How do I access structrure fields from input parser optional inputs

Question

Ron 2015-4-5

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/196244-how-do-i-access-structrure-fields-from-input-parser-optional-inputs

评论： Ron 2015-4-6

I am trying to pass in one and optionally two structures of the same type to a function using the input parser. I can access the fields of the first required structure, but I can't access the fields of the second optional structure. For the sample code below, a call of

ptest(s1)

works fine, but a call of,

ptest(s1, 's2', s2)

returns an error message of

Undefined variable "s2" or class "s2.dpri".
Error in ptest (line 22) fprintf('s2 field 1: %f\n', s2.dpri)

Here is the sample code:

function [] = ptest( s1, varargin )
%%Input Parser
p = inputParser;
p.StructExpand = false;
% Defaults for optional input
default_s2    = 'none';
addRequired(p,'s1', @(x) isstruct(x));
addParameter(p,'s2',  default_s2, @(x) isstruct(x));
parse(p,s1,varargin{:});
% Check if optional parameters were specified
opt.s2   =  ~any(strcmp('s2',p.UsingDefaults));
%%Actions based on s1
fprintf('s1 field 1: %f\n', s1.dpri)
fprintf('s1 field 2: %f\n', s1.dsec)
%%Actions based on s2
if opt.s2
    fprintf('s2 field 1: %f\n', s2.dpri)
    fprintf('s2 field 2: %f\n', s2.dsec)
end
end

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Answer 1

Mohammad Abouali 2015-4-5

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https://ww2.mathworks.cn/matlabcentral/answers/196244-how-do-i-access-structrure-fields-from-input-parser-optional-inputs#answer_174061

编辑：Mohammad Abouali 2015-4-5

在 MATLAB Online 中打开

That's not how varargin works if you have

function ptest(s1,varargin)
....
end

then once you call it as:

ptest(s1,'s2',s2)

to access s2 within ptest you need to use varargin{2} for example you need to change the following part of your code as shown here

%%Actions based on s2
if opt.s2
    %fprintf('s2 field 1: %f\n', s2.dpri)
    %fprintf('s2 field 2: %f\n', s2.dsec)
    fprintf('s2 field 1: %f\n', varargin{2}.dpri)
    fprintf('s2 field 2: %f\n', varargin{2}.dsec)
end