Leaderboard

SmithD's response seems to be the general consensus I think. Mark, this is a good quote I'm stealing "if more than one class uses a typedef than is belongs to neither " Interesting about the translation classes. Translating the types was actually something I considered, but then I ruled it out because I thought I'd end up with too many types that were essentially duplicates of each other. I'll take a look at his presentation if I can dig it up. I started thinking about other languages such as C# and how they would handle this. I realized most methods would return classes or interfaces, not structures. And I started thinking about why that would be decoupled, and it's because the classes being returned are not owned by any other class. So this gave me my answer. Make sure the typedef isn't owned by any other class, and it effectively just becomes a POCO.

That's a good thread. We use a conceptually and practically simpler approach to interfaces. The tradeoff for the simplicity and clarity is that our approach does not allow a class to implement multiple interfaces. To date we have found the simplicity to be worthwhile. The thread here http://lavag.org/topic/14213-strategy-pattern-example/page__hl__strategy__fromsearch__1 has a link to a document in which we discuss abstract classes and interfaces, what those mean, how we implement them, reasons to use them, and some use cases. (See especially the appendix.) For more real-world examples you might see our slides from our NI Week 2012 presentation, "TS 8237 State Pattern Implementation for Scalable Control Systems." The starting concepts, as I see them, are: Abstract Class: "A class that can be used only as a superclass of some other class; no objects of an abstract class may be created except as instances of a subclass.“Larman, C., [Applying UML and Patterns: An Introduction to Object-Oriented Analysis and Design and Iterative Development], Pearson, Upper Saddle River, 689 (2005). Pure Virtual Method (Abstract Method): A method that has no implementation. This means that if we have a pure virtual method in a parent class, every child must implement that method. Budd, T. [An Introduction to Object-Oriented Programming, 3d ed.], Addison-Wesley, Boston, 170 (2002). Interface: "A class can have abstract (or pure virtual) methods and nonabstract methods. A class in which all methods were declared as abstract (or pure virtual) would correspond to the Java idea of an interface.“Budd, T. [An Introduction to Object-Oriented Programming, 3d ed.], Addison-Wesley, Boston, 170 (2002). We implement LabVIEW interfaces as abstract classes (never instantiated, by policy) with all "pure virtual methods" (in LabVIEW meaning we have implementations that do nothing). The key advantages we derive from using interfaces are source code isolation and the ability to do design by contract. Some of the many cases where we use interfaces are in the Factory Method Pattern and the State Pattern.