Question

我有一个在组件中调用的服务，在尝试实现一些代码重用策略之前，该服务已经正常工作，但是现在http客户端没有按定义进入。该组件将调用适当的函数，如下所示：

//actions object that maps the request on the object
//split between the different areas of the app.
serviceActions: {[name: string]: {[name: string]:(...args: any[]) => Observable<any>}} = {
    'Customer':{
        GetCategories: this._service.GetCategories,
    }
    'Admin':{...}
};
// source string referenced in the function call
source: string = 'Customer';

//the actual call being made
this.serviceActions[this.Source].GetCategories(...).subscribe(...)

此代码正在将http作为参数的服务上调用函数：

//service constructor:
 constructor(private httpClient: Http) { }
//service method:
public GetCategories(showAll = false, parentId = 0): Observable<Array<SelectModel>> {
        let link = AppSettings.API_COMMON_CATEGORIES;
        let params: URLSearchParams = new URLSearchParams();
        params.set('showAll', showAll.toString());
        params.set('parentId', parentId != null ? parentId.toString() : null);
        let requestOptions = new RequestOptions();
        requestOptions.search = params;

        return this.httpClient.get(link, requestOptions).map(response => {
            let result = JSON.parse(response.json());
            let list = new Array<SelectModel>();
            let caregories: Array<any> = result;

            caregories.forEach(category => {
                list.push(this.CreateSelectModel(category));
            });

            return list;
        });
    }

当直接调用service方法时，这很好用，但是现在我实现了serviceActions对象，就是说cannot read property get of undefined

给什么？

Answer 1

问题源于以下事实：对象上的打包函数从定义它的类中解引用this。为了解决这个问题，我们应该将函数包包装在另一个匿名函数中，并附带参数。

所以代替：

serviceActions: {[name: string]: {[name: string]:(...args: any[]) => Observable<any>}} = {
    'Customer':{
        GetCategories: this._service.GetCategories,
    }
    'Admin':{...}
};

它应该确实是：

serviceActions: {[name: string]: {[name: string]:(...args: any[]) => Observable<any>}} = {
    'Customer':{
        GetCategories: (params) => this._service.GetCategories(params),
    }
    'Admin':{...}
};

保留对类中this的引用。

未定义角度服务参数

1 个答案: