What Is Difference Between Urlwithstring and Fileurlwithpath of Nsurl

NSURL path vs absoluteString

Question 1:

What is the actual difference between these methods?

Let's analyze this writing 6 lines of code - 3 for a local and 3 for http URL - and playing around with them a little bit.

Let's create an NSURL using the file:// scheme. If you ask yourself why there are 3 / after file: you should remember that a complete URL exists of a scheme (file:// and absolute or relative path (you can find more information on creating URLs in RFC 1808 on page 3). We use an absolute path which starts with a / so that we end up with ///.

NSURL *aLocalURL = [NSURL URLWithString:@"file:///Users/dennis/Desktop/"];
NSLog(@"absolute string: %@", aLocalURL.absoluteString);
NSLog(@"path: %@", aLocalURL.path);

Output:

absolute string: file:///Users/dennis/Desktop/

path: /Users/dennis/Desktop

So we see that absoluteString still knows its scheme whereas path doesn't have this information anymore.

Note: path is a file (directory) URL and as the docs state, the trailing slash it is stripped.

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Now let's take a look at remote URLs. With these type of URLs most people are more familiar. We create it using the same procedure as for local URLs. Our scheme is now http:// and our path is www.apple.com/.

NSURL *anHTTPURL = [NSURL URLWithString:@"http://www.apple.com/"];  
NSLog(@"absolute string: %@", anHTTPURL.absoluteString);
NSLog(@"path: %@", anHTTPURL.path);

Output:

absolute string: http://www.apple.com/

path: /

Again, we see that the absolute string still knows its scheme but path is now /. So path seems to be not an appropriate way when working with remote URLs.

However, when we have an URL like http://www.apple.com/index.html we get

absolute string: http://www.apple.com/index.html

path: /index.html

Reading the docs helps here, too:

Per RFC 3986, the leading slash after the authority (host name and port) portion is treated as part of the path.

So the path is everything beginning (and including) at the slash after the authority which is www.apple.com in our case.

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Question 2

Is there a time when one should be used over the other?

From the docs: (method: path)

If this URL object contains a file URL (as determined with isFileURL), the return value of this method is suitable for input into methods of NSFileManager or NSPathUtilities.

In my opinion that sentence states clearly that you should use path when you work with NSFileManager or NSPathUtilities.

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Conclusion:

When you work with remote URLs you (generally) use absoluteString, otherwise the result is not what you (generally) want.

When you work with local URLs use path.

Sources:

http://www.ietf.org/rfc/rfc1808.txt

http://www.ietf.org/rfc/rfc3986.txt

NSURL Class Reference

NSURL fileURLWithPath where NSString has a space

Try this:

NSString *fnam = [@"Localizable" stringByAppendingPathExtension:@"strings"];
NSArray *parts = [NSArray arrayWithPathComponents:@"~", @"SP BB", fnam, (void *)nil];
NSString *path = [[NSString pathWithComponents:parts] stringByStandardizingPath];
NSURL *furl = [NSURL fileURLWithPath:path];

Foundation has a host of platform-independent, path-related methods. Prefer those over hard-coding path extension separators (often ".") and path component separators (often "/" or "\").

What’s the correct way to create an NSURL from an NSString?

A path is not a valid URL by itself. You have to use this:

NSURL *pathURL = [NSURL fileURLWithPath:filePath];

And read the documentation. (And don’t overuse / abuse format strings.)

NSString to NSurl

When making URL from NSString, don't forget to encode it first, so try this:

NSString *urlString = [NSString stringWithFormat:@"%@", item.image];
NSURL *url = [NSURL URLWithString:[urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];  

For IOS ≥ 9.0 use

NSURL *url = [NSURL URLWithString:[urlString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]]];

Check if NSString is Local File

After trying all kinds of URL example, I think the NSURL class may not the final way for this to check the local file path. Now I use the following function.

BOOL IsLocalFilePath(NSString *path)
{
    NSString *fullpath = path.stringByExpandingTildeInPath;
    return [fullpath hasPrefix:@"/"] || [fullpath hasPrefix:@"file:/"];
}

It covers the local file paths like /path/to/foo, file:///path/to/foo, ~/path/to/foo, ../path/to/foo.

It works great for Unix-like path so far, punch me there are some exceptions.

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