-scoping-1):
|
2016-04-05 09:27:10 +03:00
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### :host
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Use the `:host` pseudo-class selector to target styles in the element that *hosts* the component (as opposed to
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targeting elements *inside* the component's template):
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+makeExample('component-styles/ts/app/hero-details.component.css', 'host')(format='.')
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:marked
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This is the *only* way we can target the host element. We cannot reach
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it from inside the component with other selectors, because it is not part of the
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component's own template. It is in a parent component's template.
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Use the *function form* to apply host styles conditionally by
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including another selector inside parentheses after `:host`.
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In the next example we target the host element again, but only when it also has the `active` CSS class.
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+makeExample('component-styles/ts/app/hero-details.component.css', 'hostfunction')(format=".")
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:marked
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### :host-context
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Sometimes it is useful to apply styles based on some condition *outside* a component's view.
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For example, there may be a CSS theme class applied to the document `<body>` element, and
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we want to change how our component looks based on that.
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Use the `:host-context()` pseudo-class selector. It works just like the function
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form of `:host()`. It looks for a CSS class in *any ancestor* of the component host element, all the way
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up to the document root. It's useful when combined with another selector.
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In the following example, we apply a `background-color` style to all `<h2>` elements *inside* the component, only
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if some ancestor element has the CSS class `theme-light`.
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+makeExample('component-styles/ts/app/hero-details.component.css', 'hostcontext')(format='.')
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:marked
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|
### /deep/
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Component styles normally apply only to the HTML in the component's own template.
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|
We can use the `/deep/` selector to force a style down through the child component tree into all the child component views.
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|
The `/deep/` selector works to any depth of nested components, and it applies *both to the view
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|
children and the content children* of the component.
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|
In this example, we target all `<h3>` elements, from the host element down
|
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|
|
through this component to all of its child elements in the DOM:
|
|
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|
|
+makeExample('component-styles/ts/app/hero-details.component.css', 'deep')(format=".")
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|
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|
:marked
|
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|
|
The `/deep/` selector also has the alias `>>>`. We can use either of the two interchangeably.
|
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|
|
|
|
2016-04-06 11:46:21 -07:00
|
|
|
.alert.is-important
|
2016-04-05 09:27:10 +03:00
|
|
|
:marked
|
|
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|
|
The `/deep/` and `>>>` selectors should only be used with **emulated** view encapsulation.
|
|
|
|
|
This is the default and it is what we use most of the time. See the
|
2016-05-10 00:51:23 -07:00
|
|
|
[Controlling View Encapsulation](#view-encapsulation)
|
2016-04-05 09:27:10 +03:00
|
|
|
section for more details.
|
|
|
|
|
|
|
|
|
|
a(id='loading-styles')
|
|
|
|
|
.l-main-section
|
|
|
|
|
:marked
|
|
|
|
|
## Loading Styles into Components
|
|
|
|
|
|
|
|
|
|
We have several ways to add styles to a component:
|
|
|
|
|
* inline in the template HTML
|
|
|
|
|
* by setting `styles` or `styleUrls` metadata
|
|
|
|
|
* with CSS imports
|
|
|
|
|
|
|
|
|
|
The scoping rules outlined above apply to each of these loading patterns.
|
|
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|
|
|
|
|
|
|
### Styles in Metadata
|
|
|
|
|
|
2016-05-10 00:51:23 -07:00
|
|
|
We can add a `styles` #{_array} property to the `@Component` #{_decorator}.
|
|
|
|
|
Each string in the #{_array} (usually just one string) defines the CSS.
|
2016-04-05 09:27:10 +03:00
|
|
|
|
|
|
|
|
+makeExample('component-styles/ts/app/hero-app.component.ts')
|
|
|
|
|
|
|
|
|
|
:marked
|
|
|
|
|
### Template Inline Styles
|
|
|
|
|
|
|
|
|
|
We can embed styles directly into the HTML template by putting them
|
|
|
|
|
inside `<style>` tags.
|
|
|
|
|
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|
|
|
|
+makeExample('component-styles/ts/app/hero-controls.component.ts', 'inlinestyles')
|
|
|
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|
|
|
|
|
|
:marked
|
|
|
|
|
### Style URLs in Metadata
|
|
|
|
|
|
|
|
|
|
We can load styles from external CSS files by adding a `styleUrls` attribute
|
2016-06-02 21:34:11 +01:00
|
|
|
into a component's `@Component` #{_decorator}:
|
2016-04-05 09:27:10 +03:00
|
|
|
|
|
|
|
|
+makeExample('component-styles/ts/app/hero-details.component.ts', 'styleurls')
|
|
|
|
|
|
2016-05-10 00:51:23 -07:00
|
|
|
block style-url
|
|
|
|
|
.alert.is-important
|
|
|
|
|
:marked
|
|
|
|
|
The URL is ***relative to the application root*** which is usually the
|
|
|
|
|
location of the `index.html` web page that hosts the application.
