[VisualBasic] A few questions on commands

[yatzr]

I know java pretty well and am now learning Visual Basic and I'm having some problems.

First, what is the Visual Basic equivalent to Java's try-catch error resolving? I can't find this anywhere in my VB book. Does Basic have something similar?

Second, Is there a command to see if a file exists?

Thanks

[Stiltzkin]

I think starting with Visual Basic.NET, you can use:

Try (arguments)

Catch

End Try

[yatzr]

well, i'm not using the .net version...VB6 doesn't have that but I found it anway.
I do have another question now though.

Can someone explain the structure of a class and relate it to a typical java class? I understand java classes pretty good but I'm pretty lost on VB classes (at least with the variables and properties...I don't understand what those are). Also, with methods, how do I "return" a value?

[Kadath]

Originally Posted by yatzr

well, i'm not using the .net version...VB6 doesn't have that but I found it anway.
I do have another question now though.

Can someone explain the structure of a class and relate it to a typical java class? I understand java classes pretty good but I'm pretty lost on VB classes (at least with the variables and properties...I don't understand what those are). Also, with methods, how do I "return" a value?

I am not spectacular with VB, but instead of returning, you can pass a variable ByRef instead of byVal and the actual variable is changed. So if you declare the variable in the main, then run a module with the variable passed as an argument ByRef and when you finish the module the variable itself will have changed.

A VB Class is not a whole lot different to a Java class. It needs to be defined within a class module, and is simply a collection of hidden variables that are accessed via 'Property Let' and 'Property Get' statements - So, say I want to create a class that represents a Cartesian Coordinate called CartCoord, I'd create a class module Called CartCoord and fill it with the following:

Private privX as Double
Private privY as Double

Property Let X (aValue as Double) 
privX = aValue
End Property

Property Get X () as Double
X = privX
End Property

Property Let Y (aValue as Double) 
privY = aValue
End Property

Property Get Y () as Double
Y = privY
End Property

Property Get DistanceFromOrigin() as Double
DistanceFromOrigin = Sqr(PrivX^2 + PrivY^2)
End Function

So after creating an instance of the object, I can populate the X and Y values, and then ask it to tell me the distance the represented point is from the Origin like so:

Set MyPoint = New CartCoord
MyPoint.X = 3
MyPoint.Y = 4
Z = MyPoint.DistanceFromOrigin

So later, when I query Z (assuming I remember my trigonometry right), I should have a value of 5.