Check if object's property is empty

I have an xmlcomp.Edits object that was created when performing a comparison via the command

root = slxmlcomp.compare(...)

In this case, an xmlcomp.Edits object was created (see attached file) but all properties are empty. However, I don't know how to check if the properties are empty so I can catch the error that occurs when I try to access the properties. Is there a command to use when the object's properties are empty?

[Rik]

Maybe numel works as expected?

[Monika Jaskolka]

>> numel(root)
ans =
    1

I'm not sure how this helps in determining whether or not LeftFileName exists.

[Image Analyst]

What does this show

p = properties(xmlcomp)
if isfield(xmlcomp, 'Edits') && isempty(xmlcomp.Edits)
    % Structure has the field but it's empty so do sommething with that knowledge.
end

[Monika Jaskolka]

[Ive J]

r = load("root").root

r = 
  Edits with no properties.

isfield(r, "LeftFileName")

ans = logical
   0

BTW, I think you still can catch the error when trying to access the property:

  try; r.Version; catch; fprintf('oops! empty!\n'); end

oops! empty!

[Monika Jaskolka]

Even when not empty, isfield returns 0, so it doesn't look like it's the right function to use.

Also, I realize I can catch the error, but I want to have an if statement to prevent the error, like below. I just can't figure out what function I can use to check that the property exists.

try
    if SOME_FUNCTION(root, 'LeftFileName')
        % do something else because the data is missing
    else
        % proceed with getting the value
        model_left = root.LeftFileName;
    end
catch ME
    % handle errors
end

[per isakson]

See: isprop - True if property exists

[Monika Jaskolka]

As the original question shows, isprop returns 1 when the property does not exist. Trying to access the property gives an error.

[per isakson]

Sorry for the noise.

[Rik]

If you don't find anything, you could also put the if in catch block. That's what I do sometimes as well. (e.g. to catch a memory error, which isn't really possible to catch in advance)

[Ive J]

Easiest way that comes to my mind is struct itself:

r = load("root.mat").root;
r2 = load("root2.mat").root2;

warning off MATLAB:structOnObject
checkr = struct(r)

checkr = struct with fields:
    BaseEdits: []

checkr2 = struct(r2)

checkr2 = struct with fields:
          Filters: [1×3 struct]
     LeftFileName: 'C:\Users\bialym2\PhD\model1.slx'
         LeftRoot: [1×1 xmlcomp.Node]
    RightFileName: 'C:\Users\bialym2\PhD\model2.slx'
        RightRoot: [1×1 xmlcomp.Node]
        TimeSaved: '20-Feb-2022 18:26:07'
          Version: '2.0'
        BaseEdits: [1×1 xmlcomp.internal.edits.Edits]

warning off MATLAB:structOnObject

[per isakson]

I'm confused. Could it be that 'TimeSaved' exists in root.mat and rootOP.mat, but isn't shown. I would ask @MathWorks Support Team. Anyhow, there is no property named 'missing'.

%%  R2018b
OP = load("rootOP.mat");
r1 = load("root.mat");
r2 = load("root2.mat");
%%
isprop( r1.root,  'TimeSaved' )

ans = logical
   1

isprop( r2.root2, 'TimeSaved' )

ans = logical
   1

isprop( OP.root,  'TimeSaved' )

ans = logical
   1

isprop( OP.root,  'missing' )

ans = logical
   0

[Henry Barth]

if you want a function for your check, you could implement it for your needs like this:

function ispropOut = SOME_FUNCTION(objIn,nameIn)
    ispropOut = false(size(objIn));
    for nObjRow = 1:size(objIn,1)
        for nObjCol = 1:size(objIn,2)
            try
                objIn(nObjRow,nObjCol).(nameIn);
                ispropOut(nObjRow,nObjCol) = true;
            catch
            end
        end
    end
end

[Adam Danz]

I second Rik's advice.

Answer 1

[Fangjun Jiang]

Might this help?

>> EmptyRoot=xmlcomp.Edits('')
EmptyRoot = 
Edits with no properties.
>> isequal(root,EmptyRoot)
ans =
logical
1
>> isequal(root2,EmptyRoot)
ans =
logical
0