一、思路来历

研究自定义运算符的时分,又从头看了一下重载运算符,觉得挺有意思的,顺手封装了几个。

二、基础类型 String 为例

重载乘法运算符:将一段字符串重复 n 次拼接在一起;
let c = "abc"*3;
print("c: \(c)");//c: abcabcabc
源码完成:
public extension String{
  static func * (lhs: String, rhs: Int) -> String {
    return String(repeating: lhs, count: rhs);
  }
}

三、目标类型 UIEdgeInsets 为例

重载加法运算符将:将 top, left, bottom, right 特点逐个求和;
let edg1 = UIEdgeInsets(top: 1, left: 2, bottom: 3, right: 4);
let edg2 = UIEdgeInsets(top: 4, left: 3, bottom: 2, right: 1);
let e = edg1 + edg2;
print("edg1: \(edg1)");//edg1: UIEdgeInsets(top: 1.0, left: 2.0, bottom: 3.0, right: 4.0)
print("edg2: \(edg2)");//edg2: UIEdgeInsets(top: 4.0, left: 3.0, bottom: 2.0, right: 1.0)
print("e: \(e)");//e: UIEdgeInsets(top: 5.0, left: 5.0, bottom: 5.0, right: 5.0)
源码完成:
public extension UIEdgeInsets{
  static func + (lhs: UIEdgeInsets, rhs: UIEdgeInsets) -> UIEdgeInsets {
    return UIEdgeInsets(lhs.top + rhs.top,
              lhs.left + rhs.left,
              lhs.bottom + rhs.bottom,
              lhs.right + rhs.right
    );
  }
}

四、总结

1、重载运算符可以将繁琐的操作简单化,复杂的操作封装化,归于质变的重构方法;

2、编程的核心是发明力,你发明各种工具函数的能力越强则作业越轻松,反之亦然。