Identifying errors in datetime input strings

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phenan08 2023-5-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1961569-identifying-errors-in-datetime-input-strings

编辑： phenan08 2023-5-12

采纳的回答： Star Strider

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During application development using appdesigner, I want to check that an input string is a time object or not.

As an example, a correct string input does not generate any errors:

str = "31/05/2022" ;
datetime(str,"Format","dd/MM/uuuu")

which returns:

ans =

datetime

31/05/2022

However, when the input string does not match with a true date, then an error follows:

str = "32/05/2022" ;
datetime(str,"Format","dd/MM/uuuu")

Error using datetime

Unable to convert '32/05/2022' to datetime using the format 'dd/MM/uuuu'.

Is there any way to check that the input string corresponds to a date or not, without generating any errors? I intend to compile the code at the end of the project, so I cannot use the try catch statements, since they were not supported by MATLAB Coder up to now (which is a bit of a shame, considering the prices of the coder and the compiler...).

Any suggestion to deal with that issue?

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Stephen23 2023-5-11

编辑：Stephen23 2023-5-11

"Is there any way to check that the input string corresponds to a date or not"

Of course, but it depends on how broad you want to check the input data:

Can the values be negative as well?

Can the months also be out of range?

Can non-digit characters occur?

phenan08 2023-5-11

编辑：phenan08 2023-5-12

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Then, based on Star Strider's proposal, I assume that you just have to check the following command as well:

test = 1 <= str2double(flds(2)) & str2double(flds(2)) <= 12

Before that, the input string format can be checked using the following command:

test = matches(string(str),digitsPattern(2)+"/"+digitsPattern(2)+"/"+digitsPattern(4))

Thank you Stephen23 for having permitted to share a deeper approach of the present problem.

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Answer 1

Star Strider 2023-5-11

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1961569-identifying-errors-in-datetime-input-strings#answer_1233149

编辑：Star Strider 2023-5-11

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If you already know the date fields for day, month, and year, one approach would be to use the eomday function to determine the maximum number of days in a month for the matching month and year —

str = "32/05/2022" ;
flds = strsplit(str,'/')
flds = 1×3 string array
    "32"    "05"    "2022"
dmax = eomday(str2double(flds(3)),str2double(flds(2)))
dmax = 31
Check = 1 <= str2double(flds(1)) & str2double(flds(1)) <= dmax
Check = logical
   0