iphone - 如何使用 NSXMLParser 解析同名的父子元素

Question

有谁知道如何使用事件驱动模型 NSXMLParser 类解析以下 xml？

<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？

Answer 1

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.

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

This is the implementation:

#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

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

Answer 2

- (NSInteger)columnNumber

为您提供嵌套级别NSXMLParser

Answer 3

对于短 XML 文件，一种比公认答案更容易解决的方法：

XML 示例：

<cotacoes>
    <bovespa>
            <cotacao>50058</cotacao>
            <variacao>-0.16</variacao>
    </bovespa>
    <dolar>
            <cotacao>3.4610</cotacao>
            <variacao>+0.29</variacao>
    </dolar>
    <euro>
            <cotacao>3.7673</cotacao>
            <variacao>-0.25</variacao>
    </euro>
    <atualizacao>04/08/15 - 18:14</atualizacao>
</cotacoes>

实现一个计数器：

@implementation className{
    int parserCounter;
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
    parserCounter++;

    NSLog(@"%d: %@",contadorParser,string);

    if (parserCounter == 3) doAnythingFor3;
    if (parserCounter == 5) doAnythingFor5;
    if (parserCounter == 9) doAnythingFor9;
    if (parserCounter == 11) doAnythingFor11;
    if (parserCounter == 15) doAnythingFor15;
    if (parserCounter == 17) doAnythingFor17;
    if (parserCounter == 20) doAnythingFor20;

}

我怎么知道女巫号码是女巫节点？通过查看日志。它会是这样的：

2015-08-04 23:36:08.070 Tesouro Direto[7252:1554402] 1:     
2015-08-04 23:36:08.070 Tesouro Direto[7252:1554402] 2:     
2015-08-04 23:36:08.071 Tesouro Direto[7252:1554402] 3:     50058
2015-08-04 23:36:08.105 Tesouro Direto[7252:1554402] 4:     
2015-08-04 23:36:08.105 Tesouro Direto[7252:1554402] 5:     -0.16
2015-08-04 23:36:08.131 Tesouro Direto[7252:1554402] 6:     
2015-08-04 23:36:08.132 Tesouro Direto[7252:1554402] 7:     
2015-08-04 23:36:08.132 Tesouro Direto[7252:1554402] 8:     
2015-08-04 23:36:08.132 Tesouro Direto[7252:1554402] 9:     3.4610
2015-08-04 23:36:08.156 Tesouro Direto[7252:1554402] 10:    
2015-08-04 23:36:08.156 Tesouro Direto[7252:1554402] 11:    +0.29   
2015-08-04 23:36:08.180 Tesouro Direto[7252:1554402] 12:    
2015-08-04 23:36:08.180 Tesouro Direto[7252:1554402] 13:    
2015-08-04 23:36:08.180 Tesouro Direto[7252:1554402] 14:    
2015-08-04 23:36:08.180 Tesouro Direto[7252:1554402] 15:    3.7673
2015-08-04 23:36:08.203 Tesouro Direto[7252:1554402] 16:    
2015-08-04 23:36:08.203 Tesouro Direto[7252:1554402] 17:    -0.25
2015-08-04 23:36:08.226 Tesouro Direto[7252:1554402] 18:    
2015-08-04 23:36:08.227 Tesouro Direto[7252:1554402] 19:    
2015-08-04 23:36:08.227 Tesouro Direto[7252:1554402] 20:    04/08/15   - 18:14
2015-08-04 23:36:08.227 Tesouro Direto[7252:1554402] 21: 

日志将显示每个节点的女巫编号。