Interface coding by contract design and dependency injection

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

···

--
pdtct

Thee third google result for "dependency injection" is ruby-specific.

···

On 1/29/07, PerfectDayToChaseTornados <noone@emailaddress.invalid> wrote:

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

--
pdtct

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://copland.rubyforge.org/

···

--
Olivier Renaud

Le lundi 29 janvier 2007 19:45, PerfectDayToChaseTornados a écrit :

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

SonOfLilit wrote:

Thee third google result for "dependency injection" is ruby-specific.

For me, it's a German Wikipedia article on DI.

- Phill

Thanks Guys,

I'll check out Copland & Needle, anyone have any experience with either of
these with Rails?

···

--
pdtct

Did you mean http://onestepback.org/index.cgi/Tech/Ruby/DependencyInjectionInRuby.rdoc ?

Paulo Jorge Duarte Köch
paulo.koch@gmail.com

Paulo Köch wrote:

Did you mean http://onestepback.org/index.cgi/Tech/Ruby/DependencyInjectionInRuby.rdoc ?

Paulo Jorge Duarte Köch
paulo.koch@gmail.com

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.

···

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