Question

我在ios开发中非常新，我试着解析一个RSS文件（xml）。

这里是xml：（对不起语言）

<item>
<category> General < / category >
<title> killed in a tractor accident , was critically injured windsurfer </ title>
<description>
< ! [ CDATA [
<div> <a href='http://www.ynet.co.il/articles/0,7340,L-4360016,00.html'> <img src = 'http://www.ynet.co. il/PicServer3/2012/11/28/4302844/YOO_8879_a.jpg ' alt =' photo: Yaron Brener 'title =' Amona 'border = '0' width = '116 'height = '116'> </ a> < / div >
] ] >
Tractor driver in his 50s near Kfar Yuval flipped and trapped underneath . Room was critically injured windsurfer hurled rocks because of strong winds and wind surfer after was moderately injured in Netanya
< / description >
<link>
http://www.ynet.co.il/articles/0 , 7340, L- 4360016 , 00.html
< / link >
<pubDate> Fri, 22 Mar 2013 17:10:15 +0200 </ pubDate>
<guid>
http://www.ynet.co.il/articles/0 , 7340, L- 4360016 , 00.html
< / guid >
<tags> Kill , car accidents , surfing < / tags >
< / item >

，这是我的xmlparser代码：

    - (void)parserDidStartDocument:(NSXMLParser *)parser
    {
       self.titles = [[NSMutableArray alloc]init];
       self.descriptions = [[NSMutableArray alloc]init];
        self.links = [[NSMutableArray alloc]init];
    }

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
    if ([elementName isEqualToString:@"item"]) {
        isItem = YES;
    }

    if ([elementName isEqualToString:@"title"]) {
        isTitle=YES;
        self.titlesString = [[NSMutableString alloc]init];
    }

    if ([elementName isEqualToString:@"description"]) {
        isDesription = YES;
        self.descriptionString = [NSMutableString string];
        self.data = [NSMutableData data];
    }



}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{
    if(isItem && isTitle){
        [self.titlesString appendString:string];
    }
    if (isItem && isDesription) {
        if (self.descriptionString)
            [self.descriptionString appendString:string];
    }






}

- (void)parser:(NSXMLParser *)parser foundCDATA:(NSData *)CDATABlock
{
    if (self.data)
        [self.data appendData:CDATABlock];

}


- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
    if ([elementName isEqualToString:@"item"]) {
        isItem = NO;
        [self.titles addObject:self.titlesString];

        [self.descriptions addObject:self.descriptionString];


    }

    if ([elementName isEqualToString:@"title"]) {
        isTitle=NO;

    }
    if ([elementName isEqualToString:@"description"]) {

        NSString *result = [self.descriptionString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        NSLog(@"string=%@", result);


        if ([self.data length] > 0)
        {
            NSString *htmlSnippet = [[NSString alloc] initWithData:self.data encoding:NSUTF8StringEncoding];
            NSString *imageSrc = [self firstImgUrlString:htmlSnippet];
            NSLog(@"img src=%@", imageSrc);
            [self.links addObject:imageSrc];
        }



        self.descriptionString = nil;
        self.data = nil;
    }


}

- (NSString *)firstImgUrlString:(NSString *)string
{
    NSError *error = NULL;
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(<img\\s[\\s\\S]*?src\\s*?=\\s*?['\"](.*?)['\"][\\s\\S]*?>)+?"
                                                                           options:NSRegularExpressionCaseInsensitive
                                                                             error:&error];

    NSTextCheckingResult *result = [regex firstMatchInString:string
                                                     options:0
                                                       range:NSMakeRange(0, [string length])];

    if (result)
        return [string substringWithRange:[result rangeAtIndex:2]];

    return nil;
}

@end

就像我说我对iPhone开发还很陌生，我找了几个小时解决它的方法但却一无所获。我决定打开一个主题，然后提出几个问题：

一个。解析器不会忽略CDATA正在解析的所有内容。为什么会这样？你可以看到描述本身不在cdata中，我只有第一步，但即使我没有使用foundCDATA，我也得到了其余的:( NSData *）CDATABlock

两个。我想拍摄图片链接，该怎么做？我在网上搜索了一下，发现很多指南只解释了使用函数foundCDATA：（NSData *）CDATABlock 但它是如何使用的？我在代码中使用的方式？

