解析云代码。 无法定义关系

Question

I am calling this function from my android app,

Parse.Cloud.define('addFriendRequest', function(request, response) {
var userObjectId = request.params.userObjectId;


var User = Parse.Object.extend('_User'),
    user = new User({ objectId: userObjectId });

var relation = Parse.Relation(user, 'friendRequests');
relation.add(request.user);

Parse.Cloud.useMasterKey();
user.save().then(function(user) {
    response.success("Successfully added friend Request");
}, function(error) {
    response.error("An error has occurred")
});

});

And an errror is being thrown of type

TypeError: Cannot call method 'add' of undefined at main.js:10:11

I am relatively new to javascript so any advice would be great. Also the relation friendRequests exists already.

Answer 1

This should work.

Parse.Cloud.define('addFriendRequest', function(request, response) {
Parse.Cloud.useMasterKey();
var userObjectId = request.params.userObjectId;
var user = Parse.User.createWithoutData(userObjectId);
var relation = user.relation('friendRelation');
relation.add(request.user);
user.save().then(function(user) {
    response.success("Successfully added friend Request");
}, function(error) {
    response.error("An error has occurred")
});
});

Some clarification of what is going on here and why your code did not work.

1. First of all, it is a good practice to put Parse.Cloud.useMasterKey(); right in the beginning of the function.
2. I see that you have the objectId of user in the beginning and that you would like to use the user based on its objectId. I order to do that, you should use Parse.User.createWithoutData('yourObjectIdHere') method. What you are actually doing for this step, is that you are creating a new user, rather then creating a reference for the one you already have in the database.
3. If you want to get a relation of a particular object (User object in your case) your use Parse.Object.relation('putRelationKeyHere') . You are actually creating a new relation instead of accessing the existing one.

I would recommend you to read Parse Javascript Guide in order to learn the recommended techniques.