Cocoa: Dynamically Loading Resources From an “External” Bundle

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In a typical OS X application, UI elements are often created in Interface Builder and stored inside the application bundle, in the form of one or more nib files. Bundles are central to Apple’s application ecosystem, and the documentation on them is extensive: The Bundle Programming Guide and Code Loading Programming Topics, for example, describe how to create frameworks and application plug-ins, how to load code and resources, and on and on. Impressive, but rather daunting, and the examples they provide often obfuscate the basics. This post shows a very simple example of how an “external” bundle can be loaded on demand, and provide functionality and UI elements to the main program. This is a detailed, step-by-step tutorial that explains a fairly simple use of bundles, so the intended audience is Cocoa programmers who have enough experience to create custom window or view controllers, but who have not yet dealt with creating or using bundles that are created separately from the application.

Code for the projects can be found on github.

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AV Foundation: Saving a Sequence of Raw RGB Frames to a Movie

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An application may generate a sequence of images that are intended to be viewed as a movie, outside of that application. These images may be created by, say, a software 3D renderer , a procedural texture generator, etc. In a typical OS X application, these images may be in the form of a CGImage or NSImage. In such cases, there are a variety of approaches for dumping such objects to a movie. However, in some cases the image is stored simply as an array of RGB (or ARGB) values. This post discusses how to create a movie from a sequence of such “raw” (A)RGB data.

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NSSavePanel: Adding an Accessory View

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Cocoa’s NSSavePanel allows one to programmatically add essentially arbitrary interface elements and functionality to it, in the form of an accessory view. In this post, I show a very simple accessory view example: allowing the user to control the file type (that is, suffix) of the file to be saved. I’ll present this in two contexts: first, in a purely Objective-C usage; and second, in the case of using an NSSavePanel inside a C/C++ function. In the latter case, I show an example of using a selector in a separate object, to handle “callbacks”. This post is aimed at novice Cocoa programmers; experienced programmers looking to add a file type selection are encouraged to check out JFImageSavePanel or  JAMultiTypeSavePanelController. Apple’s Customizing NSSavePanel shows other uses for the accessory view.

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OS X: Launching Another Application Programmatically

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Occasionally an application may require that another application be run. This other application may be some behind-the-scenes “helper” or auxiliary app, or it may be necessary for the user as part of a larger workflow. In this post, we go over some techniques for launching an application programmatically. In the process, I’ll go over a general method for passing parameters to a bundled AppleScript.

An Xcode project for this is available on github.

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iOS Bézier Clock

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I recently stumbled on Jack Frigaard’s Bézier Clock web page, which demonstrates his use of Processing.js to show an animated “digital” clock. He links to another page containing his Javascript code.

[Update: Jack’s original web pages are MIA, but can be found via the Internet Archive Wayback Machine here and here.]

I thought it would be fun to see if I could translate this into an iOS app; this project is the result of that effort. In truth, this is more of a transliteration than a proper translation…I converted it to Objective-C by creating equivalents to Jack’s classes, adding some UIViewControllers and UIViews, and pasting his code in. My goal was to try to simultaneously keep his code and algorithms as intact as possible, while writing fairly “proper” Objective-C. So, the resulting code is probably not quite what one would do if one started from scratch on iOS. Continue reading iOS Bézier Clock