[Rails] What is a dot (.) Or a colon (:)?

I often see :: and .. This is a clarification that the notation changes due to the difference in method call.

Dot notation

python


class User
  def method
    puts "Hello"
  end
end

python


> user = User.new

> user.method
Hello
=> nil

Colon notation

python


class User
  def method
    puts "Welcome"
  end
end

python


> user = User.new
> user::method
Welcome
=> nil

Difference between dot notation and colon notation

The difference between dot notation and colon notation is whether you can call a constant.

notation Method call Calling a constant
Dot notation ×
Colon notation

In Ruby, classes and modules are also treated as constants.

python


require 'uri'
require 'net/http'

url = URI.parse("http://yahoo.co.jp")
http = Net::HTTP.start(url.host, url.port)

python


> document = http.get(url.path)

> puts document.body
#View document

Summary

In this way, the colon notation allows you to access items in a class or module in another specified file.

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