定义类：var，val之间的差异并将其排除在外？

Question

以下三个Scala声明之间有什么区别？我理解general distinction between val and var。

class A(x: T){ ... }
class B(val x: T){ ... }
class C(var x: T){ ... }

Answer 1

A和B之间的差异（val和var创建访问者）：

class A(a: Int) {}

// Doesn't compile (value a is not a member of)
// (new A(1)).a

class B(val b: Int) {}

(new B(1)).b                                    //> res0: Int = 1