CODEWITHSUNDEEP
ruby-on-railsruby
Gupta
Gupta

Reputation: 10378

definition of ruby inbuilt methods

I go throw this guide-ruby-collections-iv-tips-tricks article

Array.new(3, rand(100))

That wasn’t exactly random. It looks like rand(100) is only being evaluated once. Fortunately, Array#new can take a block, and it will run the block for each element, assigning the element the result.

Array.new(3) { rand(100) }
=> [10,53,27]

That' ok

But where I could see the actual implementation of #new method of Array class, I checked with Array's New Method But Still not getting the point.

As I'm using Rubymine I checked with there also ,this is I found there

def self.new(*several_variants)
    #This is a stub, used for indexing
end

1: What is meaning of *several_variants here.

2: Where if the actual definition of this method.

Suppose I've a class Test; end

How might I could write #new method which can accept array, optional-hash and block ?

Upvotes: 2

Views: 334

Answers (1)

Steve Klabnik
Steve Klabnik

Reputation: 15559

1: what is meaning of *several_variants here.

It's a 'splat.':

$ irb
irb(main):001:0> def foo(*bar)
irb(main):002:1> puts bar
irb(main):003:1> puts bar.class
irb(main):004:1> end
=> :foo
irb(main):005:0> foo([1, 2, 3])
1
2
3
Array
=> nil
irb(main):006:0> foo("hello")
hello
Array
=> nil
irb(main):007:0> foo("Hello", "world")
Hello
world
Array
=> nil
irb(main):008:0> foo(a: "hash")
{:a=>"hash"}
Array
=> nil

2: where if the actual definition of this method.

It's in C: https://github.com/ruby/ruby/blob/trunk/array.c#L5746 and https://github.com/ruby/ruby/blob/trunk/array.c#L722-L777

rb_ary_initialize(int argc, VALUE *argv, VALUE ary)

Of course, that's not as helpful, since:

how might i write #new method which can accept array, optional hash and block ?

Usually, in Ruby, you don't write a new, you write an initialize. new calls initialize. Doing this is as easy as:

class Foo
  def initialize(*args, &blk)
    # stuff goes here
  end
end

args will have all the arguments, and &blk will have a block, if you were passed one.

Upvotes: 3

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