在VB6中实现String.Format()

Question

可以String.Format()在VB6中实现,至少是一个足够接近的版本,在用'VB6'进行编程时可能会有用吗？

关于VB6字符串操作性能的良好资源:http://www.aivosto.com/vbtips/stringopt2.html

在一个相关的不,我也想出了几个字符串比较函数,在CodeReview.SE上找到它们

这些函数对于提高VB6的可读性非常有用,特别是如果你最近被.net代码宠坏了,突然被要求潜入VB6代码库......享受!

Answer 1

我找不到任何地方,所以我自己做了:

Public PADDING_CHAR As String

Public Function StringFormat(format_string As String, ParamArray values()) As String
'VB6 implementation of .net String.Format(), slightly customized.
'Tested with Office 2010 VBA (x64)

        Dim return_value As String
        Dim values_count As Integer

        'some error-handling constants:
        Const ERR_FORMAT_EXCEPTION As Long = vbObjectError Or 9001
        Const ERR_ARGUMENT_NULL_EXCEPTION As Long = vbObjectError Or 9002
        Const ERR_SOURCE As String = "StringFormat"
        Const ERR_MSG_INVALID_FORMAT_STRING As String = "Invalid format string."
        Const ERR_MSG_FORMAT_EXCEPTION As String = "The number indicating an argument to format is less than zero, or greater than or equal to the length of the args array."

        'use SPACE as default padding character
        If PADDING_CHAR = vbNullString Then PADDING_CHAR = Chr$(32)

        'figure out number of passed values:
        values_count = UBound(values) + 1

        Dim regex As RegExp
        Dim matches As MatchCollection
        Dim thisMatch As Match
        Dim thisString As String
        Dim thisFormat As String

        'when format_string starts with "@", escapes are not replaced 
        '(string is treated as a literal string with placeholders)        
        Dim useLiteral As Boolean 
        Dim escapeHex As Boolean 'indicates whether HEX specifier "0x" is to be escaped or not
        'validate string_format:
        Set regex = New RegExp
        regex.Pattern = "{({{)*(\w+)(,-?\d+)?(:[^}]+)?}(}})*"
        regex.IgnoreCase = True
        regex.Global = True
        Set matches = regex.Execute(format_string)

        'determine if values_count matches number of unique regex matches:
        Dim uniqueCount As Integer
        Dim tmpCSV As String
        For Each thisMatch In matches
            If Not StringContains(tmpCSV, thisMatch.SubMatches(1)) Then
                uniqueCount = uniqueCount + 1
                tmpCSV = tmpCSV & thisMatch.SubMatches(1) & ","
            End If
        Next

        'unique indices count must match values_count:
        If matches.Count > 0 And uniqueCount <> values_count Then _
            Err.Raise ERR_FORMAT_EXCEPTION, _
            ERR_SOURCE, ERR_MSG_FORMAT_EXCEPTION

        useLiteral = StringStartsWith("@", format_string)

        'remove the "@" literal specifier
        If useLiteral Then format_string = Right(format_string, Len(format_string) - 1)

        If Not useLiteral And StringContains(format_string, "\\") Then _
            format_string = Replace(format_string, "\\", Chr$(27))

        If StringContains(format_string, "\\") Then _
            format_string = Replace(format_string, "\\", Chr$(27))

        If matches.Count = 0 And format_string <> vbNullString And UBound(values) = -1 Then
        'only format_string was specified: skip to checking escape sequences:
            return_value = format_string
            GoTo checkEscapes
        ElseIf UBound(values) = -1 And matches.Count > 0 Then
            Err.Raise ERR_ARGUMENT_NULL_EXCEPTION, _
                ERR_SOURCE, ERR_MSG_FORMAT_EXCEPTION
        End If

        return_value = format_string

        'dissect format_string:

        Dim i As Integer, v As String, p As String 'i: iterator; v: value; p: placeholder
        Dim alignmentGroup As String, alignmentSpecifier As String
        Dim formattedValue As String, alignmentPadding As Integer

