What is the difference between Methods and Attributes in Ruby?

Question

Can you give me an example?

Answer 1

Attributes are, strictly speaking, the instance variables of a class instance. In more general terms, attributes are usually declared using the attr_X type methods, while methods are simply declared as is.

A simple example might be:

attr_accessor :name
attr_reader :access_level

# Method
def truncate_name!
  @name = truncated_name
end

# Accessor-like method
def truncated_name
  @name and @name[0,14]
end

# Mutator-like method
def access_level=(value)
  @access_level = value && value.to_sym
end

The distinction between these two is somewhat arbitrary in Ruby since no direct access to them is specifically provided. This contrasts quite strongly with other languages such as C, or C++ and Java where access of an objects properties and calling methods is done through two different mechanisms. Java in particular has accessor/mutator methods that are spelled out as such, whereas in Ruby these are implied by name.

It is often the case, as in the example, where the difference between an "attribute accessor" and a utility method that provides data based on an attribute's value, such as truncated_name, is minor.