angular - typescript 中的 CollectionResult

Question

我正在尝试为从服务器获取响应的代理服务创建一个通用类。当我留下来实现这个类时，我遇到了一个问题，从泛型类调用一个方法。如何从 Js(item) 调用以泛型类型声明的静态方法？

export class CollectionResult<T> implements ICollectionResult<T> {
    items: Array<T>;

    constructor(data?: T) {
        if (data) {
            for (var property in data) {
                if (data.hasOwnProperty(property))
                    (<any>this)[property] = (<any>data)[property];
            }
        }
    }

    init(data?: any) {
        if (data) {
            Object.assign(this, data);
            this.items = [];
            for (let item of data.items) {
                this.items.push(T//NOTE: Error here//.fromJS(item));
            }
        }
    }

     fromJS(data: any): CollectionResult<T> {
        let result = new CollectionResult<T>();
        result.init(data);
        return result;
    }

    toJSON(data?: any) {
        data = typeof data === 'object' ? data : {};
        Object.assign(data, this);
        if (this.items && this.items.constructor === Array) {
            data["items"] = [];
            for (let item of this.items) {
                data["items"].push(item);
            }
        }
        return data;
    }
}

export interface ICollectionResult<T> {
    items: Array<T>;
}

//传递 CollectionResult 的通用类

export class ProgramDto implements 
IProgramDto {
    year: number;
    month: number;
    accounts: number;

    constructor(data?: ProgramDto) {
        if (data) {
            for (var property in data) {
                if (data.hasOwnProperty(property))
                    (<any>this)[property] = (<any>data)[property];
            }
        }
    }

    init(data?: any) {
        if (data) {
            Object.assign(this, data);
        }
    }

    static fromJS(data: any): ProgramDto {
        let result = new ProgramDto();
        result.init(data);
        return result;
    }

    toJSON(data?: any) {
        data = typeof data === 'object' ? data : {};
        Object.assign(data, this);

        return data;
    }
}

export interface IProgramDto {
    year: number;
    month: number;
    accounts: number;
}

//代理方法中的用法

Get(): Observable<CollectionResult<ProgramDto >> {
        let url = `${this.baseUrl}/Api/Controller/Method`;
        url = url.replace(/[?&]$/, "");
        let options = this.getOptions();
        return this.sendRequestWithResponse(url, options, CollectionResult<ProgramDto>.fromJS, new CollectionResult<ProgramDto>());
    }

Answer 1

您不能访问泛型类型参数的成员。类型参数在编译期间被删除，因此除了类型检查之外，您不能依赖它们做任何其他事情。

您可以将类作为参数传入并限制它具有 fromJs 方法:

type CollectionResultDataClass<T> = {
    new(...a: any[]): T
    fromJs(o: any): T
}

export class CollectionResult<T> implements ICollectionResult<T> {
    items: Array<T>;

    constructor(private cls: CollectionResultDataClass<T>, data?: T) {
        // ...
    }

    init(data?: any) {
        if (data) {
            Object.assign(this, data);
            this.items = [];
            for (let item of data.items) {
                this.items.push(this.cls.fromJs(item));
            }
        }
    }

    fromJS(data: any): CollectionResult<T> {
        let result = new CollectionResult<T>(this.cls);
        result.init(data);
        return result;
    }

    toJSON(data?: any) {
        //..
    }
}

//Usage
class MyDataClass {
    static fromJs(o: any) {
        return Object.assign(new MyDataClass(), o);
    }
}

new CollectionResult(MyDataClass, new MyDataClass());