angular-docs-cn/public/docs/js/latest/api/di_annotations/Optional-class.jade

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<span class="location-badge">exported from <a href="/angular2/di_annotations">angular2/di_annotations</a></span>
defined in <a href="https://github.com/angular/angular/tree/master/modules/angular2/src/di/annotations.js#L77">angular2/src/di/annotations.js (line 77)</a>
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A parameter annotation that marks a dependency as optional. <a href="angular2/di/Injector-class"><code>Injector</code></a> provides `null` if the dependency is not
found.
```
class AComponent {
constructor(@Optional() aService:MyService) {
this.aService = aService;
}
}
```
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