Create a nested structure using a variable as field name

Question

Luca Amerio 2016-11-3

2
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https://ww2.mathworks.cn/matlabcentral/answers/310439-create-a-nested-structure-using-a-variable-as-field-name

评论： Luca Amerio 2016-11-3

采纳的回答： Jan

Hi everybody

Lets say that I have a variable

path='\levelOne\levelTwo\levelThree'

of which I don't know the number of levels and that I would like to use this path as "address" of a variable inside a structure, such that

S.levelOne.levelTwo.levelThree=1;

Now, I know that I can use string variables to set or get structure fileds using a notation like

   fieldName='myField';
   S.(fieldName)=1;

But this works with one level or, with a bit of string manipulation, if I know the number of levels I must call. I'm thinking at something like:

   path='\levelOne\levelTwo\levelThree'
   fields=strsplit(path,'\');
   [fieldOne,fieldTwo,fieldThree]=deal(fields{2:end});
   S.(fieldOne).(fieldTwo).(fieldThree)=1;

Can you think of any kind of trick so that I can write a function that adapt itself to the number of levels I pass it through the path variable?

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Answer 1

Jan 2016-11-3

3
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https://ww2.mathworks.cn/matlabcentral/answers/310439-create-a-nested-structure-using-a-variable-as-field-name#answer_241815

编辑：Jan 2016-11-3

This is a job for the getfield and setfield commands:

PathStr = '\levelOne\levelTwo\levelThree';  % Do not shadow the PATH command
Fields  = strsplit(PathStr,'\');   % Ignore initial blank field later
S = [];
S = setfield(S, Fields{2:end}, 1)
V = getfield(S, Fields{2:end})

Internally this calls subsassgn, which can be done directly also. I'd move this into a function, which ignores at least a leading separator automatically:

function S = SetPathField(S, PathStr, Value)
if length(PathStr) >= 1 && PathStr(1) == '\'
  Fields = regexp(PathStr(2:end), '\', 'split');
else
  Fields = regexp(PathStr, '\', 'split');
end
Types    = cell(1, numel(Fields));
Types(:) = {'.'};
S        = subsasgn(S, struct('type', Types, 'subs', Fields), Value);
end