Protocol:

A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality.

C#: Interface。ただし、inerfaceのメソッドはすべて実装する必要あり

Protocol Syntax

定義

protocol SomeProtocol {
    // protocol definition goes here
}

実装(struct)

struct SomeStructure: FirstProtocol, AnotherProtocol {
    // structure definition goes here
}

class

class SomeClass: SomeSuperclass, FirstProtocol, AnotherProtocol {
    // class definition goes here
}

C#:

interface SomeProtocol {
    void Do (); 
}

public struct SomeStructure :SomeProtocol
    //, AnotherProtocol
{
    public void Do(){
        Console.WriteLine ("struct do");
    }   
}
public class SomeClass: SomeProtocol
    //,SomeSuperclass, FirstProtocol, AnotherProtocol 
{
    public void Do(){
        Console.WriteLine ("class do");
    }   
}

Property Requirements

  1> protocol FullyNamed { 
  2.     var fullName: String { get } 
  3. }

  4>  
  5> struct Person: FullyNamed { 
  6.     var fullName: String 
  7. } 
  8.  
  8> let john = Person(fullName: "John Appleseed")                                                                                                          
john: Person = {
  fullName = "John Appleseed"
}

C#:

interface FullyNamed 
{
    string fullName { 
        get;
    }
}

public struct Person: FullyNamed {

    public Person(string fullName)
    { _fullName = fullName; }

    public string fullName { 
        get{ return _fullName;}
    }
   
    public string _fullName;    // public はあまり意味ないけど
}

var john = new Person("John Appleseed") 
Console.WriteLine(john.fullName);

Method Requirements

プロトコル

  2> protocol RandomNumberGenerator { 
  3.     func random() -> Double 
  4. }

実装

  6> class LinearCongruentialGenerator: RandomNumberGenerator { 
  7.     var lastRandom = 42.0 
  8.     let m = 139968.0 
  9.     let a = 3877.0 
 10.     let c = 29573.0 
 11.     func random() -> Double { 
 12.         lastRandom = ((lastRandom * a + c) % m) 
 13.         return lastRandom / m 
 14.     } 
 15. }

Mutating Method Requirements

破壊メソッド要件 = mutatin func

protocol Togglable {
    mutating func toggle()
}

Initializer Requirements

イニシャライザ

protocol Togglable {
    mutating func toggle()
}

Class Implementations of Protocol Initializer Requirements

サブクラスへの required 強制 (designated initializer/convenience initializer)

class SomeClass: SomeProtocol {
    required init(someParameter: Int) {
        // initializer implementation goes here
    }
}

( Required Initializers )

プロトコルイニシャライザinit()

protocol SomeProtocol {
    init()
}

スーパークラスで init()を定義済み

class SomeSuperClass {
    init() {
        // initializer implementation goes here
    }
}

よって、サブクラスでは override 必要

class SomeSubClass: SomeSuperClass, SomeProtocol {
    // "required" from SomeProtocol conformance; "override" from SomeSuperClass
    required override init() {
        // initializer implementation goes here
    }
}

Protocols as Types

プロパティ(メンバー)の型を Protocolで宣言できる

  1> protocol PersonProtocol {  
  2.     var name: String { get set }  
  3.     init(name: String)  
  4. }

  7. class Person: PersonProtocol {  
  8.     var name: String  
  9.     required init(name: String ) { self.name = name }  
 10. }

 12. class Student : Person { }  

 15. class Employee : Person { }

 18. class Circle {  
 19.     var members : [PersonProtocol] = [] 
 20.     init(members: [PersonProtocol]) { self.members = members } 
 21. }

 22> var c = Circle(members:[Student(name:"Alice"), Employee(name:"Bob")])

c: Circle = {
  members = 2 values {
    [0] = {
      __lldb_expr_1.Person = {
        name = "Alice"
      }
    }
    [1] = {
      __lldb_expr_1.Person = {
        name = "Bob"
      }
    }
  }
}

 23> c.members[0] is PersonProtocol
/var/folders/3n/0lk686q1129clzkw38blpwdc0000gp/T/lldb/43277/repl14.swift:2:14: error: 'is' test is always true
c.members[0] is PersonProtocol
             ^

