How do I create a temporary file with Cocoa?

问题:

Years ago when I was working with C# I could easily create a temporary file and get its name with this function:

Path.GetTempFileName();

This function would create a file with a unique name in the temporary directory and return the full path to that file.

In the Cocoa API's, the closest thing I can find is:

NSTemporaryDirectory

Am I missing something obvious or is there no built in way to do this?

回答1:

A safe way is to use mkstemp(3).

回答2:

[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

回答3:

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

回答4:

Though it's nearly a year later, I figured it's still helpful to mention a blog post from Cocoa With Love by Matt Gallagher. http://cocoawithlove.com/2009/07/temporary-files-and-folders-in-cocoa.html He shows how to use mkstemp() for files and mkdtemp() for directories, complete with NSString conversions.

回答5:

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.

回答6:

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

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

回答7:

You could use mktemp to get a temp filename.

回答8:

Updated for Swift 3, copied straight from a Playground:

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)

回答9:

The modern way to do this is FileManager's url(for:in:appropriateFor:create:).

With this method, you can specify a SearchPathDirectory to say exactly what kind of temporary directory you want. For example, a .cachesDirectory will persist between runs (as possible) and be saved in the user's library, while a .itemReplacementDirectory will be on the same volume as the target file.

回答10:

You could use an NSTask to uuidgen to get a unique file name, then append that to a string from NSTemporaryDirectory(). This won't work on Cocoa Touch. It is a bit long-winded though.

回答11:

Adding to @Philipp:

- (NSString *)createTemporaryFile:(NSData *)contents {
    // Create a unique file in the system temporary directory
    NSString *guid = [[NSProcessInfo processInfo] globallyUniqueString];
    NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:guid];
    if(![self createFileAtPath:path contents:contents attributes:nil]) {
        return nil;
    }
    return path;
}