Question

The result of this code is that url is null

NSString* home = [NSHomeDirectory() stringByAppendingPathComponent:@"/Library/Application Support/"];
NSURL *url = [NSURL URLWithString:home];

and so is this:

NSString* home = [NSHomeDirectory() stringByAppendingPathComponent:@"/Library/Application Support/"];
home = [home stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL *url = [NSURL URLWithString:home];

Answer 1

Your question is not about creating an URL from a string containing spaces, but from a path string containing spaces.

For a path, you should not use URLWithString. Mac OS X and iOS include convenience functions for building NSURLs for file paths that handle this and more for you automatically. Use one of them instead.

Apple’s documentation for [NSURL fileURLWithPath: path] says:

This method assumes that path is a directory if it ends with a slash. If path does not end with a slash, the method examines the file system to determine if path is a file or a directory. If path exists in the file system and is a directory, the method appends a trailing slash. If path does not exist in the file system, the method assumes that it represents a file and does not append a trailing slash.

As an alternative, consider using fileURLWithPath:isDirectory:, which allows you to explicitly specify whether the returned NSURL object represents a file or directory.

Also, you should be using NSSearchPathForDirectoriesInDomains to find the Application Support directory.

Putting this all together, you’d end up with something like this:

NSArray *paths = NSSearchPathForDirectoriesInDomains(
                     NSApplicationSupportDirectory, NSUserDomainMask, YES);
NSString *applicationSupportDirectory = [paths objectAtIndex:0];
NSURL *url = [NSURL fileURLWithPath: applicationSupportDirectory isDirectory: YES];

Source:

• iOS Developer Library: NSURL Class Reference