“="和“="有什么区别?&“="和“@variable"、“@@variable"和“:变量"在红宝石? [英] What's the difference between "=" & "=>" and "@variable", "@@variable" and ":variable" in ruby?

问题描述

我知道这些是 Rails 的基础知识，但我仍然不知道 = 符号和 => 之间的全部区别以及 @ 之间的区别rails 中的 some_variable、@@some_variable 和 :some_variable.

I know these are the basics of rails but i still don't know the full difference between = sign and => and the difference between @some_variable, @@some_variable and :some_variable in rails.

谢谢.

推荐答案

好的.

= 和 => 运算符之间的区别在于，第一个是赋值，第二个表示散列(关联数组)中的关联.所以 { :key =>'val' } 是说创建一个关联数组，其中 :key 是键，'val' 是值".如果你想听起来像一个 Rubyist，我们称之为hashrocket".(信不信由你，这不是 Ruby 中最奇怪的运算符；我们还有 <=>，或太空船运算符".)

The difference between the = and the => operators is that the first is assignment, the second represents an association in a hash (associative array). So { :key => 'val' } is saying "create an associative array, with :key being the key, and 'val' being the value". If you want to sound like a Rubyist, we call this the "hashrocket". (Believe it or not, this isn't the most strange operator in Ruby; we also have the <=>, or "spaceship operator".)

您可能会感到困惑，因为在方法中可以使用一些快捷方式，如果最后一个参数是散列，则可以省略波浪括号 ({}).所以调用 render :partial =>'foo' 基本上是调用 render 方法，传入一个带有单个键/值对的哈希值.正因为如此，你经常看到一个散列作为最后一个参数来排序一个穷人的可选参数(你在 JavaScript 中也看到了类似的东西).

You may be confused because there is a bit of a shortcut you can use in methods, if the last parameter is a hash, you can omit the squiggly brackets ({}). so calling render :partial => 'foo' is basically calling the render method, passing in a hash with a single key/value pair. Because of this, you often see a hash as the last parameter to sort of have a poor man's optional parameters (you see something similar done in JavaScript too).

在 Ruby 中，任何普通单词都是局部变量.所以foo 在方法内部是一个作用域为方法级别的变量.用 @ 前缀变量意味着将变量作用于实例.所以@foo 在方法中是一个实例级别.

In Ruby, any normal word is a local variable. So foo inside a method is a variable scoped to the method level. Prefixing a variable with @ means scope the variable to the instance. So @foo in a method is an instance level.

@@ 表示类变量，表示@@ 变量在类的作用域内，以及所有实例.

@@ means a class variable, meaning that @@ variables are in scope of the class, and all instances.

: 表示符号.Ruby 中的符号是一种特殊的字符串，暗示它将用作键.如果您来自 C#/Java，它们的使用类似于枚举的关键部分.还有一些其他的区别，但基本上任何时候你要把一个字符串当作任何类型的键，你都可以使用符号来代替.

: means symbol. A symbol in Ruby is a special kind of string that implies that it will be used as a key. If you are coming from C#/Java, they are similar in use to the key part of an enum. There are some other differences too, but basically any time you are going to treat a string as any sort of key, you use a symbol instead.

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