为什么，将nil作为参数从Objc C发送到swift类初始化器，用新对象替换nil参数

I created this Swift class:

我创建了这个Swift类：

@objc public class Tester: NSObject {
    private var name: String
    private var user: Users
    init(string:String, user: Users) {
        print(user.empId)
        print(user.name)
        self.user = user
        self.name = string
        super.init()
    }
}
@