MATLAB null conditional operator

Hi, All

I'm interested in MATLAB null conditional operator or something very similar.

Suppose I have logger in MATLAB class/methods but want to use this class in another small project, where no logger is set up.

In C# I would code would look like

logger?.warn('WARNING');

...

logger?.debug('Three is 3');

and if external code sets logger to null, no calls would be made. So code continues to work just fine, like no logger is present. This is called null conditional operator.

Is there a similar idiom for MATLAB? How it could be done in most simple and elegant way?

Our logger is a singleton wrapping around log4j java class

Answer 1

[Stephen23]

"How it could be done in most simple and elegant way?"

I assume that the aim is to not change the logging calls within the project code.

One approach would be to define a simple class that accepts any method call and does ... nothing:

logger = MyLogger();

logger.warn('WARNING');     % no error!

logger.debug('Three is 3'); % no error!

The class really is simple and does nothing:

type MyLogger

classdef MyLogger
    methods
        function obj = MyLogger()
        end
        function subsref(varargin)
        end
    end
end

Answer 2

[Hassaan]

Example Using 'isempty'

If your logger can be [] (empty) when it's not set:

if ~isempty(logger)
    logger.warn('WARNING');
    ...
    logger.debug('Three is 3');
end

Example Using 'isvalid'

If your logger is an object handle that can be invalid when not set:

if isvalid(logger)
    logger.warn('WARNING');
    ...
    logger.debug('Three is 3');
end

To make it more elegant and less repetitive, especially if you are doing this check frequently, you could wrap this logic in a method within your class or as a separate function:

function safeLog(logger, logType, message)
    if ~isempty(logger) && ismethod(logger, logType)
        logger.(logType)(message);
    end
end

And use it like:

safeLog(logger, 'warn', 'WARNING');
...
safeLog(logger, 'debug', 'Three is 3');

Making your code cleaner and easier to maintain. It also adds flexibility, as you can easily extend or modify the logging behavior in one place. Remember that MATLAB's object-oriented capabilities are different from those in C#, so some adaptations are necessary.

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