參數正則表達式

Question

我需要幫助創建用於驗證參數字符串的正則表達式。

參數字符串由2個可選的顯式字符組組成。 第一組只能包含一個P，O，Z字符（順序無關緊要）。 第二組具有相同的限制，但只能包含字符t，c，p，m。 如果呈現兩個組，則需要用單個空格字符分隔。

所以有效的字符串是：

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

等等

Answer 1

為什么不拋棄正則表達式，並使用字符串來表示非字符串數據，並且這樣做

[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);
}

---

然后你可以像這樣調用YourMethod 。

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

或者，如果你覺得這樣

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

---

如果您想了解更多有關其工作原理的信息， 請參閱此問題 。

Answer 2

我不認為正則表達式在這里是一個很好的解決方案，因為它必須非常復雜：

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

這應該給你你需要的東西：

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