Perceive Designs » Objective-C

Finally Found the Error I’ve Been Looking for (or “OSX Error Code Lookup Tool”)

eric — Tue, 22 Dec 2009 19:29:25 +0000

In a recent project, I kept receiving a -10000 error in the console when running my app. Quite frustrating to say the least since the error description was useless, and Google wasn’t any help at all either.

So I was completely thrilled to come across the OSX Error Code Lookup Tool. Download, compile, and plug in your error code — it’ll give you something good back!

Color Me Crazy (or “When a Color Isn’t Just a Color”)

eric — Thu, 19 Nov 2009 18:04:47 +0000

Ever need to use an image as a background, but can’t figure out how? It’s quite simple — colors aren’t always colors:


UIImage *patternImage = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"patternImage" ofType:@"png"]];

[myView setBackgroundColor:[UIColor colorWithPatternImage: patternImage]];

We are a Billion Fragments (or “Removing URL Fragments with NSURL”)

eric — Thu, 19 Nov 2009 17:24:35 +0000

NSURL is a wonderfully powerful Cocoa object, bet there is at least one thing it leaves out, but I’ll show you how to fix that. URLs are composed of several distinct parts. Given the example URL of http://www.example.com:80/path/to/file/page.htm?key=val#foo this is broken into these parts:

scheme (http://)
authority (www.example.com:80)
path (/path/to/file/page.htm)
query (key=val)
fragment (foo)

You can read more about all of this in RFC3986. Today I’m just focusing on the fragment part.

Frequently, you have an NSURL object and may just want the URL without the fragment, to find distinct pages in a site for example.

This Objective-C category on the NSURL object does just that.

header:

//
//  PDNSURLExtras.h
//
//  Created by Eric Vitiello on 11/5/09.
//  Copyright 2009 Eric Vitiello. All rights reserved.
//

#import 

@interface NSURL (PDExtras)
- (NSURL *)urlByRemovingFragment;
@end

implementation:

//
//  PDNSURLExtras.m
//
//  Created by Eric Vitiello on 11/5/09.
//  Copyright 2009 Eric Vitiello. All rights reserved.
//

#import "PDNSURLExtras.h"

@implementation NSURL (PDExtras)

-(NSURL *)urlByRemovingFragment {
	NSString *urlString = [self absoluteString];
	// Find that last component in the string from the end to make sure to get the last one
	NSRange fragmentRange = [urlString rangeOfString:@"#" options:NSBackwardsSearch];
	if (fragmentRange.location != NSNotFound) {
		// Chop the fragment.
		NSString* newURLString = [urlString substringToIndex:fragmentRange.location];
		return [NSURL URLWithString:newURLString];
	} else {
		return self;
	}
}

@end

To use:

NSURL *url = [NSURL URLWithString:@"http://www.example.com:80/path/to/file/page.htm?key=val#foo"];
NSURL *urlWithoutFragment = [url urlByRemovingFragment];

Nice and simple. Enjoy!

If I Had a Photograph of You (or “How to Cache Images in CocoaTouch”)

eric — Wed, 14 Jan 2009 02:44:44 +0000

A quick note. Wanting to cache images in an iPhone app? Load the image using:

[UIImage imageNamed:]

if you use:

[UIImage imageWithContentsOfFile:]

the image will not be cached.