Ruby make 2 different constructors with same ammount of parameters [duplicate] - ruby

Question

This question already has answers here:
In Ruby is there a way to overload the initialize constructor?
(7 answers)
Closed 9 years ago.
I've got a class just like this:
class Equipment
attr_reader :text
attr_reader :name
attr_reader :array1
attr_reader :number
end
then, I want to make 2 constructors with 3 parameters each:
1º one -> (text,name,array1)
2º one -> (text, name,number)
The first one as an argument has an array and the other one has an integer (1,2...), so I need to define both constructors so when I create an object of this class it makes a difference between array or integer as the 3º argument.
Any ideas?
EDIT.: I thought this:
def initialize(text = "", name = "", array = array.new, number =0)
#text = text
#name = name
#array1 = array
#number = number
end
(initializing all of them) then:
def Equipment.newc_witharray(sometext, somename, somearray)
#text = sometext
#name = somename
#array1 = somearray
end
def Equipment.newc_withint(sometext, somename, somenumber)
#text = text
#name = name
#number = somenumber
end
and finally calling objects like this:
character1 = Equipment.newc_withint("Barbarian", "conan", 3)
shouldn't this work?

Answer 1

You can create as many constructors as you want on the class with whatever name you want. There is one constructor new, which is inherited from Object, and that can be used to write other constructors. What other answers mention as the constructor, namely the instance method initialize is not a constructor. That is the method called by the constructor method new by default.
class Foo
def self.new1 text, name, array1
obj = new
# do something on obj with text, name, array1
obj
end
def self.new2 text, name, number
obj = new
# do something on obj with text, name, number
obj
end
end
Foo.new1(text, name, array1)
Foo.new2(text, name, number)

Answer 2

There are various ways to achieve this.
Hash arguments
You could pass a hash and extract the values you're interested in:
def initialize(options={})
#text = options.fetch(:text) # raises KeyError if :text is missing
#name = options.fetch(:name) # raises KeyError if :name is missing
#array = options.fetch(:array, []) # returns [] if :array is missing
#number = options.fetch(:number, 0) # returns 0 if :number is missing
end
Keyword arguments
In Ruby 2.0 you can use keyword arguments with default values:
def initialize(text: text, name: name, array: [], number: 0)
#text = text
#name = name
#array = array
#number = number
end
Switching on argument type
This makes the method harder to read, but would work, too:
def initialize(text, name, number_or_array)
#text = text
#name = name
#number = 0
#array = []
case number_or_array
when Integer then #number = number_or_array
when Array then #array = number_or_array
else
raise TypeError, "number_or_array must be a number or an array"
end
end

Answer 3

Built into the language, no, Ruby does not give you that ability.
However, if you want that ability, I would create an initialize method which takes a hash as its parameter. Then you could create an instance of the class using any number of parameters.
E.g:
class Equipment
attr_reader :text, :name, :array1, :number
def initialize(options)
[:text, :name, :array1, :number].each do |sym|
self.send(sym) = options[sum]
end
end
end

Answer 4

The ruby interpreter wouldn't be able to differentiate between the constructors, as the types are not known until runtime :(
However, you can use a very nice workaround:
class Foobar
def initialize(h) # <-- h is a hash
# pass combination of params into the hash, do what you like with them
end
end
and then, using this pattern, you can pass any combination of params into the constructor:
foobar = Foobar.new(:foo => '5', :bar => 10, :baz => 'what?')