iOS开发之将XML转换成树

    开发中由于服务端与客户端是两种不同的平台，而且服务端又是老系统，不具备很好的面向对象的性质，所以导致客户端与服务端只好通过一些制定好的xml进行通信。

    在iOS中对XML的解析不像donet这么方便。当然也存在一些很方便的开源类库去调用，但是有些开源的类库显得很笨重。这篇文章我将封装一个简单操作XML转换成树的类方便自己操作：首先通过NSXMLParser从服务端获取XML，它可以一边下载，一边解析，然后转换成树形结构，最后我们可以从树形结构中去取值。

使用NSXMLParser解析XML：

NSXMLParser中主要有三个委托方法来解析XML：

1、parser：didStartElement： 当解析器对象遇到xml的开始标记时，调用这个方法。

2、parser：didEndElement：当解析器对象遇到xml的结束标记时，调用这个方法。

3、parser：foundCharacters：当解析器找到开始标记和结束标记之间的字符时，调用这个方法。

了解了NSXMLParser机制。然后我们来封装解析XML的类：XMLParser。

#import <CoreFoundation/CoreFoundation.h>#import "TreeNode.h"@interface XMLParser : NSObject{NSMutableArray*stack;}+ (XMLParser *) sharedInstance;- (TreeNode *) parseXMLFromURL: (NSURL *) url;- (TreeNode *) parseXMLFromData: (NSData*) data;@end

shareInstance使用一个单例。

调用parseXMLFromURL方法，需要一个NSURL的参数，返回我们需要的树节点。

调用parseXMLFromData方法，需要一个NSData的参数，返回我们需要的树节点。
在此之前，先定义TreeNode类：

#import <CoreFoundation/CoreFoundation.h>@interface TreeNode : NSObject{TreeNode*parent;NSMutableArray*children;NSString*key;NSString*leafvalue;}@property (nonatomic, retain) TreeNode*parent;@property (nonatomic, retain) NSMutableArray*children;@property (nonatomic, retain) NSString*key;@property (nonatomic, retain) NSString*leafvalue;@property (nonatomic, readonly) BOOLisLeaf;@property (nonatomic, readonly) BOOLhasLeafValue;@property (nonatomic, readonly) NSArray*keys;@property (nonatomic, readonly) NSArray*allKeys;@property (nonatomic, readonly) NSArray*uniqKeys;@property (nonatomic, readonly) NSArray*uniqAllKeys;@property (nonatomic, readonly) NSArray*leaves;@property (nonatomic, readonly) NSArray*allLeaves;@property (nonatomic, readonly) NSString*dump;+ (TreeNode *) treeNode;- (NSString *) dump;- (void) teardown;// Leaf Utils- (BOOL) isLeaf;- (BOOL) hasLeafValue;- (NSArray *) leaves;- (NSArray *) allLeaves;// Key Utils- (NSArray *) keys; - (NSArray *) allKeys; - (NSArray *) uniqKeys;- (NSArray *) uniqAllKeys;// Search Utils- (TreeNode *) objectForKey: (NSString *) aKey;- (NSString *) leafForKey: (NSString *) aKey;- (NSMutableArray *) objectsForKey: (NSString *) aKey;- (NSMutableArray *) leavesForKey: (NSString *) aKey;- (TreeNode *) objectForKeys: (NSArray *) keys;- (NSString *) leafForKeys: (NSArray *) keys;// Convert Utils- (NSMutableDictionary *) dictionaryForChildren;@end

