Heres a nice big chunk of info that can be found both in the user manual and in the help files.:-
USER DEFINED TYPES
If the current set of datatypes is inadequate for your needs, you can can create your own data types
using user-defined-type. User defined types are useful for storing data using logical fields rather than the
unfriendly list of subscripts used by arrays.
To create a user defined type, you must first declare it at the top of your program. To do so, you would
give your type a name and a list of fields it contains:
TYPE MyType
Fieldname1
Fieldname2
Fieldname3
ENDTYPE
The above code creates a type called MyType with three fields contained within it. As the fields have no
declaration, they are assumed to be integers. The same code could also be truncated to a single line like
so:
TYPE MyType Fieldname1 Fieldname2 Fieldname3 ENDTYPE
To use your type, you simply create a variable and declare it with your new type. To declare a variable as
a specific type, you would use the AS statement:
MyVariable AS MyType
You can then assign data to your variable as normal, with the added bonus of the fields you have given
your variable like so:
MyVariable.Fieldname1 = 41
MyVariable.Fieldname2 = 42
MyVariable.Fieldname3 = 43
At the moment, the type is assuming our fields are integers. We may wish to declare our fields as a real
number, string or other datatype. We can do so using the same AS statement within the type definition.
So the following code makes more sense we shall give our type and fields sensible names:
TYPE AccountEntryType
Number AS INTEGER
Name AS STRING
Amount AS FLOAT
ENDTYPE
You can use a type like any other, so creating and using an array of the above is simply a case of
declaring the array with your new type:
DIM Accounts(100) AS AccountEntryType
Accounts(1).Number=12345
Accounts(1).Name="Lee"
Accounts(1).Amount=0.42
As you will eventually discover you can have types within types for more complex data structures so we
can imagine one of the fields contains more than one value. We would define two user defined types, and
then use one of them in the declaration of one of the fields of the section user defined type, as follows:
TYPE AmountsType
CurrentBalance AS FLOAT
SavingsBalance AS FLOAT
CreditCardBalance AS FLOAT
ENDTYPE
TYPE AccountEntryType
Number AS INTEGER
Name AS STRING
Amount AS AmountsType
ENDTYPE
DIM Accounts(100) AS AccountEntryType
Accounts(1).Number=12345
Accounts(1).Name="Lee"
Accounts(1).Amount.CurrentBalance=0.42
Accounts(1).Amount.SavingsBalance=100.0
Accounts(1).Amount.CreditCardBalance=-5000.0
As you can see, user defined types are not only powerful, they make the readability of your programs far
easier. Using named fields instead of a subscript value within an array, you can save yourself many hours
all for the sake of an incorrect subscript value throwing out your program results.
Specs:- 1GHZ athlon, Radeon8500, 192mb ram, winxp
