MATLAB: How to use a variable number of structure fields as function arguments

argumentsfieldnamesfieldsfunctionfunction handleshandlesinputmatlab functionstructstructuresvararginvariable

Hello,
I have a structure that conatins a function handle and any number of other variables (in this case 4), like so:
MyStruct = struct('MyFun',@example,'a',1,'b',2,'c',5,'d',37);
where example is a simple function that takes in a variable number of arguments and displays them, like so:
function [] = example(varargin)
    for n = 1:2:length(varargin)    
        disp(['Argument ' varargin{n} ' = ' num2str(varargin{n+1})])
    end
I would like to call the function handle (in this case @example) using the variables stored in MyStruct, like so:
>>  X = fieldnames(MyStruct)
X =
  5×1 cell array
    {'MyFun'}
    {'a'    }
    {'b'    }
    {'c'    }
    {'d'    }
    
>>  MyStruct.MyFun(X{2}, MyStruct.(X{2}), X{3}, MyStruct.(X{3}), X{4}, MyStruct.(X{4}), X{5}, MyStruct.(X{5}))
Argument a = 1
Argument b = 2
Argument c = 5
Argument d = 37
Is there a way to do this for a structure with any number of fields/variables?
[Note: the function handle can point to one of several functions]
For example:
>>  MyStruct.MyFun(X{2}, MyStruct.(X{2}), X{3}, MyStruct.(X{3}),   . . .   , X{999}, MyStruct.(X{999}))
Any help at all would be greatly appreciated!
Thanks!

Best Answer

Use struct2cell and a comma-separated list:
>> X = fieldnames(MyStruct);
>> Y = struct2cell(MyStruct);
>> C = [X(2:end),Y(2:end)].'; % assumes that the function is the first field!
>> MyStruct.MyFun(C{:})
Argument a = 1
Argument b = 2
Argument c = 5
Argument d = 37
https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html
https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists
A more robust solution would be to not use positional input arguments for the function, but write it to accept the structure itself.
Related Question