IsField method not returning correct value

21 次查看（过去 30 天）

显示更早的评论

Tim Lenardo 2015-4-10

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/197044-isfield-method-not-returning-correct-value

编辑： Paul 2023-12-13

采纳的回答： David Foti

在 MATLAB Online 中打开

The isfield() method is not currently working for me. Check out this output from the console:

K>> TFORM
TFORM = 
projective2d with properties:
                 T: [3x3 double]
    Dimensionality: 2
K>> TFORM.T
ans =
    0.9889   -0.0068   -0.0000
    0.0003    0.9918   -0.0000
    3.7452    5.5412    1.0000
K>> isfield(TFORM, 'T')
ans =
     0

I can see that my object (TFORM) is there, and that it has a field named 'T'. However, when I run isfield(TFORM, 'T'), I get a 0 result. What gives?

*Edit*

I'm running R2015a (8.5.0.197613), on a 64-bit Mac.

AND

I was able to work around this by using:

any(strcmp(fieldnames(TFORM),'T'))

In place of:

isfield(TFORM, 'T')

采纳的回答

David Foti 2016-4-8

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/197044-isfield-method-not-returning-correct-value#answer_217054

isfield finds fields in structs. The isprop function finds properties in objects.

8 个评论
显示 6更早的评论隐藏 6更早的评论

Steven Lord 2023-12-12

In my opinion this behaviour of isfield is the source of unexpected behaviour of code more often than not in case of handling of structs and classes.

If you feel strongly about this, you could send a bug report or enhancement request to Technical Support directly using this link. Be sure to explain your use case for why we should change this behavior that has been in the product literally for decades. [I just checked and in one of the older releases I can run on this machine, release R11 which was released in January 1999, isfield(1, 'field') returns 0.]

Paul 2023-12-12

编辑：Paul 2023-12-13

My issue is that the Input Arguments section of the doc page strongly implies (at least to me) that the only valid input for the first argument is a structure array. Insofar that it seems the intent of the function is to accept any type of input, it seems to me that should be clearly indicated in the Input Arguments section that describes S.

I don't feel strongly enough about this to file a suggestion with the doc support folks.

请先登录，再进行评论。