Protocols

Question 1

Protocol

Answer 1

A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality. The protocol can then be adopted by a class, structure, or enumeration to provide an actual implementation of those requirements. Any type that satisfies the requirements of a protocol is said to conform to that protocol.

Question 2

Adding Property Requirements

Answer 2

• A protocol can have properties as well as methods that a class, enum or struct conforming to this protocol can implement.
• A protocol declaration only specifies the required property name and type. It doesn’t say anything about whether the property should be a stored one or a computed one.
• A protocol also specifies whether each property must be gettable or gettable and settable.
• Property requirements are always declared as variable properties, prefixed with the var keyword.
• Gettable and settable properties are indicated by writing { get set } after their type declaration, and gettable properties are indicated by writing { get }.

Question 3

Protocols with mutating methods

Answer 3

Mutating methods are methods that we use on value types like structs and enums. These methods are allowed to modify the instance it belongs to and any properties of that instance.

Question 4

Protocols as Types

Answer 4

Protocol is a type. You can use it in many places like:

As a parameter type or return type in a function, method, or initializer

As the type of a constant, variable, or property

As the type of items in an array, dictionary, or other container

Question 5

Delegation

Answer 5

Delegation is a design pattern that enables a class or structure to hand off (or delegate) some of its responsibilities to an instance of another type. Delegation pattern can also be used as a callback kind of mechanism.

Question 6

Adding Protocol Conformance with an Extension

Answer 6

You can extend an existing type to adopt and conform to a new protocol, even if you do not have access to the source code for the existing type. Extensions can add new properties, methods, and subscripts to an existing type, and are therefore able to add any requirements that a protocol may demand.

Question 7

Declaring Protocol Adoption with an Extension

Answer 7

If a type already conforms to all of the requirements of a protocol, but has not yet stated that it adopts that protocol, you can make it adopt the protocol with an empty extension:
Types do not automatically adopt a protocol just by satisfying its requirements. They must always explicitly declare their adoption of the protocol.

Question 8

Protocol Inheritance

Answer 8

A protocol can inherit one or more other protocols. The syntax of protocol inheritance is similar to class inheritance.
Suppose there is a struct conforming to the Inheriting protocol, it should also conform and satisfy all the other protocols that Inheriting protocol inherits from.