打印日志是程序员调试代码的无上利器，俗话说“不会打印日志的开发不是好码农”。但在发布环境中，日志打印又会影响代码性能，带来不必要的开销。嗯哼，上线前一行行注释或删除调试代码的滋味好受吗？
只需两步，让你不再忧愁
-
设置
Other Swift FlagsDEBUG标志
-D DEBUG 重写
print&debugPrint
func print(_ items: Any..., separator: String = " ", terminator: String = "\n") {
#if DEBUG
Swift.print(items[0], separator:separator, terminator: terminator)
#endif
}
func debugPrint(_ items: Any..., separator: String = " ", terminator: String = "\n") {
#if DEBUG
Swift.debugPrint(items[0], separator:separator, terminator: terminator)
#endif
}
如果你要重写Swift 2.x的版本，请参考 stack overflow
