Binding in OSX: class is not key value coding-compliant for the key {name of binding var}

Question

I was trying to follow instructions from Learning Swift book (creating note taking app) by B.A. Paris & Co, but faced with the following problem with binding. I am mostly practicing iOS programming, so binding concept is new for me.

Steps I made (tried both xcode 9 beta 5 and 8.3.3):

1. Create OSX Cocoa App (not using storyboard, document based app – on, document extension “test”, don’t use core data)
2. Add “var text = NSAttributedString()” to Document.swift
3. Add a NSTextView to Document.xib
4. In Bindings inspector of NSTextView setting “Attributed String” to File’s owner “self.text” (Model Key Path)

And I see exclamation mark with notion “Xcode cannot resolve the entered key path” Build is successful, but when I run it says “2017-09-03 22:17:40.739643+0200 test3[6017:424072] [<test3.Document 0x6180000c3410> valueForUndefinedKey:]: this class is not key value coding-compliant for the key text.”

I tried to control drag from Xib to Swift, it warns that “Xcode cannot locate the class Document in the current workspace”.

I tried to convert to workspace instead of proj, checked the file owner, checked the stackoverflow threads witch relate to the error – but they mostly concerned about some connection made by mistake or non actual connections (I can delete the connection, I know what connection is wrong, the question is how to make it right). So far could not find solution.

Thanks in advance

Answer 1

You need to declare the text property with the @objc attribute to make it accessible via dynamic dispatch like Key-Value Coding.

Also, because you want modifications of the property to be observable via Key-Value Observing (for Bindings), you need to tell Swift to always dispatch modifications of it dynamically. So, you need to use the dynamic modifier on the declaration, too:

@objc dynamic var text = NSAttributedString()