Smalltalk相当于Java的静态是什么？ [英] What is the Smalltalk equivalent of Java's static?

问题描述

Smalltalk相当于Java的静态字段和方法是什么？ IOW，Smalltalkers在需要类级数据和/或方法时会做什么？

What is the Smalltalk equivalent of Java's static fields and methods? IOW, what do the Smalltalkers do when they need class level data and/or methods?

推荐答案

我们使用类方法/实例变量。毕竟一个类是一个对象，所以可以有方法。

We use class-side methods/instance variables. A class is an object, after all, so can have methods.

例如，Rectangle类有一个方法#origin：corner：所以你可以写

For instance, the Rectangle class has a method #origin:corner: so you may write

Rectangle origin: 0@0 corner: 100@100

创建一个Rectangle。这只是消息#origin：corner：发送到名为Rectangle的对象（一个类是一个对象！），其中两个Point作为参数。

to create a Rectangle. This is just the message #origin:corner: sent to the object called Rectangle (a class is an object!) with the two Points as parameters.

类侧实例变量的工作方式大致相同。作为对象的类可以具有实例变量。来自SUnit库：

Class-side instance variables work much the same way. A class, being an object, may have instance variables. From the SUnit library:

TestCase class
  instanceVariableNames: 'history'

然后TestCase类以通常的方式暴露这个，使用getter / setter（#history和#history：）。

and then TestCase class exposes this in the usual way, with a getter/setter (#history and #history:).

编辑：我使用的 @ 引起了一些讨论。这就是所谓的二进制消息，它允许用户定义只看其他语言的选择器会打电话给中缀运营商。例如， 3 + 4 ，或 0 @ 0 。在 @ 的情况下， Number 类定义了一个名为 @ 获取参数 y ，定义为 ^ Point x：self y：y - 返回一个Point x坐标是我自己的值，其y坐标是参数。

The @ I used has caused a fair bit of discussion. It's what's called a binary message, which allows one to define selectors that look just what other languages would call infix operators. For instance, 3 + 4, or 0@0. In the case of @, the Number class defines a method called @ taking a parameter y, defined as ^Point x: self y: y - "return a Point whose x coordinate is my own value and whose y coordinate is the parameter".

Point是一个有序对，但当然没有什么可以阻止定义更高维度的版本。 Point 可能会定义一个名为 @ 的方法，例如： ^ Triple x ：self xy：self yz：z - 返回R ^ 3中的一个点，其x，y坐标是我自己的，其z坐标是给定参数。

Point is an ordered pair, but of course there's nothing stopping one from defining higher-dimensional versions. Point might define a method called @ that looked like this, for instance: ^Triple x: self x y: self y z: z - "return a point in R^3 whose x, y coordinates are my own, and whose z coordinate is the given parameter".

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