34.6.1 Creating a classdef Class

A very basic classdef value class (see Value Classes vs. Handle Classes) is defined by:

classdef some_class
  properties
  endproperties

  methods
  endmethods
endclassdef

In contrast to old style classes, the properties-endproperties block as well as the methods-endmethods block can be used to define properties and methods of the class. Because both blocks are empty, they can be omitted in this particular case.

For simplicity, a more advanced implementation of a classdef class is shown using the polynomial example again (see Creating a Class):

classdef polynomial2
  properties
    poly = 0;
  endproperties

  methods
    function p = polynomial2 (a)
      if (nargin > 1)
        print_usage ();
      endif

      if (nargin == 1)
        if (isa (a, "polynomial2"))
          p.poly = a.poly;
        elseif (isreal (a) && isvector (a))
          p.poly = a(:).';  # force row vector
        else
          error ("polynomial2: A must be a real vector");
        endif
      endif
    endfunction

    function disp (p)
      a = p.poly;
      first = true;
      for i = 1 : length (a);
        if (a(i) != 0)
          if (first)
            first = false;
          elseif (a(i) > 0 || isnan (a(i)))
            printf (" +");
          endif
          if (a(i) < 0)
            printf (" -");
          endif
          if (i == 1)
            printf (" %.5g", abs (a(i)));
          elseif (abs (a(i)) != 1)
            printf (" %.5g *", abs (a(i)));
          endif
          if (i > 1)
            printf (" X");
          endif
          if (i > 2)
            printf (" ^ %d", i - 1);
          endif
        endif
      endfor

      if (first)
        printf (" 0");
      endif
      printf ("\n");
    endfunction
  endmethods
endclassdef

An object of class polynomial2 is created by calling the class constructor:

>> p = polynomial2 ([1, 0, 1])
⇒ p =

 1 + X ^ 2