就xml解析来讲，目前用过的最简洁，速度最快的当属tbxml，是基于C框架的所以直接拿在iPhone上用了。

先说下用法，把tbxml的4个文件拖入class，然后为工程添加libz.dylib框架即可。

废话就不说了，直接看代码，如下：

定义了两个方法（其中一个带着递归子方法），分别处理已知结构和未知结构的xml。

//调用

- (void)viewDidLoad {
tbXml = [TBXML tbxmlWithXMLFile:@"books.xml"];

TBXML *tbXml2 = [TBXML tbxmlWithXMLString:@"<root><elem1 attribute1=\"elem1-attribute1\"/><elem2 attribute2=\"attribute2\"/></root>"];
TBXML *tbXml3 = [[TBXML alloc] initWithURL:[NSURL URLWithString:@"http://www.ifanr.com/feed"]];

[self testTBXM:tbXml];
[self dealUnknow:tbXml3];

[super viewDidLoad];
}

1.解析已知结构的xml。先看下xml的基本结构：

<?xml version="1.0"?>
<authors>
<author name="J.K. Rowling">
<book title="Harry Potter and the Philosopher's Stone" price="119.99">
<description>
Harry potter thinks he is an ordinary boy - until he is rescued from a beetle-eyed giant of a man, enrolls at Hogwarts School of Witchcraft and Wizardry, learns to play quidditch and does battle in a deadly duel.
</description>
</book>
<book title="Harry Potter and the Chamber of Secrets" price="8.99">
<description>
When the Chamber of Secrets is opened again at the Hogwarts School for Witchcraft and Wizardry, second-year student Harry Potter finds himself in danger from a dark power that has once more been released on the school.
</description>
</book>
<book title="Harry Potter and the Prisoner of Azkaban" price="12.99">
<description>
Harry Potter, along with his friends, Ron and Hermione, is about to start his third year at Hogwarts School of Witchcraft and Wizardry. Harry can't wait to get back to school after the summer holidays. (Who wouldn't if they lived with the horrible Dursleys?) But when Harry gets to Hogwarts, the atmosphere is tense. There's an escaped mass murderer on the the loose, and the sinister prison guards of Azkaban have been called in to guard the school.
</description>
</book>
</author>
<author name="Douglas Adams">
<book title="The Hitchhiker's Guide to the Galaxy" price="15.49">
<description>
Join Douglas Adams's hapless hero Arthur Dent as he travels the galaxy with his intrepid pal Ford Prefect, getting into horrible messes and generally wreaking hilarious havoc.
</description>
</book>
<book title="The Restaurant at the End of the Universe " price="14.36">
<description>
Arthur and Ford, having survived the destruction of Earth by surreptitiously hitching a ride on a Vogon constructor ship, have been kicked off that ship by its commander. Now they find themselves aboard a stolen Improbability Drive ship commanded by Beeblebrox, ex-president of the Imperial Galactic Government and full-time thief.
</description>
</book>
</author>
</authors>

//解析代码

- (void)testTBXM:(TBXML *)tbx {  
TBXMLElement *root = tbx.rootXMLElement;
TBXMLElement *author = [TBXML childElementNamed:@"author" parentElement:root];
NSString *name = [TBXML valueOfAttributeNamed:@"name" forElement:author];
NSLog(@"author:%@", name);
TBXMLElement *book = [TBXML childElementNamed:@"book" parentElement:author];
TBXMLElement *descriptionElem = [TBXML childElementNamed:@"description" parentElement:book];
NSString * description = [TBXML textForElement:descriptionElem];
NSLog(@"author:%@", description); 
}

2.递归解析未知结构的xml。

//主调用方法

- (void)dealUnknow:(TBXML *)tbx {
if (tbx.rootXMLElement) {
TBXMLElement *element = tbx.rootXMLElement;  
[self recurrence:element];
}
else {
NSLog(@"Format Error!");
} 
}

//递归子方法

- (void)recurrence:(TBXMLElement *)element {
do {

NSLog(@"<%@>:{%@}",[TBXML elementName:element], [TBXML textForElement:element]);// Display the name of the element

//迭代处理所有属性
TBXMLAttribute * attribute = element->firstAttribute;
while (attribute) {
//显示
NSLog(@"<%@>->[%@ = %@]", [TBXML elementName:element], [TBXML attributeName:attribute], [TBXML attributeValue:attribute]);
//迭代
attribute = attribute->next;
}

//递归处理子树
if (element->firstChild) {
[self recurrence:element->firstChild];
}

//迭代处理兄弟树
} while ((element = element->nextSibling)); 
}

总之，tbxml解析xml飞速、简洁，可惜不能操作回写，仅陷于解析，做rss巨合适不过了！

如想进步了解，请参加下篇，tbxml常用api：

==============================================================================

tbxml常用api：
文件

tbxml“框架”中包含的文件：
TBXML.h - tbxml声明
TBXML.m - tbxml实现
NSDataAdditions.h - NSData类别等的声明
NSDataAdditions.m - NSData类别等的实现，包括base64，gzip，NSData类别等等

