Re: DI/wiring
On 18/04/2013 21:16, markspace allegedly wrote:
On 4/18/2013 9:03 AM, Stefan Ram wrote:
I have ?invented? myself something that also seems to be
known as ?dependency injection? or ?wiring?. I am doing it
I should have a look at Joerg's answer myself, but here's another idea.
Make an app context object that holds the state of your app.
class Context {
Engine getEngine()....
Printer getPrinter()...
}
Inject that into submodules in the code. Submodules are larger than
classes and can treat the context as immutable. The context then
becomes global but only for that module. The idea is that you still get
dependency injecting, but you can still test reasonably as well.
class SomeConfig {
Context context;
public SomeConfig( Context c ) { context = c; }
public init() {
Component c0 = new Component( context );
....
}
}
class Component {
Context context;...
public printIt() {
context.getPrinter().do something...
}
}
This reduces boilerplate but doesn't eliminate it. For some projects it
might be better to get a real dependency injection framework.
As a side note, since this approach has the drawback of requiring
additional constructor or method parameters (and hence targeted
factoring), I have in such cases often found it useful to provide the
context object via the threadlocal functionality.
In code terms, instead of:
class Actor {
void act( Context c ){ doSomethingWith( c.getXXX() ); }
}
You'd have:
class Actor {
void act(){
doSomethingWith( ContextHelper.getThreadLocalContext().getXXX() );
}
}
--
DF.