如何使用 NSXMLParser 解析同名的父子元素 [英] How to use NSXMLParser to parse parent-child elements that have the same name

问题描述

有人知道如何使用事件驱动模型 NSXMLParser 类解析以下 xml 吗?

Does anyone have some idea how to parse the following xml using event-driven model NSXMLParser class?

<Node>
  <name> Main </name>
  <Node>
    <name> Child 1 </name>
  </Node>

  <Node>
    <name> Child 2 </name>
  </Node>
</Node>

我想从这个 xml 文件中收集所有三个名称，是否可以，或者我必须更改为基于树的解析?

I want to collect all three names from this xml file, is it possible, or I have to change to Tree-based parsing?

推荐答案

这是SAX 类型"解析器的一个常见问题，您必须手动跟踪您的 XML 树的当前深度'在.问题一如既往，是不可能将整个树加载到内存中的 DOM 结构中，具体取决于您要操作的数据的大小.

This is a common problem with parsers like this one, of "type SAX", where you have to manually keep track of the current depth of the XML tree you're in. The problem, as always, is that loading the entire tree in a DOM structure in memory can be impossible, depending on the size of the data you want to manipulate.

以下代码显示了一个完成这项工作的类:

The following code shows a class that does this job:

#import <Foundation/Foundation.h>

@interface Test : NSObject <NSXMLParserDelegate> 
{
@private
    NSXMLParser *xmlParser;
    NSInteger depth;
    NSMutableString *currentName;
    NSString *currentElement;
}

- (void)start;

@end

这是实现:

#import "Test.h"

@interface Test ()
- (void)showCurrentDepth;
@end


@implementation Test

- (void)dealloc
{
    [currentElement release];
    [currentName release];
    [xmlParser release];
    [super dealloc];
}

- (void)start
{
    NSString *xml = @"<?xml version="1.0" encoding="UTF-8" ?><Node><name>Main</name><Node><name>Child 1</name></Node><Node><name>Child 2</name></Node></Node>";
    xmlParser = [[NSXMLParser alloc] initWithData:[xml dataUsingEncoding:NSUTF8StringEncoding]];
    [xmlParser setDelegate:self];
    [xmlParser setShouldProcessNamespaces:NO];
    [xmlParser setShouldReportNamespacePrefixes:NO];
    [xmlParser setShouldResolveExternalEntities:NO];
    [xmlParser parse];

}

#pragma mark -
#pragma mark NSXMLParserDelegate methods

- (void)parserDidStartDocument:(NSXMLParser *)parser 
{
    NSLog(@"Document started", nil);
    depth = 0;
    currentElement = nil;
}

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError 
{
    NSLog(@"Error: %@", [parseError localizedDescription]);
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName 
  namespaceURI:(NSString *)namespaceURI 
 qualifiedName:(NSString *)qName 
    attributes:(NSDictionary *)attributeDict
{
    [currentElement release];
    currentElement = [elementName copy];

    if ([currentElement isEqualToString:@"Node"])
    {
        ++depth;
        [self showCurrentDepth];
    }
    else if ([currentElement isEqualToString:@"name"])
    {
        [currentName release];
        currentName = [[NSMutableString alloc] init];
    }
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName 
  namespaceURI:(NSString *)namespaceURI 
 qualifiedName:(NSString *)qName
{

    if ([elementName isEqualToString:@"Node"]) 
    {
        --depth;
        [self showCurrentDepth];
    }
    else if ([elementName isEqualToString:@"name"])
    {
        if (depth == 1)
        {
            NSLog(@"Outer name tag: %@", currentName);
        }
        else 
        {
            NSLog(@"Inner name tag: %@", currentName);
        }
    }
}        

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
    if ([currentElement isEqualToString:@"name"]) 
    {
        [currentName appendString:string];
    } 
}

- (void)parserDidEndDocument:(NSXMLParser *)parser 
{
    NSLog(@"Document finished", nil);
}

#pragma mark -
#pragma mark Private methods

- (void)showCurrentDepth
{
    NSLog(@"Current depth: %d", depth);
}

@end

这是运行触发上述start"方法的命令行工具的结果:

This is the result of running a command line tool that triggers the "start" method above:

Document started
Current depth: 1
Outer name tag: Main
Current depth: 2
Inner name tag: Child 1
Current depth: 1
Current depth: 2
Inner name tag: Child 2
Current depth: 1
Current depth: 0
Document finished

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