Re: [e4-dev] A missing framework piece: contexts?

[Kevin McGuire <Kevin_McGuire@xxxxxxxxxx>]

Oleg, there is a huge intersection between
what you described below and what Paul and I have been discussing but for
us we were only thinking at the UI level.  We didn't consider POJO
injection (but that's cool).  We were thinking about hierarchically
scoped contexts to parallel visual scoping in the workbench (e.g. workbench
window, perspective, view stack, view), with matching algorithms for getting/setting
values.  All this as a way to detach those who need the values (e.g.
menu enablement) from those who supply the values so that the shape of
the application can change but everything still works. 

Anyway, we should talk... :)

Kevin

Oleg Besedin/Ottawa/IBM@IBMCA
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01/07/2009 03:33 PM

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Subject	[e4-dev] A missing framework piece: contexts?

“Progress is made by lazy men looking for easier ways to do things”.

I think this is exactly how the concept of contexts came to life. Our code
runs in some environment; way too often we need to pass tens of arguments
from method to method and from class to class just to keep them aware of
the environment. 

To make it easier we are considering adding a concept of "context".
At the conceptual level a "context" is a combination of:
- a bag that could be stuffed with elements that compose environment, and
- a mechanism to inject elements from the bag into your POJO objects

The contexts are organized in a hierarchy. Child context can add service
objects that make sense at their level: 
        IEquinoxContext  myContext = ApplicationContext.newChild();
        myContext.addObject("log", myLog);

The service objects from the context can be injected into POJO objects
using field and method injection: 

        myContext.injectInto(object)

resulting in the field object.equinoxLog being set to "myLog".

Contexts support dynamic events and multiple service objects per ID. In
addition, contexts can be tied into creation of objects from the extension
registry and help access OSGi services. 

I'd like to raise this subject at the E4 call to see what people think
about it. The details of this work can be found in the enhancement request
259423: 

https://bugs.eclipse.org/bugs/show_bug.cgi?id=259423

Sincerely, 
Oleg Besedin _______________________________________________
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