how in matlab check for existence of a structure with fields in the workspace

Question

I have a string and want to check if in the workspace exist any variable with the same name. In the workspace I have also many structures M.N.O M.N.N M.N.M etc. I can only check if there exist a variable with the name M. How to go deeper into this structure? I tried:

exist('M.N')
YesNo = any(strcmp(who,'M.N.O'))
evalin('base','exist(''M.N.O'',''var'')')

all give me the same problem so I am stuck.

Answer 1

You can use isfield to check if a variable has a specific field. See the link for examples!

For your example, you'd need:

isfield(M,'N')

and if true, you can go deeper:

isfield(M.N,'O')

Notice that

isfield(M,'N.O')

won't work ;)

Answer 2

One option: write a recursive function to expand structures down to their leaf fields, appending the fields to a list.

(untested, conceptual code - probably won't work quite right as is)

function varlist = getStructFields(var,varlist)
if isstruct(var)
    fn = fieldnames(var);
    varlist = vertcat(varlist,fn); %# append fields to the list
    for field = fn' %# ' create row vector; iterate through fields
         varlist = getStructFields(var.(char(field)), varlist); %# recursion here 
    end
end
end

Then you can use the any(strcmp(who,'M.N.O')) check you already came up with.