We create handle and objects for a class.What are the major differences between handle and object.When we need to create handle.
Hi,
See a screenshot from our regular VSV training (http://www.cvcblr.com/trng_profiles/CVC_LG_VSV_profile.pdf) that covers this topic.
HTH
Ajeetha, CVC
In reply to Ajeetha Kumari CVC:
I like to think of three distinct concepts: class variables, handles and objects.
A class object is an instance of a class definition that you create when you call its constructor function - new(). In SystemVerilog, all class objects are created dynamically; on or after time 0. The LRM does not specify how or when an object can be destroyed - only when it cannot be destroyed.
A class variable is variable whose value represents a reference to a class object. Like any other variable, the lifetime of a class variable depends on how and where it is defined (static, automatic, or dynamic).
The value that represents a reference to class object is called a handle. You can never see or represent the literal value of a handle (except for the special handle: null). You must use the class variable in an expression to reference members or methods in the class object using the class handle stored in the variable.
In reply to dave_59:
Hi Dave,
Iam pretty confused with your explaination.Actually class variables means either Objects/handles which will be created in below fashion.
Class_name clss_variable;//class variable nothing but object/handle.
I just need when we use handle and when we use object,What is the difference between both of them.
Regards
Bharath
In reply to Lucky:
Bharath
If you run this complete example
module top;
class class_name
int i;
endclass
class_name class_variable;;
initial $display("Hello World");
endmodule
you will have created a static variable class_name but no class object. So no handle exists to class_name. Now a call to the constructor.
initial begin
class_variable = new();
class_variable.i = 1;
$display(class_variable.i);
end
new() is a function that returns a handle to an object of class_name.class_variable.i means use the handle stored in class_variable to reference an object, and select variable i of that object. In C/C++, this would look like the pointer reference class_name->i; In SystemVerilog, you never use the object directly, you always reference is using a handle stored in a class variable.
1 Like
In reply to dave_59:
Hi Dave,
What happens when I pass the object handle as an input argument to a function ?
Is it a pass-by-value or pass-by-reference ?
If the function changes the value of a variable inside the object, will it affect the original object’s handle ?