==============================================================================
结构体

TBXMLElement结构体，包含XML中对应element的信息. 包括元素标签名、元素text值、指向第一个属性对象的指针、父元素、首个子元素，以及下一个兄弟元素.可以用这个结构体创建一个链表（树）来表示一个完整的xml文件.
结构如下：
typedef struct _TBXMLElement {
char * name;
char * text;
TBXMLAttribute * firstAttribute;
struct _TBXMLElement * parentElement;
struct _TBXMLElement * firstChild;
struct _TBXMLElement * currentChild;
struct _TBXMLElement * nextSibling;
struct _TBXMLElement * previousSibling;
} TBXMLElement;

TBXMLAttribute结构体，包含了xml中的属性信息. 包括属性名、属性值和下一个兄弟属性对象的指针. 使用这个结构可以创建一个Element的属性链表.
typedef struct _TBXMLAttribute {
char * name;
char * value;
struct _TBXMLAttribute * next;
} TBXMLAttribute;

TBXMLElementBuffer结构体，是用来缓存TBXMLElement结构体对象的. 当被使用时, 将新建一个缓存区并连接到前一个上（链表）.这样可以有效的管理Element在内存的创建和回收.
typedef struct _TBXMLElementBuffer {
TBXMLElement * elements;
struct _TBXMLElementBuffer * next;
struct _TBXMLElementBuffer * previous;
} TBXMLElementBuffer;

TBXMLAttributeBuffer结构体，是用来缓存TBXMLAttribute对象的. 当被使用时, 将新建一个缓存区并连接到前一个上（链表）. 这样可以有效的管理Attribute在内存的创建和回收.
typedef struct _TBXMLAttributeBuffer {
TBXMLAttribute * attributes;
struct _TBXMLAttributeBuffer * next;
struct _TBXMLAttributeBuffer * previous;
} TBXMLAttributeBuffer;

==============================================================================
方法

1.实例化
+ (id)tbxmlWithXMLFile:(NSString*)aXMLFile;
用xml文件名(包括扩展名)实例化一个tbxml对象
例如：TBXML * tbxml = [[TBXML alloc] initWithXMLFile:@"books.xml"];

- (id)initWithXMLFile:(NSString*)aXMLFile fileExtension:(NSString*)aFileExtension
用xml文件名和扩展名实例化一个tbxml对象
例如：TBXML * tbxml = [[TBXML alloc] initWithXMLFile:@"books" fileExtension:@"xml"];

- (id)initWithXMLString:(NSString*)aXMLString
用一段xml内容代码来实例化一个tbxml对象
例如：tbxml = [[TBXML alloc] initWithXMLString:@"<root><elem1 attribute1=\"elem1 attribute1\"/><elem2 attribute2=\"elem2 attribute2\"/></root>;"];

- (id)initWithXMLData:(NSData*)aData
用一个封装了xml内容的NSData对象来实例化tbxml对象
例如：TBXML * tbxml = [[TBXML alloc] initWithXMLData:myXMLData];

- (id)initWithURL:(NSURL*)aURL
用一个URL来实例化一个tbxml
例如：tbxml = [[TBXML alloc] initWithURL:[NSURL URLWithString:@"http://www.ifanr.com/feed"]];

2.成员方法
+ (TBXMLElement*) childElementNamed:(NSString*)aName parentElement:(TBXMLElement*)aParentXMLElement
获得aParentXMLElement元素的首个名字为aName的元素
例如：TBXMLElement * author = [TBXML childElementNamed:@"author" parentElement:rootXMLElement];

+ (TBXMLElement*) nextSiblingNamed:(NSString*)aName searchFromElement:(TBXMLElement*)aXMLElement
返回下一个名为aName的兄弟元素
例如：TBXMLElement * author = [TBXML nextSiblingNamed:@"author" searchFromElement:author];

+ (NSString*) valueOfAttributeNamed:(NSString *)aName forElement:(TBXMLElement*)aXMLElement
返回aXMLElement元素中，名为aName的属性的属性值。
例如：NSString * authorName = [TBXML valueOfAttributeNamed:@"name" forElement:authorElement];

+ (NSString*) textForElement:(TBXMLElement*)aXMLElement
返回元素aXMLElement的text值
例如：NSString * bookDescription = [TBXML textForElement:bookElement];

+ (NSString*) elementName:(TBXMLElement*)aXMLElement;
返回元素aXMLElement的标签名
例如：NSString * elementName = [TBXML elementName:element];

+ (NSString*) attributeName:(TBXMLAttribute*)aXMLAttribute;
返回属性aXMLAttribute的属性名
例如：NSString * attributeName = [TBXML attributeName:attribute];

+ (NSString*) attributeValue:(TBXMLAttribute*)aXMLAttribute;
返回属性aXMLAttribute的属性值
例如：NSString * attributeValue = [TBXML attributeValue:attribute];

常用的基本就这些，通过合理的迭代，递归等组合调用，基本可以解决所有的解析问题。