        'iterate regex matches (each match is a placeholder):
        For i = 0 To matches.Count - 1

            'get the placeholder specified index:
            Set thisMatch = matches(i)
            p = thisMatch.SubMatches(1)

            'if specified index (0-based) > uniqueCount (1-based), something's wrong:
            If p > uniqueCount - 1 Then _
                Err.Raise ERR_FORMAT_EXCEPTION, _
                ERR_SOURCE, ERR_MSG_FORMAT_EXCEPTION
            v = values(p)

            'get the alignment specifier if it is specified:
            alignmentGroup = thisMatch.SubMatches(2)
            If alignmentGroup <> vbNullString Then _
                alignmentSpecifier = Right$(alignmentGroup, LenB(alignmentGroup) / 2 - 1)


            'get the format specifier if it is specified:
            thisString = thisMatch.Value
            If StringContains(thisString, ":") Then

                Dim formatGroup As String, precisionSpecifier As Integer
                Dim formatSpecifier As String, precisionString As String

                'get the string between ":" and "}":
                formatGroup = Mid$(thisString, InStr(1, thisString, ":") + 1, (LenB(thisString) / 2) - 2)
                formatGroup = Left$(formatGroup, LenB(formatGroup) / 2 - 1)

                precisionString = Right$(formatGroup, LenB(formatGroup) / 2 - 1)
                formatSpecifier = Mid$(thisString, InStr(1, thisString, ":") + 1, 1)

                'applicable formatting depends on the type of the value (yes, GOTO!!):
                If TypeName(values(p)) = "Date" Then GoTo DateTimeFormatSpecifiers
                If v = vbNullString Then GoTo ApplyStringFormat

NumberFormatSpecifiers:
                If precisionString <> vbNullString And Not IsNumeric(precisionString) Then _
                    Err.Raise ERR_FORMAT_EXCEPTION, _
                        ERR_SOURCE, ERR_MSG_INVALID_FORMAT_STRING

                If precisionString = vbNullString Then precisionString = 0

                Select Case formatSpecifier

                    Case "C", "c" 'CURRENCY format, formats string as currency.
                    'Precision specifier determines number of decimal digits.
                    'This implementation ignores regional settings
                    '(hard-coded group separator, decimal separator and currency sign).

                    precisionSpecifier = CInt(precisionString)
                    thisFormat = "#,##0.$"

                    If LenB(formatGroup) > 2 And precisionSpecifier > 0 Then 
                        'if a non-zero precision is specified...
                        thisFormat = _
                        Replace$(thisFormat, ".", "." & String$(precisionString, Chr$(48)))
                    End If


                    Case "D", "d" 'DECIMAL format, formats string as integer number.
                    'Precision specifier determines number of digits in returned string.


                    precisionSpecifier = CInt(precisionString)
                    thisFormat = "0"
                    thisFormat = Right$(String$(precisionSpecifier, "0") & thisFormat, _
                        IIf(precisionSpecifier = 0, Len(thisFormat), precisionSpecifier))


                    Case "E", "e" 'EXPONENTIAL NOTATION format (aka "Scientific Notation")
                    'Precision specifier determines number of decimals in returned string.
                    'This implementation ignores regional settings'
                    '(hard-coded decimal separator).


                    precisionSpecifier = CInt(precisionString)
                    thisFormat = "0.00000#" & formatSpecifier & "-#" 'defaults to 6 decimals

                    If LenB(formatGroup) > 2 And precisionSpecifier > 0 Then
                        'if a non-zero precision is specified...
                        thisFormat = "0." & String$(precisionSpecifier - 1, Chr$(48)) & "#" & formatSpecifier & "-#"

                    ElseIf LenB(formatGroup) > 2 And precisionSpecifier = 0 Then
                        Err.Raise ERR_FORMAT_EXCEPTION, _
                            ERR_SOURCE, ERR_MSG_INVALID_FORMAT_STRING
                    End If


