从泛型类中的类型参数创建一个新对象 [英] Create a new object from type parameter in generic class

问题描述

我正在尝试在我的泛型类中创建一个类型参数的新对象.在我的类 View 中，我有 2 个泛型类型的对象列表作为类型参数传递，但是当我尝试制作 new TGridView() 时，TypeScript 说:

I'm trying to create a new object of a type parameter in my generic class. In my class View, I have 2 lists of objects of generic type passed as type parameters, but when I try to make new TGridView(), TypeScript says:

找不到符号'TGridView

Could not find symbol 'TGridView

这是代码:

module AppFW {
    // Represents a view
    export class View<TFormView extends FormView, TGridView extends GridView> {
        // The list of forms 
        public Forms: { [idForm: string]: TFormView; } = {};

        // The list of grids
        public Grids: { [idForm: string]: TGridView; } = {};

        public AddForm(formElement: HTMLFormElement, dataModel: any, submitFunction?: (e: SubmitFormViewEvent) => boolean): FormView {
            var newForm: TFormView = new TFormView(formElement, dataModel, submitFunction);
            this.Forms[formElement.id] = newForm;
            return newForm;
        }

        public AddGrid(element: HTMLDivElement, gridOptions: any): GridView {
            var newGrid: TGridView = new TGridView(element, gridOptions);
            this.Grids[element.id] = newGrid;
            return newGrid;
        }
    }
}

我可以从泛型类型创建对象吗?

Can I create objects from a generic type?

推荐答案

因为编译后的 JavaScript 已经删除了所有的类型信息，所以你不能使用 T 来新建一个对象.

Because the compiled JavaScript has all the type information erased, you can't use T to new up an object.

您可以通过将类型传递给构造函数来以非通用方式执行此操作.

You can do this in a non-generic way by passing the type into the constructor.

class TestOne {
    hi() {
        alert('Hi');
    }
}

class TestTwo {
    constructor(private testType) {

    }
    getNew() {
        return new this.testType();
    }
}

var test = new TestTwo(TestOne);

var example = test.getNew();
example.hi();

您可以使用泛型扩展此示例以收紧类型:

You could extend this example using generics to tighten up the types:

class TestBase {
    hi() {
        alert('Hi from base');
    }
}

class TestSub extends TestBase {
    hi() {
        alert('Hi from sub');
    }
}

class TestTwo<T extends TestBase> {
    constructor(private testType: new () => T) {
    }

    getNew() : T {
        return new this.testType();
    }
}

//var test = new TestTwo<TestBase>(TestBase);
var test = new TestTwo<TestSub>(TestSub);

var example = test.getNew();
example.hi();

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