解析云中的关系替换

Question

In a Parse Cloud function I need to replace the value of a relation. How do I do that?

Here is my code:

Parse.Cloud.define
(“myCloudFunction”, function(request, response) {
    // Code to get myObject …….
    // ………
    // Now I have myObject in the hand.
    myObject.relation("author").add(NewAuthor);
});

If I keep this code myObject will have 2 authors: OldAuthor (whatever that was) and NewAuthor. I do not want 2 authors.

I need to get rid of what was there before first. So is there some thing like:

myObject.relation("author").replace(NewAuthor);

to just change what was there previously. I didn't find any thing browsing the net.

Answer 1

What you want is not a relation (intended for many-to-many or one-to-many relationships), you want a pointer (intended for one-to-one relationships).

This can be done by changing the column field from a relation of authors, to a pointer of authors.

Parse.Cloud.define
(“myCloudFunction”, function(request, response) {
    // Code to get myObject …….
    // ………
    // Now I have myObject in the hand.
    myObject.set("author", NewAuthor);
});

Alternatively you can just remove the old author, and add a new author to the relationship. You can do this like so:

var relation = myObject.relation("authors");

var query = relation.query();

query.find(
{
    success: function(oldAuthors)
    {
        // Code to remove all old authors from the relation
        for (var i = 0; i < oldAuthors.length; i++)
        {
            relation.remove(oldAuthors[i]);
        }
        relation.add(newAuthor);
        myObject.save();
    },
    error: function(error)
    {

    }
});