                    Case "F", "f" 'FIXED-POINT format
                    'Precision specifier determines number of decimals in returned string.
                    'This implementation ignores regional settings'
                    '(hard-coded decimal separator).

                    precisionSpecifier = CInt(precisionString)
                    thisFormat = "0"
                    If LenB(formatGroup) > 2 And precisionSpecifier > 0 Then
                        'if a non-zero precision is specified...
                        thisFormat = (thisFormat & ".") & String$(precisionSpecifier, Chr$(48))
                    Else
                        'no precision specified - default to 2 decimals:
                        thisFormat = "0.00"
                    End If


                    Case "G", "g" 'GENERAL format (recursive)
                    'returns the shortest of either FIXED-POINT or SCIENTIFIC formats in case of a Double.
                    'returns DECIMAL format in case of a Integer or Long.

                    Dim eNotation As String, ePower As Integer, specifier As String
                    precisionSpecifier = IIf(CInt(precisionString) > 0, CInt(precisionString), _
                        IIf(StringContains(v, "."), Len(v) - InStr(1, v, "."), 0))

                    'track character case of formatSpecifier:
                    specifier = IIf(formatSpecifier = "G", "D", "d")

                    If TypeName(values(p)) = "Integer" Or TypeName(values(p)) = "Long" Then
                        'Integer types: use {0:D} (recursive call):
                        formattedValue = StringFormat("{0:" & specifier & "}", values(p))

                    ElseIf TypeName(values(p)) = "Double" Then
                        'Non-integer types: use {0:E}
                        specifier = IIf(formatSpecifier = "G", "E", "e")

                        'evaluate the exponential notation value (recursive call):
                        eNotation = StringFormat("{0:" & specifier & "}", v)

                        'get the power of eNotation:
                        ePower = Mid$(eNotation, InStr(1, UCase$(eNotation), "E-") + 1, Len(eNotation) - InStr(1, UCase$(eNotation), "E-"))

                        If ePower > -5 And Abs(ePower) < precisionSpecifier Then
                            'use {0:F} when ePower > -5 and abs(ePower) < precisionSpecifier:
                            'evaluate the floating-point value (recursive call):
                             specifier = IIf(formatSpecifier = "G", "F", "f")
                             formattedValue = StringFormat("{0:" & formatSpecifier & _
                                 IIf(precisionSpecifier <> 0, precisionString, vbNullString) & "}", values(p))
                        Else
                            'fallback to {0:E} if previous rule didn't apply:
                            formattedValue = eNotation
                        End If

                    End If

                    GoTo AlignFormattedValue 'Skip the "ApplyStringFormat" step, it's applied already.


                    Case "N", "n" 'NUMERIC format, formats string as an integer or decimal number.
                    'Precision specifier determines number of decimal digits.
                    'This implementation ignores regional settings'
                    '(hard-coded group and decimal separators).

                    precisionSpecifier = CInt(precisionString)
                    If LenB(formatGroup) > 2 And precisionSpecifier > 0 Then
                        'if a non-zero precision is specified...
                        thisFormat = "#,##0"
                        thisFormat = (thisFormat & ".") & String$(precisionSpecifier, Chr$(48))

                    Else 'only the "D" is specified
                        thisFormat = "#,##0"
                    End If


                    Case "P", "p" 'PERCENT format. Formats string as a percentage.
                    'Value is multiplied by 100 and displayed with a percent symbol.
                    'Precision specifier determines number of decimal digits.

                    thisFormat = "#,##0%"
                    precisionSpecifier = CInt(precisionString)
                    If LenB(formatGroup) > 2 And precisionSpecifier > 0 Then
                        'if a non-zero precision is specified...
                        thisFormat = "#,##0"
                        thisFormat = (thisFormat & ".") & String$(precisionSpecifier, Chr$(48))

                    Else 'only the "P" is specified
                        thisFormat = "#,##0"
                    End If

                    'Append the percentage sign to the format string:
                    thisFormat = thisFormat & "%"


