iOS 随笔

#import UIKit 和#import 的区别

• #import UIKit

是去项目的Build Setting中的Header Search Paths中寻找

• #import

是去项目的Build Setting中的Framework Search Paths中寻找

自定义操作符--Swift

操作符分为三种类型

• 前缀操作符：prefix

extension Int {
        static prefix func --(num: Int) -> Int {
                return num - 1
        }
}
let a = 3
let b = --a
print(b)
# b = 2

• 中缀操作符：infix

extension Double {
    static func +=(left: Double, right: Double) -> Double {
        return (left + right) * right
    }
}
let a: Double = 2
let b: Double = 4
let c = a += b
print(c)
#c = 24.0

• 后缀操作符：postfix

extension Float {
        static postfix func --(num: inout Float) -> Float {
                 let numTmp = num
                 num = numTmp - 1
                 return numTmp
        }
}
var a: Float = 7.0
let b = a--
print(a)
#a = 6.0
print(b)
#b = 7.0