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!

View the log output of any app on iPhone or iPad

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

This method shows you how you can view the log output (e.g. what you see in Xcode when running in debug mode) on any app, whether it's an AppStore build or an AdHoc build.

Some apps are more talkative than others - it all depends on how careful the developers were to remove log messages in release builds.

I find this most useful for debugging issues in release versions of our apps. If a user reports a sequence of actions causes a crash, you can try this out while watching the log from your app.

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:

idevicesyslog

Up pops a real-time display of the device's system log.

With it being a console app, you can filter the log using unix commands, such as grep


For instance, see all log messages from a particular app:

idevicesyslog | grep myappname

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!

AppCode Delegate Pattern Live Template

Here's a Live Template to generate a common delegate pattern in AppCode, JetBrain's Objective-C IDE.

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.

Get version number of live app on App Store in Phonegap app

A nice feature you might want to add to your iOS app is to notify the user when a new version is available on the App Store. Of course the user can go to the App Store manually and install the update, but we've noticed quite a few users don't do this very often. Some carefully-judged prompting is bound to help.

It turns out there's an API that Apple run that can return, in a handy JSON or JSONP format, the metadata for a particular app on the app store. This includes both the version number of the app, and even better, the 'what's new in this version' text.

You can use this information on your app's startup to check if a new version is available, and tell the user what's in it, and then finally, link them to the update page for the app.

Here's some bare-bones bits of example code to get you going. You'll need to know your app's Apple ID (e.g. 387022138). You can find this in the iTunes Connect interface). I'm also assuming that you're using jQuery or Zepto in your app.

The below also works in the browser.

// Alert the version number and release notes of an app.

    $.ajax({
        url:"http://itunes.apple.com/lookup?id=<APPLE ID HERE>&callback=?",
        success:function(data) {
            if (data && data.results && data.results.length) {
                alert(data.results[0].version);
                alert(data.results[0].releaseNotes);
            }
        }
    });

Here's the full list of data you might want to use:

Screengrab showing properties of the response from the API call. Click to view full size.

To open iTunes looking at your App's update page open the following URL:

itms-apps://phobos.apple.com/WebObjects/MZStore.woa/wa/viewSoftwareUpdate?id=<APPLE ID HERE>&mt=8