Parse.com / Javascript - 将用户 objectid 字符串保存为用户指针

Question

当我拥有用户的对象 ID 时，如何保存指向对象的用户指针。

我可以将对象保存到 Parse 中的类，但受让人在 Parse 中始终是“未定义”。

例如我已经检索到用户对象，并且可以通过以下方式获取用户名/对象 ID 等：

function getUserFromUsername(username) {

Parse.initialize("...", "...");

console.log('The username passed in is: ' + username);

var User = Parse.Object.extend("_User");
var query = new Parse.Query(User);
query.equalTo("username", username);

query.first({
     success : function(result) {
        // Do something with the returned Parse.Object values
            var userPointer = new Parse.User();
            userPointer = result;
            console.log(userPointer.get('username')); // this returns the correct username
            return userPointer;

    },
    error : function(error) {
        alert("Error: " + error.code + " " + error.message);
    }
});
}

从下面的保存任务函数中调用：（注意，我已经记录了所有相关字段并且它们按预期返回。

function saveNewTask(clientName, taskTitle, taskDue, assigneeArray) {

Parse.initialize("...", "...");

var x;
for (x in assigneeArray) {

    var Task = Parse.Object.extend("Tasks");
    var task = new Task();

    task.set("title", taskTitle);
    task.set("date", taskDue);

    var thisAssignee = GetUserFromUsername(assigneeArray[x]);
    task.set('assignee', thisAssignee);

    task.save(null, {
        success : function(task) {
            // Execute any logic that should take place after the object is saved.
            console.log('New object created with objectId: ' + task.id);
        },
        error : function(gameScore, error) {
            // Execute any logic that should take place if the save fails.
            // error is a Parse.Error with an error code and message.
            console.log('Failed to create new object, with error code: ' + error.message);
        }
    });
}

}

Answer 1

所以你应该保存一个指向用户任务的指针。

var Task = Parse.Object.extend("Tasks");
var task = new Task();

task.set("user", user);
task.set("title", "taskTitle");
task.set("date", taskDue);

task.save(null, {
    success : function(task) {
        // Execute any logic that should take place after the object is saved.
        console.log('New object created with objectId: ' + task.id);
    },
    error : function(gameScore, error) {
        // Execute any logic that should take place if the save fails.
        // error is a Parse.Error with an error code and message.
        console.log('Failed to create new object, with error code: ' + error.message);
    }
});

默认情况下，在获取对象时，不会获取相关的 Parse.Objects。这些对象的值在被获取之前无法检索，如下所示：

var user = task.get("user");
user.fetch({
  success: function(user) {
       //fetch user is here
  }
});

这里有解释：https://parse.com/docs/js_guide#objects-pointers

您的脚本的问题是当您在 Parse 中查询时，它是异步完成的，因此您无法立即返回用户。相反，您需要返回承诺，然后在调用 getUserFromUsername 时处理它：

function getUserFromUsername(username) {
    var User = Parse.Object.extend("_User");
    var query = new Parse.Query(User);
    query.equalTo("username", username);
    return query.first();
}

getUserFromUsername('testUsername').then(function(result) {
    //use User here
}, function(error) {
    alert("Error: " + error.code + " " + error.message);
});

查看this document on promise chaining 了解有关承诺的更多信息：