MATLAB Object-Oriented Programming

Modify nargout and nargin for Indexing Methods

In this section...

“When to Modify Number of Arguments” on page 17-9

“How to Modify Number of Arguments” on page 17-9

When to Modify Number of Arguments

By default, the number of values referenced by an indexing operation determines how

many output arguments MATLAB uses to call subsref. Similarly, the number of values to

assign in an indexed assignment operation determines how many input arguments

MATLAB uses to call subsasgn.

If your class design requires that indexing operations return or assign a different number

of values than the number defined by the indexing operation, use

numArgumentsFromSubscript to specify the required number.

numArgumentsFromSubscript provides control over nargout for subsref and

nargin for subsasgn.

If your class uses numArgumentsFromSubscript, implement subsref and subsasgn

methods to define the actual values returned or assigned by indexing operations.

Before MATLAB release R2015b, MATLAB produced different results for some indexing

expressions that return or assign to a comma-separated list. Use

numArgumentsFromSubscript to support code that relies on the behavior of previous

releases. Also, now you can overload numArgumentsFromSubscript instead of numel

to achieve specific results without redefining how numel works.

How to Modify Number of Arguments

When a class overloads numArgumentsFromSubscript, MATLAB calls this method

instead of numel to compute the number of arguments expected for subsref nargout

and subsasgn nargin.

If classes do not overload numArgumentsFromSubscript, MATLAB calls numel to

compute the values of nargout or nargin.

MATLAB calls numArgumentsFromSubscript with three input arguments:

Modify nargout and nargin for Indexing Methods