Objective-C / Cocoa Touch 中的 HTML 字符解码

Question

首先，我发现了这个：Objective C HTML escape/unescape，但它对我不起作用。

我的编码字符（来自 RSS 提要，顺便说一句）如下所示：&

我在网上搜索并找到了相关的讨论，但没有解决我的特定编码，我认为它们被称为十六进制字符。

Answer 1

查看我的NSString category for HTML。以下是可用的方法：

- (NSString *)stringByConvertingHTMLToPlainText;
- (NSString *)stringByDecodingHTMLEntities;
- (NSString *)stringByEncodingHTMLEntities;
- (NSString *)stringWithNewLinesAsBRs;
- (NSString *)stringByRemovingNewLinesAndWhitespace;

Answer 2

丹尼尔的那个基本上很好，我在那里修复了一些问题：

1. 删除了 NSSCanner 的跳过字符（否则两个连续实体之间的空格将被忽略

   [扫描仪 setCharactersToBeSkipped:nil];

2. 修复了当存在孤立的“&”符号时的解析（我不确定这个的“正确”输出是什么，我只是将它与 firefox 进行了比较）：

例如

    &#ABC DF & B'  & C' Items (288)

这里是修改后的代码：

- (NSString *)stringByDecodingXMLEntities {
    NSUInteger myLength = [self length];
    NSUInteger ampIndex = [self rangeOfString:@"&" options:NSLiteralSearch].location;

    // Short-circuit if there are no ampersands.
    if (ampIndex == NSNotFound) {
        return self;
    }
    // Make result string with some extra capacity.
    NSMutableString *result = [NSMutableString stringWithCapacity:(myLength * 1.25)];

    // First iteration doesn't need to scan to & since we did that already, but for code simplicity's sake we'll do it again with the scanner.
    NSScanner *scanner = [NSScanner scannerWithString:self];

    [scanner setCharactersToBeSkipped:nil];

    NSCharacterSet *boundaryCharacterSet = [NSCharacterSet characterSetWithCharactersInString:@" \t\n\r;"];

    do {
        // Scan up to the next entity or the end of the string.
        NSString *nonEntityString;
        if ([scanner scanUpToString:@"&" intoString:&nonEntityString]) {
            [result appendString:nonEntityString];
        }
        if ([scanner isAtEnd]) {
            goto finish;
        }
        // Scan either a HTML or numeric character entity reference.
        if ([scanner scanString:@"&" intoString:NULL])
            [result appendString:@"&"];
        else if ([scanner scanString:@"'" intoString:NULL])
            [result appendString:@"'"];
        else if ([scanner scanString:@""" intoString:NULL])
            [result appendString:@"\""];
        else if ([scanner scanString:@"<" intoString:NULL])
            [result appendString:@"<"];
        else if ([scanner scanString:@"&gt;" intoString:NULL])
            [result appendString:@">"];
        else if ([scanner scanString:@"&#" intoString:NULL]) {
            BOOL gotNumber;
            unsigned charCode;
            NSString *xForHex = @"";

            // Is it hex or decimal?
            if ([scanner scanString:@"x" intoString:&xForHex]) {
                gotNumber = [scanner scanHexInt:&charCode];
            }
            else {
                gotNumber = [scanner scanInt:(int*)&charCode];
            }

            if (gotNumber) {
                [result appendFormat:@"%C", (unichar)charCode];

                [scanner scanString:@";" intoString:NULL];
            }
            else {
                NSString *unknownEntity = @"";

                [scanner scanUpToCharactersFromSet:boundaryCharacterSet intoString:&unknownEntity];


                [result appendFormat:@"&#%@%@", xForHex, unknownEntity];

                //[scanner scanUpToString:@";" intoString:&unknownEntity];
                //[result appendFormat:@"&#%@%@;", xForHex, unknownEntity];
                NSLog(@"Expected numeric character entity but got &#%@%@;", xForHex, unknownEntity);

            }

        }
        else {
            NSString *amp;

            [scanner scanString:@"&" intoString:&amp];  //an isolated & symbol
            [result appendString:amp];

