Nested interface
Protocols
Declaration and initialization
Method requirements
Property requirements
Constructor requirements
Subscript requirements
Inheritance of protocols
Protocol composition
Conformance checking (is, as)
Collection of protocols
Type extension
Protocol extension
Class-only protocols
Optional requirements
Associated type
Mutating methods
Protocol adoption
Protocol extension constraints
Nested interface
class
Button
{
protocol
Style
{}
}
class
ImageButton
:
Button
.
Style
{}
Languages
Objective-C