TreeNode 实现：

#import "TreeNode.h"// String stripper utility macro#define STRIP(X)[X stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]@implementation TreeNode@synthesize parent;@synthesize children;@synthesize key;@synthesize leafvalue;#pragma mark Create and Initialize TreeNodes- (TreeNode *) init{if (self = [super init]) {self.key = nil;self.leafvalue = nil;self.parent = nil;self.children = nil;}return self;}+ (TreeNode *) treeNode{return [[[self alloc] init] autorelease];}#pragma mark TreeNode type routines- (BOOL) isLeaf{return (self.children.count == 0);}- (BOOL) hasLeafValue{return (self.leafvalue != nil);}#pragma mark TreeNode data recovery routines// Return an array of child keys. No recursion- (NSArray *) keys{NSMutableArray *results = [NSMutableArray array];for (TreeNode *node in self.children) [results addObject:node.key];return results;}// Return an array of child keys with depth-first recursion.- (NSArray *) allKeys{NSMutableArray *results = [NSMutableArray array];for (TreeNode *node in self.children) {[results addObject:node.key];[results addObjectsFromArray:node.allKeys];}return results;}- (NSArray *) uniqArray: (NSArray *) anArray{NSMutableArray *array = [NSMutableArray array];for (id object in [anArray sortedArrayUsingSelector:@selector(caseInsensitiveCompare:)])if (![[array lastObject] isEqualToString:object]) [array addObject:object];return array;}// Return a sorted, uniq array of child keys. No recursion- (NSArray *) uniqKeys{return [self uniqArray:[self keys]];}// Return a sorted, uniq array of child keys. With depth-first recursion- (NSArray *) uniqAllKeys{return [self uniqArray:[self allKeys]];}// Return an array of child leaves. No recursion- (NSArray *) leaves{NSMutableArray *results = [NSMutableArray array];for (TreeNode *node in self.children) if (node.leafvalue) [results addObject:node.leafvalue];return results;}// Return an array of child leaves with depth-first recursion.- (NSArray *) allLeaves{NSMutableArray *results = [NSMutableArray array];for (TreeNode *node in self.children) {if (node.leafvalue) [results addObject:node.leafvalue];[results addObjectsFromArray:node.allLeaves];}return results;}#pragma mark TreeNode search and retrieve routines// Return the first child that matches the key, searching recursively breadth first- (TreeNode *) objectForKey: (NSString *) aKey{TreeNode *result = nil;for (TreeNode *node in self.children) if ([node.key isEqualToString: aKey]){result = node;break;}if (result) return result;for (TreeNode *node in self.children){result = [node objectForKey:aKey];if (result) break;}return result;}// Return the first leaf whose key is a match, searching recursively breadth first- (NSString *) leafForKey: (NSString *) aKey{TreeNode *node = [self objectForKey:aKey];return node.leafvalue;}// Return all children that match the key, including recursive depth first search.- (NSMutableArray *) objectsForKey: (NSString *) aKey{NSMutableArray *result = [NSMutableArray array];for (TreeNode *node in self.children) {if ([node.key isEqualToString: aKey]) [result addObject:node];[result addObjectsFromArray:[node objectsForKey:aKey]];}return result;}// Return all leaves that match the key, including recursive depth first search.- (NSMutableArray *) leavesForKey: (NSString *) aKey{NSMutableArray *result = [NSMutableArray array];for (TreeNode *node in [self objectsForKey:aKey]) if (node.leafvalue)[result addObject:node.leafvalue];return result;}// Follow a key path that matches each first found branch, returning object- (TreeNode *) objectForKeys: (NSArray *) keys{if ([keys count] == 0) return self;NSMutableArray *nextArray = [NSMutableArray arrayWithArray:keys];[nextArray removeObjectAtIndex:0];for (TreeNode *node in self.children){if ([node.key isEqualToString:[keys objectAtIndex:0]])return [node objectForKeys:nextArray];}return nil;}// Follow a key path that matches each first found branch, returning leaf- (NSString *) leafForKeys: (NSArray *) keys{TreeNode *node = [self objectForKeys:keys];return node.leafvalue;}#pragma mark output utilities// Print out the tree- (void) dumpAtIndent: (int) indent into:(NSMutableString *) outstring{for (int i = 0; i < indent; i++) [outstring appendString:@"--"];[outstring appendFormat:@"[%2d] Key: %@ ", indent, key];if (self.leafvalue) [outstring appendFormat:@"(%@)", STRIP(self.leafvalue)];[outstring appendString:@"\n"];for (TreeNode *node in self.children) [node dumpAtIndent:indent + 1 into: outstring];}- (NSString *) dump{NSMutableString *outstring = [[NSMutableString alloc] init];[self dumpAtIndent:0 into:outstring];return [outstring autorelease];}#pragma mark conversion utilities// When you're sure you're the parent of all leaves, transform to a dictionary- (NSMutableDictionary *) dictionaryForChildren{NSMutableDictionary *results = [NSMutableDictionary dictionary];for (TreeNode *node in self.children)if (node.hasLeafValue) [results setObject:node.leafvalue forKey:node.key];return results;}#pragma mark invocation forwarding// Invocation Forwarding lets node act like array- (id)forwardingTargetForSelector:(SEL)sel { if ([self.children respondsToSelector:sel]) return self.children; return nil;}// Extend selector compliance- (BOOL)respondsToSelector:(SEL)aSelector{if ( [super respondsToSelector:aSelector] )return YES;if ([self.children respondsToSelector:aSelector]) return YES;return NO;}// Allow posing as NSArray class for children- (BOOL)isKindOfClass:(Class)aClass{if (aClass == [TreeNode class]) return YES;if ([super isKindOfClass:aClass]) return YES;if ([self.children isKindOfClass:aClass]) return YES;return NO;}#pragma mark cleanup- (void) teardown{for (TreeNode *node in [[self.children copy] autorelease]) [node teardown];[self.parent.children removeObject:self];self.parent = nil;}- (void) dealloc{self.parent = nil;self.children = nil;self.key = nil;self.leafvalue = nil;[super dealloc];}@end

从上面的代码可以看出，定义了很多方便的方法来获取数据。

1、teardown：清除所有节点

2、isLeaf：判断是否是叶子节点

3、hasLeafValue：判断节点是否有值

4、- (NSArray *) leaves：返回节点的所有一级子节点值

5、- (NSArray *) allLeaves：返回节点的所有子节点的值

6、keys; 返回节点所有一级子节点名称。
7、 allKeys; 返回节点所有子节点名称。
8、 uniqKeys;返回节点一级子节点名称，不重复。
9、uniqAllKeys;返回节点子节点名称，不重复。

10、- (TreeNode *) objectForKey：根据节点名称查询节点

11、- (NSString *) leafForKey: (NSString *) aKey：根据节点名称查询出节点的值

12、- (NSMutableArray *) objectsForKey: (NSString *) aKey;根据节点名称查询出所以满足条件的节点

13、- (NSMutableArray *) leavesForKey: (NSString *) aKey;根据节点名称查询出所以满足条件的节点的值

  14、- (TreeNode *) objectForKeys: (NSArray *) keys;：根据节点名称路径查询出第一个满足条件的节点。

   15、- (NSString *) leafForKeys: (NSArray *) keys 根据节点名称路径查询出第一个满足条件的节点的值。

16、- (NSMutableDictionary *) dictionaryForChildren：将树转换成dictionary
 树定义好了，下面实现XMLParser类：

#import "XMLParser.h"@implementation XMLParserstatic XMLParser *sharedInstance = nil;// Use just one parser instance at any time+(XMLParser *) sharedInstance {    if(!sharedInstance) {sharedInstance = [[self alloc] init];    }    return sharedInstance;}// Parser returns the tree root. You may have to go down one node to the real results- (TreeNode *) parse: (NSXMLParser *) parser{stack = [NSMutableArray array];TreeNode *root = [TreeNode treeNode];root.parent = nil;root.leafvalue = nil;root.children = [NSMutableArray array];[stack addObject:root];[parser setDelegate:self];[parser parse];    [parser release];    // pop down to real rootTreeNode *realroot = [[root children] lastObject];root.children = nil;root.parent = nil;root.leafvalue = nil;root.key = nil;realroot.parent = nil;return realroot;}- (TreeNode *)parseXMLFromURL: (NSURL *) url{TreeNode *results;NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];    NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:url];results = [self parse:parser];[pool drain];return results;}- (TreeNode *)parseXMLFromData: (NSData *) data{TreeNode *results;NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];    NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data];results = [self parse:parser];[pool drain];return results;}// Descend to a new element- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{    if (qName) elementName = qName;TreeNode *leaf = [TreeNode treeNode];leaf.parent = [stack lastObject];[(NSMutableArray *)[[stack lastObject] children] addObject:leaf];leaf.key = [NSString stringWithString:elementName];leaf.leafvalue = nil;leaf.children = [NSMutableArray array];[stack addObject:leaf];}// Pop after finishing element- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{[stack removeLastObject];}// Reached a leaf- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{if (![[stack lastObject] leafvalue]){[[stack lastObject] setLeafvalue:[NSString stringWithString:string]];return;}[[stack lastObject] setLeafvalue:[NSString stringWithFormat:@"%@%@", [[stack lastObject] leafvalue], string]];}@end

