In Ruby is there a way to overload the initialize constructor?

Question

In Java you can overload constructors:

public Person(String name) {   this.name = name; } public Person(String firstName, String lastName) {    this(firstName + " " + lastName); } 

Is there a way in Ruby to achieve this same result: two constructors that take different arguments?

Answer 1

The answer is both Yes and No.

You can achieve the same result as you can in other languages using a variety of mechanisms including:

• Default values for arguments
• Variable Argument lists (The splat operator)
• Defining your argument as a hash

The actual syntax of the language does not allow you to define a method twice, even if the arguments are different.

Considering the three options above these could be implemented with your example as follows

# As written by @Justice class Person   def initialize(name, lastName = nil)     name = name + " " + lastName unless lastName.nil?     @name = name   end end   class Person   def initialize(args)     name = args["name"]     name = name + " " + args["lastName"] unless args["lastName"].nil?     @name = name   end end  class Person   def initialize(*args)     #Process args (An array)   end end 

You will encounter the second mechanism frequently within Ruby code, particularly within Rails as it offers the best of both worlds and allows for some syntactic sugar to produce pretty code, particularly not having to enclose the passed hash within braces.

This wikibooks link provides some more reading

Answer 2

I tend to do

class Person   def self.new_using_both_names(first_name, last_name)     self.new([first_name, last_name].join(" "))   end    def self.new_using_single_name(single_name)     self.new(single_name)   end    def initialize(name)     @name = name   end end 

But I don't know if this is the best approach.