                    Case "R", "r" 'ROUND-TRIP format (a string that can round-trip to an identical number)
                    'example: ?StringFormat("{0:R}", 0.0000000001141596325677345362656)
                    '         ...returns "0.000000000114159632567735"

                    'convert value to a Double (chop off overflow digits):
                    v = CDbl(v)


                    Case "X", "x" 'HEX format. Formats a string as a Hexadecimal value.
                    'Precision specifier determines number of total digits.
                    'Returned string is prefixed with "&H" to specify Hex.

                    v = Hex(v)
                    precisionSpecifier = CInt(precisionString)

                    If LenB(precisionString) > 0 Then 'precision here stands for left padding
                        v = Right$(String$(precisionSpecifier, "0") & v, IIf(precisionSpecifier = 0, Len(v), precisionSpecifier))
                    End If

                    'add C# hex specifier, apply specified casing:
                    '(VB6 hex specifier would cause Format() to reverse the formatting):
                    v = "0x" & IIf(formatSpecifier = "X", UCase$(v), LCase$(v))


                    Case Else

                        If IsNumeric(formatSpecifier) And val(formatGroup) = 0 Then
                            formatSpecifier = formatGroup
                            v = Format(v, formatGroup)
                        Else
                            Err.Raise ERR_FORMAT_EXCEPTION, _
                                ERR_SOURCE, ERR_MSG_INVALID_FORMAT_STRING
                        End If
                End Select

                GoTo ApplyStringFormat


DateTimeFormatSpecifiers:
                Select Case formatSpecifier

                    Case "c", "C" 'CUSTOM date/time format
                    'let VB Format() parse precision specifier as is:
                        thisFormat = precisionString

                    Case "d" 'SHORT DATE format
                        thisFormat = "ddddd" 

                    Case "D" 'LONG DATE format
                        thisFormat = "dddddd"

                    Case "f" 'FULL DATE format (short)
                        thisFormat = "dddddd h:mm AM/PM"

                    Case "F" 'FULL DATE format (long)
                        thisFormat = "dddddd ttttt"

                    Case "g"
                        thisFormat = "ddddd hh:mm AM/PM"

                    Case "G"
                        thisFormat = "ddddd ttttt"

                    Case "s" 'SORTABLE DATETIME format
                        thisFormat = "yyyy-mm-ddThh:mm:ss"

                    Case "t" 'SHORT TIME format
                        thisFormat = "hh:mm AM/PM"

                    Case "T" 'LONG TIME format
                        thisFormat = "ttttt"

                    Case Else
                        Err.Raise ERR_FORMAT_EXCEPTION, _
                            ERR_SOURCE, ERR_MSG_INVALID_FORMAT_STRING
                End Select
                GoTo ApplyStringFormat

            End If


ApplyStringFormat:
            'apply computed format string:
            formattedValue = Format(v, thisFormat)


AlignFormattedValue:
            'apply specified alignment specifier:
            If alignmentSpecifier <> vbNullString Then

                alignmentPadding = Abs(CInt(alignmentSpecifier))
                If CInt(alignmentSpecifier) < 0 Then
                    'negative: left-justified alignment
                    If alignmentPadding - Len(formattedValue) > 0 Then _
                        formattedValue = formattedValue & _
                            String$(alignmentPadding - Len(formattedValue), PADDING_CHAR)
                Else
                    'positive: right-justified alignment
                    If alignmentPadding - Len(formattedValue) > 0 Then _
                        formattedValue = String$(alignmentPadding - Len(formattedValue), PADDING_CHAR) & formattedValue
                End If
            End If

            'Replace C# hex specifier with VB6 hex specifier, 
            'only if hex specifier was introduced in this function:
            If (Not useLiteral And escapeHex) And _
                StringContains(formattedValue, "0x") Then _
            formattedValue = Replace$(formattedValue, "0x", "&H")

            'replace all occurrences of placeholder {i} with their formatted values:
            return_value = Replace(return_value, thisString, formattedValue, Count:=1)

