Jeff,
Oddly enough, it sounds almost exactly like EObject, only we call them
features rather than properties. And strangely coincidental to your
preference reference, someone was just recently asking how best to use
EMF to better support preferences:
http://www.eclipse.org/newsportal/article.php?id=38544&group=eclipse.tools.emf#38544
<http://www.eclipse.org/newsportal/article.php?id=38544&group=eclipse.tools.emf#38544>
It's a small world. Go figure! :-P
Cheers,
Ed
Jeff McAffer wrote:
My heart has been warmed on this cold winter day by the mere mention
of Smalltalk...
That aside, this datastructure here sounds like Properties with
notification. That in turn sounds like our preference mechanism.
funny that.
Jeff
John Arthorne wrote:
"Bag" is just a Smalltalk term for an unordered collection.
Essentially a context is just a map, with extra logic for tracking
dynamic changes, injection, and a notion of a parent context. If the
most local context can't supply a value, it delegates to the parent.
As Kevin suggested this allows modeling of things like the widget
hierarchy where a tab in a view might be one context, the view itself
another context, another context for the window, etc, up to a global
application context. You're right that the injection logic can (and
probably should) be separated from the context logic since it's
unlikely to change.
*Ed Merks <[email protected]>*
Sent by: [email protected]
01/07/2009 04:41 PM
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Subject
Re: [e4-dev] A missing framework piece: contexts?
Oleg,
Comments below.
Oleg Besedin wrote:
“Progress is made by lazy men looking for easier ways to do things”.
I'm exceedingly lazy...
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
Couldn't we just use Map<String, Object>? What's the significance of
the term "bag"?
- a mechanism to inject elements from the bag into your POJO objects
Such a mechanism could be independent of how the "bag" itself is
implemented.
The contexts are organized in a hierarchy. Child context can add
service objects that make sense at their level:
IEquinoxContext myContext = ApplicationContext.newChild();
Will we expect people to create context with specialized behavior?
Which parts will be specialized and why?
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".
I could imagine a static Injector.inject(Map<String, Object> values,
Object target) utility doing all this type of work with no additional
interfaces or implementations of those interfaces. Of course then
there's be only one implementation of this, which conceptually seems
less flexible, but that's the question earlier. What parts of which
mechanisms would clients be trying to specialize?
Contexts support dynamic events and multiple service objects per ID.
What are those? :-P
In addition, contexts can be tied into creation of objects from the
extension registry and help access OSGi services.
I think I'm missing a lot of the picture even looking in the
bugzilla. It sounds interesting though...
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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