ZBasic Language Reference
104
ZBasic Microcontrollers
The syntax for a member definition is given by the two descriptions below – the first being for a non-array
member and the second being for a member that is an array.
{Public | Private | Dim} <name> As <type>
or
{Public | Private | Dim} <name>(<dim-spec-list>) As <type>
As with ordinary variables, Dim has exactly the same effect as Private. The names of the members of
each class may be any legal identifier but a particular name may be used only once in each class. The
use of a name as a member in one class does not preclude it from also being used as a member name in
a different class or structure or as a variable, constant, parameter, etc.
The <type> specified for a member may be any of the pre-defined types like Integer, Byte, String,
etc. or it may be a user-defined type like an enumeration, a structure or another class. It is important to
note that recursive class definitions, with members that are or contain (directly or indirectly) an object of
the class being defined, are not allowed. Defining a class that contains one or more members that are of
different class types, known as composition, is an important aspect of object-oriented programming.
Examples
Class MyDate
Public year as UnsignedInteger
Public month as Byte
Public day as Byte
End Class
Class MyTime
Public hour as Byte
Public minute as Byte
Public seconds as Single
End Class
Class MyTimeStamp
Public tdate as MyDate
Public ttime as MyTime
Private isCurrent as Boolean
End Class
Sub Main()
Dim ts as MyTimeStamp
Call GetTimeStamp(ts.tdate.year, ts.tdate.month, ts.tdate.day, _
ts.ttime.hour, ts.ttime.minute, ts.ttime.seconds)
End Sub
The example above emphasizes the similarities between structures and classes; except for the different
keyword used, the syntax is identical. As with structures, instances of classes (called objects) can be
passed to subroutines and functions either by reference or by value. If an object is passed by value, it will
be read-only within the receiving procedure.
A variable that is an instance of a class may be assigned to another variable that is an instance of the
same class using the standard assignment operator. If the class has members that are an allocated
string type or other objects, special, automatically generated “copy procedures” are invoked to perform
the copying. This achieves the desired result in most cases, but there are certain special cases where
the compiler cannot produce a logically correct copy using this strategy. For such cases, there is a way to
specify how the object should be copied. See the discussion about assignment constructors in Section
4.6.
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