NSFileManager createFileAtPath在iPad上失败但在Simulator上运行

Question

I am trying to write a simple log file for each execution of my app. The logfile name is based on the current time and is stored in the app directory. The code below is what I am trying which works on the simulator but when I execute on an iPad it fails with 'Operation not permitted' (EPERM in errno.h).

-(BOOL)CreateLogFile
{
    mLogFilePath = [self GetLogFileNameForTimeNow];
    BOOL Success = [[NSFileManager defaultManager] createFileAtPath:mLogFilePath contents:nil attributes:nil];

    /*BOOL Success = [[NSFileManager defaultManager] createFileAtPath:mLogFilePath contents:nil attributes:[NSDictionary dictionaryWithObject:NSFileProtectionComplete
                                                                                                                                     forKey:NSFileProtectionKey]];*/

    if ( Success )
    {
        NSLog( @"Successfully created file: %@", mLogFilePath );
        mLogFileHandle = [NSFileHandle fileHandleForWritingAtPath:mLogFilePath];
        [self WriteInstanceInformationToLog];
    }
    else
    {
        NSLog( @"Failed to create file: %@ %s", mLogFilePath, strerror(errno) );
    }

    return Success;
}

I tried the commented out code too but that also fails. I am new to iOS programming so might be missing something basic. Anyway the output form the above shows the following on iPad:

2013-05-10 14:54:51.794 RichTest1[128:907] Failed to create file:
/var/mobile/Applications/XXXX/RichTest1.app/20130510145451.log Operation not permitted

but on the simulator it works:

2013-05-10 15:07:14.696 RichTest1[1604:c07] Successfully created file:
Users/abruce/Library/Application Support/iPhone Simulator/6.1/Applications/XXXX/RichTest1.app/20130510150714.log

Where am I going wrong?

--edit Here is the code for the GetLogFileNameForTimeNow

-(NSString*)GetLogFileNameForTimeNow
{
    NSString* FileName = [NSString stringWithFormat:@"%@.log", [self GetTimeAsString] ];
    NSString* AppFolderPath = [[NSBundle mainBundle] resourcePath];
    return [NSString stringWithFormat:@"%@/%@", AppFolderPath, FileName];
}

-(NSString*)GetTimeAsString
{
    return [mDateFormatter stringFromDate:[NSDate date]];
}

and the date formatter is setup as follows in the constructor of my class:

mDateFormatter = [[NSDateFormatter alloc] init];
NSString* DateFormat = @"yyyyMMddHHmmss";
[mDateFormatter setDateFormat:DateFormat];

Answer 1

You are trying to create a file inside app bundle, which is read-only on the device. Put your files into Documents or Library directories of the application.

Answer 2

You are trying to create a file in a place where you don't have permissions to create files,

Create your files inside documents folder,

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0]; // Get documents folder
NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"20130510150714.log"];
BOOL Success = [[NSFileManager defaultManager] createFileAtPath:filePath contents:nil attributes:nil];

Answer 3

I have fixed the problem by changing my GetLogFileNameForTimeNow function as follows:

-(NSString*)GetLogFileNameForTimeNow
{
    NSString* FileName = [NSString stringWithFormat:@"%@.log", [self GetTimeAsString] ];

    NSArray* Paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString* DocumentsDirectory = [Paths objectAtIndex:0]; // Get documents folder
    return [NSString stringWithFormat:@"%@/%@", DocumentsDirectory, FileName];
}