Question

我正在调用getWeeklyDates，它正在调用cachingGlobalConfigurationService，如果在localstorage中找不到globalConfiguration数据，它将再次调用globalConfigurationService。

代码=＆gt;

return cachingGlobalConfigurationService.getGlobalConfiguration()
                   .then(function(response1){

在没有缓存globalConfiguration时工作正常，因为我进行了ajax调用并返回了一个promise。

但上面的代码行.then（函数（response1）是未定义的，当我的globalConfiguration可以在localStorage中找到时，只返回：

 else {
          return cachedGlobalConfiguration;
        }

我想在这种情况下我不能使用.then，但我想。

我该如何解决？

1

this.getWeeklyDates= function (projectId, currentDate) {

        return cachingGlobalConfigurationService.getGlobalConfiguration()
               .then(function(response1){

        // do business logic
    });

2

'use strict';
angular.module('test').service('cachingGlobalConfigurationService', function (localStorageService, globalConfigurationService) {
  this.getGlobalConfiguration = function () {

    var cachedGlobalConfiguration = localStorageService.get('globalConfiguration');
    if (!cachedGlobalConfiguration) {
      return globalConfigurationService.getGlobalConfiguration().then(
        function (globalConfiguration) {
          localStorageService.set('globalConfiguration', globalConfiguration);
          return globalConfiguration;
        },
        function (error) {
          console.log('error', error);
        });
    }
    else {
      return cachedGlobalConfiguration;
    }
  };

  this.saveGlobalConfiguration = function (globalConfiguration) {

    // TODO: Only save to local storage when service.save was successfully
    localStorageService.set('globalConfiguration', globalConfiguration);
    globalConfigurationService.saveGlobalConfiguration(globalConfiguration);
  }
});

第3

'use strict';
angular.module('test').service('globalConfigurationService', function ($http) {
  this.getGlobalConfiguration = function () {

    // TODO get from db
    var path = 'scripts/model/globalConfiguration.json';
    return $http.get(path).then(function (response) {
      return response.data.globalConfiguration;
    });
  };

  this.saveGlobalConfiguration = function (globalConfiguration) {

    // TODO: save on db
    //var path = 'scripts/model/globalConfiguration.json';
    //return $http.post(path, globalConfiguration).then(function (response) {
    //  alert('global configuration was saved succesfully!');
    //});
  }

}）;

Answer 1

您可以注入$q服务并使用$q.when在返回时包装对象，这样您总是从api返回一个promise（并且只删除了多余的else）。还记得拒绝承诺的回调承诺（如果需要）。

'use strict';
angular.module('test').service('cachingGlobalConfigurationService', function (localStorageService, globalConfigurationService, $q) {
  this.getGlobalConfiguration = function () {

    var cachedGlobalConfiguration = localStorageService.get('globalConfiguration');
    if (cachedGlobalConfiguration) {
        //Return a promise
        return $q.when(cachedGlobalConfiguration);
     }

     return globalConfigurationService.getGlobalConfiguration().then(
        function (globalConfiguration) {
          localStorageService.set('globalConfiguration', globalConfiguration);
          return globalConfiguration;
        },
        function (error) {
          console.log('error', error);
          return $q.reject(error); //<-- reject
        });
  };

  //....
});

$ q.when - 将一个可能是值的对象或（第三方）包装成$ q保证。当您处理可能会或可能不是承诺的对象，或者承诺来自不可信任的来源时，这非常有用。

service返回promise，但cachingService没有

1 个答案: