How do I create a temporary file with Cocoa?

Question

A safe way is to use mkstemp(3).

[Note: This applies to the iPhone SDK, not the Mac OS SDK]

From what I can tell, these functions aren't present in the SDK (the unistd.h file is drastically pared down when compared to the standard Mac OS X 10.5 file). I would use something along the lines of:

[NSTemporaryDirectory() stringByAppendingPathComponent: [NSString stringWithFormat: @"%.0f.%@", [NSDate timeIntervalSinceReferenceDate] * 1000.0, @"txt"]];

Not the prettiest, but functional

Apple has provided an excellent way for accessing temp directory and creating unique names for the temp files.

- (NSString *)pathForTemporaryFileWithPrefix:(NSString *)prefix
{
    NSString *  result;
    CFUUIDRef   uuid;
    CFStringRef uuidStr;

    uuid = CFUUIDCreate(NULL);
    assert(uuid != NULL);

    uuidStr = CFUUIDCreateString(NULL, uuid);
    assert(uuidStr != NULL);

    result = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"%@-%@", prefix, uuidStr]];
    assert(result != nil);

    CFRelease(uuidStr);
    CFRelease(uuid);

    return result;
}

LINK :::: http://developer.apple.com/library/ios/#samplecode/SimpleURLConnections/Introduction/Intro.html#//apple_ref/doc/uid/DTS40009245 see file :::AppDelegate.m

I created a pure Cocoa solution by way of a category on NSFileManager that uses a combination of NSTemporary() and a globally unique ID.

Here the header file:

@interface NSFileManager (TemporaryDirectory)

-(NSString *) createTemporaryDirectory;

@end

And the implementation file:

@implementation NSFileManager (TemporaryDirectory)

-(NSString *) createTemporaryDirectory {
 // Create a unique directory in the system temporary directory
 NSString *guid = [[NSProcessInfo processInfo] globallyUniqueString];
 NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:guid];
 if (![self createDirectoryAtPath:path withIntermediateDirectories:NO attributes:nil error:nil]) {
  return nil;
 }
 return path;
}

@end

This creates a temporary directory but could be easily adapted to use createFileAtPath:contents:attributes: instead of createDirectoryAtPath: to create a file instead.

If targeting iOS 6.0 or Mac OS X 10.8 or higher:

NSString *tempFilePath = [NSTemporaryDirectory() stringByAppendingPathComponent:[[NSUUID UUID] UUIDString]];

Swift 5 and Swift 4.2

import Foundation

func pathForTemporaryFile(with prefix: String) -> URL {
    let uuid = UUID().uuidString
    let pathComponent = "\(prefix)-\(uuid)"
    var tempPath = URL(fileURLWithPath: NSTemporaryDirectory())
    tempPath.appendPathComponent(pathComponent)
    return tempPath
}

let url = pathForTemporaryFile(with: "blah")
print(url)
// file:///var/folders/42/fg3l5j123z6668cgt81dhks80000gn/T/johndoe.KillerApp/blah-E1DCE512-AC4B-4EAB-8838-547C0502E264

Or alternatively Ssswift's oneliner:

let prefix = "blah"
let url2 = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("\(prefix)-\(UUID())")
print(url2)