swift中下划线怎么用

swift中的下划线，可以用于忽略外部参数名，一般第一个参数的外部名是被自动忽略的。
代码如下

//用下划线前func myFunc(name: String, age: Int = 20, grade: Int = 2){    println("add: name = \(name), age = \(age), grade = \(grade)")}myFunc(name:"Bob", age: 19, grade: 2)//用下划线忽略外部名后func myFunc(name: String, _ age: Int = 20, _ grade: Int = 2){    println("add: name = \(name), age = \(age), grade = \(grade)")}myFunc("Bob", 19, 2)