不调用委托方法并且解析属性始终为 FALSE

Question

我正在尝试解析应用程序委托 didFinishLaunchingWithOptions: 方法上的 xml 提要：

//Parse XML Data
    NSXMLParser *xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://xxxxxxxxxxxxxxxxx/xml"]];//url is just fine :)
    [xmlParser setDelegate:self];
    BOOL parseState = [xmlParser parse];
    if (parseState) {
        NSLog(@"parse succeeded");
    }else{
        NSLog(@"parse failed");//Always parse failed, parse is always "NO"
    }

委托协议方法（没有被调用）：

#pragma mark - NSXMLParserDelegate

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict{
    NSLog(@"parser:didStartElement:namespaceURI:qualifiedName:attributes:");

}

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

    NSLog(@"parser:foundCharacters:");
}
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{
    NSLog(@"parser:didEndElement:namespaceURI:qualifiedName:");


}

当然，AppDelegate.h 符合NSXMLParserDelegate 协议：

@interface AppDelegate : UIResponder <UIApplicationDelegate,NSXMLParserDelegate>

我错过了什么？为什么不调用协议方法以及为什么[xmlParser parse] 总是返回NO？谢谢。

Answer 1

可能是 ARC 错误，尝试将 xmlparser 设置为强属性，以便在完成文件解析之前不会释放它。

您可能希望在使用 nsurlconnection 解析之前从网络下载 xml

Answer 2

您在 AppDelegate 中塞满 XML 解析器是有原因的吗？无一例外，我发现总是实例化一个解析器类来处理解析任务是有益的。比如……

myParser.h

@class parseClass;

@interface myXMLParser : NSObject <NSXMLParserDelegate> {

}

- (myXMLParser *) initmyXMLParser;

myParser.m

//I do my instantiating like this so it can only be done once
//If you need to instantiate the class more than once do NOT use dispatch_once!
- (myXMLParser *)initmyXMLParser
{
    static myXMLParser *newInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        newInstance = [[myXMLParser alloc]init];
    });
    return newInstance;
}
//include other delegate methods as well

AppDelegate.m

#import "myParser.h"

NSXMLParser *xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:[NSURL      URLWithString:@"http://xxxxxxxxxxxxxxxxx/xml"]];//url is just fine :)
myXMLParser *theParser = [[myXMLParser alloc]initmyUpdateXMLParser];
[xmlParser setDelegate:theParser];
BOOL parseState = [xmlParser parse];
if (parseState) {
    NSLog(@"parse succeeded");
}else{
    NSLog(@"parse failed");//Always parse failed, parse is always "NO"
}