String to string EXC_BAD_ACCESS why? - cocoa

Question

whats I missed?
NSString * configPath = nil;
-(IBAction)setPlistPathAndWriteData:(id)sender{
NSOpenPanel *panel = [NSOpenPanel openPanel];
[panel setDirectory:#"/Volumes/"];
[panel setNameFieldStringValue:#"config.plist"];
[panel setRequiredFileType:#"plist"];
NSInteger ret = [panel runModal];
if ( ret == NSFileHandlingPanelOKButton ) {
NSString *filePath= [[panel URL] path];
// with this works fine
//configPath = [NSString stringWithFormat:#"/Volumes/Macintosh HD/config.plist"];
// with this EXC BAD ACCESS
configPath = [NSString stringWithFormat:#"%#", filePath];
[self writeData];
}
}
-(void)writeData {
SET_TEMP_PLIST
NSTask *task = [[NSTask alloc] init];
NSPipe *pipe = [[NSPipe alloc] init];
NSFileHandle *writeHandle = [pipe fileHandleForWriting];
NSData *configData = [NSPropertyListSerialization dataFromPropertyList:tmpPlist format:
NSPropertyListXMLFormat_v1_0 errorDescription:nil];
[task setLaunchPath:#"/usr/libexec/authopen"];
////////////////////////////////////////////////////////EXC_BAD_ACCESS HERE////////
[task setArguments:[NSArray arrayWithObjects:#"-c", #"-w", configPath, nil]];
[task setStandardInput:pipe];
[writeHandle writeData:configData];
[task launch];
close([writeHandle fileDescriptor]);
[task waitUntilExit];
[task release];
}
EDIT
well... works fine with this code:
NSString *filePath= [[[panel URL] path] retain];
const char * cString = [filePath UTF8String];
configPath = [[NSString stringWithUTF8String:cString] retain];
but this is not perfect method.. thought

Answer 1

Your app crashes likely because configPath is nil, and later in writeData you try to initialize a new array with nil as the third object :
[NSArray arrayWithObjects:#"-c", #"-w", configPath, nil]
// ^^^ this is nil
I suggest you copy the string returned by path :
if(ret == NSFileHandlingPanelOKButton ) {
// you become the owner of the string,
// don't forget to release configPath later
configPath = [[[panel URL] path] copy];
[self writeData];
}
This may run without any problem.