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