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how use address operator on a class constructor?
my class menu have a constructor:
how can i convert the submenu to address variable instead a pointer?
Menu(string caption, Menu *submenu=NULL, HWND MainHWND=WindowMain, bool systmenu=false)how can i convert the submenu to address variable instead a pointer?
Not sure I understand. A pointer is an object that contains the memory address of some other object.
that constructor make me use it on these way:
the address operator before the mnuFile. can i change the Menu contructor for accept it without the address operator?
(but continueing with 1 default value)
Menu mnuFile("&File"), mnuExit("&Exit",&mnuFile);the address operator before the mnuFile. can i change the Menu contructor for accept it without the address operator?
(but continueing with 1 default value)
You could make the second parameter a reference and then use the & operator inside the constructor to get the pointer instead.
References can't be null so to allow all but the first argument to be left out you could add another constructor that only takes a string as argument.
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References can't be null so to allow all but the first argument to be left out you could add another constructor that only takes a string as argument.
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i'm sorry but what you think about:
?
but i don't know compare the value.
another question: being a pointer, i can use NULL, but why not with adress operator?
Menu(string caption, Menu &submenu=*(Menu*)NULL, HWND MainHWND=WindowMain, bool systmenu=false)?
but i don't know compare the value.
another question: being a pointer, i can use NULL, but why not with adress operator?
Null means the pointer is not pointing to a valid object. It is not allowed to dereference a null pointer. If you do, it means the behaviour is undefined so anything could happen.
If you need to handle null I really think you should use pointers. References are not the correct tool for the job. It isn't that much of a job having to type & when you pass the object, is it?
If you need to handle null I really think you should use pointers. References are not the correct tool for the job. It isn't that much of a job having to type & when you pass the object, is it?
the problem isn't the job. but.. i did that class, but after sometime i was trying to use it, but i forget the '&', the compiler give me errors, but i was not understanding them :(
that's why i must do your 1st advice and overloading the constructor. it's the best.
that's why i must do your 1st advice and overloading the constructor. it's the best.
i'm overloading the Menu() constructor. but the 1st parameter it's, always the same. why i get some errors?
Last edited on
seems now that i understand why.
we must, when overloading, avoid default values\parameters or we can get some errors
we must, when overloading, avoid default values\parameters or we can get some errors
Menu(string caption, HMENU systemmenu, HWND window=ActivatedForm)
Menu(string caption,HWND MainHWND=ActivatedForm)
Menu(string caption, Menu &submenu, HWND MainHWND=ActivatedForm)like you see, only the 3rd parameter have defult value. so no error.
i hope these information help more people that needs overloading functions
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