Question

我对承诺很新，我的后续代码产生了一些意想不到的结果，但我不知道为什么。

Main.js中的Taskrunner.SyncObjects函数应该等待填充的selectedCourses变量，但它不会立即触发。这会导致使用空的selectedCourses变量。

为什么在获得结果之前运行TaskRuner.SyncObjects函数？

Main.js

function StartSync(){

var a = Settings.LoadCourseList(standardOSPathUserData);
var b = a.then(function(){
    console.log("b is running");
    var selectedCourses = Settings.courseList;

    return TaskRunner.SyncObjects(selectedCourses).then(function(){
        fileSyncRunning = false;
    });
}).catch(function(error){
    console.log("StartSync Error message: " + error);
});

}

Settings.js

Settings.LoadCourseList = function(osPath){
  var pathToCourseListSettings = osPath + courseListFileName;
  return new Promise(function(resolve, reject){
            try {
                return connection.Login().then(function(){
                    return connection.GetCourseList().then(function(result){
                        var allCourses = [];
                        for(var p=0; p<=result.length-1;p++){
                          allCourses.push({courseID: result[p].courseID, courseName: result[p].courseName, selected: true});
                        }
                        courseListJSON = JSON.stringify(allCourses);
                        return courseListJSON;
                    }).then(function(courseListJSON){
                        fs.appendFileSync(pathToCourseListSettings,courseListJSON,encoding='utf8');
                        console.log("New Course settings file created and filled: " + pathToCourseListSettings);
                        return resolve();
                    });
                }).then(function(){
                    return resolve();
                });
            } catch (e) {
                console.log("FAIL courseList settingsfile creation - Error: " + e.code);
                return reject(e);
            }
  });
};

Answer 1

在Settings.js

中似乎从未为Settings.courseList分配值

您可以尝试添加

Unhandled rejection TypeError: expecting an array or an iterable object but got [object Null]

之前的

app.get('/test/models', function(req, res) {

        var values = { 
            where: { user_id: 7 } 
        };

        MercadoLibre.findOne(values)
        .spread(function(err, meli) {

            console.log(err);

            if (typeof meli !== null) {
                console.log("undefined");
            } else {
                console.log(meli);    
            }

            res.redirect('/dashboard');
        });
    });

或者更好的是，您可以采用承诺方式，并通过allCourses解决承诺。

从Settings.LoadCourseList（standardOSPathUserData）做出承诺;返回allCourse，改变

Settings.courseList = allCourses;

到

courseListJSON = JSON.stringify(allCourses);

并接收该承诺结果更改

return connection.Login().then(function(){
    return connection.GetCourseList().then(function(result){
        var allCourses = [];
        for(var p=0; p<=result.length-1;p++){
          allCourses.push({courseID: result[p].courseID, courseName: result[p].courseName, selected: true});
        }
        courseListJSON = JSON.stringify(allCourses);
        return courseListJSON;
    }).then(function(courseListJSON){
        fs.appendFileSync(pathToCourseListSettings,courseListJSON,encoding='utf8');
        console.log("New Course settings file created and filled: " + pathToCourseListSettings);
        return resolve();
    });
}).then(function(){
    return resolve();
});

到

return connection.Login().then(function(){
    return connection.GetCourseList().then(function(result){
        var allCourses = [];
        for(var p=0; p<=result.length-1;p++){
          allCourses.push({courseID: result[p].courseID, courseName: result[p].courseName, selected: true});
        }
        var courseListJSON = JSON.stringify(allCourses);
        fs.appendFileSync(pathToCourseListSettings,courseListJSON,encoding='utf8');
        console.log("New Course settings file created and filled: " + pathToCourseListSettings);
        return allCourses;
    });
});

在等待结果之前，承诺被解雇

1 个答案: