Open Radar

 
Area:
Xcode

Summary:
Swift 3.1 / Xcode 8.3 brought a bug regarding KVO notification and Swift dictionaries.
When a label is bound (cocoa bindings) to a dynamic Swift dictionary value, and the value is updated, the app crashes with a following message:

Cannot update for observer for the key path "myDict.String" from , most likely because the value for the key "myDict" has changed without an appropriate KVO notification being sent. Check the KVO-compliance of the exceptiontest.ViewController class.

Steps to Reproduce:
1. Create a simple mac app with a button and a label
2. Bind the label to a dictionary dynamic var myDict = ["String":"Initial String"] using the keypath myDict.String
3. Create an action on the button changing the value of myDict["String"]
=> app crashes

OR download the attached Xcode project for your convenience...

Expected Results:
Label to updated its value.

Actual Results:
App crashes with the following error message:

Cannot update for observer for the key path "myDict.String" from , most likely because the value for the key "myDict" has changed without an appropriate KVO notification being sent. Check the KVO-compliance of the exceptiontest.ViewController class.

Version:
10.12.4 (16E195)

Notes:


Configuration:
Xcode 8.3

Attachments:
'testappmac.zip' was successfully uploaded.