[Swift] Extension 스위프트 형식의 확장

안녕하십니까 공부하는 개발자 입니다.

오늘의 포스팅은 extension입니다.

 

 

⚙️Extension 형식의 확장

class, struct, enumeration, protocol

멤버의 확장은 가능하지만 기존에 있던 멤버를 overriding하는 것은 불가능하다.

struct Size {
    var width = 0.0
    var height = 0.0
}
 
extension Size{
    var area: Double{
        return width * height
    }
}
 
let s = Size()
s.height //0
s.width //0
s.area //0

 

⚙️Adding Properties

//계산속성만 가능
extension Date{
    var year: Int{
        let cal = Calendar.current
        return cal.component(.year, from: self)
    }
    var month: Int{
        let cal = Calendar.current
        return cal.component(.month, from: self)
    }
}
 
let today = Date()
today.year
today.month
 
extension Double{
    var radianValue: Double{
        return Double.pi * self / 180.0
    }
    
    var degreeValue: Double{
        return self * 180.0 / Double.pi
    }
}
 
let dv = 45.0
dv.radianValue
dv.radianValue.degreeValue

 

⚙️Adding Methods

 

extension Double{
    func toFahrenheit() -> Double{
        return self * 9 / 5 + 32
    }
    
    func toCelsius() -> Double{
        return (self - 32) * 5 / 9
    }
    //-----------인스턴스 메서드 -------------
    
    
    static func converToFahrenheit(from celsius: Double) -> Double{
        return celsius.toFahrenheit()
    }
    static func converToCelsius(from fahrenheit: Double) -> Double{
        return fahrenheit.toFahrenheit()
    }
    //-----------타입 메서드 -------------
    
}
 
let c = 30.0
c.toFahrenheit()
Double.converToFahrenheit(from: 30.0)
 
extension Date{
    func toString(format: String = "yyyyMMdd") -> String{
        let privateFormatter = DateFormatter()
        privateFormatter.dateFormat = format
        return privateFormatter.string(from: self)
    }
}
 
let day = Date()
day.toString()
day.toString(format: "MM.dd.yyyy")

 

 

⚙️Adding Initializers

extension Date{
    init?(year: Int, month: Int, day: Int){
        let cal = Calendar.current
        var comp = DateComponents()
        comp.year = year
        comp.month = month
        comp.day = day
        
        guard let date = cal.date(from: comp) else{
            return nil
        }
        self = date
    }
}
 
Date.init(year: 1993, month: 12, day: 10)
 
 
//RGB
extension UIColor{
    convenience init(red: Int, green: Int, blue: Int){
        self.init(red: CGFloat(red) / 255, green: CGFloat(green) / 255, blue: CGFloat(blue) / 255, alpha: 1.0)
    }
}
 
UIColor.init(red: 0, green: 0, blue: 255)
 
struct Size{
    var width = 0.0
    var height = 0.0
    
//    init(value: Double){
//        self.width = value
//        self.height = value
//    }
}
 
extension Size{
    init(value: Double){
        self.width = value
        self.height = value
    }
}
 
Size()
Size(width: 12, height: 34)

 

⚙️Adding SubScripts

extension String{
    subscript(idx: Int) -> String?{
        guard (0..<count).contains(idx)else{
            return nil
            
        }
        
        let target = index(startIndex, offsetBy: idx)
        return String(self[target])
    }
}
 
let str = "Swift"
str[1]
str[100]
 
 
 
 
extension Date{
    subscript(componet: Calendar.Component) -> Int?{
        let cal = Calendar.current
        return cal.component(componet, from: self)
    }
}
 
let today = Date()
today[.year]
today[.month]
today[.day]