2.3File locking

If you take one habit away from this book, take this one.

Unreal's binary files do not merge. Two people editing the same level means one of them loses the work, and no version control system — not this one, not Perforce, not anything — can reconcile it afterwards. The only real fix is to make the collision impossible, and that means claiming the file before you open it.

Taking a lock

1. 1

   Right-click the file and choose Lock

   You can select several files first and lock them together — the whole level plus the Blueprints you are about to touch.

2. 2

   Everyone sees it immediately

   The file shows a padlock with the holder's name and face in the desktop app, and in the project's file browser on the web. Nobody has to ask in chat who has the level.

3. 3

   Release it when you push

   Right-click and choose Release lock. The habit worth building is lock, work, commit, release — in that order, every time.

  Sarah                                        Marcus
    │                                            │
    ├── locks MainLevel.umap ──────────────────► sees the padlock
    │                                            and Sarah's face
    ├── opens it in the editor                   │
    ├── works                                    picks a different task
    ├── commits                                  │
    └── releases the lock ─────────────────────► padlock clears

Locks are advisory, and that is the point

A lock does not make the file read-only on anyone's disk. It could — and some systems do that — but a hard lock turns every forgotten release into someone else being blocked at 2am with nobody around to clear it.

What a lock does is make the situation visible before it becomes expensive. In practice that is what prevents the collision: nobody opens a level they can see is checked out.