UIManagedDocument migrate data model
问题 I am working on an iPhone app that uses a subclass of UIManagedDocument and stores its documents on iCloud. It was all working fine until I changed my core data model / scheme (adding a new model version - like I had several times in the past few weeks). I added a new property and changed the data type of one of the existing properties. Now when I run my app I don't seem to be able to load my documents with UIManagedDocument 's -openWithCompletionHandler: . I can create new documents and read