How to remove struct fields of a specific type

I have a struct that contains data of various formats including further structs and instances of class objects. I would like to remove all fields that are of a specific type without needing to use their field names.

For example, the trackingScenario struct contains a varying number of "Tracker" objects that I would like to remove if desired. I have posted an example of the struct below.

struct with fields:

configData: [1×1 struct]

simulation: [1×1 struct]

Platform_1: [1×1 struct]

Platform_2: [1×1 struct]

Platform_3: [1×1 struct]

Platform_4: [1×1 struct]

Target_1: [1×1 struct]

Target_2: [1×1 struct]

new_test_tracker2: [1×1 Tracker]

The desired output would be the struct without the "Tracker" field. This has stumped me so thanks in advance!

Answer 1

[Paul]

The function class can be used in a loop over the fieldnames to identify the fields to be removed with rmfield.

s.w = int32(0);
s.x = 1;
s.y = 2;
s.z = int32(3);
s

s = struct with fields:
    w: 0
    x: 1
    y: 2
    z: 3

% remove the int32 fields
fnames = fieldnames(s);
for ii = 1:numel(fnames)
    if string(class(s.(fnames{ii}))) == "int32"
        s = rmfield(s,fnames{ii});
    end
end
s

s = struct with fields:
    x: 1
    y: 2

The function isa might also do the job of identifying the field to be removed, depending on the class hierarchy and if you want to remove objects basedon their superclass.

[engdancili]

Very useful. If the struct has several nested fields, one can exploit recursive functions to get the job done. Here is my (GitHub CoPilot) edit to remove function handles from a struct.

function s = removeFunctionHandles(s)

fnames = fieldnames(s);

for ii = 1:numel(fnames)

if isstruct(s.(fnames{ii}))

s.(fnames{ii}) = removeFunctionHandles(s.(fnames{ii}));

elseif isa(s.(fnames{ii}), 'function_handle')

s = rmfield(s, fnames{ii});

end

end

end

Off topic: Simulink allows you to work with struct variables, but if a struct is passed to a MATLAB function block (as a not tunable parameter) it will throws you an error since:

"You can use function handles in a MATLAB Function block. You cannot use function handles for Simulink® signals, parameters, or data store memory." From: Function Handle Limitations for Code Generation

Answer 2

[sushma swaraj]

Hi,

You can use the rmfield function to remove a specified field from structure array.

Refer to this documentation :

https://www.mathworks.com/help/matlab/ref/rmfield.html

Hope it helps!