# Interface coding by contract design and dependency injection **URL:** \ **Category:** Ruby\ **Created:** [January 29, 2007, 7:46pm UTC](https://www.ruby-forum.com/t/interface-coding-by-contract-design-and-dependency-injection/83795 "2007-01-29T19:46:12Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![PerfectDayToChaseTo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/898d66/32.png) [@PerfectDayToChaseTo](https://www.ruby-forum.com/u/PerfectDayToChaseTo)\ **Post date:** [January 29, 2007, 7:46pm UTC](https://www.ruby-forum.com/t/interface-coding-by-contract-design-and-dependency-injection/83795/1 "2007-01-29T19:46:12Z")
Hi All, I am a Java developer of many years & just starting to get into Ruby (& really enjoying it!). However I am used to ‘coding by contract’ using interfaces. This is especially great when using dependency injection (usually via Spring). It makes testing very easy, as ‘mocks’ can be written simply & then plugged in. I know that there isn’t an equvalent for an interface in Ruby, but is there a pattern which would typically be used? I was wondering whether to create Modules in place of my interfaces & provide them with methods which throw Exceptions, thus forcing them to be overrriden in the classes that include them? Also how does one manage dependency injection in Ruby? Is there a good framework/library/pattern typically used for this, or are there good ‘Ruby reasons’ not to use DI? Many thanks ---
**Author:** ![PerfectDayToChaseTo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/898d66/32.png) [@PerfectDayToChaseTo](https://www.ruby-forum.com/u/PerfectDayToChaseTo)\ **Post date:** [January 29, 2007, 8:10pm UTC](https://www.ruby-forum.com/t/interface-coding-by-contract-design-and-dependency-injection/83795/2 "2007-01-29T20:10:17Z")
Thee third google result for “dependency injection” is ruby-specific. ---
**Author:** ![PerfectDayToChaseTo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/898d66/32.png) [@PerfectDayToChaseTo](https://www.ruby-forum.com/u/PerfectDayToChaseTo)\ **Post date:** [January 29, 2007, 9:28pm UTC](https://www.ruby-forum.com/t/interface-coding-by-contract-design-and-dependency-injection/83795/3 "2007-01-29T21:28:35Z")
SonOfLilit wrote: > Thee third google result for “dependency injection” is ruby-specific. For me, it’s a German Wikipedia article on DI. > **[Dependency Injection](https://de.wikipedia.org/wiki/Dependency_Injection)** > > Als Dependency Injection (DI, englisch dependency ‚Abhängigkeit‘ und injection ‚Injektion‘, deutsch Abhängigkeitsinjektion oder Einbringen von Abhängigkeiten) wird in der objektorientierten Programmierung ein Entwurfsmuster bezeichnet, welches die Abhängigkeiten eines Objekts zur Laufzeit reglementiert: Benötigt ein Objekt beispielsweise bei seiner Initialisierung ein anderes Objekt, ist diese Abhängigkeit an einem zentralen Ort hinterlegt – es wird also nicht vom initialisierten Objekt selbst Di... - Phill ---
**Author:** ![PerfectDayToChaseTo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/898d66/32.png) [@PerfectDayToChaseTo](https://www.ruby-forum.com/u/PerfectDayToChaseTo)\ **Post date:** [January 29, 2007, 11:13pm UTC](https://www.ruby-forum.com/t/interface-coding-by-contract-design-and-dependency-injection/83795/4 "2007-01-29T23:13:58Z")
Did you mean [http://onestepback.org/index.cgi/Tech/Ruby/](http://onestepback.org/index.cgi/Tech/Ruby/) DependencyInjectionInRuby.rdoc ? Paulo Jorge Duarte Köremoved\_email\_address@domain.invalid ---
**Author:** ![PerfectDayToChaseTo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/898d66/32.png) [@PerfectDayToChaseTo](https://www.ruby-forum.com/u/PerfectDayToChaseTo)\ **Post date:** [January 30, 2007, 12:24am UTC](https://www.ruby-forum.com/t/interface-coding-by-contract-design-and-dependency-injection/83795/5 "2007-01-30T00:24:11Z")
Hi, I’m really new to dependency injection in general, but I hope I can help, though. I am aware of two libraries for what you want to do. Copland, first, is an Inversion of Control (IoC) container, based on the Hivemind IoC container for java. As you said, there is no interface in Ruby, so Interface based injection is not supported. However, Type 2 IoC (Setter Injection) and type 3 IoC (Constructor Injection) are supported. The second is Needle, which is a Dependency Injection container. I don’t know much about it, except it supports a Service Locator mechanism. By the way, the documentations are great for both ! Read them both and make your choice ! [http://needle.rubyforge.org/](http://needle.rubyforge.org/) [http://copland.rubyforge.org/](http://copland.rubyforge.org/) – Olivier R. Le lundi 29 janvier 2007 19:45, PerfectDayToChaseTornados a écrit : ---
**Author:** ![PerfectDayToChaseTo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/898d66/32.png) [@PerfectDayToChaseTo](https://www.ruby-forum.com/u/PerfectDayToChaseTo)\ **Post date:** [January 30, 2007, 9:38pm UTC](https://www.ruby-forum.com/t/interface-coding-by-contract-design-and-dependency-injection/83795/6 "2007-01-30T21:38:53Z")
Paulo Köch wrote: > Did you mean > [http://onestepback.org/index.cgi/Tech/Ruby/DependencyInjectionInRuby.rdoc](http://onestepback.org/index.cgi/Tech/Ruby/DependencyInjectionInRuby.rdoc) ? > > Paulo Jorge Duarte Köch > removed\_email\_address@domain.invalid That didn’t show up for me. Google results are depending on which data center you catch, so just saying “google, and result #X will be relevant” is a questionable technique to answer a question. – Over by the window lie the raiment and the weapons That we need to take into this world today Armoured by opinion, with statistic and schoolboy’s charm We take our place amongst the rank and file Skyclad - A Survival Campaign ---
**Author:** ![PerfectDayToChaseTo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/898d66/32.png) [@PerfectDayToChaseTo](https://www.ruby-forum.com/u/PerfectDayToChaseTo)\ **Post date:** [January 30, 2007, 8:55pm UTC](https://www.ruby-forum.com/t/interface-coding-by-contract-design-and-dependency-injection/83795/7 "2007-01-30T20:55:48Z")
Thanks Guys, I’ll check out Copland & Needle, anyone have any experience with either of these with Rails?