[Lazarus] Inversion of control (IoC) and Dependency injection (DI)

[luiz americo pereira camara]

2015-01-11 17:12 GMT-03:00 silvioprog <silvioprog at gmail.com>:

> On Mon, Jan 5, 2015 at 5:07 PM, luiz americo pereira camara <
> luizmed at oi.com.br> wrote:
>
>> I created a IoC Container that can be found at
>> https://code.google.com/p/luipack/source/browse/trunk/luicomponents/luiioccontainer.pas
>> . It has no dependencies.
>>
>
> Awesome!
>

Thanks.


>
> With it is possible to implement Service Locator and Property Injection
>> patterns. Constructor Injection is not possible due to lacking of Extended
>> RTTI support in fpc.
>>
>
> Can you send a small (and isolated) sample showing how to use it?
>

There's a demo in demos/ioccontainer folder

In a real project, in the app start, i do:

  FPresentations := TPresentationManager.Create(Self);
  Services.Register(IPresentationManager, FPresentations);

When i need the service i do:

  FPresentations :=
IPresentationManager(Services.Resolve(IPresentationManager));

The global, nor the actual implementation is exposed, making easier to test.
There's still a dependency to the container (Services), this is the whole
point of criticism to service locator pattern.
In the other side there always be a place where the dependency is set, even
in other DI patterns.

BTW: Custom Attributes support would help to have a nicer Property
>> Injection implementation
>>
>
> I've plan to use something like this (CDI inspirations:
> http://cdi-spec.org):
>
>
Seems a full ORM plus a MVC like framework.

I'm more modest. I use these classes to make modular code thus a bit more
maintanable.

All in all i use the IoC container little, in my project i register only
two interfaces. In other places, i configure the dependency manually

Luiz
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