Question

在beforeSave挂钩中，我希望在更新之前获取对象的状态。在这种特殊情况下，它是阻止用户在完成选择后改变他们的选择。伪代码看起来像：

If (user has already voted) {
  deny;
} else {
  accept;
}

到目前为止我的代码是：

Parse.Cloud.beforeSave('votes', function(request, response) {
  if (!request.object.isNew()) {
    // This is an update.  See if the user already voted
    if (request.object.get('choice') !== null) {
      response.error('Not allowed to change your choice once submitted');
    }
  }
  response.success();
}

但request.object是已应用更新的对象的状态。

请注意，'votes'对象是单独创建的，因此不允许插入但不允许更新是不够的;我需要知道数据库中是否已经设置了一个给定的字段。

Answer 1

虽然Krodmannix的回答是正确的（并且对我有帮助），但它有完整查询的开销。如果你在beforeSave中做事，你真的想简化它们。因此，我相信fetch命令是更可取的。

Parse.Cloud.beforeSave('votes', function(request, response) {
    if (!request.object.isNew()) {
      var Votes = Parse.Object.extend("votes");
      var oldVote = new Votes();
      oldVote.set("objectId",request.object.id);
      oldVote.fetch({
        success: function(oldVote) {
            if (oldVote('choice') !== null) {
                response.error('Not allowed to change your choice once submitted');
            }
            else {
                response.success(); // Only after we check for error do we call success
            }
        },
        error: function(oldVote, error) {
            response.error(error.message);
        }
    });
});

Answer 2

您可以使用Parse DirtyKeys来识别哪个字段已更改。

   Parse.Cloud.beforeSave(Parse.User, function(request, response) {
  for (dirtyKey in request.object.dirtyKeys()) {
    if (dirtyKey === "yourfieldname") {
      response.error("User is not allowed to modify " + dirtyKey);
      return;
    }
  }
  response.success();
});

Answer 3

request变量是更新的行本身。您可以通过request.object.id获取它的对象ID，并使用它从数据库中获取当前行并检查当前值，如下所示：

Parse.Cloud.beforeSave('votes', function(request, response) {
    if (!request.object.isNew()) {
    var query = new Parse.Query("votes");
    query.get(request.object.id, { // Gets row you're trying to update
        success: function(row) {
            if (row.get('choice') !== null) 
                response.error('Not allowed to change your choice once submitted');
            response.success(); // Only after we check for error do we call success
        },
        error: function(row, error) {
            response.error(error.message);
        }
    });
}

Answer 4

如果您使用的是自托管的Parse Server，则会根据请求提供一个名为＆＃34; original＆＃34;这是改变前的对象。

Parse.Cloud.beforeSave("Post", function(request, response) {
    console.log(request.object);    //contains changes
    console.log(request.original);  //contains original
    response.success();
});

Answer 5

这项工作：

var dirtyKeys = request.object.dirtyKeys();
var query = new Parse.Query("Question");
var clonedData = null;
        query.equalTo("objectId", request.object.id);
        query.find().then(function(data){
            var clonedPatch = request.object.toJSON();
            clonedData = data[0];
            clonedData = clonedData.toJSON();
            console.log("this is the data : ", clonedData, clonedPatch, dirtyKeys);
            response.success();
        }).then(null, function(err){
            console.log("the error is : ", err);
        });

解析云代码之前获取预更新的对象

5 个答案: