NSMutableCopying

NSMutableCopying is a protocol in Objective-C that allows mutable objects to provide a way to create a shallow copy of themselves. This protocol is part of the Foundation framework. An object that conforms to NSMutableCopying is expected to implement the mutableCopy method. This method returns a new mutable object that is a copy of the original object. The term "shallow copy" means that the new object is a separate instance, but if the original object contains references to other objects, the new object will contain references to the same other objects, not copies of them.

To conform to the NSMutableCopying protocol, a class must declare that it conforms and implement the required method: -(id)mutableCopy. This method should create and return a new instance of the object, populating it with the state of the receiver. The returned object should be mutable, meaning its contents can be changed after creation. For example, a mutable array that conforms to NSMutableCopying can create a new mutable array containing the same elements.

The NSCopying protocol, which is often used in conjunction with NSMutableCopying, provides a way to create immutable copies. While NSCopying's copy method typically returns an immutable object, NSMutableCopying's mutableCopy method specifically returns a mutable object. This distinction is important for developers who need to create modifiable copies of their mutable objects without affecting the original. Using mutableCopy is a standard way to ensure that modifications to a copy do not alter the source object.