javascript-Angular Promises：最佳做法和不同技术的优点/缺点

这个问题已经在这里有了答案：            >            What is the explicit promise construction antipattern and how do I avoid it?                                    2个
我正在学习Angular,遇到了两种方法来进行返回诺言的呼叫.我想知道一种方法是否比另一种更好,和/或何时使用每种方法.

第一种技术：

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

    if (myData) {
        // call to backend was prevIoUsly made and myData is already loaded 
        deferred.resolve(myData);
    } else {
        // get data from server
        $http.get(my_url_endpoint).then(function(response) {
            // cacheResult() will set myData = response.data
            deferred.resolve(cacheResult(response));
        });
    }

    return deferred.promise;
}

第二种技术：

function getSomeDataFromServer() {

    if (myData) {
        // call to backend was prevIoUsly made and myData is already loaded 
        return $q.when(myData);
    } else {
        // get data from server
        return $http.get(my_url_endpoint).then(function(response) {
            // cacheResult() will set myData = response.data
            return cacheResult(response);
        });
    }
}

解决方法:

总是喜欢第二种选择.第一种选择是一种反模式,通常在开发人员不完全了解承诺的性质时出现.延迟对象(var deferred = $q.defer();)使用when you have some asynchronous code that uses callbacks but needs to work with your promise based code.

您在Angular中所做的大多数异步操作都会返回Promise,因此,在处理依赖于回调的第3方库时,通常只使用deferreds.

在此示例中,$http本身返回一个promise,因此不必创建新的延迟对象.返回$http承诺本身就足够了.