Use of swift extension

//
//  ExtensionsProtocols.swift
//  SwiftCode
//
//  Created by Alisa on 2022/4/14.
//  Copyright  2022 Alisa. All rights reserved.
//

import Foundation

/*
     Extension is used to add new functions to existing data types , The protocol is used to contract attributes and methods for the implementation of data types that comply with it 
 
**  Expand 
     stay oc There are categories in the syntax , Its function is to add new functions to existing classes , stay swift You can use extensions to achieve similar functions , Different from categories , Category has name , The extension has no name 
 
     Expand supported functions , as follows ：
        <1>  Add calculation properties 
        <2>  Defining instance methods and class methods 
        <3>  Define a new construction method 
        <4>  Define subscript method 
        <5>  Define nested methods 
        <6>  Make an existing type conform to the protocol 
        <7>  Extend the protocol 、 Add a new property or method Convention 
 
     Expand the use of keywords extension

    
*/

class Mirror{
    var color:String
    var purpose:String
    var mirrorSize:Float = 0.0
    init() {
        self.color = ""
        self.purpose = ""
    }
    
}
extension Mirror{
    
    // Extend a calculated property 
    var size:Float{
        set{
            self.mirrorSize = newValue
        }
        get{
            return self.mirrorSize
        }
    }
    // Extend an instance method 
    func showTheBrightLight(){
        print("The mirror show this bright light,  Sunny weather ！")
    }
    // Extend a class method 
    class func cleanMirror(){
        print(" Clean it  this mirror")
    }
    // Extend a new construction method 
    convenience init(color:String){
        self.init()
        self.color = color
    }
    // Extension cannot add ordinary attributes , Only calculation properties can be added 
    //var size:Float      //Extensions must not contain stored properties
}

protocol BreadTalking{
    
    func showTheBreadName()->Void
}

class BreadFat{
    var color:String
    var name:String
    init() {
        self.color = "yellow"
        self.name = ""
    }
}
extension BreadFat:BreadTalking{
    
    func showTheBreadName() {
        print("This Bread name is: \(self.name)")
    }
}

// Extend the existing types of the system , Change yourself 
extension Int{
    // The modification itself requires the use of mutating
    mutating func change(){
        self = self * self
    }
}

class Extensions{
    
    // Use the extension to add calculation properties 、 Example method 、 Class method 、 Construction method ( Convenient construction method )
    func useExtensions(){
        
        let mirror = Mirror(color: "Pink")
        mirror.size = 45.0  // Use extended calculation properties 
        mirror.showTheBrightLight()     // Use the extended instance method 
        
        // Use extended class methods 
        Mirror.cleanMirror()
        
        /*  Print information ：
         The mirror show this bright light,  Sunny weather ！      Use the extended instance method 
          Clean it  this mirror        Use extended class methods 
        */
    }
    
    // Use extensions to add protocols to existing classes 
    func useExtentionForProtocl(){
        
        let bread = BreadFat()
        bread.name = "Buttered Toast"
        // A method implemented using an extended accepted protocol 
        bread.showTheBreadName()
        
        /*  Print information 
         This Bread name is: Buttered Toast
        */
    }
    
    // Use extensions to change the instance itself 
    func useExtentionForInt(){
        var value = 3
        value.change()
        print("current value is: \(value)")
        
        /*  Print information 
         current value is: 9
        */
    }
}