swift 常量使用注意事项

//: Playground - noun: a place where people can play//1.swift中如何导入框架import UIKit//创建一个常量对象let view : UIView = UIView()//设置view的颜色view.backgroundColor = UIColor.red//设置尺寸view.frame = CGRect(x: 10, y: 10, width: 20, height: 20)//设置透明度view.alpha = 0.5//设置控件隐藏view.isHidden = true