In Swift, what does it mean for protocol to inherit from class keyword?

Question

In Swift, what does it mean for protocol to inherit from class keyword?

e.g.

protocol MyDelegate: class {

}

Answer 1

From the Apple docs:

You can limit protocol adoption to class types (and not structures or enumerations) by adding the class keyword to a protocol’s inheritance list.

Example:

protocol AProtocol: class {   
}

//Following line will produce error: Non-class type 'aStruct' cannot conform to class protocol 'AProtocol'
struct aStruct: AProtocol { 
}

The line declaring the structure will spit an error. Following line will produce error:

Non-class type 'aStruct' cannot conform to class protocol 'AProtocol'