Question

是iOS编程的新手，我正在尝试构建一个小应用程序，它与另一台服务器通信以检索XML并解析它。现在我已经在同一个View Controller中实现了NSXML解析器委托，我想编写一个单独的类来接受XML路径，解析它并返回有意义的数据。

所以在视图控制器中我有这个

// On Foo Button Click
XMLParser* xmlParser = [[XMLParser alloc] init];
// XMLParser would be my class file which has a method to parse XML
xmlParser.readXMLFromPath(pathToXML);

在XMLParser类文件中：

- (NSMutableDictionary*) readXMLFromPath: (NSString* pathToXML) {
  NSMutableDictionary* resultSet;
  // Alloc NSXMLParser and implement its delegate methods
  // resultSet would now hold the needed Data
}

那么我现在应该如何将resultSet返回给viewController？

Answer 1

让XML解析器的客户端在块中传递以在结果准备好时执行，而不是立即返回它们。您也可以让客户端在单独的错误块中传递，以及在出现问题时。

- (void)readXMLFromPathWithSuccessBlock:(void (^)(NSMutableDictionary *results))successBlock;
 {
  // Alloc NSXMLParser and implement its delegate methods
  // Save successBlock in a property
}

- (void)parserDidEndDocument:(NSXMLParser *)parser {
  // Call success block and pass results to the client
}

Answer 2

这是我用来在NSOperationQueue上进行所有xml解析的NSOperation的子类：

#import <Foundation/Foundation.h>
#import "GDBaseParser.h"

@class ParseXMLOperation;

@protocol ParseXMLCallbackDelegate <NSObject>

-(void)parseOperationComplete:(ParseXMLOperation *)completedOperation;

@end

@interface ParseXMLOperation : NSOperation 
{
    GDBaseParser *xmlParserDelegate;
    NSData *dataToParse;
    id <ParseXMLCallbackDelegate> callbackDelegate;
}

@property(nonatomic,strong)GDBaseParser *xmlParserDelegate;
@property(nonatomic,strong)NSData *dataToParse;
@property(nonatomic,strong)id <ParseXMLCallbackDelegate> callbackDelegate;
-(id)initWithParser:(GDBaseParser *)inParserDelegate;
@end


@implementation ParseXMLOperation

@synthesize xmlParserDelegate, dataToParse, callbackDelegate;

-(id)initWithParser:(GDBaseParser *)inParserDelegate
{
    self = [super init];
    if( self != nil )
    {
        self.xmlParserDelegate = inParserDelegate;
    }
    return self;
}

-(void)main
{
    @autoreleasepool
    {

        NSXMLParser *parser  = [[NSXMLParser alloc] initWithData:dataToParse];
        xmlParserDelegate.currentContext = localContext;
        [parser setDelegate:xmlParserDelegate];
        [parser setShouldProcessNamespaces:NO];
        [parser setShouldReportNamespacePrefixes:NO];
        [parser setShouldResolveExternalEntities:NO];
        [parser parse];
        [self performSelectorOnMainThread:@selector(sendOperationComplete) withObject:nil waitUntilDone:NO];

    }


}


-(void)sendOperationComplete
{
    if( callbackDelegate != nil && [callbackDelegate     respondsToSelector:@selector(parseOperationComplete:)] )
    {
        [callbackDelegate parseOperationComplete:self];
    }
}

然后，我可以设置操作并通过执行以下操作将其添加到队列中：

         MyParser *parserDelegate = [[MyParser alloc] init];
ParseXMLOperation *parseOperation = [[ParseXMLOperation alloc]   initWithParser:parserDelegate];
         parseOperation.dataToParse = parseData;
         parseOperation.completionBlock = ^{
             localOperation.messageHeaderDict = parserDelegate.messageHeaders;
             dispatch_async(dispatch_get_main_queue(), ^{
                 //notify your UI that you are done with your parsing
             });

         };
         [self.xmlParsingQueue addOperation:parseOperation];

异步调用后返回Mutable Dictionary

2 个答案: