Polymorphism over conditionals

poly-over-cond.rb

# Conditional reach-around

User = Struct.new(:name, :role) do; end

def greet(user)
  if user.name && user.role
    "Hello, I am an #{user.role} user. My name is #{user.name}."
  elsif user.name
    "Hello, my name is #{user.name}."
  else
    "Hello, I am a guest user. I have no name."
  end
end

puts greet User.new
puts greet User.new('james')
puts greet User.new('james','admin')

# Polymorphism

class GuestUser
  def greet
    "Hello, I am a guest user. I have no name."
  end
end

NormalUser = Struct.new(:name) do
  def greet
    "Hello, my name is #{name}."
  end
end

AdminUser = Struct.new(:name) do
  def role
    'admin'
  end

  def greet
    "Hello, I am an #{role} user. My name is #{name}."
  end
end

def greet(user)
  user.greet
end

puts greet GuestUser.new
puts greet NormalUser.new('james')
puts greet AdminUser.new('james')