 23> c.members[0] is Employee
$R0: Bool = false
 24> c.members[0] is Student
$R1: Bool = true
 25> c.members[0] is Person
$R2: Bool = true

C#:

public interface IPerson
{
    string name {get;set;}
}

public class Person: IPerson{
    public string name {get;set;}
}

public class Student: Person {}
public class Employee: Person {}

public class Circle 
{
   public List<IPerson>  members {get;set; }
}

C#

var c = new Circle{ members = new List<IPerson>{
        new  Student{name="Alice"},
        new  Employee{name="Bob"},
    }};

foreach(var p in c.members){
   Console.WriteLine(p.name + "********");
   Console.Write(p is IPerson); Console.Write(",");
   Console.Write(p is Person);Console.Write(",");
   Console.Write(p is Student);Console.Write(",");
   Console.Write(p is Employee);Console.WriteLine(",");

Alice********
True,True,True,False,
Bob********
True,True,False,True,

Delegation

"Delegation Pattern":

, the delegation pattern is a design pattern in object-oriented programming where an object, instead of performing one of its stated tasks, delegates that task to an associated helper object.

There is an Inversion of Responsibility in which a helper object, known as a delegate, is given the responsibility to execute a task for the delegator.

Apple "Delegation"

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.

This design pattern is implemented by defining a protocol that encapsulates the delegated responsibilities, such that a conforming type (known as a delegate) is guaranteed to provide the functionality that has been delegated.

  1> protocol MonotonousDelegate 
  2. { 
  3.    func send_fax() 
  4.    func check_mail() 
  5. } 
  6.  
  7. protocol MamagementDelegate 
  8. { 
  9.    func allocate() 
 10.    func review() 
 11. } 
 12.  
 13. class Employee 
 14. { 
 15.    var name : String 
 16.    init(name: String){ self.name = name } 
 17. } 
 18.  
 19. class Secretary : Employee, MonotonousDelegate 
 20. { 
 21.   func send_fax(){ println("\(name) is sending a fax.") } 
 22.   func check_mail(){ println("\(name) is checking mails .") } 
 23. } 
 24. class Manager: Employee, MonotonousDelegate, MamagementDelegate 
 25. { 
 26.     var secretary : Secretary? 
 27.     init (name: String, secretary: Secretary? = nil ) 
 28.     { super.init(name: name) ; self.secretary = secretary } 
 29.  
 30.     func send_fax(){ secretary?.send_fax() } 
 31.     func check_mail() { secretary?.check_mail() } 
 32.     func allocate(){ println("\(name) is allocation a tast.") } 
 33.     func review(){ println("\(name) is review outcome.") } 
 34. }

 38> var bob = Manager(name: "Bob")
bob: Manager = {
 __lldb_expr_1.Employee = {
   name = "Bob"
 }
 secretary = nil
}

 39> var dave = Manager(name: "Dave", secretary: Secretary(name:"Alice")) 
dave: Manager = {
  __lldb_expr_1.Employee = {
    name = "Dave"
  }
  secretary = Some {
    __lldb_expr_1.Employee = {
      name = "Alice"
    }
  }
}

 40> bob.check_mail()
 41> dave.check_mail()
Alice is checking mails .

Adding Protocol Conformance with an Extension

既存クラス(別人が作ったクラス)に"Extensions"の仕組みでプロトコルを追加できる

 36. public protocol CleanerProtocol{ 
 37.     func clean_desk() 
 38. }

 41. extension Manager: CleanerProtocol  
 42. { 
 43.     public func clean_desk () { println("\(name) is clearing hes/her desk.") } 
 44. }

 47> edit.clean_desk()
Edie is clearing hes/her desk.
 48> var edie = Manager(name:"Edie")
edie: Manager = {
  __lldb_expr_1.Employee = {
    name = "Edie"
  }
  secretary = nil
}

 49> edit.clean_desk()
Edie is clearing hes/her desk.

これでいいような気もするんですが

 40> class ManagerEx: Manager, CleanerProtocol 
 41. { 
 42.     func clean_desk () { println("\(name) is clearing hes/her desk.") } 
 43. }

 44> var fred = ManagerEx(name:"Fred")
fred: ManagerEx = {
  __lldb_expr_1.Manager = {
    __lldb_expr_1.Employee = {
      name = ""
    }
    secretary = nil
  }
}
 45> fred.clean_desk()
Fred is clearing hes/her desk.

