问题
I want to developpe a search component. Here is the use case:
- This component calls a service with search's terms parameters.
- The service call the api endpoint and returns the resulting objects as a collection.
- The component display the results in the template.
I want to write only one search component able to call different service depending on the case. Imagine I have two service:
- SearchInMaleEmployeeService
- SearchInFemaleEmployeeService
Both of these services implements a search function returning a list of employee. I would like to tell my component which service depending on the case. In C#, we can use interface to tell the component constructor which service to use.
How can I do that in Angular2?
Bonus question: How can I say to my component which template to use to render the search results depending of the type of object returned by the service?
回答1:
You can achieve this via dependency injection.
As you said, create two different services implementing same ISearchService interface.
When using SearchComponent, provide appropriate service class from module to ServiceComponent.
Your SearchComponent would look like
constructor(private searchService: ISearchService) {}
And when using SearchComponent at different places provide service instance:
providers: [
{ provide: ISearchService, useValue: SearchInMaleEmployeeService}
]
or
providers: [
{ provide: ISearchService, useValue: SearchInFemaleEmployeeService}
]
More information about Angular2 dependency injection here.
Update:
As pointed out by Ben
Provide statement needs to be coded as
provide('ISearchService', {useClass: SearchInMaleEmployeeService})
And to inject the class to component:
constructor(@Inject('ISearchService') private searchService:ISearchService) {}
回答2:
Yes, you can do it like Sefa Ümit Oray answered above. But as I understand, you are trying to filter two type of object in list and you want to use both. So why you don't write a service that has two difference search methods. Or you can write a method that do search in both types of object.
As you ask, you can use instance of to check the type of object. Then, use Pipe combine with ngIf to do render what you want.
https://angular.io/docs/ts/latest/guide/pipes.html https://angular.io/docs/ts/latest/api/common/index/NgIf-directive.html
来源：https://stackoverflow.com/questions/40068456/angular-2-interface-for-service