Default Save location of document in Cocoa document based application - cocoa

Question

I have created a Cocoa document based picture drawing application. I want that the default location of a new document created using my app in Save/Save As dialog should be in ~/Pictures/MyAppName/ directory.
How can I achieve this?
I tried more or less what Ole suggested below, but it doesn't work. Here is my implementation of prepareSavePanel. What am I doing wrong?
- (BOOL)prepareSavePanel:(NSSavePanel *)savePanel
{
if ([self fileURL] == nil) {
//new, not saved yet
[savePanel setExtensionHidden:NO];
//set default save location
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSPicturesDirectory, NSUserDomainMask, YES);
if ([paths count] > 0) {
NSString *userPicturesPath = [paths objectAtIndex:0];
NSString *myDirPath = [userPicturesPath stringByAppendingPathComponent:#"MyAppName"];
//create directory is it doesn't already exist
NSFileManager *fileManager = [NSFileManager defaultManager];
BOOL isDir;
BOOL useMyAppDir = NO;
if([fileManager fileExistsAtPath:myDirPath isDirectory:&isDir]){
if (isDir) {
useMyAppDir = YES;
}
} else {
//create the directory
if([fileManager createDirectoryAtPath:myDirPath withIntermediateDirectories:YES attributes:nil error:nil]){
useMyAppDir = YES;
}
}
if (useMyAppDir) {
NSURL * myAppDirectoryURL = [NSURL URLWithString:myDirPath];
[savePanel setDirectoryURL:myAppDirectoryURL];
}
}
} else {
[savePanel setExtensionHidden:[self fileNameExtensionWasHiddenInLastRunSavePanel]];
}
return YES;
}

Answer 1

In your NSDocument subclass, override -prepareSavePanel:
- (BOOL) prepareSavePanel:(NSSavePanel *)savePanel
{
// Set default folder if no default preference is present
NSDictionary *userDefaults = [[NSUserDefaults standardUserDefaults] persistentDomainForName:[[NSBundle mainBundle] bundleIdentifier]];
if ([userDefaults objectForKey:#"NSNavLastRootDirectory"] == nil) {
NSArray *picturesFolderURLs = [[NSFileManager defaultManager] URLsForDirectory:NSPicturesDirectory inDomains:NSUserDomainMask];
if ([picturesFolderURLs count] > 0) {
NSURL *picturesFolderURL = [[picturesFolderURLs objectAtIndex:0] URLByAppendingPathComponent:#"MyAppName"];
[savePanel setDirectoryURL:picturesFolderURL];
}
}
return YES;
}