Rails optional argument

Question

I have a class

class Person
    attr_accessor :name,:age
    def initialize(name,age)
        @name = name
        @age = age
    end
end

I

Answer 1

This is more of a Ruby thing. You can define optional arguments for a method like this:

def initialize(name="", age=0)
  @name = name
  @age = age
end

By doing it this way, you will be able to call Person.new and then have name default to a blank string if it's not passed and age default to 0. If you want age to be something but name to be blank you'll need to pass an empty string anyway:

Person.new("", 24)

Answer 2

If you want both arguments to be optional but also set default values when nil then you could go with:

class Person

def initialize(name = nil, age = 0)
  @name ||= "Default name"
  @age = age
end

end

This gets over the issue of passing nil as the first option but still getting a useable default value.

@person = Person.new nil, 30
@person.name # => "Default name"
@person.age # => 30

Answer 3

Use hash for ruby 1.8/1.9 as follow:

def myMethod(options={})
  @email = options[:email]
  @phone = options[:phone]
end

# sample usage
myMethod({:email => "example@email.ir", :phone => "0098-511-12345678"})

Also on ruby 2.0/2.1 you can use keyword arguments as follow:

def myMethod(email: 'default@email.ir', phone: '0098-000-00000000')
  @email = email
  @phone = phone
end

# sample usage
myMethod(email: "example@email.ir", phone: "0098-511-12345678")

Answer 4

It's as simple as this:

class Person
    attr_accessor :name, :age

    def initialize(name = '', age = 0)
        self.name = name
        self.age = age
    end
end


Person.new('Ivan', 20)
Person.new('Ivan')

However, if you want to pass only age, the call would look pretty ugly, because you have to supply blank string for name anyway:

Person.new('', 20)

To avoid this, there's an idiomatic way in Ruby world: options parameter.

class Person
    attr_accessor :name, :age

    def initialize(options = {})
        self.name = options[:name] || ''
        self.age = options[:age] || 0
    end
end

Person.new(name: 'Ivan', age: 20)
Person.new(age: 20)
Person.new(name: 'Ivan')

You can put some required parameters first, and shove all the optional ones into options.

Edit

It seems that Ruby 2.0 will support real named arguments.

def example(foo: 0, bar: 1, grill: "pork chops")
  puts "foo is #{foo}, bar is #{bar}, and grill is #{grill}"
end

# Note that -foo is omitted and -grill precedes -bar
example(grill: "lamb kebab", bar: 3.14)