ZBasic Language Reference
109
ZBasic Microcontrollers
Public Sub _Assign(ByVal src as MyTime)
hour = src.hour
minute = src.minute
seconds = src.seconds
End Sub
4.7 Object Self-reference and Parent Reference
Occasionally, it is necessary or expedient to be able to refer to the particular object instance in a method.
For such purposes, the special identifier _this is recognized. This identifier can be used as a qualifier
on a member reference (e.g. _this.hour) or as a prefix to the DataAddress qualifier:
_this.DataAddress.
Similarly, it is sometimes useful to be able to refer to a method of the parent class of an object. For this
purpose, the special identifier _parent can be used as a prefix to a class method, e.g. Call
_parent.DoSomething(). This is only necessary, of course, if the class in which the reference occurs
has a method with the same signature (name plus parameter types), e.g. it is often useful for invoking a
parent’s constructor. If needed, the _parent prefix can be used multiple times to refer to a particular
ancestor class, e.g. _parent._parent._parent.DoSomething().
4.8 Explicit Class References and Default Namespace References
In some cases, it may be necessary to refer to a method or data member of a specific class, overriding
the method or member that would otherwise be matched by a particular name. You can refer to the
namespace of a specific class by adding a class name prefix to the identifier. The class name prefix has
the form of the class’ name followed by two colons, e.g. MyTime::hour. The class name prefix is useful
inside of class methods as well as in non-class subroutines and functions and for referring to static
methods of a class.
Occasionally, it may be necessary to refer to an identifier that is outside of a class when the class
contains a method or data member having the same name. Adding the default namespace prefix (two
colons) to the identifier allows you to refer to the namespace outside of the class hierarchy, e.g. ::foo.
4.9 Class Sections
When defining a class, the various members have default visibility attributes identical to those that would
apply if the same type of member were being defined outside of a class. For example, if a data member
is defined using Dim, it will be private. Similarly the default visibility for a method is public just as it is for
subroutines and functions outside of a class.
The differing default visibility attributes for different types of member can lead to confusion about the
visibility of a particular element of a class. To mitigate this issue, one could adopt the practice of
specifying the Public or Private attribute for every member. An alternative strategy is to use section
labels in the class to override the default visibility of the members in the section. The MyTime class
definition is rewritten below using section labels.
Class MyTime
Public:
Sub _Create(ByVal h as Byte = 0, ByVal m as Byte = 0, _
ByVal s as Single = 0.0)
Call SetTime(h, m, s)
End Sub
Sub SetTime(ByVal h as Byte = 0, ByVal m as Byte = 0, _
ByVal s as Single = 0.0)
hour = Min(h, 23)
minute = Min(m, 59)
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