在IOS上写大文件

Question

我在iPhone上写大文件时遇到问题。我的代码在模拟器上工作得很好，但在iPhone上没有任何反应，文件大小为0！ 我认为这取决于文档目录，但我不确定。

for (int i = 1; i <= [_anzahl.text intValue]; i++)
{
NSString *book = [@"book" stringByAppendingFormat:@"%i", i];
NSLog(@"%@", book);
NSString *dummyFilePath = [[NSBundle mainBundle] resourcePath];
NSString  *filePath = [dummyFilePath stringByAppendingPathComponent:[NSString  stringWithFormat:@"%@", book]];
NSFileHandle *file = [NSFileHandle fileHandleForWritingAtPath:filePath];
if (file == nil) {
    [[NSFileManager defaultManager] createFileAtPath:filePath contents:nil attributes:nil];
    file = [NSFileHandle fileHandleForWritingAtPath:filePath];
}
int zahl = [_sizeMB.text intValue];
[file seekToFileOffset:zahl * 1024 * 1024];
const unsigned char bytes[] = {1};
[file writeData:[NSData dataWithBytes:bytes length:sizeof(bytes)]];
    //Dateigröße ermitteln
    int fileSize = [file seekToEndOfFile];
    NSLog(@"book Size =%i" , fileSize) ;
}

所有新手的更新：

NSString *dummyFilePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES) objectAtIndex:0];