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Jet
Guest
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 Posted: Fri Aug 13, 2004 3:51 am Post subject: My own class type of Property |
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hi again folks! i have another problem, and hope that you can
help me out, like you always do. =)
this is related to my previous post, about events with
parameters.
I wanted to use Valedit::TItemProp for my customized
ListView to use the properties of the ValueListEditor's
ItemProps.
So I declared my own
__property Valedit::TItemProp ColumnProps[int] =
{read = GetColumnProps, write = SetColumnProps};
but it says "VCL-style classes must be constructed using the
operator new."
so I just decided to have my own class,
class TColumnProp {
// members
};
then use it as a property :
__property TColumnProp ColumnProps[int] = { // read and write};
but now the error is "Not an allowed type".
Am I allowed to use my own class as a type for a property?
Or do you have any other suggestions on how I can implement
TValueListEditor's ItemProps?
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Remy Lebeau (TeamB)
Guest
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| Posted: Fri Aug 13, 2004 6:19 am Post subject: Re: My own class type of Property |
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"Jet" <jettosan (AT) yahoo (DOT) com> wrote
| Quote: | __property Valedit::TItemProp ColumnProps[int] =
{read = GetColumnProps, write = SetColumnProps};
but it says "VCL-style classes must be constructed using the
operator new."
|
You need to declare your property to use pointers:
// notice the asteriks
Valedit::TItemProp* __fastcall GetColumnProps(int index);
void __fastcall SetColumnProps(int index, Valedit::TItemProp *value);
__property Valedit::TItemProp* ColumnProps[int] = {read=GetColumnProps,
write=SetColumnProps};
Gambit
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Jet
Guest
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| Posted: Fri Aug 13, 2004 8:11 am Post subject: Re: My own class type of Property |
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"Remy Lebeau (TeamB)" <gambit47.no.spam (AT) no (DOT) spam.yahoo.com> wrote:
| Quote: | You need to declare your property to use pointers:
// notice the asteriks
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Thanks, but what if I want to use
__property TColumnProp ColumnProps[int] =
{read = GetColumnProps, write = SetColumnProps};
class TColumnProp {
// members
};
instead? Because I want to create an EditStyle with a different
enum set.
Can't I use a user-defined class as a property type?
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Remy Lebeau (TeamB)
Guest
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| Posted: Fri Aug 13, 2004 5:26 pm Post subject: Re: My own class type of Property |
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"Jet" <jettosan (AT) yahoo (DOT) com> wrote
| Quote: | Thanks, but what if I want to use
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You should still be using pointers anyway, it is more efficient than
creating temporary instances every time your property is accessed.
| Quote: | Can't I use a user-defined class as a property type?
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Of course you can. But that is not the issue here. Your original code
could not use Valedit::TItemProp because you were not using pointers. VCL
objects cannot be instantiated on the stack, they must always be on the
heap, thus the need for pointers. Once you get that working, it is simple
to adapt the code to use a custom class instead of Valedit::TItemProp, but I
still recommend the use of pointers for the property.
Gambit
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Jet
Guest
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| Posted: Sun Aug 15, 2004 3:05 am Post subject: Re: My own class type of Property |
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"Remy Lebeau (TeamB)" <gambit47.no.spam (AT) no (DOT) spam.yahoo.com> wrote:
| Quote: | You should still be using pointers anyway, it is more efficient than
creating temporary instances every time your property is accessed.
--)) Ok, i'll remember that. Thanks. |
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