奇怪的错误 - 可以访问 NSURLConnection & NSMutableData 的描述方法，但不是它们的 ivar

Question

所以我上课了：
DataFetcher.h

#import <Foundation/Foundation.h>

@interface DataFetcher : NSObject 
{
    NSURLConnection *networkConnection;
    NSMutableData *recievedData;
    BOOL isFetchingFinished;
}

@property (nonatomic, retain) NSMutableData *recievedData;
@property (nonatomic, retain) NSURLConnection *networkConnection;

- (void)fetchDataWithRequest:(NSMutableURLRequest *)request;

DataFetcher.m：

#import "DataFetcher.h"

@implementation DataFetcher

@synthesize recievedData;
@synthesize networkConnection;

- (id)init
{
    self = [super init];
    if (self) {
        NSMutableData *data = [[NSMutableData alloc] initWithLength:0];
        self.recievedData = data;
        [data release];
    }

    return self;
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"Connection Error:%@\n Failure Reason:%@", [error localizedDescription], [error localizedFailureReason]);
    [networkConnection release];
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [self.recievedData appendData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    [networkConnection release];
    NSLog(@"%@", self.recievedData.length);
    [self processData];
}

- (void)fetchDataWithRequest:(NSMutableURLRequest *)request
{
    NSURLConnection *aConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO];
    self.networkConnection = aConnection;
    [aConnection release];
    [self.networkConnection start];
    if( !self.networkConnection )
    {
        NSLog(@"Connection failed! recieved nil at alloc point");
    }
}

- (void)dealloc
{
    [super dealloc];
    [recievedData release];
}

@end

通常它会因 EXC_BAD_ACCESS 而崩溃（ NSZombie 不会检测到任何东西）。 我注意到，如果您将 connectionDidFinishLoading 的 self.recievedData.length 切换为 self.recievedData，它不会崩溃，并且看起来有一些里面有数据。我对 self.networkConnection 得到的结果是一样的 - 如果我只打印 self.networkConnection ，那没问题，但是如果我打印 self.networkConnection.retainCount code> （例如，任何 ivar 都可以工作）它会因相同的信号而崩溃。

我似乎无法掌握问题出在哪里，而且我已经安静地寻找它一段时间了，我将不胜感激一些帮助:)
Tnx！

哦，我用以下代码调用它：
<代码> DataFetcher *fetcher = [[DataFetcher alloc] init];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"http://www.google.com"]]; [获取器 fetchDataWithRequest:请求]; [获取器释放]； [请求释放]；

Answer 1

NSLog(@"%@", self.recievedData.length);

这里 %@ 格式说明符意味着您将记录 Objective-C 对象，而您实际上将普通整数传递给它 - 这会使您的应用程序崩溃。将您的日志更改为

 NSLog(@"%d", self.recievedData.length);