参数正则化

Question

我需要帮助为验证参数字符串创建regex。

参数字符串包含两个可选的显式字符组。第一组只能包含一个P、O、Z字符(顺序不重要)。第二组具有相同的限制，但只能包含字符t、c、p、m，如果出现这两个组，则需要用单个空格字符分隔。

因此，有效的字符串是：

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

等。

Answer 1

我不认为正则表达式是一个很好的解决方案，因为它必须非常复杂：

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 2

为什么不放弃regex，使用string来表示非字符串数据？

[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，您可以这样调用YourMethod。

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

或者，如果你想

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

如果您想知道更多关于这是如何工作的see this question。

Answer 3

这应该能满足你的需要：

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