Do you format and comment your regular expressions?
Last updated by Igor Goldobin 11 months ago.See historyRegular expressions are a very powerful tool for pattern matching, but a complicated regex can be very difficult for a human to read and to comprehend. That is why, like any good code, a good regular expression must be well formatted and documented.
Here are some guidelines when formatting and documenting your regex:
- Keep each line under 80 characters, horizontal scrolling reduces readability
- Break long patterns into multiple lines, usually after a space or a line break
- Indent bracers to help think in the right scope
- Format complicated OR patterns into multiple blocks like a case statement
- Comment your regex on what it does, don't just translate it into English
# Match <BODY
<BODY
# Match any non > char for zero to infinite number of times
[^>]*
# MATCH >
>Bad example: Comment that translates the regex into English
# Match the BODY tag
<BODY
# Match any character in the body tag
[^>]*
# Match the end BODY tag
>Good example: Comment that explains the purpose of the pattern
(?six-mn:(Label|TextBox)\s+(?<Name>\w+).*(?<Result>\k<Name>\.TextAlign\s*=\s* ((System\.)?Drawing\.)?ContentAlignment\.(?! TopLeft|MiddleLeft|TopCenter|MiddleCenter)\w*)(?!(?<=\k<Name>\.Image.*)|(?
=.*\k<Name>\.Image)))Bad example: Pray you never have to modify this regex
(?six-mn:
# Match for Label or TextBox control
# Store name into <name> group
(Label|TextBox)\s+(?<Name>\w+).*
# Match any non-standard TextAlign
# Store any match in Result group for error reporting in CA
(?<Result>
# Match for control's TextAlign Property
\k<Name>\.TextAlign\s*=\s*
# Match for possible namespace
((System\.)?Drawing\.)?ContentAlignment\.
# Match any ContentAlignment that is not in the group
(?!TopLeft|MiddleLeft|TopCenter|MiddleCenter)\w*
)
# Skip any Control that has image on it
(?!
(?<=
\k<Name>\.Image
.*
)
|
(?=
.*
\k<Name>\.Image
)
)
)Good example: Now it make sense!
