我正在学习 Ruby令人心酸的 Ruby 指南 http://www.rubyinside.com/media/poignant-guide.pdf在一些代码示例中，我遇到了双冒号和点的使用，它们似乎用于相同的目的：
File::open( 'idea-' + idea_name + '.txt', 'w' ) do |f|
f << idea
end
在上面的代码中，双冒号用于访问open的方法File班级。然而，我后来遇到了使用点来达到相同目的的代码：
require 'wordlist'
# Print each idea out with the words fixed
Dir['idea-*.txt'].each do |file_name|
idea = File.read( file_name )
code_words.each do |real, code|
idea.gsub!( code, real )
end
puts idea
end
这次，一个点被用来访问read的方法File班级。有什么区别：
File.read()
and
File::open()
这是范围解析运算符 http://en.wikipedia.org/wiki/Scope_resolution_operator#Ruby.
维基百科的一个例子：
module Example
Version = 1.0
class << self # We are accessing the module's singleton class
def hello(who = "world")
"Hello #{who}"
end
end
end #/Example
Example::hello # => "Hello world"
Example.hello "hacker" # => "Hello hacker"
Example::Version # => 1.0
Example.Version # NoMethodError
# This illustrates the difference between the message (.) operator and the scope
# operator in Ruby (::).
# We can use both ::hello and .hello, because hello is a part of Example's scope
# and because Example responds to the message hello.
#
# We can't do the same with ::Version and .Version, because Version is within the
# scope of Example, but Example can't respond to the message Version, since there
# is no method to respond with.
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