Starting a new thread.

2015-01-05 15:16 GMT-03:00 silvioprog :

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.

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.

While the C# crowd praises the Constructor Injection pattern ( http://www.devtrends.co.uk/blog/how-not-to-do-dependency-injection-the-static-or-singleton-container ), i had hard times figuring how it would work in real world / Lazarus projects. Also, polluting the constructor signature is not something that i like. And finally with Constructor Injection is not possible to use with TComponent / TForm

So in the end, i use the service locator and have plans to use Property Injection pattern

BTW: Custom Attributes support would help to have a nicer Property Injection implementation

Luiz
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Interesting.
Could you give us some example how this class works?

Regards,
Marcos Douglas

2015-01-05 21:44 GMT-03:00 Marcos Douglas :

There's a demo in demos/ioccontainer

In a working project i use a IPresentationManager
https://code.google.com/p/luipack/source/browse/trunk/luicontrols/presentationmanager.pas#36

When a class needs to use it, resolves from a TIoCContainer (Service Locator pattern). The global variable and concrete class are not exposed. In the other hand depends of the IoCContainer. I have plans to switch to a Property Injection pattern that helps to decouple a bit more.

Luiz
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On Mon, Jan 5, 2015 at 5:07 PM, luiz americo pereira camara <

Awesome!

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?

I've plan to use something like this (CDI inspirations: http://cdi-spec.org ):

The model:

uses

  My.Company.MySDK.EntityAttributes, My.Company.MySDK.TableAttributes ...;

type
[Entity]
[Table('products')]
TProduct = class(TObject)

  public
    [Id][GeneratedValue]
    property Id: LongInt ...;
    [ManyToOne][JoinColumn('OrderId')]
    property OrderId: LontInt ...;
    [NotNull][NotEmpty][Size(1, 10)][Unique]
    property Name: String ...;
    [Nulls][Lenght(100)][Unique]
    property Description: String ...;
    [MyCustomCurrConversion(TypeInfo(Currency), TypeInfo(String), ',0.00')]
    [MyCustomMinMax('Price must be >= %d and <= %d.', [1, 1000])]
    property Price: Currency ...;
  end;

The DAO:

type
  [RequestScoped]
  TProductDao = class(TObject)
  private
    [Inject] property Session: TSession ... ;
    [Transational] procedure Add(AProduct: TProduct);
    ...
  end;
...procedure TProductDao.Add(AProduct: TProduct);begin
  Session.Save(AProduct);end;

The *produces* (to use external libs like *JCore*):

type
  [ApplicationScoped]
  TSessionCreator = class(TObject)
  private
    [Inject] property SessionFactory: TJCoreSession ... ;
    [Produces] function GetSession: TSession;
...
  end;
...
TSessionCreator.GetSession: TSession;begin
  Result := ASessionFactory.OpenSession;end;
TSessionCreator.Close([Disposes]ASession: TSession) {begin  if
ASession.IsOpen    ASession.Close;end;

The controller:

uses
  My.Company.ControllerAttributes ... ;
type
  [Controller]
  TProcuctController = class(TObject)
  public
    [Post][Transational] procedure Add([Valid] AProduct: TProduct); //
[Valid]: to validade properties
    [Get][Path('./product')][Transational] procedure
List([Pagination('page={[0-9]}&rows={[0-9]}')] AProducts:
TArrayList<TProduct>); // to paginate products
    [Inject] property ProductDao: TProductDao ...; // inject DAO
    [Inject] property Result: TResponse ...; // inject Response
  end;
...
procedure TProcuctController.Add(AProduct: TProduct);begin
  ProductDao.Add(AProduct);
  Result.SetAttribute(AProduct,
'product').RedirectTo(TProductController).List;end;
procedure TProcuctController.List(AProducts: TArrayList<TProduct>);begin
  Result.SetAttribute(AProducts, 'products'); // to create a variable
"products" in my BSP viewend;

The view:

<html>
<ul>
<c:forEach items="${products}" var="product">
<li> ${product.name} - <fmt:currency value="${product.price}" mask="R$ ,0.00"/></li>
</c:forEach>
</ul>
</html>

But I think that I'll still wait some years to make it possible in Free Pascal hehe ...

2015-01-11 17:12 GMT-03:00 silvioprog :

Thanks.

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

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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