            'reset before reiterating:
            thisFormat = vbNullString
        Next


checkEscapes:
        'if there's no more backslashes, don't bother checking for the rest:
        If useLiteral Or Not StringContains(return_value, "\") Then GoTo normalExit

        Dim escape As New EscapeSequence
        Dim escapes As New Collection
        escapes.Add escape.Create("\n", vbNewLine), "0"
        escapes.Add escape.Create("\q", Chr$(34)), "1"
        escapes.Add escape.Create("\t", vbTab), "2"
        escapes.Add escape.Create("\a", Chr$(7)), "3"
        escapes.Add escape.Create("\b", Chr$(8)), "4"
        escapes.Add escape.Create("\v", Chr$(13)), "5"
        escapes.Add escape.Create("\f", Chr$(14)), "6"
        escapes.Add escape.Create("\r", Chr$(15)), "7"

        For i = 0 To escapes.Count - 1
            Set escape = escapes(CStr(i))
            If StringContains(return_value, escape.EscapeString) Then _
                return_value = Replace(return_value, escape.EscapeString, escape.ReplacementString)

            If Not StringContains(return_value, "\") Then _
                GoTo normalExit
        Next

        'replace "ASCII (oct)" escape sequence
        Set regex = New RegExp
        regex.Pattern = "\\(\d{3})"
        regex.IgnoreCase = True
        regex.Global = True
        Set matches = regex.Execute(format_string)

        Dim char As Long
        If matches.Count <> 0 Then
            For Each thisMatch In matches
                p = thisMatch.SubMatches(0)
                '"p" contains the octal number representing the ASCII code we're after:
                p = "&O" & p 'prepend octal prefix
                char = CLng(p)
                return_value = Replace(return_value, thisMatch.Value, Chr$(char))
            Next
        End If

        'if there's no more backslashes, don't bother checking for the rest:
        If Not StringContains("\", return_value) Then GoTo normalExit

        'replace "ASCII (hex)" escape sequence
        Set regex = New RegExp
        regex.Pattern = "\\x(\w{2})"
        regex.IgnoreCase = True
        regex.Global = True
        Set matches = regex.Execute(format_string)

        If matches.Count <> 0 Then
            For Each thisMatch In matches
                p = thisMatch.SubMatches(0)
                '"p" contains the hex value representing the ASCII code we're after:
                p = "&H" & p 'prepend hex prefix
                char = CLng(p)
                return_value = Replace(return_value, thisMatch.Value, Chr$(char))
            Next
        End If

normalExit:
        Set escapes = Nothing
        Set escape = Nothing
        If Not useLiteral And StringContains(return_value, Chr$(27)) Then _
            return_value = Replace(return_value, Chr$(27), "\")
        StringFormat = return_value
End Function

请注意ParamArray方法签名(感谢@wqw):这样做可以省去多个可选参数的使用(以及在使用调用语句命名参数时能够分配value2而无需分配的使用错误value1).因为它是a ParamArray,单个值Variant意味着每个参数可以是不同的类型,VB正在幕后进行字符串转换.

然后可以像这样使用该函数:

?StringFormat("(C) Currency: . . . . . . . . {0:C}\n" & _
    "(D) Decimal:. . . . . . . . . {0:D}\n" & _
    "(E) Scientific: . . . . . . . {1:E}\n" & _
    "(F) Fixed point:. . . . . . . {1:F}\n" & _
    "(N) Number: . . . . . . . . . {0:N}\n" & _
    "(P) Percent:. . . . . . . . . {1:P}\n" & _
    "(R) Round-trip: . . . . . . . {1:R}\n" & _
    "(X) Hexadecimal:. . . . . . . {0:X}\n",-123, -123.45)

输出:

(C) Currency: . . . . . . . . -123.00$
(D) Decimal:. . . . . . . . . -123
(E) Scientific: . . . . . . . -1.23450E2
(F) Fixed point:. . . . . . . -123
(N) Number: . . . . . . . . . -123
(P) Percent:. . . . . . . . . -12,345%
(R) Round-trip: . . . . . . . -123.45
(X) Hexadecimal:. . . . . . . &HFFFFFF85