            /*
            NSString *unknownEntity = @"";
            [scanner scanUpToString:@";" intoString:&unknownEntity];
            NSString *semicolon = @"";
            [scanner scanString:@";" intoString:&semicolon];
            [result appendFormat:@"%@%@", unknownEntity, semicolon];
            NSLog(@"Unsupported XML character entity %@%@", unknownEntity, semicolon);
             */
        }

    }
    while (![scanner isAtEnd]);

finish:
    return result;
}

Answer 3

从 iOS 7 开始，您可以使用带有 NSHTMLTextDocumentType 属性的 NSAttributedString 本地解码 HTML 字符：

NSString *htmlString = @" & & < > ™ © ♥ ♣ ♠ ♦";
NSData *stringData = [htmlString dataUsingEncoding:NSUTF8StringEncoding];

NSDictionary *options = @{NSDocumentTypeDocumentAttribute:NSHTMLTextDocumentType};
NSAttributedString *decodedString;
decodedString = [[NSAttributedString alloc] initWithData:stringData
                                                 options:options
                                      documentAttributes:NULL
                                                   error:NULL];

解码后的属性字符串现在将显示为： & & ™ © ♥ ♣ ♠ ♦。

注意：这只有在主线程上调用时才有效。

Answer 4

那些被称为Character Entity References。当它们采用&#<number>; 的形式时，它们被称为数字实体引用。基本上，它是应该被替换的字节的字符串表示形式。以&为例，表示ISO-8859-1字符编码方案中值为38的字符，即&。

＆符号必须在 RSS 中编码的原因是它是一个保留的特殊字符。

您需要做的是解析字符串并将实体替换为与&# 和; 之间的值匹配的字节。我不知道在目标 C 中有什么好方法可以做到这一点，但 this stack overflow question 可能会有所帮助。

编辑：自从两年前回答这个问题以来，有一些很好的解决方案；请参阅下面的@Michael Waterfall 的答案。

Answer 5

似乎没有人提到最简单的选项之一：Google Toolbox for Mac
（尽管名称如此，但它也适用于 iOS。）

https://github.com/google/google-toolbox-for-mac/blob/master/Foundation/GTMNSString%2BHTML.h

/// Get a string where internal characters that are escaped for HTML are unescaped 
//
///  For example, '&' becomes '&'
///  Handles   and 2 cases as well
///
//  Returns:
//    Autoreleased NSString
//
- (NSString *)gtm_stringByUnescapingFromHTML;

而且我只需要在项目中包含三个文件：header、implementation 和 GTMDefines.h。

Answer 6

我应该在 GitHub 或其他地方发布这个。这属于 NSString 类别，使用 NSScanner 进行实现，并处理十六进制和十进制数字字符实体以及通常的符号实体。

此外，它相对优雅地处理格式错误的字符串（当您有一个 & 后跟无效的字符序列时），这在我使用此代码的 released app 中证明是至关重要的。

- (NSString *)stringByDecodingXMLEntities {
    NSUInteger myLength = [self length];
    NSUInteger ampIndex = [self rangeOfString:@"&" options:NSLiteralSearch].location;

    // Short-circuit if there are no ampersands.
    if (ampIndex == NSNotFound) {
        return self;
    }
    // Make result string with some extra capacity.
    NSMutableString *result = [NSMutableString stringWithCapacity:(myLength * 1.25)];

    // First iteration doesn't need to scan to & since we did that already, but for code simplicity's sake we'll do it again with the scanner.
    NSScanner *scanner = [NSScanner scannerWithString:self];
    do {
        // Scan up to the next entity or the end of the string.
        NSString *nonEntityString;
        if ([scanner scanUpToString:@"&" intoString:&nonEntityString]) {
            [result appendString:nonEntityString];
        }
        if ([scanner isAtEnd]) {
            goto finish;
        }
        // Scan either a HTML or numeric character entity reference.
        if ([scanner scanString:@"&" intoString:NULL])
            [result appendString:@"&"];
        else if ([scanner scanString:@"'" intoString:NULL])
            [result appendString:@"'"];
        else if ([scanner scanString:@""" intoString:NULL])
            [result appendString:@"\""];
        else if ([scanner scanString:@"<" intoString:NULL])
            [result appendString:@"<"];
        else if ([scanner scanString:@"&gt;" intoString:NULL])
            [result appendString:@">"];
        else if ([scanner scanString:@"&#" intoString:NULL]) {
            BOOL gotNumber;
            unsigned charCode;
            NSString *xForHex = @"";