|
|
|
|
|
The style file URL is *not* relative to the component file.
|
|
|
|
|
That's why the example URL begins `app/`.
|
|
|
|
|
See [Appendix 2](#relative-urls) to specify a URL relative to the
|
|
|
|
|
component file.
|
|
|
|
|
|
|
|
|
|
block module-bundlers
|
|
|
|
|
.l-sub-section
|
|
|
|
|
:marked
|
|
|
|
|
Users of module bundlers like Webpack may also use the `styles` attribute
|
|
|
|
|
to load styles from external files at build time. They could write:
|
|
|
|
|
|
|
|
|
|
`styles: [require('my.component.css')]`
|
|
|
|
|
|
|
|
|
|
We set the `styles` property, **not** `styleUrls` property! The module
|
|
|
|
|
bundler is loading the CSS strings, not Angular.
|
|
|
|
|
Angular only sees the CSS strings *after* the bundler loads them.
|
|
|
|
|
To Angular it is as if we wrote the `styles` array by hand.
|
|
|
|
|
Refer to the module bundler's documentation for information on
|
|
|
|
|
loading CSS in this manner.
|
2016-04-05 09:27:10 +03:00
|
|
|
|
|
|
|
|
:marked
|
|
|
|
|
### Template Link Tags
|
|
|
|
|
|
|
|
|
|
We can also embed `<link>` tags into the component's HTML template.
|
|
|
|
|
|
2016-05-10 00:51:23 -07:00
|
|
|
As with `styleUrls`, the link tag's `href` URL is relative to the
|
|
|
|
|
application root, not relative to the component file.
|
2016-04-05 09:27:10 +03:00
|
|
|
|
|
|
|
|
+makeExample('component-styles/ts/app/hero-team.component.ts', 'stylelink')
|
|
|
|
|
|
|
|
|
|
:marked
|
|
|
|
|
### CSS @imports
|
|
|
|
|
|
|
|
|
|
We can also import CSS files into our CSS files by using the standard CSS
|
|
|
|
|
[`@import` rule](https://developer.mozilla.org/en/docs/Web/CSS/@import).
|
|
|
|
|
|
2016-05-10 00:51:23 -07:00
|
|
|
block css-import-url
|
|
|
|
|
:marked
|
|
|
|
|
In *this* case the URL is relative to the CSS file into which we are importing.
|
2016-04-05 09:27:10 +03:00
|
|
|
|
|
|
|
|
+makeExample('component-styles/ts/app/hero-details.component.css', 'import', 'app/hero-details.component.css (excerpt)')
|
2016-05-10 00:51:23 -07:00
|
|
|
|
|
|
|
|
a#view-encapsulation
|
2016-04-05 09:27:10 +03:00
|
|
|
.l-main-section
|
|
|
|
|
:marked
|
|
|
|
|
## Controlling View Encapsulation: Native, Emulated, and None
|
|
|
|
|
|
|
|
|
|
As discussed above, component CSS styles are *encapsulated* into the component's own view and do
|
|
|
|
|
not affect the rest of the application.
|
|
|
|
|
|
|
|
|
|
We can control how this encapsulation happens on a *per
|
|
|
|
|
component* basis by setting the *view encapsulation mode* in the component metadata. There
|
|
|
|
|
are three modes to choose from:
|
|
|
|
|
|
|
|
|
|
* `Native` view encapsulation uses the browser's native [Shadow DOM](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Shadow_DOM)
|
|
|
|
|
implementation to attach a Shadow DOM to the component's host element, and then puts the component
|
|
|
|
|
view inside that Shadow DOM. The component's styles are included within the Shadow DOM.
|
|
|
|
|
|
|
|
|
|
* `Emulated` view encapsulation (**the default**) emulates the behavior of Shadow DOM by preprocessing
|
|
|
|
|
(and renaming) the CSS code to effectively scope the CSS to the component's view.
|
|
|
|
|
See [Appendix 1](#inspect-generated-css) for details.
|
|
|
|
|
|
|
|
|
|
* `None` means that Angular does no view encapsulation.
|
|
|
|
|
Angular adds the CSS to the global styles.
|
|
|
|
|
The scoping rules, isolations, and protections discussed earlier do not apply.
|
|
|
|
|
This is essentially the same as pasting the component's styles into the HTML.
|
|
|
|
|
|
|
|
|
|
Set the components encapsulation mode using the `encapsulation` property in the component metadata:
|
|
|
|
|
|
|
|
|
|
+makeExample('component-styles/ts/app/quest-summary.component.ts', 'encapsulation.native')(format='.')
