method_interceptor

ParameterTransformers

This gem provides a proxy which can encapsulate transformers to be applied to given method/parameter combinations before the target method is called or method response after it is called.

It is useful for scenarios where you might have a stateful value that needs to be consistently applied to other parameters being passed to library code.

Installation

Add this line to your application's Gemfile:

gem 'parameter_transformers'

And then execute:

$ bundle

Or install it yourself as:

$ gem install parameter_transformers

Usage

Here's an example of using the proxy to consistently apply an authentication header to all requests made with the RestClient gem and parse responses as JSON:

require 'rest_client'
require 'parameter_transformers'
require 'json'

add_auth_header = ->(headers) { (headers || {}).merge('AUTH-HEADER' => 'key') }
p_transformers = [:get, :post, :put, :delete].map do |method|
  [[method, :headers], add_auth_header]
end
r_transformers = [:get, :post, :put, :delete].map do |method|
  [method, JSON.method(:parse)]
end
rc = ParameterTransformers::Proxy.new(RestClient, Hash[p_transformers], Hash[r_transformers])

# automatically adds {'AUTH-HEADER' => 'key'} to headers on all calls now
# and automatically parses responses as json
rc.get('http://somesite.com')
rc.post('http://somesite.com', {foo: 'bar'})
rc.put('http://somesite.com', {foo: 'bar'})
rc.delete('http://somesite.com')

Note per example above the format for transformers is a hash where keys are an array of [:method_name, :argument_name] and values are procs which receive a copy of the passed argument, and return the transformed value to be passed to the method on the target object

Meanwhile for the response transformers, the format is a hash where keys are the method name, and values are procs which receive the actual response

Contributing

1. Fork it ( https://github.com/[my-github-username]/parameter_transformers/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request