蓝鸟承诺返回“未定义"当在“then"里面返回时功能

问题描述

限时删除！！

这是我的代码:

检查用户是否关注官方 Twitter 帐户(这里我返回了新的 Promise

var isFollowing = function(sender) {
    return new promise(function(resolve, reject) {
        var following = false;
        var params = {
            source_id: sender,
            target_screen_name: config.get('twitter.official_account')
        };
        TwitObj.get('friendships/show', params, function(err, data) {
            if (!err) {
                following = data.relationship.source.following;
                resolve(following);
            } else {
                reject(err);
            }
        });
    });
};

验证:

var validateMsg = function(dm) {
    var sender = getSender(dm);
    var result = [];
    isFollowing(sender.id)
        .then(function(response) {
            if (!response) {
                result = interactiveMessage(false, lang.__('FOLLOW_MAIN', sender.name));
                console.log(result); // Displays as expected
                return result; // Not returning value Do I need to return promise again? If yes, WHY?
            }
        });
};

主要实现:

var direct_message = function(msg) {
    verifyAccount().catch(function(err) {
        console.error(err);
    });
    var dm = msg.direct_message;
    var result = validateMsg(dm);

    console.log(result);
};

问题是我应该如何强制 validateMsg 函数在 then 函数中返回 result 变量.

Questions is how should I force validateMsg function to return result variable inside then function.

更新:在调试时，我了解到，console.log(response) 在抛出 undefined 后，验证函数稍后显示then"函数，表示程序无法得到响应由于异步性质，I/O 不会立即被阻塞.如何解决这个问题?

推荐答案

您实际上并未在 validateMsg 函数中返回任何内容.您在 .then 函数中返回一个同步值 ( result )，这是一个单独的函数.

You're not actually returning anything in the validateMsg function. You're returning a synchronous value ( result ) in the .then function which is a separate function.

要考虑的第二件事是您期待 validateMsg 函数，它是异步的以同步行为.

The second thing to consider is that you're expecting the validateMsg function, which is asynchronous to behave synchronously.

var 结果 = validateMsg(dm);

实现我认为您想要做的事情的方法包括进行以下更改:1)在validateMsg函数中返回promise链.

The way to achieve what I believe you're looking to do involves making the following changes:1) Return the promise chain in the validateMsg function.

    var validateMsg = function(dm) {
    var sender = getSender(dm);
    var result = [];
    return isFollowing(sender.id)
      .then(function(response) {
          if (!response) {
              result = interactiveMessage(false, lang.__('FOLLOW_MAIN', sender.name));
              return result;
          }
        // Not sure what you want to do here if there is a response!
        // At the moment you're not doing anything if the validation
        // is successful!
        return response;
    });

};

2) 更改您的函数调用，因为您现在要返回一个 promise.

2) Change your function call, since you're now returning a promise.

    validateMsg(dm).then( function( result ){
      console.log( result );
    })

3) 如果只是为了帮助您调试，请考虑在某处添加一个 catch :)

3) Consider adding a catch somewhere if only to help you debug :)

    validateMsg(dm).then( function( result ){
      console.log( result );
    })
    .catch( function( err ){
      console.log( "Err:::", err );
    });

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