如何将 Angular $http 与 typescript 泛型一起使用

Question

我正在尝试通过以下方式返回通用承诺

public getUserPreferences: () => ng.IPromise <string> = () => {
        var promise = this.makeRequest<string>('http://someurl.com',null)
            .then((response:string) => {
                    let res: string = response;
                    return res;
                }
            )
            .catch((error) => {
            });

        return promise;
    };

        public makeRequest<T>(וrl: string, data?: any,
                          config?: any, verb?: HttpMethod): ng.IPromise<T> {
        // Cache key contains both request url and data
        var cacheKey = url + '*' + JSON.stringify(data);

        var deferred = this.$q.defer();
        var httpRequest: any;
        var responseData: T;
        var start = new Date().getTime();

        // Trying to retrieve cache data if needed
        if (!config || config.cache != false) {
            responseData = this.cacheService.get(cacheKey);
        }

        if (responseData) {
            deferred.resolve(responseData);
        }
        else {
            switch (verb) {
                case HttpMethod.GET:
                    httpRequest = this.$http.get(url, config);
                    break;
                case HttpMethod.POST:
                    httpRequest = this.$http.post(url, data, config);
                    break;
                case HttpMethod.PATCH:
                    httpRequest = this.$http.patch(url, data, config);
                    break;
                default:
                    httpRequest = this.$http.post(url, data, config);
                    break;

            }

            httpRequest
                .then((res: any) => {
                    responseData = res.data;
                    this.cacheService.put(cacheKey, responseData);
                    deferred.resolve(responseData);
                })
                .catch((error: any) => {
                    deferred.reject(error);
                });
        }

        return deferred.promise;
    }

但我在 getUserPreferences 上收到以下错误：

错误:(132, 9) TS2322: 类型 '() => IPromise' 不可分配 输入'() => IPromise'。类型 'IPromise' 不是 可分配给类型“IPromise”。类型 'void' 不可分配 输入“字符串”。

Answer 1

看起来问题是你永远不会用responseData 解决promise：没有resolve(responseData) 意味着promise 是用undefined 隐式解决的。

试试这个：

public makeRequest<T>(url:string, data?: any): ng.IPromise<T> {
    return this.$http.post(url, data)
           .then((res: any) => {
               return res.data;
           });
}

我还删除了多余的延迟对象，你不需要，因为你可以直接返回承诺。

另一个区别。我放弃了catch 块，因为最好将它放在承诺链的末尾（在getUserPreferences 中）。