javascript - 工厂方法不返回 - TypeError : Cannot read property 'then' of undefined

Question

我被这个问题困扰了。我了解到我的工厂方法应该返回，但我在代码中尝试了许多不同的位置返回但无济于事。

我从中调用服务的 Controller :

    $scope.updateChosenSet = function(){
        var chosenMeds = $scope.medications.chosenMedications;
        if(chosenMeds.length){
            var n = ['provigil', 'improvest', 'provenge'];

            // in console, Angular is complaining about the below line (just before the dot)
            medicationByNameFactory.callToAPI().then(
                    function(data){
                        console.log("Works!");  // this never fires in the console!!
                    }
                );
        }
    };

和我的服务:

angular.module('hsToolkit.services')
        .factory('medicationByNameFactory', medicationByName);


medicationByName.$inject = ['$http'];
function medicationByName($http){


    // first returning callable properties as suggested here: https://github.com/johnpapa/angularjs-styleguide
    // tried the conventional way, but it's the same
    return {
        callToAPI: callToAPI
    };


    function callToAPI(){

        // this array will be supplied as an argument from controller when this starts to work
        var fff = ['provigil', 'improvest', 'provenge'];

        angular.forEach(fff, makeCall);

        function makeCall(item){
            return $http({
                    method: 'GET',
                    url: 'path/to/api/?name='+item,
                    headers: {
                        'Content-type': 'application/json'
                    }
                })
                    .then(
                        function(response){
                            // this DOES output to console!
                            console.log(response.data.drugGroup);

                            // I'm getting error with or w/o this!
                            return response.data.drugGroup;
                        }
                    );
        } // closing: makeCall

    }; // closing: callToAPI

}; // closing: medicationByName

Answer 1

您的问题是，您没有从工厂的 callToApI 方法返回任何内容，即使您从 forEach 迭代器函数返回 promise (这不是但任何用途)它只是该函数的返回值，并且不会从外部函数返回。您所需要做的就是返回一个满足所有潜在 promise 的 promise 。所以利用 $q.all并从您的服务方法返回 return $q.all(fff.map(_makeCall)); 。仅当所有底层 promise 都得到解决时，q.all 才会解决，如果其中一个 promise 被拒绝，则整个集合将被拒绝。

medicationByName.$inject = ['$http', '$q'];
function medicationByName($http){

   return {
        callToAPI: callToAPI
    };


    function callToAPI(){
        var fff = ['provigil', 'improvest', 'provenge'];
        return $q.all(fff.map(_makeCall));
   }; 

    function _makeCall(item){
            return $http({
                    method: 'GET',
                    url: 'path/to/api/?name='+item,
                    headers: {
                        'Content-type': 'application/json'
                    }
                }).then(function(response){
                    // this DOES output to console!
                     console.log(response.data.drugGroup);

                     // I'm getting error with or w/o this!
                     return response.data.drugGroup;
                });
        }
   };

在你的 Controller 中:-

medicationByNameFactory.callToAPI().then(function(data){
    console.log("Works!");  // this never fires in the console!!
}).catch(function(){
   //Atleast one of the call failed
});