One Instance of class
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Hi. I am not sure about this. I have a Cedit derived class in a DLL. In this I want to add a member of a keypad class I made. But I would like that EVERY CEdit derived class will only use ONE copy of this keypad. Can this be done just by declaring the keypad as a static member. Then when something it is entered into the keypad, it will be sent to the perspective Cedit class. Can someone help me shed some light on this? Thanks ahead of time. Stan the man
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Hi. I am not sure about this. I have a Cedit derived class in a DLL. In this I want to add a member of a keypad class I made. But I would like that EVERY CEdit derived class will only use ONE copy of this keypad. Can this be done just by declaring the keypad as a static member. Then when something it is entered into the keypad, it will be sent to the perspective Cedit class. Can someone help me shed some light on this? Thanks ahead of time. Stan the man
A static member would work well. You could keep a static reference count as well which tracks how many edit controls are in existence (initialize to 0). When an edit control is created increment the reference count. If the count is now 1, create the keypad. When an edit control is destroyed, decrement the count, and if it's 0, destroy the keypad. The edit controls can set another static variable when they gain focus, so the keypad knows which one to direct input to. Mark
Mark Salsbery Microsoft MVP - Visual C++ This episode brought to you by the number 3
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A static member would work well. You could keep a static reference count as well which tracks how many edit controls are in existence (initialize to 0). When an edit control is created increment the reference count. If the count is now 1, create the keypad. When an edit control is destroyed, decrement the count, and if it's 0, destroy the keypad. The edit controls can set another static variable when they gain focus, so the keypad knows which one to direct input to. Mark
Mark Salsbery Microsoft MVP - Visual C++ This episode brought to you by the number 3
Is it possible for me to decalre the keypad class in the edit class with a static? I would like to have the edit class somehow manage the keypad. Ex: class Keypad { } class Edit { static Keypad; } ... Is there someway to do that? Or do I have to manage the keypad in my mainfrm class or something? This way, when I declare an edit class, the keypad is "built in" but only has one copy (for memory sake) even with many edit controls. The keypad will direct the inputs to the correct parent. Thanks.
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Is it possible for me to decalre the keypad class in the edit class with a static? I would like to have the edit class somehow manage the keypad. Ex: class Keypad { } class Edit { static Keypad; } ... Is there someway to do that? Or do I have to manage the keypad in my mainfrm class or something? This way, when I declare an edit class, the keypad is "built in" but only has one copy (for memory sake) even with many edit controls. The keypad will direct the inputs to the correct parent. Thanks.
Like you've shown it is what I was thinking... class CKeypadWnd : public CWnd { }; class CKeypadEdit : public CEdit { static CKeypadWnd *pKeypadWnd; static int KeypadRefCount; static CKeypadWnd *pActiveKeypadWnd; ... }; ... // In the CPP file: CKeypadWnd *CKeypadEdit::pKeypadWnd = NULL; int CKeypadEdit::KeypadRefCount = 0; CKeypadWnd *CKeypadEdit::pActiveKeypadWnd = NULL; ... Mark
Mark Salsbery Microsoft MVP - Visual C++ This episode brought to you by the number 3
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Hi. I am not sure about this. I have a Cedit derived class in a DLL. In this I want to add a member of a keypad class I made. But I would like that EVERY CEdit derived class will only use ONE copy of this keypad. Can this be done just by declaring the keypad as a static member. Then when something it is entered into the keypad, it will be sent to the perspective Cedit class. Can someone help me shed some light on this? Thanks ahead of time. Stan the man
There's only a couple of reasons I can think of to share a class this way: 1) You're sharing data between the various CEdit objects 2) There are a lot of your CEdit objects in existance at a time and you're concerned with memory usage, performance (the time to create the keypad object), or memory fragmentation. I try to avoid static members unless the class is intended to provide static methods. If it were me, and if item 2 is the issue, I would dynamically create a single application global instance of the keypad and just use it wherever it's needed.
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
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"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001 -
There's only a couple of reasons I can think of to share a class this way: 1) You're sharing data between the various CEdit objects 2) There are a lot of your CEdit objects in existance at a time and you're concerned with memory usage, performance (the time to create the keypad object), or memory fragmentation. I try to avoid static members unless the class is intended to provide static methods. If it were me, and if item 2 is the issue, I would dynamically create a single application global instance of the keypad and just use it wherever it's needed.
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
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"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001Actually, I do have lots of Edits. But I wanted to have a simple way to just declare each edit and then have the keypad function all built in without additionally allocating it again globally and then tie it to each Edit somehow. Thanks for all the responses and comments!
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Actually, I do have lots of Edits. But I wanted to have a simple way to just declare each edit and then have the keypad function all built in without additionally allocating it again globally and then tie it to each Edit somehow. Thanks for all the responses and comments!
Well, once you allocate your CEdit iobject on the heap, everything inside it also resides on the heap, so you can declare your keybad object like so:
class CMyEdit { private: CMyKedPad m_KeyPad; };...and then initialize it in the CMyEdit constructor. At that point, there's no overhead involved in allocating that object on the heap, and you don't have to worry about delete/null it when your CMyEdit object cleans itself up. My guess is that your KeyPad object doesn't contain much data, so it's not like multiple instances is going to take up much space (probably less than 64 bytes). I still see no need for a static object (which is my entire point)."Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
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"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001 -
Well, once you allocate your CEdit iobject on the heap, everything inside it also resides on the heap, so you can declare your keybad object like so:
class CMyEdit { private: CMyKedPad m_KeyPad; };...and then initialize it in the CMyEdit constructor. At that point, there's no overhead involved in allocating that object on the heap, and you don't have to worry about delete/null it when your CMyEdit object cleans itself up. My guess is that your KeyPad object doesn't contain much data, so it's not like multiple instances is going to take up much space (probably less than 64 bytes). I still see no need for a static object (which is my entire point)."Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
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"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001Well, the keypad will be a dialog of sort (enable touchscreen capability). In this case, would you still think a static is not necessary and then just declare the kaypad class in the Edit class? Thanks. Stan