还像这样:

?StringFormat("(c) Custom format: . . . . . .{0:cYYYY-MM-DD (MMMM)}\n" & _
    "(d) Short date: . . . . . . . {0:d}\n" & _
    "(D) Long date:. . . . . . . . {0:D}\n" & _
    "(T) Long time:. . . . . . . . {0:T}\n" & _
    "(f) Full date/short time: . . {0:f}\n" & _
    "(F) Full date/long time:. . . {0:F}\n" & _
    "(s) Sortable: . . . . . . . . {0:s}\n", Now())

输出:

(c) Custom format: . . . . . .2013-01-26 (January)
(d) Short date: . . . . . . . 1/26/2013
(D) Long date:. . . . . . . . Saturday, January 26, 2013
(T) Long time:. . . . . . . . 8:28:11 PM
(f) Full date/short time: . . 1/26/2013 8:28:11 PM
(F) Full date/long time:. . . Saturday, January 26, 2013 8:28:11 PM
(s) Sortable: . . . . . . . . 2013-01-26T20:28:11

也可以指定对齐(/ padding)和使用转义序列:

?StringFormat ("\q{0}, {1}!\x20\n'{2,10:C2}'\n'{2,-10:C2}'", "hello", "world", 100)

"hello, world!"
'   100.00$'
'100.00$   '

查看来自http://msdn.microsoft.com/fr-fr/library/b1csw23d(v=vs.80).aspx的示例,只有少数格式说明符未实现,主要是日期/时间说明符...但我会认为"c"自定义日期/时间格式说明符弥补了这一点.

该函数使用简单的实现String.Contains():

Public Function StringContains(string_source As String, find_text As String, _
    Optional ByVal caseSensitive As Boolean = True) As Boolean
    StringContains = StringContainsAny(string_source, caseSensitive, find_text)
End Function

编辑:此代码现在正确处理"\\"转义,如评论中所述.此外,虽然StringContains肯定是实用的,并提供比InStr()通话更舒适的阅读,下面的StringContainsAny功能更好:

Public Function StringContainsAny(string_source As String, ByVal caseSensitive As Boolean, _
    ParamArray find_values()) As Boolean

    Dim i As Integer, found As Boolean
    If caseSensitive Then
        For i = LBound(find_values) To UBound(find_values)
            found = (InStr(1, string_source, _
                find_values(i), vbBinaryCompare) <> 0)
            If found Then Exit For
        Next
    Else
        For i = LBound(find_values) To UBound(find_values)
            StringContainsAny = (InStr(1, LCase$(string_source), _ 
                LCase$(find_values(i)),   vbBinaryCompare) <> 0)
            If found Then Exit For
        Next
    End If
    StringContainsAny = found
End Function

考虑以下:

foo = Instr(1, source, "value1") > 0 Or Instr(1, source, "value2") > 0 _
   Or Instr(1, source, "value3") > 0 Or Instr(1, source, "value4") > 0 _
   Or Instr(1, source, "value5") > 0 Or Instr(1, source, "value6") > 0 _

在VB可以确定是否foo是,TRUE或者FALSE每次InStr()调用之前.但是StringContainsAny(),条件满足第一个找到的值,这使得它更快.

编辑:以前的编辑几乎消除了转义序列; 恢复它们,使用一个小类"EscapeSequence"暴露两个属性和一个工厂方法 - 这样做可以保持for-each循环并处理所有简单的转义而不会复制很多代码.

此代码还使用了一个StringStartsWith函数,实现如下:

Public Function StringStartsWith(ByVal find_text As String, ByVal string_source As String, Optional ByVal caseSensitive As Boolean = True) As Boolean

    If caseSensitive Then
        StringStartsWith = (Left$(string_source, LenB(find_text) / 2) = find_text)
    Else
        StringStartsWith = (Left$(LCase(string_source), LenB(find_text) / 2) = LCase$(find_text))
    End If

End Function