NSFileManager+DirectoryLocations.m

//
//  NSFileManager+DirectoryLocations.m
//
//  Created by Matt Gallagher on 06 May 2010
//
//  Permission is given to use this source code file, free of charge, in any
//  project, commercial or otherwise, entirely at your risk, with the condition
//  that any redistribution (in part or whole) of source code must retain
//  this copyright and permission notice. Attribution in compiled projects is
//  appreciated but not required.
//

#import "NSFileManager+DirectoryLocations.h"

enum
{
	DirectoryLocationErrorNoPathFound,
	DirectoryLocationErrorFileExistsAtLocation
};
	
NSString * const DirectoryLocationDomain = @"DirectoryLocationDomain";

@implementation NSFileManager (DirectoryLocations)

//
// findOrCreateDirectory:inDomain:appendPathComponent:error:
//
// Method to tie together the steps of:
//	1) Locate a standard directory by search path and domain mask
//  2) Select the first path in the results
//	3) Append a subdirectory to that path
//	4) Create the directory and intermediate directories if needed
//	5) Handle errors by emitting a proper NSError object
//
// Parameters:
//    searchPathDirectory - the search path passed to NSSearchPathForDirectoriesInDomains
//    domainMask - the domain mask passed to NSSearchPathForDirectoriesInDomains
//    appendComponent - the subdirectory appended
//    errorOut - any error from file operations
//
// returns the path to the directory (if path found and exists), nil otherwise
//
- (NSString *)findOrCreateDirectory:(NSSearchPathDirectory)searchPathDirectory
	inDomain:(NSSearchPathDomainMask)domainMask
	appendPathComponent:(NSString *)appendComponent
	error:(NSError **)errorOut
{
	//
	// Search for the path
	//
	NSArray* paths = NSSearchPathForDirectoriesInDomains(
		searchPathDirectory,
		domainMask,
		YES);
	if ([paths count] == 0)
	{
		if (errorOut)
		{
			NSDictionary *userInfo =
				[NSDictionary dictionaryWithObjectsAndKeys:
					NSLocalizedStringFromTable(
						@"No path found for directory in domain.",
						@"Errors",
					nil),
					NSLocalizedDescriptionKey,
					[NSNumber numberWithInteger:searchPathDirectory],
					@"NSSearchPathDirectory",
					[NSNumber numberWithInteger:domainMask],
					@"NSSearchPathDomainMask",
				nil];
			*errorOut =
				[NSError 
					errorWithDomain:DirectoryLocationDomain
					code:DirectoryLocationErrorNoPathFound
					userInfo:userInfo];
		}
		return nil;
	}
	
	//
	// Normally only need the first path returned
	//
	NSString *resolvedPath = [paths objectAtIndex:0];

	//
	// Append the extra path component
	//
	if (appendComponent)
	{
		resolvedPath = [resolvedPath
			stringByAppendingPathComponent:appendComponent];
	}
	
	//
	// Check if the path exists
	//
	BOOL exists;
	BOOL isDirectory;
	exists = [self
		fileExistsAtPath:resolvedPath
		isDirectory:&isDirectory];
	if (!exists || !isDirectory)
	{
		if (exists)
		{
			if (errorOut)
			{
				NSDictionary *userInfo =
					[NSDictionary dictionaryWithObjectsAndKeys:
						NSLocalizedStringFromTable(
							@"File exists at requested directory location.",
							@"Errors",
						nil),
						NSLocalizedDescriptionKey,
						[NSNumber numberWithInteger:searchPathDirectory],
						@"NSSearchPathDirectory",
						[NSNumber numberWithInteger:domainMask],
						@"NSSearchPathDomainMask",
					nil];
				*errorOut =
					[NSError 
						errorWithDomain:DirectoryLocationDomain
						code:DirectoryLocationErrorFileExistsAtLocation
						userInfo:userInfo];
			}
			return nil;
		}
		
		//
		// Create the path if it doesn't exist
		//
		NSError *error = nil;
		BOOL success = [self
			createDirectoryAtPath:resolvedPath
			withIntermediateDirectories:YES
			attributes:nil
			error:&error];
		if (!success) 
		{
			if (errorOut)
			{
				*errorOut = error;
			}
			return nil;
		}
	}
	
	if (errorOut)
	{
		*errorOut = nil;
	}
	return resolvedPath;
}

//
// applicationSupportDirectory
//
// Returns the path to the applicationSupportDirectory (creating it if it doesn't
// exist).
//
- (NSString *)applicationSupportDirectory
{
	NSString *executableName =
		[[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleExecutable"];
	NSError *error;
	NSString *result =
		[self
			findOrCreateDirectory:NSApplicationSupportDirectory
			inDomain:NSUserDomainMask
			appendPathComponent:executableName
			error:&error];
	if (!result)
	{
		NSLog(@"Unable to find or create application support directory:\n%@", error);
	}
	return result;
}

@end