DZone Snippets: Vinterbleg's Code Snippets

With object do...

vinterbleg (Simon Ask Ulsnes) — Thu, 03 Apr 2008 11:03:54 GMT

This code enters the scope of an object, so you can temporarily avoid having to reference it by name.

Effectively changes the value of 'self' in the block scope. This also enables you to run private methods on the object without using __send__.



def with(object, &block)

    object.instance_eval(&block)

end

Example of usage:



numbers = [1, 2, 3]



with numbers do

	map! { |n| n + 100 }

	reject! { |n| n % 2 == 0}

end



p numbers # => [101, 103]



n = 15

n = with n do

    self + 13

end

p n # => 28

This gets much more interesting with complex objects that have lots of attributes and you want strict control over how they're set.

In-place map_with_index

vinterbleg (Simon Ask Ulsnes) — Fri, 08 Feb 2008 10:29:44 GMT

// This code is similar to Enumerable#map, but like each_with_index, it also yields the index of the current element.



class Array

    def map_with_index!

       each_with_index do |e, idx| self[idx] = yield(e, idx); end

    end



    def map_with_index(&block)

        dup.map_with_index!(&block)

    end

end

Map array to hash, with custom key and value

vinterbleg (Simon Ask Ulsnes) — Wed, 21 Nov 2007 10:29:46 GMT

This code creates a hash from an array, using a block to determine the keys and values of the hash.



class Array

	def map_to_hash

		map { |e| yield e }.inject({}) { |carry, e| carry.merge! e }

	end

end

Use like this:



[1, 2, 3].map_to_hash { |e| {e => e + 100} } # => {1 => 101, 2 => 102, 3 => 103}