Solved: Manage similar events with textboxes

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Originally Posted by GTO

Personally, I'm hoping (subliminal hint) Bob wants to explain a bit about the scary dark world of classes...

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I have been trying to write a decent paper on that subject for years now ...

And I have been waiting to read a decnt paper for even longer.

However, this usage of classes is not an example of the 'real' usage of classes IMO, which is to create a custom object type.

People don't understand them (object classes), and thus do not use them (my brother still doesn't 'get' them, even after 10 years of me badgering him about them), but they have nothing to do with ranges, userforms or controls per se.

Any discourse on classes would be primarily about object classes. The usage of classes to manage control arrays is using classes because classes are the only way to use a variable WithEvents. An object (class) might interact with such controls, but it should be generic in its interface, the front-end should handle those matters.

...and my big yap gets me in trouble again... no wonder I was scared!

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Originally Posted by xld

However, this usage of classes is not an example of the 'real' usage of classes IMO, which is to create a custom object type.

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Okay, here is where the youngster who's just barely trusted to do valve jobs is listening to an experienced race engine builder casually mention the effects of cam phasing and overlap on calculated compression ratio vs effective... Ya lost me at the term "custom object type".

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Originally Posted by xld

People don't understand them (object classes), and thus do not use them (my brother still doesn't 'get' them, even after 10 years of me badgering him about them)

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Well... of course it remains frustrating (for me I mean) when one is trying to expand knowledge in something that appears to have some potential, but least I don't feel so glitched...

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Originally Posted by xld

..., but they have nothing to do with ranges, userforms or controls per se.

Any discourse on classes would be primarily about object classes. The usage of classes to manage control arrays is using classes because classes are the only way to use a variable WithEvents. An object (class) might interact with such controls, but it should be generic in its interface, the front-end should handle those matters.

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The first part of this is making sense to me in that using the class as an aid to the userform (controls) is not the primary goal of classes (though even the WithEvents is a bit abstract to me), but a custom object type is where I go utterly void.

Besides the help file topics of course, would you have any suggestions as to internet searches (keywords), books, or other sources for me to gain at least a workable knowledge of WithEvents and examples of a Custom Object Type?

As always, thank you so much for your time and help Bob,

Mark

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Originally Posted by GTO

.Okay, here is where the youngster who's just barely trusted to do valve jobs is listening to an experienced race engine builder casually mention the effects of cam phasing and overlap on calculated compression ratio vs effective... Ya lost me at the term "custom object type".

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There is nothing complicated about it. There are objects, or things, everywhere. An object is just something that has attributes (properties in the definition), and can do things or have things done to it (methods). A car is an object, a person is an object, a seat is, and so on. Even Excel is an object, an application object. But, and here is where it gets good, properties of an object can be objects within their own right. So a car, which has properties (wheels, seats, etc.), has object properties too, a wheel has spokes properties, has a tyre property, has an inflate/deflate method, and so on. Excel too has the same, the application object has workbook properties, the workbook has worksheets and so on. You should be able to see where we are going with this, we are describing an object model, a full description of the object, its properties, and its methods.

That is what a custom object is, it is the description of a thing that we need to address. In code terms, when you want to create an object, you create a class and describe the object within that class.

Quote:

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Originally Posted by GTO

The first part of this is making sense to me in that using the class as an aid to the userform (controls) is not the primary goal of classes (though even the WithEvents is a bit abstract to me), but a custom object type is where I go utterly void.

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As I said above, the class describes the object. The developer determines what properties and methods of the object (class) are exposed. As a (trivial) example you could have a house object, which has a number of chimneys, but if you don't expose that properties, the code that interfaces with the class cannot set the number of chimneys, nor query the class to tell it how many chimneys the house has.

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Originally Posted by GTO

Besides the help file topics of course, would you have any suggestions as to internet searches (keywords), books, or other sources for me to gain at least a workable knowledge of WithEvents and examples of a Custom Object Type?

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WithEvents examples will normally just be examples to provide event control that Excel has not provided (examples of not exposing aspects of the class that I mentioned above), such as application events, control arrays and so on. There are plenty of examples of these, but custom objects is another story, there is no good write-up that I have seen.

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Originally Posted by xld

I have been trying to write a decent paper on that subject for years now ...

And I have been waiting to read a decnt paper for even longer.

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I'd love to read the paper if you ever find/write one.

@XLD:

Greetings Bob,

Sorry I did not acknowledge your answer in a more timely manner. I wanted to read through and think about it, and well... the thinking part was a bit slow and then I got busy.

As I have only really used a class to access the app's events, I certainly believe your explanation helps in increasing my ability to conceptualize it a bit better. As you noted, examples of where classes can be used very effectively seem a bit sparse, and I hope you won't mind having to beat it into my head a bit as I continue to learn. To me leastwise, the first hurdle of conceptualizing objects is not nearly as high a hurdle as the "I get it" hurdle of when/how/what object could be created (wherein said would be advantageuous).

Thank you so much for your time and help :-)

Mark

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Originally Posted by GTO

To me leastwise, the first hurdle of conceptualizing objects is not nearly as high a hurdle as the "I get it" hurdle of when/how/what object could be created (wherein said would be advantageuous).

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Exactly, that is precisely the problem.

There are a myriad of examples out there of a person class, where you create such a class and populate the proerties (name, gender, DoB, etc.) and they are very good at describing the mechanics of the class. But to quote my dear brother, but I can do all that without a class with just modular code so why a class?

The best answer IMO is that it helps conceptualise the design of the application, you think better of the structure of the code. You can have any number of ways of designing the class, but by getting a good clean design, with a good interface, you abstract the elements of the business model (and every application has a business model as its heart) and can break the problem into easy manageable chunks; you create a good testing model; you provide an straightforward extensibility model.

To me they are essential. But even then I forget just how much. I am just building an application using Excel styles, and I have got into a number of problems in managing them all across many workbooks. On reflection, I think I could have done it better with classes (I think I didn't spot this originally because I was just tapping into Excel objects, why replicate that), and am going to try this today.

I've also had a very hard time learning about classes in the past. I also bugged Bob, asking him to explain classes to me :)

I've recently found a book that I think gives the best description of classes that I've ever read. It also takes you through very real examples of creating classes; complete with objects, properties, and methods. It is Visual Basic 2005 Express Edition Starter Kit from Wrox. It is a Visual Basic Express book, not a VBA book, but if you know VBA, then you pretty much know Visual Basic. And since you can download Visual Basic 2005 Express for free from MSDN, the book would be the only real cost involved.

If you're serious about learning more about classes and want to stretch yourself from an office dev to an office and applications dev, then you should take a look at this book.

@Bob: I can't wait to read your paper, if you ever get it finished.

Greetings Randy,

Thank you so much for the suggestion. Not sure if I'll ever get into app development, but I like learning and can certainly spring for a book.

Thank you again,

Mark