Matlab mustBeA is one of the most frequently used features we used from Matlab R2020b and newer. mustBeA is used in function argument validation to check as variable is in one of multiple classes, instead of the single class coercion used by Matlab by default.

Simply create a file in the project directory “mustBeA.m”, or under private/mustBeA.m if it’s a Matlab package.

function mustBeA(x, classes)
% for Matlab < R2020b
arguments
  x
  classes (1,:) string
end

mustBeMember(class(x), classes)

end

Matlab mustBeFile and mustBeFolder can fail to validate when the filename starts with a tilde “~”. Tilde is used by most terminal shells to indicate the user home directory. However, Matlab does not currently recognize tilde.

Workaround this issue with expanduser.m in the mustBe{File,folder} call.

Example: myfun.m:

function myfun(A, B)
arguments
  A {mustBeA(A, ["string", "char"])}
  B (1,1) {mustBeNumeric}
end

...

end