Cancel Edit View Realm.io Database

Question

I want to create an edit view for an existing object model in a Realm.io database. The view controller has a save button which should persist the changes and a cancel button which should discard the changes.

I can not modify a RLMObject outside of a write transaction, so what is the recommended method of temporarily modifying a RLMObject enabling me to discard the changes later if necessary?

Answer 1

You could pass your realm object in to your edit view controller as an in-memory object to do your editing. Like so:

RLMRealm *realm = [RLMRealm defaultRealm];
[realm beginWriteTransaction];
[StringObject createInDefaultRealmWithObject:@[@"a"]];
[realm commitWriteTransaction];

StringObject *obj = [[StringObject alloc] initWithObject:[[StringObject allObjects] firstObject]];
XCTAssertEqualObjects(obj.stringCol, @"a");
obj.stringCol = @"b"; // not in a write transaction
XCTAssertEqualObjects(obj.stringCol, @"b");

If the user presses "Save", you can then call createOrUpdateInDefaultRealmWithObject: and pass in your in-memory object, which will then pass in all the values and update that object in Realm. Note that your object must have a primary key for this to work.

If the user presses "Cancel", you can just discard that in-memory object as if nothing happened.

Note that we intend to add transaction rollback functionality in the future, which will simplify this pattern.