The correct way to use your own NSError objects in your app

Thanks to Mike Abdullah @mikeabdullah for pointing out the 'deliberate' (ahem) mistake in this post the first time around. Oops.

Take an iPhone or iPad Screenshot from the Command-line

Here's another tip using the great libimobiledevice library http://www.libimobiledevice.org/, originally built to manage iOS devices on Linux.

Taking app screenshots is a bit of a pain. We tend to do the following:

• Run the app
• Press Home+Power together to take a photo,
• Go to the photo library
• Find the photos
• Email them to ourselves.

Using this method you can type a Terminal command, and have the screen appear directly on your computer. Much easier.

Here's how:

• Grab the libimobiledevice binary for Mac OS X from my github account athttps://github.com/benvium/libimobiledevice-macosx/zipball/master
• Follow the install instructions here:
  https://github.com/benvium/libimobiledevice-macosx/blob/master/README.md

Connect your device, open up Terminal.app and type:

idevicescreenshot

It'll save a .TIFF file to the current directory. Easy!

Install iPhone / iPad / iOS App IPA without iTunes or Xcode

Using the great libimobiledevice library http://www.libimobiledevice.org/, originally built to manage iOS devices on Linux, it's possible to do a bunch of cool things, including installing an app directly on a connected device without needing to use iTunes or Xcode.

Here's how:

• Grab the libimobiledevice binary for Mac OS X from my github account at https://github.com/benvium/libimobiledevice-macosx/zipball/master
• Follow the install instructions here:
  https://github.com/benvium/libimobiledevice-macosx/blob/master/README.md

Now connect your iDevice, open Terminal.app and type:

ideviceinstaller -i myApp.ipa

Note: Your IPA will need to have a valid code signature and mobileprovision file for the install to succed. This system is NOT a way around iOSs security!

Script to automatically create retina and non-retina versions of images

I often get sets of files from graphic designers for iOS apps. Ensuring that the standard and @2x versions of all the files are present and correct is a bit of a pain, for the artist and for myself. The number of times there's been a mispelling in one of the images has been.. well .. many.
Instead I now ask them to send only the retina versions of the images, without the @2x tag in the filename (this has caused confusion).

I then run this script on the whole folder of files, and out pops a folder containing all the files properly renamed and resized. I use the incredible useful 'sips' command-line application that comes with OSX.

The fiddly bit of this script was working out the new size of non-retina images. Yes, they're half the size, but sips doesn't support percentages.
Credit to (person on superuser.com who I'll find eventually) for the neat sed command to extract the pixel size from the output of sips.
Note: clearly the file extension part can be done better. But it works for me right now.