javascript - 如何使 jQuery Deferred 对象解析/拒绝具有与另一个 deferred 相同的 'resolved/rejected' 状态？

Question

我正在编写几个函数，这些函数实际上是依赖于其他延迟对象的不同组合的延迟对象。

function takesOneSecond() {
    return $.Deferred(function(deferred) {
        // Does something...
    }).promise();
}

function takesOneMinute() {
    return $.Deferred(function(deferred) {
        // Does something...
    }).promise();
}

function takesThreeMinutes() {
    return $.Deferred(function(deferred) {
        // Does something...
    }).promise();
}

function mySwitchingFunction() {

    return $.Deferred(function(deferred) {

        // Does something here..
        // Effectively chooses one of several other functions to call.

        if(/* choose 1 second */) {

            // We tie ourselves to the '1 second' function.

            // Call that function.
            takesOneSecond().done(function() {

                deferred.resolve(); // If that's done, I'm done too.

            }).fail(function() {

                deferred.reject(); // If that failed, I've failed too.

            });

        } else if(/* choose 1 minute */) {

            // Etc..

        } else if(/* choose 3 minutes */) {

            // Etc..

        }

    }).promise();

}

我经常写这段代码，有没有其他方法可以制作一个延迟镜像或级联另一个延迟的相同“已解决”或“拒绝”状态？

takesOneSecond().done(function() {
    deferred.resolve(); // If that's done, I'm done too.
}).fail(function() {
    deferred.reject(); // If that failed, I've failed too.
});

Answer 1

我认为你根本不需要构建一个新的 promise 。只需返回第一个 promise 即可。

function mySecondFunction() {
    // Does something here..
    // Effectively chooses one of several other functions to call.
    // In this case, assume I've just chosen the 'myFirstFunction' function.

    // Call that function and return its promise
    return myFirstFunction();
}

如果你想强调“同时”部分但可能用不同的值解决，你可以通过链接 .then 来创建一个新的:

function mySecondFunction() {
    return myFirstFunction().then(function(resultOfFirst) {
        // but ignore it and
        return differentResult;
    }); // errors will propagate automatically
}