使用这两个类：

　下面看下我们如何使用这个类：

在iis中放下面这个xml：

<?xml version="1.0" encoding="UTF-8"?><Login><LoginResult>True</LoginResult><LoginInfo>恭喜你登录成功</LoginInfo><LastLogin>2011-05-09 12:20</LastLogin><Right><A>1</A><B>1</B><C>0</C></Right></Login>

使用下面代码获取web服务器上的xml，并将xml转换成树：

  NSURL * url = [[NSURL alloc] initWithString:@"http://10.5.23.117:4444/Login.xml"];    TreeNode *node = [parser parseXMLFromURL:url];

获取xml中的登录结果：

    NSString * result =  [node leafForKey:@"LoginResult"];

类似xpath去取值：

NSArray *path =[[NSArray alloc]initWithObjects:@"Right",@"A",nil];NSString * result =  [node leafForKeys:path];

将xml显示在tableview上：

@implementation TreeBrowserController@synthesize root;// Each instance of this controller has a separate root, as// descending through the tree produces new roots.- (id) initWithRoot:(TreeNode *) newRoot{    if (self = [super init])    {        self.root = newRoot;                NSString *s =[newRoot dump];        if (newRoot.key) self.title = newRoot.key;    }    return self;}- (id)initWithStyle:(UITableViewStyle)style{    self = [super initWithStyle:style];    if (self) {        // Custom initialization    }    return self;}// The number of rows equals the number of children for a node- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{    return [self.root.children count];}// Color code the cells that can be navigated through- (UITableViewCell *)tableView:(UITableView *)tableView         cellForRowAtIndexPath:(NSIndexPath *)indexPath{    UITableViewCell *cell = [tableView                             dequeueReusableCellWithIdentifier:@"generic"];    if (!cell) cell = [[[UITableViewCell alloc]                        initWithFrame:CGRectZero reuseIdentifier:@"generic"]                       autorelease];    TreeNode *child = [[self.root children]                       objectAtIndex:[indexPath row]];    // Set text    if (child.hasLeafValue)        cell.textLabel.text = [NSString stringWithFormat:@"%@:%@",                               child.key, child.leafvalue];    else        cell.textLabel.text = child.key;    // Set color    if (child.isLeaf)        cell.textLabel.textColor = [UIColor darkGrayColor];    else        cell.textLabel.textColor = [UIColor blackColor];    return cell;}// On selection, either push a new controller or show the leaf value- (void)tableView:(UITableView *)tableViewdidSelectRowAtIndexPath:(NSIndexPath *)indexPath{    TreeNode *child =    [self.root.children objectAtIndex:[indexPath row]];    if (child.isLeaf)    {                return;    }    TreeBrowserController *tbc = [[[TreeBrowserController alloc]                                   initWithRoot:child] autorelease];    [self.navigationController pushViewController:tbc animated:YES];}// These controllers are ephemeral and need dealloc- (void) dealloc{    self.root = nil;    [super dealloc];}@end

效果：

总结：这篇文章通过封装两个类库，可以从web上很高效获取xml，将xml转换成树形结构，可以很方便的对树进行操作。