变量
- 变量

变量

Variables

变量

Ruby has three kinds of variables, one kind of constant and exactly two pseudo-variables.

Ruby 有3种类型的变量，一种是常量，另外两种是伪变量 。

The variables and the constants have no type. While untyped variables have some drawbacks, they have many more advantages and fit well with ruby’s quick and easy philosophy.

变量和常量都没有类型。尽管没有类型的变量有一些缺点，但是它们有远远更多的优点，并且与Ruby 的快速和简单的哲学相适应。

Variables must be declared in most languages in order to specify their type, modifiability (i.e., whether they are constants), and scope; since type is not an issue, and the rest is evident from the variable name as you are about to see, we do not need variable declarations in ruby.

变量在大多数语言中必须声明，以指定它们的类型、可修改性(即:它们是否是常数)和作用域；因为类型不是问题，剩下的就是从变量名中可以看到的，正如你即将要看到的，在Ruby 中使用变量不需要声明。

The first character of an identifier categorizes it at a glance:

标识符的第一个字符对它进行了分类:

标识符	类型
$	全局变量
@	实例变量
[a-z] 或 _	局部变量
[A-Z]	常量

The only exceptions to the above are ruby’s pseudo-variables: self, which always refers to the currently executing object, and nil, which is the meaningless value assigned to uninitialized variables.

上面的唯一例外是Ruby 的伪变量:总是指向当前运行对象的self和被赋给未初始化变量的无意义的值nil。

Both are named as if they are local variables, but self is a global variable maintained by the interpreter, and nil is really a constant.

虽然两者都像是局部变量一样被命名，但是self是由解释器维持的一个全局变量，而nil实际上是一个常量。

As these are the only two exceptions, they don’t confuse things too much.

因为这是仅有的2个例外，他们不会把事情搞得太混乱。

You may not assign values to self or nil. main, as a value of self, refers to the top-level object:

你不能给self或nil赋值。main，作为self的值，指的是顶级对象:

ruby> self
   main
ruby> nil
   nil