Typed interfaces and Spring4D

Question

I am trying to use typed interfaces and Spring4D, but have some issues with Resolving. Please review details below.

DB Objects:

unit u_DB;

type
  TDBObject = class
  public
    property ID: TGUID;
  end;

  TDBCRM = class(TDBObject)
  public
    property SOME_FIELD: TSomeType;
  end;

Declarations:

unit i_BaseDAL;

type
  {$M+}
  IBaseDAL<T: TDBObject, constructor> = interface
  ['{56D48844-BD7F-4FF8-A4AE-30DA1A82AD67}']
    procedure RefreshData();
    ....
  end;

unit u_BaseDAL;

type
  TBaseDAL<T: TDBObject, constructor> = class(TInterfacedObject, IBaseDAL<TDBObject>)
  public
    procedure RefreshData();
  ....
  end;

After that I was able to register the base IBaseDAL and IBaseDAL

GlobalContainer.RegisterType<IBaseDAL<TDBObject>>;
GlobalContainer.RegisterType<IBaseDAL<TDBCRM>>;

Using in project:

I need to resolve now IBaseDAL, but could not find how do it. Only below ugly approach work

DM := GlobalContainer.Resolve('i_BaseDAL.IBaseDAL<u_DB.TDBObject>@TBaseDAL<u_DBCRM.TDBCRM>').AsInterface as IBaseDAL<TDBObject>;

but I was hoping that below will work :) -

DM := GlobalContainer.Resolve(IBaseDAL<TDBCRM>);

Please advise how could it be resolved correctly?

Stefan Glienke · Accepted Answer · 2015-01-10T00:29:40.127

2

Edit: I just noticed that somehow the interface table does not contain generic interfaces so you have to explicitly register them as explained below.

~~First you need to register an implementation and not just an interface.~~

GlobalContainer.RegisterType<TBaseDAL<TDBObject>>;
GlobalContainer.RegisterType<TBaseDAL<TDBCRM>>;
GlobalContainer.Build;

The container will inspect the class you registered and register all implemented interfaces (except IInterface) so it will know about IBaseDAL<TDBObject> and IBaseDAL<TDBCRM>.

If your class might implement some interfaces you don't want the container to know you have to register explicit:

GlobalContainer.RegisterType<IBaseDAL<TDBObject>, TBaseDAL<TDBObject>>;
GlobalContainer.RegisterType<IBaseDAL<TDBCRM>, TBaseDAL<TDBCRM>>;
GlobalContainer.Build;

Then you can resolve:

GlobalContainer.Resolve<IBaseDAL<TDBCRM>>;

By the way, are you sure your class definition should not be as follows?

type
  TBaseDAL<T: TDBObject, constructor> = class(TInterfacedObject, IBaseDAL<T>)

edited Jan 10 '15 at 00:29

answered Jan 10 '15 at 00:10

Stefan Glienke

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I was trying class definition in both variants as I described and in your variant, but without changes. Also I tried your recommendation, but got the same error: `[dcc32 Error] fr_CRM.pas(231): E2250 There is no overloaded version of 'Resolve' that can be called with these arguments` – SpanishBoy Jan 10 '15 at 00:27
As you mentioned in the other question you called Resolve wrong. You did not type angle brackets but round brackets. Generics require angle brackets (`<` `>` and not `(` `)`) – Stefan Glienke Jan 10 '15 at 12:57
Thanks, but with `<` `>` I got `[dcc32 Error] frm_CRM.pas(32): E2010 Incompatible types: "i_BaseDAL.IBaseDAL" and "i_BaseDAL.IBaseDAL"` – YoungMaster Jan 10 '15 at 14:31
Not sure, I rechecked advises from Stefan and looks like everything is OK. I am about to prepare test project and push to Google group – SpanishBoy Jan 10 '15 at 14:36

Typed interfaces and Spring4D

1 Answers1