            // Is it hex or decimal?
            if ([scanner scanString:@"x" intoString:&xForHex]) {
                gotNumber = [scanner scanHexInt:&charCode];
            }
            else {
                gotNumber = [scanner scanInt:(int*)&charCode];
            }
            if (gotNumber) {
                [result appendFormat:@"%C", charCode];
            }
            else {
                NSString *unknownEntity = @"";
                [scanner scanUpToString:@";" intoString:&unknownEntity];
                [result appendFormat:@"&#%@%@;", xForHex, unknownEntity];
                NSLog(@"Expected numeric character entity but got &#%@%@;", xForHex, unknownEntity);
            }
            [scanner scanString:@";" intoString:NULL];
        }
        else {
            NSString *unknownEntity = @"";
            [scanner scanUpToString:@";" intoString:&unknownEntity];
            NSString *semicolon = @"";
            [scanner scanString:@";" intoString:&semicolon];
            [result appendFormat:@"%@%@", unknownEntity, semicolon];
            NSLog(@"Unsupported XML character entity %@%@", unknownEntity, semicolon);
        }
    }
    while (![scanner isAtEnd]);

finish:
    return result;
}

Answer 7

这是我使用RegexKitLite 框架的方式：

-(NSString*) decodeHtmlUnicodeCharacters: (NSString*) html {
NSString* result = [html copy];
NSArray* matches = [result arrayOfCaptureComponentsMatchedByRegex: @"\\&#([\\d]+);"];

if (![matches count]) 
    return result;

for (int i=0; i<[matches count]; i++) {
    NSArray* array = [matches objectAtIndex: i];
    NSString* charCode = [array objectAtIndex: 1];
    int code = [charCode intValue];
    NSString* character = [NSString stringWithFormat:@"%C", code];
    result = [result stringByReplacingOccurrencesOfString: [array objectAtIndex: 0]
                                               withString: character];      
}   
return result;  

}

希望这会对某人有所帮助。

Answer 8

你可以只使用这个函数来解决这个问题。

+ (NSString*) decodeHtmlUnicodeCharactersToString:(NSString*)str
{
    NSMutableString* string = [[NSMutableString alloc] initWithString:str];  // #&39; replace with '
    NSString* unicodeStr = nil;
    NSString* replaceStr = nil;
    int counter = -1;

    for(int i = 0; i < [string length]; ++i)
    {
        unichar char1 = [string characterAtIndex:i];    
        for (int k = i + 1; k < [string length] - 1; ++k)
        {
            unichar char2 = [string characterAtIndex:k];    

            if (char1 == '&'  && char2 == '#' ) 
            {   
                ++counter;
                unicodeStr = [string substringWithRange:NSMakeRange(i + 2 , 2)];    
                // read integer value i.e, 39
                replaceStr = [string substringWithRange:NSMakeRange (i, 5)];     //     #&39;
                [string replaceCharactersInRange: [string rangeOfString:replaceStr] withString:[NSString stringWithFormat:@"%c",[unicodeStr intValue]]];
                break;
            }
        }
    }
    [string autorelease];

    if (counter > 1)
        return  [self decodeHtmlUnicodeCharactersToString:string]; 
    else
        return string;
}