我需要一个解释，以便我能理解，谢谢！

Answer 1

回答你的两个问题：

如果您已实施foundCDATA，解析器将解析该方法中的description CDATA，而不是foundCharacters。另一方面，如果您尚未实施foundCDATA，CDATA将由foundCharacters进行解析。因此，如果您不希望foundCharacters解析CDATA，那么您必须实施foundCDATA。

如果要提取img网址，则必须以某种方式解析收到的HTML。你可以使用Hpple，但我可能只是倾向于使用正则表达式：

- (NSString *)firstImgUrlString:(NSString *)string
{
    NSError *error = NULL;
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(<img\\s[\\s\\S]*?src\\s*?=\\s*?['\"](.*?)['\"][\\s\\S]*?>)+?"
                                                                           options:NSRegularExpressionCaseInsensitive
                                                                             error:&error];

    NSTextCheckingResult *result = [regex firstMatchInString:string
                                                     options:0
                                                       range:NSMakeRange(0, [string length])];

    if (result)
        return [string substringWithRange:[result rangeAtIndex:2]];

    return nil;
}

另请参阅this other Stack Overflow answer，其中我演示了Hpple和regex解决方案：

作为示例，这里是NSXMLParserDelegate方法将解析描述，将文本（不包括CDATA）放在一个字段中，并将CDATA中的图像URL放在另一个变量中。你必须修改以适应你的过程，但希望这给你基本的想法：

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
    if ([elementName isEqualToString:@"description"])
    {
        self.string = [NSMutableString string];
        self.data = [NSMutableData data];
    }
}

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
{
    NSLog(@"%s, parseError=%@", __FUNCTION__, parseError);
}

// In my standard NSXMLParser routine, I leave self.string `nil` when not parsing 
// a particular element, and initialize it if I am parsing. I do it this way
// so only my `didStartElement` and `didEndElement` need to worry about the particulars
// and my `foundCharacters` and `foundCDATA` are simplified. But do it however you
// want.

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
    if (self.string)
        [self.string appendString:string];
}

- (void)parser:(NSXMLParser *)parser foundCDATA:(NSData *)CDATABlock
{
    if (self.data)
        [self.data appendData:CDATABlock];
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
    if ([elementName isEqualToString:@"description"])
    {
        // get the text (non-CDATA) portion

        // you might want to get rid of the leading and trailing whitespace

        NSString *result = [self.string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        NSLog(@"string=%@", result);

        // get the img out of the CDATA

        if ([self.data length] > 0)
        {
            NSString *htmlSnippet = [[NSString alloc] initWithData:self.data encoding:NSUTF8StringEncoding];
            NSString *imageSrc = [self firstImgUrlString:htmlSnippet];
            NSLog(@"img src=%@", imageSrc);
        }

        // once I've saved the data where I want to save it, I `nil` out my
        // `string` and `data` properties:

        self.string = nil;
        self.data = nil;
    }
}

Answer 2

答案1：我会同意Rob对这个问题给出的答案。

答案2：试试这个来获取图片链接......

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{   
    if([currentElement isEqualToString:@"img"]) {
        NSLog(@"%@",[attributeDict objectForKey:@"src"]);
    }
}

Answer 3

您要提取的图像链接位于CDATA块内，但rss解析器会忽略CDATA块。

如果需要从CDATA中提取字符串，可以在foundCDATA中使用此块：

    - (void)parser:(NSXMLParser *)parser foundCDATA:(NSData *)CDATABlock
    {

    NSMutableString *cdstring = [[NSMutableString alloc] initWithData:CDATABlock encoding:NSUTF8StringEncoding];
    }

现在mutablestring“cdstring”将包含：

    <div>
    <a href='http://www.ynet.co.il/articles/0,7340,L-4360016,00.html'>
    <img src='http://www.ynet.co. il/PicServer3/2012/11/28/4302844/YOO_8879_a.jpg ' alt=' photo: Yaron Brener ' title=' Amona ' border='0' width='116 ' height='116'>
    </ a>
    </ div>
    ]]>

现在只需使用stringcontainsstring搜索href ='并提取链接或使用webview来显示

 htmlContent = [NSString stringWithFormat:@"%@", cdstring];
    [webView loadHTMLString:htmlContent baseURL:nil];

NSXMLParser不会忽略CDATA

3 个答案: