Many times we might use the Base Class or Base Class library provided by third party sources. By default, These Class Members are Public in nature. It means these Class Members can be accessed directly from outside of that Class. But sometimes Base Class providers may restrict how others can access the Class members as a safety/security measure, preventing corruption of internal states and logic. To support those restrictions.
Class Members can be declared with the following two Qualifiers:
- Local: It is available only to methods inside the class. Further, these local members are not visible within subclasses.
- Protected: It is a property or method has all of the characteristics of a local member, except that it can be inherited; it is visible to subclasses.
Let us understand both the above-mentioned Qualifiers with examples:
Example: Local Variable Qualifier with Error Result
class parent; local int a; endclass program main; initial begin parent p = new(); p.a = 777; end endprogram
Example: Local variable Qualifier access using the method
class parent; local int a; task set(int b); a = b; $display(a); endtask endclass program main; initial begin parent p = new(); p.set(777); end endprogram
Example: Local Variable Qualifier access in Subclass/Child Class
class parent; local int a; endclass class child extends parent; function new(); a = 10; endfunction endclass
Example: Protected Variable Qualifier
class parent; protected int a; endclass class child extends parent; function new(); a = 101; endfunction endclass