链接promise，或者一个promise触发另一个promise

Question

  app.factory('GeolocationService',function($q,$window,$rootScope){
        return {
            getLatLon: function(){
                var deferred = $q.defer();
                if(!window.navigator){
                    $rootScope.$apply(function(){
                        deferred.reject(new Error("Geolocation not available"));
                    });
                } else {
                    $window.navigator.geolocation.getCurrentPosition(function(position){
                        $rootScope.$apply(function(){
                            deferred.resolve(position);
                        });
                    }, function(error){
                        $rootScope.$apply(function(){
                            deferred.reject(error);
                        });
                    });
                }

                return deferred.promise;
            }
        };
    });

    app.factory("WeatherService", function ($q,$http,$rootScope, GeolocationService) {
        return {
            getWeather: function(){
                var weather;
                var loc = new GeolocationService.getLatLon(); 
                var  lat= loc.lat || 37.4568202221774, 
                lon= loc.lon || -122.201366838789 ;
                var units = '';
                var url = 'http://api.openweathermap.org/data/2.5/forecast/daily?lat='+lat+'&lon='+lon+'&units='+units+'&callback=JSON_CALLBACK';
                $http.jsonp(url)
                    .success(function(data) {
                        weather=data;
                        return weather;
                    })
                    .error(function(err){
                        weather=err;
                        return err;
                    });
            }

        };
    });

Answer 1

你只需要在你的服务中使用promise，然后使用promise。对于示例，我有一个具有user.company_id的用户，如果我想获得公司的名称，我必须等待该用户被加载。和你的情况一样。

这是我的服务：

    angular.module('UserService', []) 
.factory('UserService', function($q , $http, $rootScope,$timeout) {
var currentUserPromise = null;
var currentCompanyPromise = null;
return {
    getCurrentUser: function() {
        if (currentUserPromise === null) {
            var config = {};
            config.cache = true;
            config.method = "GET"; 
            config.url = "users/get_current_user";
            currentUserPromise = $http(config)
                .then(function(response) {
                    if (typeof response.data === 'object') {
                        return response.data.user;
                    } else {
                        // invalid response
                        return $q.reject(response.data);
                    }  
                }, function(response) {
                    // something went wrong
                    return $q.reject(response.data);
                });
        }
        return currentUserPromise;
    },

    getCurrentCompany: function(company_id) {
        if (currentCompanyPromise === null){
            var config = {};
            var company = {};
            company.id = company_id; 
            config.cache = true;
            config.method = "GET"; 
            config.url = "/companies/show";
            config.params = company;
            currentCompanyPromise = $http(config)
                .then(function(response) {
                    if (typeof response.data === 'object') {
                        return response.data.company;
                    } else {
                        // invalid response
                        return $q.reject(response.data);
                    }

                }, function(response) {
                    // something went wrong
                    return $q.reject(response.data);
                });
            }
            return currentCompanyPromise;

        }
    };     
});

在我的控制器中，我这样使用：

var promiseCurrentUser = UserService.getCurrentUser();
promiseCurrentUser.then(function(user) {
    $scope.currentUser = user;
    UserService.getCurrentCompany(user.company_id).then(function(company){
        $scope.companyName = company.name;
    });
});