Function input argument block - defining multiple valid classes for input data.

Hello,

I am attempting to create a function which will accept multiple different object classes as input. I want to accept: char, string, and datetime using the arguments block. Currently I only have it accepting the input data as char and string, for example:

function [datetimeout, datetimeopt, errortype] = DateTimeCheck(data, type, output)
arguments
    data {mustBeText}
    type {mustBeText}
    output {mustBeText} = 'datetime'
end
%rest of the function%%
end

I was able to find a workaround by creating and calling another function. In the main function the syntax would be as follows:

function [datetimeout, datetimeopt, errortype] = DateTimeCheck(data, type, output)
arguments
    data {mustbedatetimecheck}
    type {mustBeText}
    output {mustBeText} = 'datetime'
end
%%rest of the function%%
end

Then in the second function:

function mustbedatetimecheck(a)
    if ~(isa(a,'datetime') || isa(a,'char') || isa(a, 'string'))
        eidType = 'mustbedatetimecheck:nottextordatetime';
        msgType = 'Input must be either a text input or datetime.';
        error(eidType,msgType)
    end
end

I'd like to consolidate these two functions into one function so I do not have the need for multiple files. I understand it's possible to complete this using isa statements after the arguments block, however this is not as concice as having the statement within the arguments block.

Thank you in advance for your time and help.

Answer 1

[Stephen23]

"I'd like to consolidate these two functions into one function so I do not have the need for multiple files."

You do not need multiple files: simply define mustbedatetimecheck as a local function in the same file:

https://www.mathworks.com/help/matlab/matlab_prog/local-functions.html

DateTimeCheck(datetime('now'), 'hello','world') % ok
DateTimeCheck("String input",  'hello','world') % ok
DateTimeCheck(cell(1,2),       'hello','world') % error!

Error using solution>DateTimeCheck (line 7)
Invalid argument at position 1. Input must be either a text input or datetime.

function DateTimeCheck(data, type, output)
arguments
    data {mustbedatetimecheck}
    type {mustBeText}
    output {mustBeText} = 'datetime'
end
%%rest of the function%%
end
function mustbedatetimecheck(a)
assert(isa(a,'datetime') || isa(a,'char') || isa(a,'string'),...
    'mustbedatetimecheck:nottextordatetime',...
    'Input must be either a text input or datetime.')
end

[John]

Thank you so much, I had already nested functions but got the error "Calling nested functions is not supported in arguments block." I didn't realize local functions were a thing/different than nested functions. Thanks and have a good day