Cocoa with Love

A big weakness in Objective-C's weak typing

Jun 30, 2011 (an Objective-C era article)

We generally assume that we can send any message we want to a variable in our code typed as "id" and Objective-C's dynamic message handling will make the invocation work correctly at runtime. In some rare cases, this assumption is wrong. I'll look at situations where you need to be careful about sending messages to "id" typed variables and a situation where a limitation in the Objective-C language requires a hideous workaround to avoid serious bugs.

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An RSS-feed and location-based iOS application

Jun 19, 2011 (an Objective-C era article)

The purpose of this post is so that I will have a link to give people when they ask: how do I write an iOS application that pulls data from an RSS feed, displays it pretty and can put things on a map. I'll show you all of that and more as I rewrite my oldest iOS application from scratch: FuelView.

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Classes for fetching and parsing XML or JSON via HTTP

May 30, 2011 (an Objective-C era article)

In this post I show two reusable classes for fetching data via HTTP: one that parses the result as XML and another that parses as JSON. These are relatively simple tasks but due to the number of required steps, they can become tiresome if you don't have robust, reusable code for the task. These classes will work on iOS or on the Mac but the optional error alerts and password dialogs are only implemented for iOS.

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Presenting a Mac dialog sheet with visual cue effects

May 5, 2011 (an Objective-C era article)

In this post, I'll show you how to use visual effects over a window to make a dialog sheet stand out when it is presented over the top. It's a pretty simple use of Core Image but is a useful technique to capture attention when needed.

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Background audio through an iOS movie player

Apr 20, 2011 (an Objective-C era article)

Background audio in iOS is supposed to be as simple as entering a setting in your Info.plist and making sure your kAudioSessionProperty_AudioCategory is appropriate. This is true unless your audio is part of a movie file or is played in a movie player that has just played video — suddenly it becomes fiddly, hard to test, unreliable and changeable from version to version of iOS.

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User interface strings in Cocoa

Apr 5, 2011 (an Objective-C era article)

In this post, I'll look at best practice for using and managing text strings in your user interface. This is a fairly simple topic but Cocoa has established "best practices" for handling user interface strings that new Cocoa developers should be aware of. Since it is inevitably related, I'll also look at the steps involved in localizing the strings in your applications but remember: you should follow good practice for string handling, even if you have no intention of ever translating your application.

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Mac QuartzGL (2D drawing on the graphics card) performance

Mar 25, 2011 (an Objective-C era article)

QuartzGL was introduced as an official feature in Mac OS X 10.5 Leopard (although it was a developer-only feature in Mac OS X 10.4 as Quartz 2D Extreme). However, it is off by default and is largely ignored by most developers. In this post, I look at how to enable QuartzGL, the performance impact it has on different kinds of drawing and whether you should use it in your Mac programs.

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A history of iOS media APIs (iPhone OS 2.0 to iOS 4.3)

Mar 20, 2011 (an Objective-C era article)

After initially starting with a small set of fairly basic media APIs in iPhone OS 2.0, the APIs and the features they provide have dramatically increased in the past 2 years and provided a rapidly moving target for developers trying to remain current. In this post, I'll try to summarize all of the different APIs in iOS 4.3 for playing media, when they arrived, what their purposes are, what their limitations are and what it's been like to remain up-to-date and support new features.

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Advanced drawing using AppKit

Jan 31, 2011 (an Objective-C era article)

In this post, I'll look at drawing a detailed image in code by combining multiple visual elements. Unlike previous posts I've done on drawing in Cocoa, this will focus on the AppKit classes. The code will use NSGraphicsContext, NSBezierPath, NSAffineTransform, NSGradient, NSGlyph and show you some simple ways to export the contents of an NSView to a file.

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Submitting functionality for a future version of iOS

Jan 26, 2011 (an Objective-C era article)

A number of websites are reporting that my application, StreamToMe 3.5 was approved with mention of a piece of future iOS functionality. While this was actually the case, it does not mean that Apple have started accepting apps for this new version of iOS.

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