为类添加字面量表达

class Persion :ExpressibleByStringLiteral{

let name :String

init(name value :String) {

self.name= value

}

required convenience init(stringLiteral value:String) {

self.init(name : value)

}

required convenience init(unicodeScalarLiteral value:String) {

self.init(name : value)

}

required convenience init(extendedGraphemeClusterLiteral value:String) {

self.init(name : value)

}

}

letp :Persion="xiaoming"

print(p.name)