参数正则表达式

Question

I need help with creating regex for validating parameter string.

Parameter string consists of 2 optional groups of explicit characters. First group can contain only one occurrence of P, O, Z characters (order doesn't matter). Second group has same restrictions but can contain only characters t, c, p, m. If both groups are presented, they need to be delimited by a single space character.

So valid strings are:

P t
PO t
OZP ct
P tcmp
P
PZ
t
tp

etc.

Answer 1

Why not ditch regex, and using string to represent non string data, and do

[Flags]
enum First
{
    None = 0,
    P = 1,
    O = 2,
    Z = 4
}

[Flags]
enum Second
{
    None = 0
    T = 1,
    C = 2,
    P = 4,
    M = 8
}

void YourMethod(First first, Second second)
{
    bool hasP = first.HasFlag(First.P);
    var hasT = second.HasFlag(Second.T);
}

---

You could then call YourMethod like this.

// equivalent to "PO mp", but checked at compile time.
YourMethod(First.P | First.O, Second.M | Second.P);

or, if you felt like it

// same as above.
YourMethod((First)3, (Second)12);

---

If you'd like to know more about how this works see this question .

Answer 2

I don't think a regex is a good solution here, because it will have to be quite complicated:

Regex regexObj = new Regex(
    @"^               # Start of string
    (?:               # Start non-capturing group:
     ([POZ])          # Match and capture one of [POZ] in group 1
     (?![POZ]*\1)     # Assert that that character doesn't show up again
    )*                # Repeat any number of times (including zero)
    (?:               # Start another non-capturing group:
     (?<!^)           # Assert that we're not at the start of the string
     \                # Match a space
     (?!$)            # Assert that we're also not at the end of the string
    )?                # Make this group optional.
    (?<!              # Now assert that we're not right after...
     [POZ]            # one of [POZ] (i. e. make sure there's a space)
     (?!$)            # unless we're already at the end of the string.
    )                 # End of negative lookahead assertion
    (?:               # Start yet another non-capturing group:
     ([tcpm])         # Match and capture one of [tcpm] in group 2
     (?![tcpm]*\2)    # Assert that that character doesn't show up again
    )*                # Repeat any number of times (including zero)
    $                 # End of string", 
    RegexOptions.IgnorePatternWhitespace);

Answer 3

这应该给你你需要的东西：

([POZ]+)? ?([tcpm]+)?