ObjectAs

A simple refinement to get Object#as

Deprecation warning

As of Ruby version 2.5, the method Object::yield_self is included in the standard Ruby library and should be preferred to Object::as.

Installation

Add this line to your application's Gemfile:

gem 'object_as'

And then execute:

$ bundle

Or install it yourself as:

$ gem install object_as

Usage

Object#as it much like Object#tap except that it returns the value of the block instead of the value being tapped.

> keys = [1, 2, 3]
> values = %w(a b c)
> keys.zip(values).as {|kv| Hash[kv] }
=> {1=>"a", 2=>"b", 3=>"c"}

Object#as is useful when chaining methods. This is a complete Ruby source file:

require 'object_as'
using ObjectAs

def square(array)
  array.map {|x| x * x }
end

[1, 2, 3].as {|array| square array }.each {|x| puts x }
# prints 1, 4, 9

For Ruby versions older than 2.1, there is a way to use Object#as without refinements. This method uses monkeypatching.

require 'object_as_no_refinements'

def square(array)
  array.map {|x| x * x }
end

[1, 2, 3].as {|array| square array }.each {|x| puts x }
# prints 1, 4, 9

Example

In this example I am using OpenCv to process an image in a method chain, but at one point I want to subtract the average value of the image from itself.

require 'object_as'
require 'opencv'

using ObjectAs

region_of_interest = 
  CvMat.load("image.png")
  sub_rect(x, y, 20, 20).
  normalize(0.0, 1.0, CV_NORM_MINMAX, CV_32F).
  as {|i| i.sub(i.avg) }

The alternative, without Object#as would look something like this:

Require 'opencv'

tmp = CvMat.load(filename) sub_rect(x, y, 20, 20). normalize(0.0, 1.0, CV_NORM_MINMAX, CV_32F)

region_of_interest = tmp.sub(tmp.avg)

The method chain is broken, and we have to introduce a temporary variable.

Contributing