Angular 2 – Metadata
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Metadata is used to decorate a class so that it can configure the expected behavior of the class. Following are the different parts for metadata.
Annotations − These are decorators at the class level. This is an array and an example having both the @Component and @Routes decorator.
Following is a sample code, which is present in the app.component.ts file.
@Component ({ selector: ''my-app'', templateUrl: ''app/app.component.html'' })
The component decorator is used to declare the class in the app.component.ts file as a component.
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Design:paramtypes − These are only used for the constructors and applied only to Typescript.
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propMetadata − This is the metadata which is applied to the properties of the class.
Following is an example code.
export class AppComponent { @Environment(‘test’) appTitle: string = ''Welcome''; }
Here, the @Environment is the metadata applied to the property appTitle and the value given is ‘test’.
Parameters − This is set by the decorators at the constructor level.
Following is an example code.
export class AppComponent { constructor(@Environment(‘test’ private appTitle:string) { } }
In the above example, metadata is applied to the parameters of the constructor.
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