A class is a user-defined data type that includes data (class properties), functions and tasks that operate on data.
functions and tasks are called as methods, both are members of the class.classes allow objects to be dynamically created, deleted, assigned and accessed via object handles.
Class declaration example
The below class has one data property x and two methods set and get.
class sv_class; //class properties int x; //method-1 task set(int i); x = i; endtask //method-2 function int get(); return x; endfunction endclass
Class Instance and Object Creation
Class declaration/Class Instance
As we know the class is a data type, Declaring class type variable is similar to declaring other variables.
the above statement shows the declaration of variable class_1 with the type sv_class.
In other words, variable class_1 can contain a handle to an instance of the class sv_class.
Class properties and methods can be accessed only after creating the object.
class_1 = new();
the above statement will create an object and assign its handle to class_1.
sv_class class_1 = new();
the above statement will do both declarations of variable and object creation.
Accessing class properties and methods
Class properties and methods can be accessed by using object names followed by property or method name.
class_1.set(10); //calling set method to set value 10 to x
$display("Vlaue of x = %0d",class_1.get(););
class sv_class; //class properties int x; //method-1 task set(int i); x = i; endtask //method-2 function int get(); return x; endfunction endclass module sv_class_ex; sv_class class_1; //Creating Handle initial begin sv_class class_2 = new(); //Creating handle and Object class_1 = new(); //Creating Object for the Handle //Accessing Class methods class_1.set(10); class_2.set(20); $display("\tclass_1 :: Value of x = %0d",class_1.get()); $display("\tclass_2 :: Value of x = %0d",class_2.get()); end endmodule
class_1 :: Value of x = 10 class_1 :: Value of x = 20