Dot notation from string

Question

Vit Krcal 2020-3-31

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/514322-dot-notation-from-string

评论： Stephen23 2020-4-1

采纳的回答： Steven Lord

在 MATLAB Online 中打开

Hi,

Is there any way to convert string with dots do a dot notation?

Let S be a structure, I want to get

I store a "path" to field to a string

path = ['field1.field2.field3'];

I want to get to a specified field3, instead of

S.field1.field2.field3

I want to call it like this, without separating it by dots.

S.(path)

If I put it like this, it treats the whole string like one name of field.

The reason is that I use a loop which creates the string "path", depending on existance of fields in each "depth" - the substructures are inconsistent. I want the "depth" (number of dots) to be variable.

THX

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Vit Krcal 2020-3-31

Thanks a lot!

Stephen23 2020-4-1

@Peng Li: due to the disadvantages of eval that approach is not recommended.

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Answer 1

Steven Lord 2020-3-31

2
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/514322-dot-notation-from-string#answer_423141

在 MATLAB Online 中打开

DON'T use eval. There's no need to use it in this case anyway. split the text representation of the nested fields into pieces then pass those pieces into getfield as a comma-separated list.

S.field1.field2.field3 = 42;
P = 'field1.field2.field3';
pathPieces = split(P, '.');
theAnswer = getfield(S, pathPieces{:})

Things get trickier if you have a more complicated indexing expression, but take a look at the help and documentation for getfield for how to handle such situations.