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This article introduces the relevant knowledge of "how to use virtual method". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Method is a class subprogram, including function and task.

When you assign a subclass directly to the parent class, and then call the method in the parent class, the method in the parent class is actually called. Unless the method is declared by virtual, the subclass can override the method in the parent class.

This is the polymorphism feature of systemverilog object-oriented language.

The SystemVerilog method declared with the keyword virtual is called virtual methods.

Virtual Functions template:

Virtual function function_name;//Function definitionendfunction

Virtual Tasks template:

Virtual task task_name;//task definitionendtask

In example 1, the method inside the parent class is declared without the virtual keyword, and b_c.display () invokes the method of the parent class after assignment.

Class base_class

Function void display; $display ("Inside base_class"); endfunction

Endclass

Class extended_class extends base_class

Function void display; $display ("Inside extended class"); endfunction

Endclass module virtual_class; initial begin base_class Banco; extended_class eBay

EExtracc = new (); biconc = etherec

B_c.display (); endendmodule

Output:

Inside base_class

In example 2, the virtual keyword is added to the method declaration within the parent class, and b_c.display () invokes the method of the subclass after the assignment.

Class base_class

Virtual function void display; $display ("Inside base_class"); endfunction

Endclass

Class extended_class extends base_class

Virtual function void display; $display ("Inside extended class"); endfunction

Endclass module virtual_class; initial begin base_class Banco; extended_class eBay

EExtracc = new (); biconc = etherec

B_c.display (); endendmodule

Output:

Inside extended class

Pure virtual method

Virtual method: this is a method that can be inherited in a derived class and can be overridden in a derived class.

Pure virtual method: this is the virtual method declared in Virtual Class (classes that can be extended but cannot be instantiated, only as base or prototype classes). You must have a concrete implementation of this method in a derived class.

Pure virtual method can only be a prototype or template.

There cannot be any implementation within pure virtual method.

Pure virtual method does not allow the use of "end" keywords, such as endfunction / endtask.

Virtual class base_class; pure virtual function void display;endclass

Class extended_class extends base_class; virtual function void display; $display ("Inside extended class"); endfunctionendclass

Module virtual_class; initial begin extended_class eRecc; eRecc = new (); e_c.display (); endendmodule

If you have a Virtual Class with pure virtual method, you must implement it in a subclass. But for virtual method, it may or may not be overridden.

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