User defined types (or UDTs) are structures that you can use in most BASIC
languages, Rapid-Q is no exception.
Using TYPE
Here's an example of a user defined type:
TYPE TWorld
CityName(100) AS STRING
Population(100) AS LONG
END TYPE
DIM World AS TWorld
As you can see, you can have arrays within UDTs. You can also create arrays of UDTs:
TYPE TWorld
CityName(100) AS STRING
Population(100) AS LONG
END TYPE
DIM Country(100) AS TWorld
There is currently an issue with the memory address of your array (within UDT). Please note that
this is hardly ever noticed unless you're going to pass one of these structures
to a DLL that require arrays within UDTs. This address problem won't affect
your program, but it's hard to explain (without getting too deep). NOTE: it only occurs when you create
arrays of UDTs that have arrays within UDTs. In the first example (higher up), there
is no address problem since you're not creating an array of UDTs. You can
safely pass that to a DLL.
Copying UDTs
To copy 2 UDTs, just assign the two:
TYPE TStuff
A AS LONG
B AS INTEGER
END TYPE
DIM S1 AS TStuff
DIM S2 AS TStuff
S1 = S2
Содержание in S2 are copied to S1. When dealing with arrays within UDTs, the
arrays are not copied, only referenced. To copy arrays of UDTs, you'll have to
manually copy each one:
DIM S1(100) AS TStuff
DIM S2(100) AS TStuff
FOR I = 1 TO 100
S1(I) = S2(I)
NEXT
Unhooking TYPE
There are actually 2 ways to create your types, with TYPE and STRUCT.
STRUCT is actually mirrored in TYPE, to unhook the two, you have to undefine
TYPE.
$UNDEF TYPE
TYPE TWorld
CityName(100) AS STRING
Population(100) AS LONG
END TYPE
DIM World AS TWorld
Using TYPE and STRUCT are not the same. If you unhook the two, TYPE now reverts
back to the old style (pre-May 17 version), where arrays of UDTs is not allowed.
Why the heck would I want a stripped down version? Well, perhaps performance.
The old style TYPE lacks in many things, but makes up in performance, if that's
really necessary.