angular-cn/public/docs/js/latest/api/di/OptionalMetadata-class.jade

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p.location-badge.
exported from <a href='../di'>angular2/di</a>
defined in <a href="https://github.com/angular/angular/tree/2.0.0-alpha.32/modules/angular2/src/di/metadata.ts#L17-L34">angular2/src/di/metadata.ts (line 17)</a>
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A parameter metadata that marks a dependency as optional. <a href='Injector-class.html'><code>Injector</code></a> provides `null` if
the dependency is not found.
```
class AComponent {
constructor(@Optional() aService:MyService) {
this.aService = aService;
}
}
```
.l-main-section
h2 Annotations
.l-sub-section
h3.annotation CONST
pre.prettyprint
code.
@CONST()
.l-main-section
h2 Members
.l-sub-section
h3 toString
pre.prettyprint
code.
toString()
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