Answer 9

这是Walty Yeung's answer 的 Swift 版本：

extension String {
    static private let mappings = ["&quot;" : "\"","&amp;" : "&", "&lt;" : "<", "&gt;" : ">","&nbsp;" : " ","&iexcl;" : "¡","&cent;" : "¢","&pound;" : " £","&curren;" : "¤","&yen;" : "¥","&brvbar;" : "¦","&sect;" : "§","&uml;" : "¨","&copy;" : "©","&ordf;" : " ª","&laquo" : "«","&not" : "¬","&reg" : "®","&macr" : "¯","&deg" : "°","&plusmn" : "±","&sup2; " : "²","&sup3" : "³","&acute" : "´","&micro" : "µ","&para" : "¶","&middot" : "·","&cedil" : "¸","&sup1" : "¹","&ordm" : "º","&raquo" : "»&","frac14" : "¼","&frac12" : "½","&frac34" : "¾","&iquest" : "¿","&times" : "×","&divide" : "÷","&ETH" : "Ð","&eth" : "ð","&THORN" : "Þ","&thorn" : "þ","&AElig" : "Æ","&aelig" : "æ","&OElig" : "Œ","&oelig" : "œ","&Aring" : "Å","&Oslash" : "Ø","&Ccedil" : "Ç","&ccedil" : "ç","&szlig" : "ß","&Ntilde;" : "Ñ","&ntilde;":"ñ",]

    func stringByDecodingXMLEntities() -> String {

        guard let _ = self.rangeOfString("&", options: [.LiteralSearch]) else {
            return self
        }

        var result = ""

        let scanner = NSScanner(string: self)
        scanner.charactersToBeSkipped = nil

        let boundaryCharacterSet = NSCharacterSet(charactersInString: " \t\n\r;")

        repeat {
            var nonEntityString: NSString? = nil

            if scanner.scanUpToString("&", intoString: &nonEntityString) {
                if let s = nonEntityString as? String {
                    result.appendContentsOf(s)
                }
            }

            if scanner.atEnd {
                break
            }

            var didBreak = false
            for (k,v) in String.mappings {
                if scanner.scanString(k, intoString: nil) {
                    result.appendContentsOf(v)
                    didBreak = true
                    break
                }
            }

            if !didBreak {

                if scanner.scanString("&#", intoString: nil) {

                    var gotNumber = false
                    var charCodeUInt: UInt32 = 0
                    var charCodeInt: Int32 = -1
                    var xForHex: NSString? = nil

                    if scanner.scanString("x", intoString: &xForHex) {
                        gotNumber = scanner.scanHexInt(&charCodeUInt)
                    }
                    else {
                        gotNumber = scanner.scanInt(&charCodeInt)
                    }

                    if gotNumber {
                        let newChar = String(format: "%C", (charCodeInt > -1) ? charCodeInt : charCodeUInt)
                        result.appendContentsOf(newChar)
                        scanner.scanString(";", intoString: nil)
                    }
                    else {
                        var unknownEntity: NSString? = nil
                        scanner.scanUpToCharactersFromSet(boundaryCharacterSet, intoString: &unknownEntity)
                        let h = xForHex ?? ""
                        let u = unknownEntity ?? ""
                        result.appendContentsOf("&#\(h)\(u)")
                    }
                }
                else {
                    scanner.scanString("&", intoString: nil)
                    result.appendContentsOf("&")
                }
            }

        } while (!scanner.atEnd)

        return result
    }
}

Answer 10

实际上 Michael Waterfall 的伟大 MWFeedParser 框架（参考他的回答）已经被 rmchaara 分叉了，他已经更新了 ARC 支持！

你可以在 Github here找到它

它真的很好用，我使用了 stringByDecodingHTMLEntities 方法并且完美无缺。

Answer 11

好像您需要另一种解决方案！这个很简单也很有效：

@interface NSString (NSStringCategory)
- (NSString *) stringByReplacingISO8859Codes;
@end


@implementation NSString (NSStringCategory)
- (NSString *) stringByReplacingISO8859Codes
{
    NSString *dataString = self;
    do {
        //*** See if string contains &# prefix
        NSRange range = [dataString rangeOfString: @"&#" options: NSRegularExpressionSearch];
        if (range.location == NSNotFound) {
            break;
        }
        //*** Get the next three charaters after the prefix
        NSString *isoHex = [dataString substringWithRange: NSMakeRange(range.location + 2, 3)];
        //*** Create the full code for replacement
        NSString *isoString = [NSString stringWithFormat: @"&#%@;", isoHex];
        //*** Convert to decimal integer
        unsigned decimal = 0;
        NSScanner *scanner = [NSScanner scannerWithString: [NSString stringWithFormat: @"0%@", isoHex]];
        [scanner scanHexInt: &decimal];
        //*** Use decimal code to get unicode character
        NSString *unicode = [NSString stringWithFormat:@"%C", decimal];
        //*** Replace all occurences of this code in the string
        dataString = [dataString stringByReplacingOccurrencesOfString: isoString withString: unicode];
    } while (TRUE); //*** Loop until we hit the NSNotFound

