Add Fields to an existing Structure

289 次查看（过去 30 天）
Paul Mitchell
Paul Mitchell 2022-6-11
评论： Stephen23 2023-12-24
Hi,
I have structure, for example
S.Level0=0
I have a field structure I want to add to S namely
S.Level1.SubLevel0.SubLevel1.SubLevel2.Text = '1234';
where i have the above fields defined in a cell array
f = {'SubLevel0','SubLevel1','SubLevel2','Text'}
and the string cvar='1234' being the required value
is there an elegant way to produce
S.Level1.SubLevel0.SubLevel1.SubLevel2.Text='1234'
using f & cvar ?
Thank You

请先登录，再回答此问题。

采纳的回答

Paul
Paul 2022-6-11
Ran in:
S.Level0=0;
f = {'SubLevel0','SubLevel1','SubLevel2','Text'};
cvar = '1234';
S = setfield(S,'Level1',f{:},cvar);
S.Level0
ans = 0
S.Level1.SubLevel0.SubLevel1.SubLevel2.Text
ans = '1234'
  4 个评论
显示 2更早的评论
Paul
Paul 2022-6-11
Ran in:
@Image Analyst
I don't know where the OP is going with this and so don't have a position on whether or not it's the right way to go. Just trying to answer the question. Having said that, getfield() can be used in a similar fashion to extract based on f.
S.Level0=0;
f = {'SubLevel0','SubLevel1','SubLevel2','Text'};
cvar = '1234';
S = setfield(S,'Level1',f{:},cvar);
plot(rand(3))
title(getfield(S.Level1,f{:}))
Paul Mitchell
Paul Mitchell 2022-6-12
Thank you very much for spending time to provide me with the solution. I thought I had tried everything possible !! Clearly I did not - Regards Paul

请先登录，再进行评论。

更多回答（2 个）

Image Analyst
Image Analyst 2022-6-11
Having field names that are unknown in advance, and their names are only determined by getting their name from a cell array variable sounds like a bad idea. It's probably one of the worst and most common ideas and it comes up every week.
However it is possible to do bad things in MATLAB and the FAQ will show you how to do it and explain why it's bad.
https://matlab.fandom.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2C_A10_in_a_loop.3F
I'm sure Stephen will also chime in with additional reasons why you really don't want to do this even though you think you do.
  2 个评论
Paul Mitchell
Paul Mitchell 2022-6-12
I know its bad, but the field names are unknown in advance (and could change - hence running the conversion process multiple times)
Image Analyst
Image Analyst 2022-6-12
The solution you accepted will do what you want but as you can see, to get this unknown field name you have to do some pretty cryptic stuff that makes the code almost unmaintainable. Would be better to use fixed and known names rather than dynamically varying names, as I hope someday you realize. But good luck with it. You might also like to read the FAQ:
https://matlab.fandom.com/wiki/FAQ#How_can_I_create_variables_A1,_A2,...,_A10_in_a_loop?
And Stephen's tutorial:
https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

请先登录，再进行评论。

Dror Liran
Dror Liran 2023-12-20
编辑：Dror Liran 2023-12-24
What you are after is called dynamic field names, the matlab documatation is here: https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html
Anyway the way to do it is something like:
names = ["name1" "name2"];
a.fld1 = 1;
a.fld2 = "a";
a.(names(1)) = "whatever";
  3 个评论
显示 1更早的评论
Dror Liran
Dror Liran 2023-12-24
I have tried it and it works for me on matlab 2023b
Stephen23
Stephen23 2023-12-24
"I have tried it and it works for me on matlab 2023b"
It should work in R2023b, dynamic fieldnames were added more than twenty years ago in R13:
https://blogs.mathworks.com/loren/2005/12/13/use-dynamic-field-references/

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Programming 的更多信息

标签

产品


版本

R2020a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by