|
2016-05-10 00:51:23 -07:00
|
|
|
|
2016-04-05 09:27:10 +03:00
|
|
|
:marked
|
|
|
|
|
`Native` view encapsulation only works on [browsers that have native support
|
|
|
|
|
for Shadow DOM](http://caniuse.com/#feat=shadowdom). The support is still limited,
|
|
|
|
|
which is why `Emulated` view encapsulation is the default mode and recommended
|
|
|
|
|
in most cases.
|
|
|
|
|
|
2016-05-10 00:51:23 -07:00
|
|
|
a#inspect-generated-css
|
2016-04-05 09:27:10 +03:00
|
|
|
.l-main-section
|
|
|
|
|
:marked
|
|
|
|
|
## Appendix 1: Inspecting The CSS Generated in Emulated View Encapsulation
|
|
|
|
|
|
|
|
|
|
When using the default emulated view encapsulation, Angular preprocesses
|
|
|
|
|
all component styles so that they approximate the standard Shadow CSS scoping rules.
|
|
|
|
|
|
|
|
|
|
When we inspect the DOM of a running Angular application with emulated view
|
|
|
|
|
encapsulation enabled, we see that each DOM element has some extra attributes
|
|
|
|
|
attached to it:
|
|
|
|
|
|
|
|
|
|
code-example(format="").
|
|
|
|
|
<hero-details _nghost-pmm-5>
|
|
|
|
|
<h2 _ngcontent-pmm-5>Mister Fantastic</h2>
|
|
|
|
|
<hero-team _ngcontent-pmm-5 _nghost-pmm-6>
|
|
|
|
|
<h3 _ngcontent-pmm-6>Team</h3>
|
|
|
|
|
</hero-team>
|
|
|
|
|
</hero-detail>
|
|
|
|
|
|
|
|
|
|
:marked
|
|
|
|
|
We see two kinds of generated attributes:
|
|
|
|
|
* An element that would be a Shadow DOM host in native encapsulation has a
|
|
|
|
|
generated `_nghost` attribute. This is typically the case for component host elements.
|
|
|
|
|
|
|
|
|
|
* An element within a component's view has a `_ngcontent` attribute
|
|
|
|
|
that identifies to which host's emulated Shadow DOM this element belongs.
|
|
|
|
|
|
|
|
|
|
The exact values of these attributes are not important. They are automatically
|
|
|
|
|
generated and we never refer to them in application code. But they are targeted
|
|
|
|
|
by the generated component styles, which we'll find in the `<head>` section of the DOM:
|
|
|
|
|
|
|
|
|
|
code-example(format="").
|
|
|
|
|
[_nghost-pmm-5] {
|
|
|
|
|
display: block;
|
|
|
|
|
border: 1px solid black;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
h3[_ngcontent-pmm-6] {
|
|
|
|
|
background-color: white;
|
|
|
|
|
border: 1px solid #777;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
:marked
|
|
|
|
|
These are the styles we wrote, post-processed so that each selector is augmented
|
|
|
|
|
with `_nghost` or `_ngcontent` attribute selectors.
|
|
|
|
|
These extra selectors enable the scoping rules described in this guide.
|
|
|
|
|
|
|
|
|
|
We'll likely live with *emulated* mode until shadow DOM gains traction.
|
|
|
|
|
|
2016-05-10 00:51:23 -07:00
|
|
|
a#relative-urls
|
2016-04-05 09:27:10 +03:00
|
|
|
.l-main-section
|
|
|
|
|
:marked
|
|
|
|
|
## Appendix 2: Loading Styles with Relative URLs
|
|
|
|
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It's common practice to split a component's code, HTML, and CSS into three separate files in the same directory:
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code-example(format='').
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quest-summary.component.ts
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quest-summary.component.html
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quest-summary.component.css
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2016-05-10 00:51:23 -07:00
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2016-04-05 09:27:10 +03:00
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:marked
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We include the template and CSS files by setting the `templateUrl` and `styleUrls` metadata properties respectively.
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Because these files are co-located with the component,
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it would be nice to refer to them by name without also having to specify a path back to the root of the application.
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2016-05-10 00:51:23 -07:00
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block module-id
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:marked
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2016-05-20 15:14:13 -07:00
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We can change the way Angular calculates the full URL be setting the component metadata's `moduleId` property to `module.id`.
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2016-05-10 00:51:23 -07:00
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+makeExample('component-styles/ts/app/quest-summary.component.ts','', 'app/quest-summary.component.ts')
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2016-05-20 15:14:13 -07:00
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:marked
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Learn more about `moduleId` in the [Component-Relative Paths](../cookbook/component-relative-paths.html) chapter.
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2016-05-10 00:51:23 -07:00
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