New Syntax in twinBASIC: Part 2
Let's cover some more new syntax in twinBASIC, including parameterized class constructors, method overloading, and return syntax for functions.
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New Syntax in twinBASIC
twinBASIC introduces several new language features beyond simple VB6 compatibility. Of course, while this syntax and these features are new compared to VB6, most of them are found in VB6's second cousin, twice-removed, VB.NET.
In Part 1, I covered the following new syntax:
- Short-circuiting boolean operators,
- The ternary operator,
- Statements to skip to the next loop operation,
Continue For, et al.
In this article, I'll cover the following new syntax:
- Parameterized class constructors
- Method overloading
- Return syntax for functions
Parameterized class constructors
One of the features I'm most excited about in twinBASIC is its support for parameterized class constructors. This feature is sorely lacking from VBA, requiring a workaround in the form of factory functions.
The VBA approach
Here's an example of how I handle this situation in VBA using a factory function:
The twinBASIC approach
Now, let's take advantage of twinBASIC's parameterized constructor feature to rewrite the above code. In addition to the familiar
Class_Initialize() method, we can now create public methods named
New() and pass zero or more variables to those methods:
Also, notice in the code below how the semantic highlighting makes it clear which
Year values go together:
Method overloading allows us to declare the same routine name more than once in the same scope but with a different number and/or type of parameters. How might this be useful? One common scenario is looking up a database record by autonumber ID or by a unique key field.
Return syntax for functions
Returning a value from a function by assigning that value to an identifier with the same name as the function felt awkward to me when I first started writing VBA. I think using the Return syntax makes code read more like plain English, which is always a good thing.
Keep in mind, though, that using the Return syntax is like including an implicit
Exit Function call immediately after the
Return line. Thus, any cleanup code you might have in place would need to be called before the Return call.
There is one last point about the new return syntax. In order to maintain full backwards compatibility with VB6/VBA, you cannot use this new syntax within a procedure that contains
GoSub subroutines. (There's no reason to use those, anyway, so this is not much of a limitation.)
CORRECTION [2021-05-27]: Updated sample code for twinBASIC constructors from Function to Sub. Constructors must be Sub's.