Parameterized Classes

Parameterized classes are same as the parameterized modules in the verilog. parameters are like constants local to that particular class.
The parameter value can be used to define a set of attributes in class. default values can be overridden by passing a new set of parameters during instantiation. this is called parameter overriding.

//---- class ----
class packet #(parameter int ADDR_WIDTH = 32,DATA_WIDTH = 32);
  bit [ADDR_WIDTH-1:0] address;
  bit [DATA_WIDTH-1:0] data   ;

  function new();
    address = 10;
    data    = 20;
  endfunction
endclass

packet pkt;    –>   creates pkt handle with default ADDR_WIDTH and DATA_WIDTH values.
The default parameter value can be overridden when the class is instantiated.

packet #(32,64) pkt;  –> creates pkt handle with ADDR_WIDTH = 32 and DATA_WIDTH = 64.

Pass a data type to a class

class packet #(parameter type T = int);
  T address;
  T data   ;

  function new();
    address = 10;
    data    = 20;
  endfunction
endclass

packet pkt;                                    –>    address and data type is int
packet #(bit [31:0]) pkt; –>    address and data type is bit [31:0]
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