CODEWITHSUNDEEP
javascriptparse-platform
user1596371
user1596371

Reputation:

Parse cloudcode beforeSave obtain pre-updated object

In a beforeSave hook I want to obtain the state of the object prior to the update. In this particular case it is to stop a user from changing their choice once they have made it. Pseudo-code looks something like:

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

And the code that I have so far is:

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();
}

But request.object is the state of the object with the update already applied.

Note that the 'votes' object is created separately so this isn't allowing an insert but not an update will not suffice; I need to know if a given field is already set in the database.

Upvotes: 12

Views: 5624

Answers (5)

Marc Smith
Marc Smith

Reputation: 349

If you are using the self hosted Parse Server, there is a property on request called "original" that is the object before changes.

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

Upvotes: 12

daksh_019
daksh_019

Reputation: 862

This Worked :

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);
        });

Upvotes: 0

krodmannix
krodmannix

Reputation: 845

The request variable is the updated row itself. You can get it's object id through request.object.idand use this to grab the current row from the database and check the current value, like so:

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);
        }
    });
}

Upvotes: 9

Abdul Vajid
Abdul Vajid

Reputation: 1411

You can use Parse DirtyKeys to identify which field has changed. 

   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();
});

Upvotes: 10

MobileVet
MobileVet

Reputation: 2958

While Krodmannix's response is correct (and was helpful to me) it has the overhead of a full query. If you are doing things in beforeSave, you really want to streamline them. As a result, I believe a fetch command is much preferable.

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);
        }
    });
});

Upvotes: 16

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