    return dataString;
}
@end

Answer 12

如果您将字符实体引用作为字符串，例如@"2318"，您可以使用 strtoul 提取具有正确 unicode 字符的重新编码的 NSString；

NSString *unicodePoint = @"2318"
unichar iconChar = (unichar) strtoul(unicodePoint.UTF8String, NULL, 16);
NSString *recoded = [NSString stringWithFormat:@"%C", iconChar];
NSLog(@"recoded: %@", recoded");
// prints out "recoded: ⌘"

Answer 13

Swift 3 版本的 Jugale 的回答

extension String {
    static private let mappings = ["&quot;" : "\"","&amp;" : "&", "&lt;" : "<", "&gt;" : ">","&nbsp;" : " ","&iexcl;" : "¡","&cent;" : "¢","&pound;" : " £","&curren;" : "¤","&yen;" : "¥","&brvbar;" : "¦","&sect;" : "§","&uml;" : "¨","&copy;" : "©","&ordf;" : " ª","&laquo" : "«","&not" : "¬","&reg" : "®","&macr" : "¯","&deg" : "°","&plusmn" : "±","&sup2; " : "²","&sup3" : "³","&acute" : "´","&micro" : "µ","&para" : "¶","&middot" : "·","&cedil" : "¸","&sup1" : "¹","&ordm" : "º","&raquo" : "»&","frac14" : "¼","&frac12" : "½","&frac34" : "¾","&iquest" : "¿","&times" : "×","&divide" : "÷","&ETH" : "Ð","&eth" : "ð","&THORN" : "Þ","&thorn" : "þ","&AElig" : "Æ","&aelig" : "æ","&OElig" : "Œ","&oelig" : "œ","&Aring" : "Å","&Oslash" : "Ø","&Ccedil" : "Ç","&ccedil" : "ç","&szlig" : "ß","&Ntilde;" : "Ñ","&ntilde;":"ñ",]

    func stringByDecodingXMLEntities() -> String {

        guard let _ = self.range(of: "&", options: [.literal]) else {
            return self
        }

        var result = ""

        let scanner = Scanner(string: self)
        scanner.charactersToBeSkipped = nil

        let boundaryCharacterSet = CharacterSet(charactersIn: " \t\n\r;")

        repeat {
            var nonEntityString: NSString? = nil

            if scanner.scanUpTo("&", into: &nonEntityString) {
                if let s = nonEntityString as? String {
                    result.append(s)
                }
            }

            if scanner.isAtEnd {
                break
            }

            var didBreak = false
            for (k,v) in String.mappings {
                if scanner.scanString(k, into: nil) {
                    result.append(v)
                    didBreak = true
                    break
                }
            }

            if !didBreak {

                if scanner.scanString("&#", into: nil) {

                    var gotNumber = false
                    var charCodeUInt: UInt32 = 0
                    var charCodeInt: Int32 = -1
                    var xForHex: NSString? = nil

                    if scanner.scanString("x", into: &xForHex) {
                        gotNumber = scanner.scanHexInt32(&charCodeUInt)
                    }
                    else {
                        gotNumber = scanner.scanInt32(&charCodeInt)
                    }

                    if gotNumber {
                        let newChar = String(format: "%C", (charCodeInt > -1) ? charCodeInt : charCodeUInt)
                        result.append(newChar)
                        scanner.scanString(";", into: nil)
                    }
                    else {
                        var unknownEntity: NSString? = nil
                        scanner.scanUpToCharacters(from: boundaryCharacterSet, into: &unknownEntity)
                        let h = xForHex ?? ""
                        let u = unknownEntity ?? ""
                        result.append("&#\(h)\(u)")
                    }
                }
                else {
                    scanner.scanString("&", into: nil)
                    result.append("&")
                }
            }

        } while (!scanner.isAtEnd)

        return result
    }
}