Ruby：冒号之前与之后
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Ruby: colon before vs after
提问by FloatingRock
When using Ruby, I keep getting mixed up with the :.
使用 Ruby 时，我总是与:.
Can someone please explain when I'm supposed to use it before the variable name, like :name, and when I'm supposed to use it after the variable like name:?
有人可以解释一下我什么时候应该在变量名之前使用它，比如:name，什么时候我应该在变量之后使用它，比如name:？
An example would be sublime.
一个例子是崇高的。
采纳答案by Arup Rakshit
You are welcome for both, while creating Hash:
欢迎您在创建时同时使用Hash：
{:name => "foo"}
#or
{name: 'foo'} # This is allowed since Ruby 1.9
But basically :nameis a Symbolobject in Ruby.
但基本上:name是SymbolRuby中的一个对象。
From docs
来自文档
Hashes allow an alternate syntax form when your keys are always symbols. Instead of
当您的键总是符号时，哈希允许另一种语法形式。代替
options = { :font_size => 10, :font_family => "Arial" }
You could write it as:
你可以把它写成：
options = { font_size: 10, font_family: "Arial" }
回答by J?rg W Mittag
This has absolutely nothing to do with variables.
这与变量完全无关。
:foois a Symbolliteral, just like 'foo'is a Stringliteral and 42is an Integerliteral.
:foo是Symbol文字，就像'foo'是一个String直译和42是Integer文字。
foo:is used in three places:
foo:用在三个地方：
- as an alternative syntax for
Symbolliterals as the key of aHashliteral:{ foo: 42 } # the same as { :foo => 42 } - in a parameter list for declaring a keyword parameter:
def foo(bar:) end - in an argument list for passing a keyword argument:
foo(bar: 42)
- 作为
Symbol文字的替代语法作为文字的键Hash：{ foo: 42 } # the same as { :foo => 42 } - 在用于声明关键字参数的参数列表中：
def foo(bar:) end - 在用于传递关键字参数的参数列表中：
foo(bar: 42)
回答by Chuck
:nameis a symbol. name: "Bob"is a special short-hand syntax for defining a Hash with the symbol :namea key and the string "Bob"as a value, which would otherwise be written as { :name => "Bob" }.
:name是一个符号。name: "Bob"是一种特殊的简写语法，用于定义一个符号:name为键、字符串"Bob"为值的哈希，否则将写为{ :name => "Bob" }.
回答by vgoff
You can use it after when you are creating a hash.
您可以在创建哈希后使用它。
You use it before when you are wanting to reference a symbol.
当你想要引用一个符号时，你会在之前使用它。
In Arup's example, {name: 'foo'}you are creating a symbol, and using it as a key.
在 Arup 的示例中，{name: 'foo'}您正在创建一个符号，并将其用作键。
Later, if that hash is stored in a variable baz, you can reference the created key as a symbol:
稍后，如果该散列存储在变量 baz 中，您可以将创建的键作为符号引用：
baz[:name]
baz[:name]
