即使我没有实现接口，Typescript也会编译

Question

I have the following interface:

interface IUpdateBusinessAddressRequest extends IReturn<IBusinessAddressResponse>
{
    BusinessId?: number;
    AddressId?: number;
    AddressLine1?: string;
    AddressLine2?: string;
    AddressLine3?: string;
    TownCity?: string;
    County?: string;
    Postcode?: string;
    Country?: string;
    IsPrimary?: boolean;
}

And this class:

export class UpdateBusinessAddressRequest implements IUpdateBusinessAddressRequest  {

}

I'm not implementing the interface in the class, yet my Typescript compiles anyway.

I have this method inside another class:

test(request: IDeleteBusinessRequest) {
    //stuff
}

IDeleteBusinessRequest is another interface. I can call it like so with no compile errors:

this.test(new UpdateBusinessAddressRequest());

UpdateBusinessAddressRequest doesn't implement IDeleteBusinessRequest , but I don't get any compile errors.

In C# for example, this wouldn't compile. Am I just expecting too much of typescript, or am I doing something wrong?

I am using Visual Studio 2015 RC with the latest Typescript compiler.

Thanks

Answer 1

The problem is the question mark "?", it means that the property is optional, that's why there is no compiler error.

I just tried your code in the TS playground and removed "?" on BusinessId and get the following error :

Class 'UpdateBusinessAddressRequest' incorrectly implements interface 'IUpdateBusinessAddressRequest'. Property 'BusinessId' is missing in type 'UpdateBusinessAddressRequest' .