AngularJS - 无法获得$ q.reject并开始工作

Take a look at my code sample:

看看我的代码示例:

I've stripped it down to (what I believe are) the bare essentials, and I'm setting getting an error deferred.reject is not a function

我已经把它剥离到(我相信的)最基本的东西,而且我设置得到一个错误deferred.reject不是一个函数

angular
    .module('myApp')
    .service('myService', MyService);

MyService.$inject = ['$http', '$q'];

function MyService($http, $q) {
    var self = this;

    self.getResult = getResult;

    function getResult(id) {
        var deferred = $q.defer();

        deferred = $http.get('my/api/method', { params: { id: id } })
            .then(getResultCompleted)
            .catch(getResultFailed);

        function getResultCompleted(response) {
            if (response.data.ID > 0) {
                deferred.resolve(response.data);
            } else {
                deferred.reject(response);
            }
        }

        function getResultFailed(response) {
            deferred.reject(response);
        }

        return deferred.promise;
    }
}

Note: I know I can get this to work by simply returning the result of the $http call, however for the purposes of understanding these promise objects, I want to see if I can get this working by declaring and returning deferred as shown above

注意:我知道我可以通过简单地返回$ http调用的结果来实现这一点,但是为了理解这些promise对象,我想看看我是否可以通过声明并返回deferred来实现这个工作,如上所示

Thanks!

2 个解决方案

#1

You are creating custom promise and returning it from your method, but mean while dealing with it you are overriding deferred(custom promise object) with $http.get, which also returns promise which has .then & .catch methods(Which doesn't have resolve & reject method). Because of that assignment, you can't have access to .resolve and .reject from deferred object.

您正在创建自定义承诺并从您的方法返回它,但在处理它时意味着您使用$ http.get覆盖延迟(自定义承诺对象),这也返回具有.then&.catch方法的promise(其中没有有解决和拒绝的方法)。由于该分配,您无法从延迟对象访问.resolve和.reject。

deferred = $http.get('my/api/method', { params: { id: id } })

should be only

应该是唯一的

$http.get('my/api/method', { params: { id: id } })

#2

Since $http.get() returns promise and success callback supports chaining API, you can define new deferred object inside of a callback and return it from there:

由于$ http.get()返回promise并且成功回调支持链接API,因此您可以在回调中定义新的延迟对象并从那里返回它:

angular
    .module('myApp')
    .service('myService', MyService);

MyService.$inject = ['$http', '$q'];

function MyService($http, $q) {
    var self = this;

    self.getResult = getResult;

    function getResultCompleted(response) { // Tip: Define callback outside of getResult in order to avoid creating new instance of it each time getResult is called
        var deferred = $q.defer();
        if (response.data.ID > 0) {
            deferred.resolve(response.data);
        } else {
            deferred.reject(response);
        }
        return deferred.promise;
    }

    function getResult(id) {
        return $http.get('my/api/method', { params: { id: id } })
            .then(getResultCompleted);
    }
}

Note, that there is no error callback any more (just because it is redundant in this case).

注意,不再有错误回调(因为在这种情况下它是多余的)。

In case request failed, the original rejected promise from $http.get() will be returned, otherwise a brand new promise from success callback will be used for follow-up .then() calls.

如果请求失败,将返回$ http.get()的原始拒绝承诺,否则成功回调的全新承诺将用于后续.then()调用。

#1

deferred = $http.get('my/api/method', { params: { id: id } })