Swift 实用技巧

1. protocol + extension 初始化后直接配置相应属性

protocol XXXBuilder {}

extension XXXBuilder {
    public func with(configure: (inout Self) -> Void) -> Self {
        var this = self
        configure(&this)
        return this
    }
}

extension NSObject: XXXBuilder {}

// 使用
let tipLab = UILabel().with { lab in
            lab.textColor = .red
            lab.backgroundColor = .black
        }

2. Double 转 String,限制小数位数

extension Double {
    func format(_ count: Int) -> String {
        String(format: "%.\(count)f", self)
    }
}