javascript - 为什么 .then() 不等待 promise ？

Question

我目前正在开发一个 Angular 项目，而且我对它还很陌生。

我不明白，为什么 .then() 函数不等待 promise ？

我认为它必须与我的 getAllStats() 函数中只有一个 $q.defer() 相关吗？当我尝试 console.log("testing: ", data); (在底部)时，它只记录出一个空数组。有人可以帮我吗？

这是我的代码:

function getAllStats(dataArray, nameOfFile) {
    var defer = $q.defer();
    var promises = [];


    for (index in dataArray) {
        if (dataArray[index].indexOf('test') > -1 ) {
            getStats(nameOfFile).then(function (data) {
                 promises.push();
            });
        }
    }

    function last() {
        defer.resolve(promises);
    }

    $q.all(promises).then(last);
    return defer.promise;
};

function getStats(nameOfFile) {
    var defer = $q.defer();
    $http.get(nameOfFile).success(function (data) {
        defer.resolve(data);
    });
        return defer.promise;
};

getAllStats('test.txt').then(function(data) {
        console.log("testing: ", data);
});

Answer 1

请参阅此代码中的注释:

function getAllStats(dataArray, nameOfFile) {
    var promises = [];
    // using `for (index in dataArray) {` is a bad idea unless
    // dataArray is a non-array object
    for (var index = 0; index < dataArray.length; index++) {
        if (dataArray[index].indexOf('test') > -1 ) {
            // Here is the trick, store the promise itself,
            // don't try to subscribe to it here
            promises.push(getStats(nameOfFile));
        }
    }
    return $q.all(promises);
};

function getStats(nameOfFile) {
    // http.get already returns a promise, see explicit promise creation antipattern
    return $http.get(nameOfFile).then(function(r) { return r.data; });
};

getAllStats('test.txt').then(function(data) {
        console.log("testing: ", data);
});

引用文献:

• Explicit promise creation antipattern
• Why is for..in bad

Deprecation Notice

The $http legacy promise methods success and error have been deprecated. Use the standard then method instead. If $httpProvider.useLegacyPromiseExtensions is set to false then these methods will throw $http/legacy error.

see: $http