How to pass a struct as name-value-pairs to a function?

Is it possible to convert a struct to name-value-pairs that is then fed to a function that takes Name-Value pairs as input arguments? The fieldname of the struct would represent the Name and and the fieldvalue the Value of the Name-Value pairs.

One particular function that use Name-Value pairs as input is the GlobalSearch function in MATLAB.

gs = GlobalSearch(Name,Value,...)

For example is the following possible

% I want this
gs = GlobalSearch('BasinRadiusFactor',.5,'NumTrialPoints',400)

% To be equal to this
options.BasinRadiusFactor = 0.5
options.NumTrialPoints = 400
gs = GlobalSearch(options)

Answer 1

[Matt J]

Some functions may enable this (in particular, those that use inputParser to parse string-value pairs will always accept a struct), but clearly not all functions, as you found out when you ran your example. However, you can always pre-convert a struct to a cell of string value pairs using the utility below.

function C=struct2pairs(S)
%Turns a scalar struct S into a cell of string-value pairs C
%
%  C=struct2pairs(S)
%
%If S is a cell already, it will be returned unchanged.


if iscell(S)
 C=S; return
elseif length(S)>1
    error 'Input must be a scalar struct or cell';
end

C=[fieldnames(S).'; struct2cell(S).'];
C=C(:).';

[Pontus Vikstål]

This seemed to work for me thank you!

Answer 2

[Hyeokjin Jho]

try namedargs2cell

[Markus Leuthold]

Unfortunately, this is still quite cumbersome since you cannot use it in one line. If you want to use this in conjunction with an

arguments
end

block, you need to convert the cell into separate arguments

options.BasinRadiusFactor = 0.5
options.NumTrialPoints = 400
optionsCell = namedargs2cell(options)
myfunction(optionsCell{:})

Why did Mathwork not allow to use a struct for a arguments/end block the same way it was possible with inputParser?

[Matt J]

Yes, perhaps an attribute syntax:

function myfunction(options)

 arguments(StructExpand=true)

 end

end

[Markus Leuthold]

Matt, sounds like a good idea!