Scala:类中的字段和构造函数中的参数之间的真正区别是什么

Question

这两个类有什么区别:

class Person {
  var name : String = _
  var surname: String = _
}

class Person (var name:String, var surname: String)

name 和 surname 始终是 Class Person 中的字段。相等？
我只是改变你实例化类 Person 的方式。
是对的吗？

Answer 1

我已经编译了一个类的两个版本:

class PersonV0 {
  var name : String = _
  var surname: String = _
}

class PersonV1 (var name:String, var surname: String)

区别在于构造函数:

public experimental.PersonV0();
  Code:
   0:   aload_0
   1:   invokespecial   #23; //Method java/lang/Object."<init>":()V
   4:   return
}

public experimental.PersonV1(java.lang.String, java.lang.String);
  Code:
   0:   aload_0
   1:   aload_1
   2:   putfield    #12; //Field name:Ljava/lang/String;
   5:   aload_0
   6:   aload_2
   7:   putfield    #16; //Field surname:Ljava/lang/String;
   10:  aload_0
   11:  invokespecial   #24; //Method java/lang/Object."<init>":()V
   14:  return
}