MATLAB Object-Oriented Programming

Specialize Subscripted Assignment — subsasgn

To support the equivalent of the indexed reference behavior with indexed assignment,

implement a subsasgn method.

• Support the default indexed assignment:

obj.Data(2,3) = 9;

• Add the functionality to assign values to the Data property with an expression like this
  statement:

obj(2,3) = 9;

Like the subsref method, the subsasgn method:

• Calls the builtin subsasgn function for '.' indexing


• Returns an error for '{}' indexing


• Defines its own version of '()' indexing.

The substruct function redefines the index type and index subscripts structure that

MATLAB passes to subsref and subsasgn.

function obj = subsasgn(obj,s,val)

if isempty(s) && isa(val,'MyDataClass')

obj = MyDataClass(val.Data,val.Description);

end

switch s(1).type

case '.'

obj = builtin('subsasgn',obj,s,val);

case '()'

if length(s)<2

if isa(val,'MyDataClass')

error('MyDataClass:subsasgn',...

'Object must be scalar')

elseif isa(val,'double')

% Redefine the struct s to make the call: obj.Data(i)

snew = substruct('.','Data','()',s(1).subs(:));

obj = subsasgn(obj,snew,val);

end

end

case '{}'

error('MyDataClass:subsasgn',...

'Not a supported subscripted assignment')

17 Specialize Object Behavior