[IoC and DI] Specific instances for object groups

[Jacek Laskowski]

Everything works on interfaces, but I skip interfaces for simplicity.

I have a base class:

 TBaseClass = class
  fLogger : TLogger;
 end;

 
Two usable classes are inherited from it:
 

 TClassA = class(TBaseClass)
  fWorkClass1 : TWorkClassA;  
  fWorkClass2 : TWorkClassB;
 end;
 
 TClassB = class(TBaseClass)
  fWorkClass3 : TWorkClassC;
  fWorkClass4 : TWorkClassD;
 end;

...which have working classes:
 

 TWorkClassA = class
  fLogger : TLogger;
 end;
 
 TWorkClassB = class
  fLogger : Tlogger;
 end;
 
 TWorkClassC = class
  fLogger : TLogger;
 end;
 
 TWorkClassD = class
  fLogger : Tlogger;
 end;

These objects I use directly in the code:

var
 ObjectA : TClassA;
 ObjectB : TClassB;

ObjectA and ObjectB create their own separate workgroups, and I would like all classes in the group to use the same fLogger instance.
 
I would like to create two instances of TLogger:
- first for objects: ObjectA, fWorkClass1, fWorkClass2
- second for object: ObjectB, fWorkClass3, fWorkClass4

How to register and get from Spring4D?

[Eddy M.]

Hi Jacek,
I think you can use Aspects oriented programming. Try DSharp library. (I haven't tried yet, but it looks impressive)

[Honza Rameš]

Hi Jacek,

I'd recommend using named injections. (Stefan has some surprises that might allow you to achieve similar functionality differently, stay tuned for 1.3 ;-) ).

Honza

[Stefan Glienke]

You can write your own resolver that handles TLogger and injects the same instance based on some criteria (like a Logger('groupname') attribute on your injection target or something like that)