Declaring Protocol Adoption with an Extension

 40> class Student 
 41. { 
 42.    var name : String 
 43.    func clean_desk() { println("Of cource, \(name) can clean hes/her desk.") } 
 44.    init(name: String) { self.name = name } 
 45. }

 46> var angie = Student(name:"Angie")
angie: Student = {
  name = "Angie"
}
 47> angie is CleanerProtocol


/var/folders/3n/0lk686q1129clzkw38blpwdc0000gp/T/lldb/44365/repl11.swift:2:7: error: cannot downcast from 'Student' to non-@objc protocol type 'CleanerProtocol'
angie is CleanerProtocol
~~~~~ ^  ~~~~~~~~~~~~~~~

Studentは clean_desk()できるが、プロトコル拡張してみる

 47> extension Student: CleanerProtocol {}

 49> var bill = Student(name:"Bill")
bill: Student = {
  name = "Bill"
}
 50> bill is CleanerProtocol
 
 
/var/folders/3n/0lk686q1129clzkw38blpwdc0000gp/T/lldb/44365/repl16.swift:2:5: error: 'is' test is always true
bill is CleanerProtocol
     ^
     ~~~

Collections of Protocol Types

 18> var members : [PersonProtocol] = [Student(name:"Angie"), Employee(name:"Bill")] 
 
 
members: [PersonProtocol] = 2 values {
  [0] = {
    __lldb_expr_1.Person = {
      name = "Angie"
    }
  }
  [1] = {
    __lldb_expr_1.Person = {
      name = "Bill"
    }
  }
}

Protocol Inheritance

継承できる

 13. protocol BossProtocol: MonotonousDelegate, MamagementDelegate 
 14. { 
 15. }

C#:

public interface IMonotonous
{
   void send_fax();
   void check_mail();
}

public interface IMamagement
{
   void allocate();
   void review();
}

public interface IBoss: IMonotonous, IMamagement
{
}


//public class DivisionManager : IBoss
//{
//    (1,15): error CS0535: `DivisionManager' does not implement interface member `IMonotonous.send_fax()'
//    (1,15): error CS0535: `DivisionManager' does not implement interface member `IMonotonous.check_mail()'
//    (1,15): error CS0535: `DivisionManager' does not implement interface member `IMamagement.allocate()'
//    (1,15): error CS0535: `DivisionManager' does not implement interface member `IMamagement.review()'
//}

Class-Only Protocols

"class" 制約で、クラスのみ実行可能なプロトコルを定義

  1> protocol Speakable : class { 
  2.     func speak() 
  3. }

  5. struct Animan: Speakable { 
  6.     func speak() { println("Can't speak") } 
  7. }
/var/folders/3n/0lk686q1129clzkw38blpwdc0000gp/T/lldb/44627/repl1.swift:6:1: error: non-class type 'Animan' cannot conform to class protocol 'Speakable'
struct Animan: Speakable {
^

Protocol Composition

It can be useful to require a type to conform to multiple protocols at once.

You can combine multiple protocols into a single requirement with a protocol composition.

  1> protocol Named { 
  2.     var name: String { get } 
  3. }    
  4. protocol Aged { 
  5.     var age: Int { get } 
  6. }    
  7. struct Person: Named, Aged { 
  8.     var name: String 
  9.     var age: Int 
 10. }

 18> func wishHappyBirthday(celebrator: protocol<Named, Aged>) { 
 19.     println("Happy birthday \(celebrator.name) - you're \(celebrator.age)!") 
 20. }

 22. let p = Person(name: "Malcolm", age: 21)

p: Person = {
  name = "Malcolm"
  age = 21
}

 23> wishHappyBirthday(p)
Happy birthday Malcolm - you're 21!

 24> struct Animal: Named { 
 25.     var name: String 
 26.     var age: Int 
 27. }

 28> let a = Animal(name: "Genie", age:7 )


a: Animal = {
  name = "Genie"
  age = 7
}

 29> wishHappyBirthday(a)
/var/folders/3n/0lk686q1129clzkw38blpwdc0000gp/T/lldb/44710/repl14.swift:2:19: error: type 'Animal' does not conform to protocol 'Aged'
wishHappyBirthday(a)
                  ^
/var/folders/3n/0lk686q1129clzkw38blpwdc0000gp/T/lldb/44710/repl6.swift:2:24: note: in initialization of parameter 'celebrator'
func wishHappyBirthday(celebrator: protocol<Named, Aged>) {

Checking for Protocol Conformance

Type Casting 参考。

is で型確認

The is operator returns true if an instance conforms to a protocol and returns false if it does not.

as? でダウンキャスト。型が合わなければnil

The as? version of the downcast operator returns an optional value of the protocol’s type, and this value is nil if the instance does not conform to that protocol.

asだとダウンキャストが失敗するとエラー

The as version of the downcast operator forces the downcast to the protocol type and triggers a runtime error if the downcast does not succeed.

~~
47> alice as MonotonousDelegate
$R1: Secretary = {
__lldb_expr_1.Employee = {
name = "Alice"
}
}


ん？

48> alice as? MamagementDelegate
/var/folders/3n/0lk686q1129clzkw38blpwdc0000gp/T/lldb/44843/repl38.swift:2:7: error: cannot downcast from 'Secretary' to non-@objc protocol type 'MamagementDelegate'
alice as? MamagementDelegate

