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May
21
comment Is Visitor Pattern valid in this scenario?
What's missing (to me) for Visitor is the class structure that accepts visitors. The motivation for Visitor is that you have many class types in some aggregate that need visiting, and it's not convenient to modify their code for each new functionality (operation). I still don't see what those aggregate objects are, and think that Visitor is not appropriate. If it's the case, you should edit your question (which refers to visitor).
May
21
comment Is Visitor Pattern valid in this scenario?
The GoF Visitor pattern says it "lets you define a new operation without changing the classes of the elements on which it operates." I think RecurringTask is the kind of operation you'd want to add easily, but I fail to see what are the "classes of the elements on which it operates." The only problem you clearly state is "where should I put EmailService?" and that's not a pattern-type problem.
May
7
comment Should I use the State Design pattern for only two states? Also, what if one object's state is affected by another state?
If the logic for changing states is simple, and you only have two states (and don't expect more), then State Pattern might be overdesign. Consider the solution that's simple. It sounds as if you're looking for a problem to solve with a pattern, rather than the other way around. To use another analogy, just because you have a drill in your toolbox, don't go looking for places to put holes in your house.
May
6
answered In MVC, who is in charge of handling observers?
May
2
comment In MVC, who is in charge of handling observers?
If you use a real object rather than objectA, say engineTemperature, then your view that displays the temperature would surely know what it's displaying. It's normal for views to be coupled to the model elements they display. The other way around, however, is different. engineTemperature should not know how it's being displayed, or who's displaying it, etc. It (as a Subject in the Observer pattern) only knows it has Observers, which all support the Observer API. Have a look at martinfowler.com/eaaDev/uiArchs.html#ModelViewController
May
2
comment In MVC, who is in charge of handling observers?
MVC isn't about total decoupling. It's about avoiding coupling to elements that are unstable. Views tend to be less stable than the model, because they're the UI (users tend to want new ways to view, etc.) E.g. how many times the GUI for Microsoft Word has changed, yet the model of a document has not changed much. Views are directly coupled to the model classes because they're more stable. Model classes are coupled to views via the Observer pattern. The Observer API is very stable, even if the views that implement it are not. So it's OK to have coupling the way you have described it.
May
2
comment In MVC, who is in charge of handling observers?
I disagree with @RobertHarvey in that MVC Views are often Observers of Model classes. The patterns are indeed related; one isn't required to use Observer with MVC, however.
May
2
comment In MVC, who is in charge of handling observers?
We've now coupled the View into the internals of the Model, which I believe violates the Law of Demeter. I'm pretty sure this also violates the concept of MVC by definition. The second point is wrong. Views do know the model. By definition, view code changes more often, so you don't want model code being coupled to it directly. As for Law of Demeter, you'd have to show why you think it violates it. It's not a hard and fast principle, either, despite it's name having the word "Law" in it. It's nearly impossible not to violate it at some point.
Apr
10
comment Is it OK to deprecate methods that need to be public due to the packaging model but are not to be used outside the codebase in Java?
A UML sequence diagram would be helpful to see the flow.
Apr
10
comment Is it OK to deprecate methods that need to be public due to the packaging model but are not to be used outside the codebase in Java?
There's a convention in Eclipse Java to use internal path for having private methods that should not be used by external classes. However, I'm not sure it solves your problem since Message can't be both internal and not (for the methods people should call).
Mar
10
awarded  Popular Question
Feb
14
comment Possible way to make java class builder more abstract by using interface required keys
Related blog explaining this builder/required technique: blog.crisp.se/2013/10/09/perlundholm/…
Feb
12
awarded  Yearling
Feb
11
revised Should I use Strategy Pattern for this task?
added 170 characters in body
Feb
10
revised Should I use Strategy Pattern for this task?
added 351 characters in body
Feb
10
answered Should I use Strategy Pattern for this task?
Feb
5
comment How to add permissions checks 'after the fact'
I think this is a great answer because it points out the trade-off between flexibility and the added complexity (obscurity) of a design pattern.
Feb
4
revised One controller to rule them all?
Fixed English
Feb
4
comment One controller to rule them all?
I would also not try to come up with your own way, before checking out recommended ways. Google found me this tutorial: pluralsight.com/training/…
Feb
4
comment One controller to rule them all?
Re: #2, I would spend time on real security and not on security by obscurity.