角度返回一个承诺[重复]

Question

我对承诺有疑问。这是详细信息页面的控制器。我想从 Web 服务（或从本地商店（如果已存储））获取项目详细信息。

app.controller('ProductCtrl', function($scope, productsService) {
    //load the product by id from productService
    productsService.get("CODE-1111").then(function(result){
        $scope.currProduct = result;
        $scope.currProductSizes = $scope.currProduct.sizes;
    });
}

app.service('productsService', function($http, localStorageService){
    var _key = 'myProducts'
    var _storedData = []
    var self = this;
    self.get = function(id){
        var i = 0;
        return self.getAll().then(function(result) {
            //get the item by id
            _storedData = result;
            for(i=0;i<_storedData.length;i++){
                if(_storedData[i].id == id)
                    break;
            }
            return _storedData[i];
         });
    }
    self.getAll = function() {
        _storedData = localStorageService.get(_key);
        if(_storedData != null){
            **//How return a promise here? Or how I can handle it**
            return _storedData instanceof Array ? _storedData : [_storedData];
        }
        else{
            var url = baseUrl + "api/GetStyles";
            return $http({method: 'GET', url: url, headers: { 'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8' }})
                    .then(function(response) {
                            _storedData = mapToProducts(JSON.parse(response.data));
                            return _storedData;
                        }, 
                        function(response) {
                            console.log(response.status);
                    });
        }
    };

})

第一次（商品不在本地商店）一切正常，因为 getAll 方法返回了一个承诺，但第二次它没有返回一个承诺，所以我得到了

Cannot read property 'then' of undefined

我该如何解决这个问题？

Answer 1

你可以像这样返回一个承诺：

return $q.when(_storedData instanceof Array ? _storedData : [_storedData]);

Answer 2

你需要在你的 get 和 getAll 函数中响应一个承诺，我改变了你的函数来做到这一点：

app.service('productsService', ['$http', '$q', 'localStorageService', function($http, $q, localStorageService){
    var q = $q;
    var _key = 'myProducts';
    var _storedData = [];
    var self = this;

    self.get = function(id){
        var deferred = q.defer(); //Initialize your own promise
        var i = 0;
        self.getAll().then(function(result) {
            //get the item by id
            _storedData = result;
            for(i=0;i<_storedData.length;i++){
                if(_storedData[i].id == id)
                    break;
            }
            return deferred.resolve(_storedData[i]); //This is your response for success
        }).catch(function(error) {
            deferred.reject(error); //This is your response for failure
        });
        return deferred.promise; //return the promise
    }

    self.getAll = function() {
        var deferred = q.defer(); //Initialize your own promise
        _storedData = localStorageService.get(_key);
        if(_storedData != null){
            var data = _storedData instanceof Array ? _storedData : [_storedData];
            deferred.resolve(data);
        } else {
            var url = baseUrl + "api/GetStyles";
            $http({method: 'GET', url: url, headers: { 'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8' }}).then(function(response) {
                _storedData = mapToProducts(JSON.parse(response.data));
                deferred.resolve(_storedData); //This is your response for success
            }, function(error) {
                deferred.reject(error); //This is your response for failure
            });
        }
        return deferred.promise;
    };
}]);