Array of pointers
in [Visual Basic]
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From: Nobody on 11 Oct 2009 19:23 One way, but I don't like it, is swapping pointers via CopyMemory, but could lead to crashes if you are not careful. Also search the newsgroups for SysAllocStringLen/SysAllocString.
From: Henning on 11 Oct 2009 19:43 "xytsrm" <xytsrm(a)discussions.microsoft.com> skrev i meddelandet news:527FC413-4CF6-4AC2-B7C9-F8BF7EA6D3F2(a)microsoft.com... > Problem" > Lets say that I have several variables defined: > > Dim A As String > Dim B As String > Dim C As String > > In the program I want to retain the references A,B and C, but I would like > to assign values to A, B and C by indexing. In other words what I would > like > to create is an array of pointers [ie. Dim X(3)] to A, B, and C, such that > by > equating X(1) = "message 1", then A = "message 1". VarPtr can be used to > make X(1) reference A by X(1) = VarPtr(A), but I'm not sure how to > indirectly > assign "message1" to A via X(1). Perhaps there's an easier way? Can > anyone > help? > > X. > This all seems as a lot of trouble to avoid a Select Case to select what var to use out of an index. There might be some other struggle not known ofcause. /Henning
From: Bob Butler on 11 Oct 2009 19:50 "xytsrm" <xytsrm(a)discussions.microsoft.com> wrote in message news:527FC413-4CF6-4AC2-B7C9-F8BF7EA6D3F2(a)microsoft.com... > Problem" > Lets say that I have several variables defined: > > Dim A As String > Dim B As String > Dim C As String > > In the program I want to retain the references A,B and C, but I would like > to assign values to A, B and C by indexing. In other words what I would > like > to create is an array of pointers [ie. Dim X(3)] to A, B, and C, such that > by > equating X(1) = "message 1", then A = "message 1". VarPtr can be used to > make X(1) reference A by X(1) = VarPtr(A), but I'm not sure how to > indirectly > assign "message1" to A via X(1). Perhaps there's an easier way? Can > anyone > help? If you created a class to hold the string you could declare A, B, and C as instances of the class and also add them to a collection or an array to reference them by index. It's a lot more overhead than some sort of Union equivalent but might suit your needs.
From: Nobody on 11 Oct 2009 20:43 Also, one alternative solution is using string arrays like others suggested, but use Enum values as index. VB's intellisense would show you the list of values in this case. Example: Dim s(1 To 3) As String Private Enum str strA strB strC End Enum Usage: s(str.strA) = "ABC" When you type "str" followed by ".", VB shows the list of values, so you don't have to remember them.
From: Dee Earley on 12 Oct 2009 06:50
On 11/10/2009 02:23, Ralph wrote: > Also notice that StrPtr() and ValPtr() do not report the same item when used > on a VB String variable. They won't. The variable has a location which you can get with VarPtr (I assume you meant VarPtr, not ValPtr) which, for numbers is the data itself. For a string, this will be another pointer which refers to the start of the string data (which you can get via StrPtr). Essentially, if you copy 4 bytes of data from varptr(stringvar), you should end up with the same value as strptr(stringvar). -- Dee Earley (dee.earley(a)icode.co.uk) i-Catcher Development Team iCode Systems |