我有一个使用内部声明实体的 XML 文件。例如:

<?xml version="1.0" encoding="UTF-8"?>

...

<!ENTITY my_symbol "my symbol value">

...

<my_element>
    <my_next_element>foo&my_symbol;bar</my_next_element>
</my_element>

...

使用 NSXMLParser 类，我如何能够解析 my_symbol实体引用？

根据实验，parser:foundInternalEntityDeclarationWithName:value:将为 my_symbol 调用委托(delegate)方法实体声明，有值 "my symbol value" .然后，当 my_next_element达到元素，NSXMLParser将调用 parser:didStartElement:namespaceURI:qualifiedName:attributes:委托(delegate)方法。

之前parser:didEndElement:namespaceURI:qualifiedName:要求</my_next_element> , parser:foundCharacters:委托(delegate)方法将使用字符串调用两次:

1. "foo"
2. "bar"

my_symbol实体引用被忽略。解析实体引用需要什么？

编辑:

删除 ENTITY my_symbol声明来自 DTD 的结果将是 NSXMLParserUndeclaredEntityError .这表明当存在实体声明时，然后在 <my_next_element> 中引用，它正在被注意到。由于某种原因，它只是没有被解析为它所代表的字符串。

此外，如果 &在元素中使用，解析器会将其正确解析为 "&"当 parser:foundCharacters: 时，它作为字符串传递委托(delegate)方法被调用。

最佳答案

我查看了 NSXMLParser.h，其中列出了以下定义的委托(delegate)支持方法:

@interface NSObject (NSXMLParserDelegateEventAdditions)
// Document handling methods
- (void)parserDidStartDocument:(NSXMLParser *)parser;
    // sent when the parser begins parsing of the document.
- (void)parserDidEndDocument:(NSXMLParser *)parser;
    // sent when the parser has completed parsing. If this is encountered, the parse was successful.

// DTD handling methods for various declarations.
- (void)parser:(NSXMLParser *)parser foundNotationDeclarationWithName:(NSString *)name publicID:(NSString *)publicID systemID:(NSString *)systemID;

- (void)parser:(NSXMLParser *)parser foundUnparsedEntityDeclarationWithName:(NSString *)name publicID:(NSString *)publicID systemID:(NSString *)systemID notationName:(NSString *)notationName;

- (void)parser:(NSXMLParser *)parser foundAttributeDeclarationWithName:(NSString *)attributeName forElement:(NSString *)elementName type:(NSString *)type defaultValue:(NSString *)defaultValue;

- (void)parser:(NSXMLParser *)parser foundElementDeclarationWithName:(NSString *)elementName model:(NSString *)model;

- (void)parser:(NSXMLParser *)parser foundInternalEntityDeclarationWithName:(NSString *)name value:(NSString *)value;

- (void)parser:(NSXMLParser *)parser foundExternalEntityDeclarationWithName:(NSString *)name publicID:(NSString *)publicID systemID:(NSString *)systemID;

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict;
    // sent when the parser finds an element start tag.
    // In the case of the cvslog tag, the following is what the delegate receives:
    //   elementName == cvslog, namespaceURI == http://xml.apple.com/cvslog, qualifiedName == cvslog
    // In the case of the radar tag, the following is what's passed in:
    //    elementName == radar, namespaceURI == http://xml.apple.com/radar, qualifiedName == radar:radar
    // If namespace processing >isn't< on, the xmlns:radar="http://xml.apple.com/radar" is returned as an attribute pair, the elementName is 'radar:radar' and there is no qualifiedName.

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName;
    // sent when an end tag is encountered. The various parameters are supplied as above.

- (void)parser:(NSXMLParser *)parser didStartMappingPrefix:(NSString *)prefix toURI:(NSString *)namespaceURI;
    // sent when the parser first sees a namespace attribute.
    // In the case of the cvslog tag, before the didStartElement:, you'd get one of these with prefix == @"" and namespaceURI == @"http://xml.apple.com/cvslog" (i.e. the default namespace)
    // In the case of the radar:radar tag, before the didStartElement: you'd get one of these with prefix == @"radar" and namespaceURI == @"http://xml.apple.com/radar"

- (void)parser:(NSXMLParser *)parser didEndMappingPrefix:(NSString *)prefix;
    // sent when the namespace prefix in question goes out of scope.

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string;
    // This returns the string of the characters encountered thus far. You may not necessarily get the longest character run. The parser reserves the right to hand these to the delegate as potentially many calls in a row to -parser:foundCharacters:

- (void)parser:(NSXMLParser *)parser foundIgnorableWhitespace:(NSString *)whitespaceString;
    // The parser reports ignorable whitespace in the same way as characters it's found.

- (void)parser:(NSXMLParser *)parser foundProcessingInstructionWithTarget:(NSString *)target data:(NSString *)data;
    // The parser reports a processing instruction to you using this method. In the case above, target == @"xml-stylesheet" and data == @"type='text/css' href='cvslog.css'"

- (void)parser:(NSXMLParser *)parser foundComment:(NSString *)comment;
    // A comment (Text in a <!-- --> block) is reported to the delegate as a single string

- (void)parser:(NSXMLParser *)parser foundCDATA:(NSData *)CDATABlock;
    // this reports a CDATA block to the delegate as an NSData.

- (NSData *)parser:(NSXMLParser *)parser resolveExternalEntityName:(NSString *)name systemID:(NSString *)systemID;
    // this gives the delegate an opportunity to resolve an external entity itself and reply with the resulting data.

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError;
    // ...and this reports a fatal error to the delegate. The parser will stop parsing.

- (void)parser:(NSXMLParser *)parser validationErrorOccurred:(NSError *)validationError;
    // If validation is on, this will report a fatal validation error to the delegate. The parser will stop parsing.
@end

根据文件中条目的顺序，找到的声明方法看起来应该在找到元素之前发生(如您所见)。我会尝试处理所有这些方法，看看它们是否会出现，但它们看起来都像是为其他用途而设计的。

我想知道是否有一种方法可以检测发送给您的委托(delegate)的所有未处理消息，以防文档/接口(interface)不完整。

关于objective-c - 如何使用 NSXMLParser 解析内部声明的 XML 实体引用，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/1541267/