Your proposed while-loop reminded me of some of my own code, which might possibly be slightly more readable, due to leveraging regexp(), so I thought I’d post..

I wrote a class ‘FieldInterface’ to encapsulate arbitrary-depth struct fields, just as you’re talking about, so I can do things like:

————————————–

A.setField(‘A.B.C.D’,20);
ans = A.getField(‘A.B.C.D’);

————————————–

The code snip below is the essence of method getField(). Note the reference to classdef constant ROOT_FIELD_NAME, which anchors the “dynamic” Fields.

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function outValue = getField(obj,varargin)
…
fieldSpecStr = varargin{1};
…
try

% Construct near-complete field name (only lacking ‘obj.’), e.g.
% ‘ROOT_FIELD_NAME.subStructName.fieldName’
fullFieldStr = [ obj.ROOT_FIELD_NAME '.' fieldSpecStr ];

% Get cell vector of sub-struct / field names within (fullFieldStr)
cvFieldSplits = regexp(fullFieldStr,’\.’,'split’);

% Initialize (outValue):
outValue = obj;

% Iterate through (cvFieldSplits)
for iSplit = 1 : numel(cvFieldSplits)

% Access next-level within (cvFieldSplits), which will either be a
% further sub-struct or else the final, desired field:
outValue = outValue.(cvFieldSplits{iSplit});
end

% Handle failure
catch exception
…
end

————————————–

Hope s/o finds this useful. Any comments appreciated,

Brad

p.s. Loren/Webmaster: I couldn’t get the “pre” tags to work for me, to set off code blocks. Maybe please compare implementation here vs. MATLAB Answers, which uses a slightly different syntax for code blocks, I think.. Also, it would be really convenient if this blog could offer a checkbox to email readers/posters when new comments are added, as does MATLAB Answers & many other forums on the Net..

You can’t reference a structure that way with multiple field names in one particular position, with or without dynamic field reference. It always requires a scalar field name.

–Loren

here’s a simple example:
B =

[1] ‘M1′ ‘test’
[1] ‘M2′ [ 2]
[AA ~] = size(B);
for xx = 1:1:AA
data.(B{xx,2}).time = B{xx,1};
data.(B{xx,2}).num = B{xx,3};
end

Is there a way to do this without resorting to a look through all the rows of B? Something closer to:
data.(B{:,2}).time = B{:,1};
data.(B{:,2}).num = B{:,3};

Thanks.

You can do what Cris says, but using eval is highly NOT recommended in general.

–Loren

A.l1.l2.l3.l4 = 1234;
fieldname = 'l1.l2.l3.l4';
eval(['A.',fieldname])

I understand the problem you are trying to solve but don’t have any way besides getting the individual fieldnames. You might put in an enhancement request to get functionality like you describe. The link for support is on the right side of my blog.

–Loren

Let me rephrase. If I have a structure of arbitrary depth:

A.L1.L2.L3...LN = value;
fullString = 'L1.L2.L3...LN';

is there a way to elegantly access a field given by fullString? It would be simple enough if the depth if fixed, but the only generalized way I can think is to parse the string and iteratively store substructures until the final result is obtained:

A.L1.L2.L3.L4.L5 = 12345;
fullString = 'L1.L2.L3.L4.L5';

dotFind = strfind(fullString,'.');
temp = A;
while ~isempty(dotFind)
  temp = temp.(fullString(1:dotFind(1)-1));
  fullString = fullString(dotFind(1)+1:end);
  dotFind = strfind(fullString,'.');
end
FinalAns = temp.(fullString);
disp(FinalAns);

While this works, it is not very elegant, efficient, or readable. fullString will change in the program. One time it may be ‘L1.L2.L3′. The next it might be ‘L1.M2.N3.L4′. Being somewhat new to dynamic field names (thank you, Loren for many other postings elsewhere), I had hoped/expected to just be able to use: A.(fullString) which obviously does not work.

The last way you note IS the generalized way.

–Loren

A.l1.l2.l3.l4 = 1234

%would like to do this:
fieldname = 'l1.l2.l3.l4'    %next time might be 'l1.l2'
A.(fieldname)
%gives:  ??? Reference to non-existent field 'l1.l2.l3.l4'.

A.('l1').('l2').('l3').('l4')
%gives correct: 1234