~~~

@obj 修飾: 

> You can check for protocol conformance only if your protocol is marked with the @objc attribute,....

え？NOTEに書く事なんですかね。

>  This attribute indicates that the protocol should be exposed to Objective-C code and is described in Using Swift with Cocoa and Objective-C. 

> Even if you are not interoperating with Objective-C, you need to mark your protocols with the @objc attribute if you want to be able to check for protocol conformance.

そしてクラスのみ

> Note also that @objc protocols can be adopted only by classes, and not by structures or enumerations. 


~~~
import Foundation

@objc protocol MonotonousDelegate
{
   func send_fax()
   func check_mail()
}

@objc protocol MamagementDelegate
{
   func allocate()
   func review()
}

~~~



~~~
 43> alice as MonotonousDelegate 
$R0: Secretary = {
  __lldb_expr_10.Employee = {
    name = "Alice"
  }
}
 44> alice as? MamagementDelegate
$R1: MamagementDelegate? = nil
~~~



# Optional Protocol Requirements

オプション要求できます。Object-cのプロトコルが、C#のインターフェースとちがってすべてのメソッドを実装しなくてもよい、ので互換性の為にあるような気がしますが、よくわかりません。:

>These requirements do not have to be implemented by types that conform to the protocol. 

>Optional requirements are prefixed by the optional modifier as part of the protocol’s definition.

~~~
  1> import Foundation
  2> @objc protocol MonotonousDelegate 
  3. { 
  4.    func send_fax() 
  5.    func check_mail() 
  6.    optional func make_money() 
  7.    optional var bonus : Int {get set}                                                                                                                  
  8. } 
~~~


~~~
  1> import Foundation  
  2.  
  3. @objc protocol MonotonousDelegate 
  4. { 
  5.    func send_fax() 
  6.    func check_mail() 
  7.    optional func make_money() 
  8.    optional var bonus : Int {get set}  
  9. } 
~~~

~~~
 21. @objc class Employee 
 22. {   
 23.    var name : String 
 24.    init(name: String){ self.name = name } 
 25. } 
 26.  
 27. @objc class Secretary : Employee, MonotonousDelegate 
 28. {  
 29.   func send_fax(){ println("\(name) is sending a fax.") } 
 30.   func check_mail(){ println("\(name) is checking mails .") } 
 31. }
~~~

~~~
 33> var alice: MonotonousDelegate? = Secretary(name:"Alice")
alice: MonotonousDelegate? = (instance_type = Builtin.RawPointer = 0x0000000100604490 -> 0x00000001003bfc70 direct type metadata for __lldb_expr_1.Secretary + 16)
~~~


~~~
 35> alice?.make_money?()
$R1: ()? = nil
~~~

~~~
 36> alice?.make_money()
/var/folders/3n/0lk686q1129clzkw38blpwdc0000gp/T/lldb/45126/repl15.swift:2:8: error: value of optional type '(() -> ())?' not unwrapped; did you mean to use '!' or '?'?
alice?.make_money()
       ^
                 !
~~~