Utility functions to create a unique file name in a given directory, with shorter helper functions for Documents, ApplicationSupport, tmp, Caches

UniqueFilename.swift

extension NSFileManager {
	class func uniqueDocumentFileURLWithBaseName(baseName: String) throws -> NSURL {
		let directoryUrl = try NSFileManager.defaultManager().URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: true)
		return try directoryUrl.URLByAppendingUniqueFileNameWithBaseName(baseName)
	}
	
	class func uniqueAppSupportFileURL(inSubdirectory subdirectory: String, uniqueFileBaseName baseName: String) throws -> NSURL {
		let appSupportUrl = try NSFileManager.defaultManager().URLForDirectory(.ApplicationSupportDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: true)
		let directoryUrl: NSURL
		if subdirectory.isEmpty {
			directoryUrl = appSupportUrl
		} else {
			directoryUrl = appSupportUrl.URLByAppendingPathComponent(subdirectory, isDirectory: true)
		}
		return try directoryUrl.URLByAppendingUniqueFileNameWithBaseName(baseName)
	}
	
	class func uniqueCacheFileURLWithBaseName(baseName: String) throws -> NSURL {
		let directoryUrl = try NSFileManager.defaultManager().URLForDirectory(.CachesDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: true)
		return try directoryUrl.URLByAppendingUniqueFileNameWithBaseName(baseName)
	}
	
	class func uniqueTemporaryFileNameWithBaseName(baseName: String) throws -> NSURL {
		let tmpDir = NSURL(fileURLWithPath: NSTemporaryDirectory())
		return try tmpDir.URLByAppendingUniqueFileNameWithBaseName(baseName)
	}
}

extension NSURL {
	func URLByAppendingUniqueFileNameWithBaseName(fileBaseName: String) throws -> NSURL {
		
		let baseName: String
		let fileExtension: String
		
		do {
			let ext = (fileBaseName as NSString).pathExtension
			if !ext.isEmpty {
				baseName = (fileBaseName as NSString).stringByDeletingPathExtension
				fileExtension = ext
			} else {
				baseName = fileBaseName
				fileExtension = ""
			}
		}
		
		enum Error: ErrorType {
			case NotADirectory
		}
		
		do {
			try NSFileManager.defaultManager().createDirectoryAtURL(self, withIntermediateDirectories: true, attributes: nil)
		} catch {
			throw Error.NotADirectory
		}
		
		let directoryURL = self
		var fileCount = 1;
		
		while true {
			let fileName = baseName + ((fileCount > 1) ? String(" (\(fileCount))") : "") + (fileExtension.isEmpty ? "" : String(".\(fileExtension)"))
			let fileUrl = directoryURL.URLByAppendingPathComponent(fileName)
			
			if !fileUrl.checkResourceIsReachableAndReturnError(nil) {
				return fileUrl
			}
			
			fileCount++
		}
	}
}