Cannot use respondsToSelector using ARC on Mac

Solution 1:

Make the protocol conform to NSObject

@protocol MTScrollViewDelegate <NSObject>

Otherwise the compiler doesn't think that the object will respond to NSObject messages like respondsToSelector, and will generate a warning. It will succeed at runtime without issues either way.

Solution 2:

For Swift this becomes:

@objc protocol MTScrollViewDelegate: NSObjectProtocol

The NSObject protocol groups methods that are fundamental to all Objective-C objects.

For more information on what NSObjectProtocol is: https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Protocols/NSObject_Protocol/index.html