Question

Given the following example taken from here:

class Post < ActiveRecord::Base
  attr_accessible :content, :name, :title

  validates :name,  :presence => true
  validates :title, :presence => true,
                    :length => { :minimum => 5 }
end

I understand we’re creating a class based on the ActiveRecord::Base class. On the next line, what is happening with attr_accessible :content, :name, :title? Are we declaring a variable, creating a method, or calling one? What are the expressions like :some_variable? What are the colons for? Could someone explain in basic understanding what is happening here?

Answer 1

attr_accessible is a method.

[It] specifies a white list of model attributes that can be set via mass-assignment.

Its argument is an array of symbols (the : business, e.g., :content is a symbol).

The method iterates over the list of properties-expressed-as-symbols and adds them to a list of properties it’s okay to mass-assign.

Most Ruby books should have discussed symbols.