I have an NSMenuItem that is enabled/disabled based on whether or not the first responder responds to a specific selector.
My problem is that there are conditions in which I do not want the item enabled for the first responder.
But I can't just conditionally remove a method definition during runtime to disable the menu item
For an example of what I mean:
I have a NSDocument-based application, and I have two main subclasses-- an ImageDocument and a VideoDocument
I have an NSMenuItem called "Capture Frame", which turns a frame of a video into an image. But obviously this should be disabled on an ImageDocument, and only enabled on a VideoDocument.
The NSMenuItem is enabled if the first responder responds to -captureFrame
The VideoDocumentController has a method, -captureFrame, so it's enabled.
The ImageDocumentController does not, so the menu item is never enabled.
But, there are specific VideoDocuments that I do not want to have that menu item enabled for. What could be the best way for me to disable this menu item in order to handle special cases?
In your VideoDocument class, override the NSDocument method validateUserInterfaceItem:. Alternatively, you can override validateUserInterfaceItem: in a subclass of NSDocumentController. Be sure to call super to keep the built-in functionality of this method. See Apple's docs on UI validation for an example.