[iPhone初级]IOS自带NSXMLParser对xml文件的解析

很多人都知道利用第三方来解析xml文件，这里我们介绍一下如何利用IOS自带的NSXMLParser来进行xml解析

我们要解析的文件如下：

<?xml version="1.0" ?><theresponse> <status>OK</status> <pricing currency="USD" symbol="$">   <price class="items">24.00</price>   <price class="shipping">6.00</price>   <price class="tax">1.57</price> </pricing></theresponse>

利用NSXMLParser解析，我们需要在需要解析的类中加入NSXMLParserDelegate，这其中有三个比较重要的方法，一个是

-(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict

这个方法主要是找到开始元素，例如我们要解析<status>，这里elementName就可以定位到status这里

-(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string

这个方法解析的是中间的值<status>OK</status>这里的OK就是这里的值

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

最后一个方法就是定位到</status>这个节点，在这个节点我们就可以把我们解析出来的数据存入NSDictionary或是NSArray中去了

我们还是来看一下代码吧

ItemParser.h

#import <Foundation/Foundation.h>@interface ItemParser : NSXMLParser <NSXMLParserDelegate>@property (readonly) NSDictionary *itemData;@end

ItemParser.m

#import "ItemParser.h"@implementation ItemParser {    NSMutableDictionary *_itemData;    NSMutableDictionary *_attributesByElement;    NSMutableString *_elementString;}-(NSDictionary *)itemData{    return [_itemData copy];}-(void)parserDidStartDocument:(NSXMLParser *)parser{    _itemData = [[NSMutableDictionary alloc] init];    _attributesByElement = [[NSMutableDictionary alloc] init];    _elementString = [[NSMutableString alloc] init];}-(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{    // Save the attributes for later.    if (attributeDict) [_attributesByElement setObject:attributeDict forKey:elementName];    // Make sure the elementString is blank and ready to find characters    [_elementString setString:@""];}-(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{    // Save foundCharacters for later    [_elementString appendString:string];}-(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{    if ([elementName isEqualToString:@"status"]){        // Element status only contains a string i.e. "OK"        // Simply set a copy of the element value string in the itemData dictionary        [_itemData setObject:[_elementString copy] forKey:elementName];    } else if ([elementName isEqualToString:@"pricing"]) {        // Pricing has an interesting attributes dictionary         // So copy the entries to the item data        NSDictionary *attributes = [_attributesByElement objectForKey:@"pricing"];        [_itemData addEntriesFromDictionary:attributes];    } else if ([elementName isEqualToString:@"price"]) {        // The element price occurs multiple times.        // The meaningful designation occurs in the "class" attribute.        NSString *class = [[_attributesByElement objectForKey:elementName] objectForKey:@"class"];        if (class) [_itemData setObject:[_elementString copy] forKey:class];    }    [_attributesByElement removeObjectForKey:elementName];    [_elementString setString:@""];}-(void)parserDidEndDocument:(NSXMLParser *)parser{    _attributesByElement = nil;    _elementString = nil;}-(void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError{    NSLog(@"%@ with error %@",NSStringFromSelector(_cmd),parseError.localizedDescription);}-(BOOL)parse{    self.delegate = self;    return [super parse];}@end

这里解析后的结果：

{    currency = USD;    items = "24.00";    shipping = "6.00";    status = OK;    symbol = "$";    tax = "1.57";}

好了，解析完毕，这里的还有一个重点就是copy，希望各位同学能多注意每个变量的记数。我自己也是JAVA做习惯了，过早释放，老是取不到值。呵呵，谨记。