-[NSString stringByAppendingPathComponent:] or just -[NSString stringByAppendingFormat:] for NSStrings for NSURLs?

Question

When calling +[NSURL URLWithString:] I have two options for building my URLs:

[[@"http://example.com" stringByAppendingPathComponent:@"foo"] stringByAppendingPathComponent:@"bar"]

or

[@"http://example.com" stringByAppendingFormat:@"/%@/%@",@"foo",@"bar"];

-[NSString stringByAppendingPathComponent:] seems like the more correct answer, but do I lose anything using -[NSString stringByAppendingFormat:] besides handling double-slashes as in the following case?

// http://example.com/foo/bar
[[@"http://example.com/" stringByAppendingPathComponent:@"/foo"] stringByAppendingPathComponent:@"bar"] 

// http://example.com//foo/bar  oops!
[@"http://example.com/" stringByAppendingFormat:@"/%@/%@",@"foo",@"bar"];

Answer 1

As you're working with URLS, you should use the NSURL methods:

NSURL * url = [NSURL URLWithString: @"http://example.com"];
url = [[url URLByAppendingPathComponent:@"foo"] URLByAppendingPathComponent:@"bar"]

---

or in Swift

var url = NSURL.URLWithString("http://example.com")
url = url.URLByAppendingPathComponent("foo").URLByAppendingPathComponent(".bar")

Answer 2

I just ran into a problem with stringByAppendingPathComponent: it removes double slashes everywhere!:

NSString* string1 = [[self baseURL] stringByAppendingString:partial];
NSString* string2 =  [[self baseURL] stringByAppendingPathComponent:partial];

NSLog(@"string1 is %s", [string1 UTF8String]);
NSLog(@"string2 is %s", [string2 UTF8String]);

for a baseURl of https://blah.com

and a partial of /moreblah

Produces the two strings:

2012-09-07 14:02:09.724 myapp string1 is https://blah.com/moreblah

2012-09-07 14:02:09.749 myapp string2 is https:/blah.com/moreblah

But for some reason my calls to blah.com to get resource work with the single slash. But it indicates to me that stringByAppendingPathComponent is for paths - NOT urls.

This is on iPhone 4 hardware running iOS 5.1.

I outputted the UTF8 strings as I wanted to make sure that the debugger output I was seeing was believable.

So I guess I am saying - don't use path stuff on URLs, use some home brew or a library.

Answer 3

How about:

[NSString pathWithComponents:@[@"http://example.com", @"foo", @"bar"]]

As pointed out in the comments a / gets stripped from protocol when using the methods from NSPathUtitlites.h, so that is the obvious downfall. The solution I could come up with that is closest to the original one I posted is:

[@[ @"http://example.com", @"foo", @"bar" ] componentsJoinedByString:@"/"]

You will just need to use a literal for the path separator which is what NSString does.

NSString represents paths generically with ‘/’ as the path separator and ‘.’ as the extension separator.