Equal sign in Ruby method definition

Question

I have come across the following definitions of methods and I would like to know the difference between the first definition and the second.

This first has no equal sign in the definition:

def nome
    nome_exibicao(:nome)   
end

Already this second has the equal sign:

def nome=(novo_nome)
  if !self[:nome_real]
    self[:nome_real] = novo_nome
    gera_nome_exibicao
  else
    if novo_nome.is_a? Hash
      self[:nome] = novo_nome.sort.map { |b| b[1] }.join(' ')
    else
      self[:nome] = novo_nome
    end
  end   
end

Answer 1

Accessors and modifiers methods are very common and give the idea of properties. There is a convention for defining these methods, which most Ruby developers follow (just as Java has the convention for getters and setters):

class Pessoa
  def nome # acessor
    @nome
  end

  def nome=(novo_nome)
    @nome = novo_nome
  end
end

Some articles that may be useful to you:

• Attributes and properties: accessors and modifiers
• Instance variable and access method

Answer 2

In summary, getter and Setter methods expose class fields. They can expose the field in a raw way, such as

[privado] meu_campo             = 25
[público] get_meu_campo         # retorna 25
[público] set_meu_campo(valor)  # seta meu_campo para valor (parâmetro)

or may use some kind of logic, such as

[privado] meu_campo             = 25
[público] get_meu_campo         # retorna 25 * 2
[público] set_meu_campo(valor)  # seta meu_campo para valor/2 (parâmetro)

If you still don’t understand what getters and setters are not reply now. Understand what they are by the links below and continue reading.

• Get and Set - Java Access Methods (is Java, but what serves is the concept)
• What are setters and getters in Ruby? (maybe that answers the question)

In most languages, the naming standard for writing a getter and a Setter is

private int propriedade;
public int getPropriedade() { ... }
public void setPropriedade(valor) { ... }

But in Ruby it’s different

@propriedade = 0
def propriedade; end
def propriedade=; end

Behold a slightly more contextualized application:

class Pessoa < ActiveRecord::Base
  attr_accessible :nome, :sobrenome

  def nome_completo # getter
    "#{@nome} #{@sobrenome}"
  end

  def nome_completo=(value) # setter
    @nome, @sobrenome = value.split(' ')
  end
end

If you don’t need any specific logic on the getter or Setter, use the attr_accessor. That is to say:

class Carro
  def velocidade # getter
    @velocidade
  end

  def velocidade=(nova_velocidade) # setter
    @velocidade = nova_velocidade
  end
end

is the same thing as

class Carro
  attr_accessor :velocidade # getter e setter
end

Know that attr_accessor is a shortcut to

class Carro
  attr_reader :velocidade # getter
  attr_writer :velocidade # setter
end