ruby-on-rails - Ruby on Rails 中的冒号放置

Question

有什么区别:

1. abc:

2. :xyz

3. abc::xyz

4. abc: :xyz

5. abc: xyz

6. :abc => xyz

Answer 1

1) abc:不能独立存在

2) :xyz 是一个符号

:xyz.class
 => Symbol

3) abc::xyz 表示命名空间

示例代码:

module ABC
    class Xyz
       def initialize
         @size = 400
       end
    end
end

x = ABC::Xyz.new

4) abc: :xyz

hash = {abc: :xyz} #hash key and value all are symbol. 

5) abc: xyz

xyz = "just a test"
hash = {abc: xyz} #hash key is symbol, value is string. 

6) :abc => xyz

xyz = "just a test"
hash = {:abc => xyz} # same with (5)， just another representation

7) 三元运算符:

abc = 1
xyz = 2
result = abc > xyz ? abc : xyz
=> result = 2