使用Objective-C将HTML文本转换为纯文本

Question

我有巨大的NSString里面有HTML文本。该字符串的长度超过3.500.000个字符。如何将此HTML文本转换为NSString内部的纯文本。我使用的是扫描仪，但效果太慢了。任何的想法 ？

Answer 1

这取决于您要定位的iOS版本。从iOS7开始，有一种内置方法，不仅可以剥离HTML标记，还可以将格式设置为字符串：

Xcode 9 / Swift 4

if let htmlStringData = htmlString.data(using: .utf8), let attributedString = try? NSAttributedString(data: htmlStringData, options: [.documentType : NSAttributedString.DocumentType.html], documentAttributes: nil) {
    print(attributedString)
}

你甚至可以创建这样的扩展：

extension String {
    var htmlToAttributedString: NSAttributedString? {
        guard let data = self.data(using: .utf8) else {
            return nil
        }

        do {
            return try NSAttributedString(data: data, options: [.documentType : NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue], documentAttributes: nil)
        } catch {
            print("Cannot convert html string to attributed string: \(error)")
            return nil
        }
    }
}

请注意，此示例代码使用UTF8编码。您甚至可以创建函数而不是计算属性，并将编码添加为参数。

斯威夫特3

let attributedString = try NSAttributedString(data: htmlString.dataUsingEncoding(NSUTF8StringEncoding)!,
                                              options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
                                              documentAttributes: nil)

Objective-C的

[[NSAttributedString alloc] initWithData:[htmlString dataUsingEncoding:NSUTF8StringEncoding] options:@{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType, NSCharacterEncodingDocumentAttribute: [NSNumber numberWithInt:NSUTF8StringEncoding]} documentAttributes:nil error:nil];

如果你只需要删除<和>之间的所有内容（脏方式!!!），如果你在字符串中有这些字符可能会有问题，请使用：

- (NSString *)stringByStrippingHTML {
   NSRange r;
   NSString *s = [[self copy] autorelease];
   while ((r = [s rangeOfString:@"<[^>]+>" options:NSRegularExpressionSearch]).location != NSNotFound)
     s = [s stringByReplacingCharactersInRange:r withString:@""];
   return s;
}

Answer 2

我用扫描仪解决了我的问题，但我不是用它来处理所有文本。在将所有部分连接在一起之前，我将它用于每10,000个文本部分。我的代码如下

-(NSString *)convertHTML:(NSString *)html {

    NSScanner *myScanner;
    NSString *text = nil;
    myScanner = [NSScanner scannerWithString:html];

    while ([myScanner isAtEnd] == NO) {

        [myScanner scanUpToString:@"<" intoString:NULL] ;

        [myScanner scanUpToString:@">" intoString:&text] ;

        html = [html stringByReplacingOccurrencesOfString:[NSString stringWithFormat:@"%@>", text] withString:@""];
    }
    //
    html = [html stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

    return html;
}

斯威夫特4：

var htmlToString(html:String) -> String {
        var htmlStr =html;
        let scanner:Scanner = Scanner(string: htmlStr);
        var text:NSString? = nil;
        while scanner.isAtEnd == false {
            scanner.scanUpTo("<", into: nil);
            scanner.scanUpTo(">", into: &text);
            htmlStr = htmlStr.replacingOccurrences(of: "\(text ?? "")>", with: "");
        }
        htmlStr = htmlStr.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines);
        return htmlStr;
}

Answer 3

对于Swift语言，

NSAttributedString(data:(htmlString as! String).dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true
            )!, options:[NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType, NSCharacterEncodingDocumentAttribute: NSNumber(unsignedLong: NSUTF8StringEncoding)], documentAttributes: nil, error: nil)!

Answer 4

- (NSString *)stringByStrippingHTML:(NSString *)inputString
{
    NSMutableString *outString;

    if (inputString)
    {
        outString = [[NSMutableString alloc] initWithString:inputString];

        if ([inputString length] > 0)
        {
            NSRange r;

            while ((r = [outString rangeOfString:@"<[^>]+>|&nbsp;" options:NSRegularExpressionSearch]).location != NSNotFound)
            {
                [outString deleteCharactersInRange:r];
            }      
        }
    }

    return outString; 
}

Answer 5

目标C.

+ (NSString*)textToHtml:(NSString*)htmlString
{
    htmlString = [htmlString stringByReplacingOccurrencesOfString:@""" withString:@"\""];
    htmlString = [htmlString stringByReplacingOccurrencesOfString:@"'" withString:@"'"];
    htmlString = [htmlString stringByReplacingOccurrencesOfString:@"&" withString:@"&"];
    htmlString = [htmlString stringByReplacingOccurrencesOfString:@"&lt;" withString:@"<"];
    htmlString = [htmlString stringByReplacingOccurrencesOfString:@"&gt;" withString:@">"];
    return htmlString;
}

希望这可以帮助！

Answer 6

您是否尝试过类似下面的内容，不确定它是否会像您在使用扫描仪之前那样更快，请检查： -

//String which contains html tags
    NSString *htmlString=[NSString stringWithFormat:@"%@",@"<b>right</b> onto <b>Kennington Park Rd/A3</b>Continue to follow A3</div><div >Entering toll zone in 1.7&nbsp;km at Newington Causeway/A3</div><divGo through 2 roundabouts</div>"];


    NSMutableString *mutStr=[NSMutableString string];
    NSString *s = nil;
//Removing html elements tags
    NSArray *arra=[htmlString componentsSeparatedByCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"</>"]];
    NSLog(@"%@",arra);
    for (s in arra)
    {
        [mutStr appendString:@" "];
        [mutStr appendString:s];
    }
            NSLog(@"%@",mutStr);//Printing the output

Answer 7

斯威夫特4：

do {
   let cleanString = try NSAttributedString(data: htmlContent.data(using: String.Encoding.utf8)!,
                                                                      options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
                                                                      documentAttributes: nil)
} catch {
    print("Something went wrong")
}

Answer 8

通过将编码类型作为参数传递可以更通用，但是作为此类别的示例：

@implementation NSString (CSExtension)

    - (NSString *)htmlToText {
        return [NSAttributedString.alloc
                initWithData:[self dataUsingEncoding:NSUnicodeStringEncoding]
                     options:@{NSDocumentTypeDocumentOption: NSHTMLTextDocumentType}
          documentAttributes:nil error:nil].string;
    }

@end