使用AngularJS在Typescript中导入模式？

Question

This may be Typescript 101 but can't seem to get a clear answer for this.

I am new to Typescript and have come across some existing code (its AngularJS) that follows this format

module App.Login {
    import IStateService = angular.ui.IStateService;

    export class LoginController {

        private _state: IStateService;

        constructor($state: angular.ui.IStateService, ...) {
            this._state = $state;
        }
    }
}

Through reading around and some experimentation I discovered this can be rewritten in a far leaner manner as the following:

module App.Login {  
    export class LoginController {

        constructor(private $state: angular.ui.IStateService, ...) {
        }
    }
}

My questions are:

• Why was it created the first way originally? Lack of knowledge or for some reason I don't understand
• Why we need to use import just to alias the interface
• A question of style, but later in my class to use $state I have to use this.$state . Coming from Angular v1 this feels odd, I presume this is ok though?

Answer 1

1. Why was it originally this way? If you mean the import, convenience. angular.ui.IStateService is right on the edge of annoyingly long. They author probably just wanted a more convenient version. If you mean the declaration of the private var, some folks (especially coming from a C#/Java background) would prefer to declare class parameters explicitly. The visibility modifier ( public / protected / private ) on constructor parameters syntax is pretty unique to typescript so folks aren't used to it / don't like it.
2. You don't. You can use the type keyword instead.
3. Yep, that's totally fine.