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October 17, 2012

Automatic Build Numbers for iOS Apps Using Xcode

by Dan

UPDATE Sep 2014: Added another idea from Jared Sinclair, who has example code for Git.
UPDATE Jan 2013: Now also updating the build version in the dSYM file.

There are many articles that discuss how to automate build numbers in Xcode. However, some are misleading for iOS apps. Many are quite long. I wanted to find a short, simple way to do this.

Background

On the target Summary tab your project settings, Xcode lets you set a Version and a Build. The version is what we are all familiar with, such as 5.0 and 5.1.1. The build is what often appears in parentheses after the version, as in 5.0 (134) and 5.1.1 (147).

Apple doesn’t seem to care what you use for Version (aka CFBundleShortVersionString), but Build (aka CFBundleVersion) must be a monotonically increasing string, comprised of one or more period-separated integers. Thus Apple will reject your update if you go from 1.1 (10) to 1.2 (0). The version is ignored and, alas, zero is clearly less than ten.

The part about integers is important too because Apple will also reject your update if you go from 1.01 (1.01) to 1.1 (1.1). The period is not a decimal place. Both (1.01) and (1.1) are interpreted as “the integer one followed by the integer one”. We saw this logic in action when OS X went from version 10.4.9 to 10.4.10.

Problem

If you do this wrong, you’ll see this error when you upload your app update:

This bundle is invalid. The key CFBundleVersion in the Info.plist file must contain a higher version than that of the previously uploaded version.

To get your monotonically increasing period-separated integer build number, you could just use the app version, like 5.1.1 (5.1.1). But I think it’s better to use a build number that can help identify the code from which that version of your app was built. Both Git and Mercurial include the ability to count commits, which is perfect—always increasing and helpful in identifying the code.

If you modify the Info.plist file in your project folder during the build process, you’ll probably need to commit the change to your code repository. This extra commit, while not harmful, is unnecessary. Instead, you can modify the Info.plist file in the app package after the build process is finished. The file will be in a binary format, but the PListBuddy tool can handle it.

Solution

Here is the script you need for Mercurial. This script also adds the bundle version to the dSYM file, which is necessary for correctly symbolicating your crash logs. It’s also required for several distribution mechanisms including TestFlight and HockeyApp.

ver = `/usr/local/bin/hg id -n`.strip
puts "Build number is #{ver}"
filepath = "#{ENV['BUILT_PRODUCTS_DIR']}/#{ENV['INFOPLIST_PATH']}"
puts "Updating #{filepath}"
`/usr/libexec/PlistBuddy -c "Set :CFBundleVersion #{ver}" "#{filepath}"`
filepath = "#{ENV['DWARF_DSYM_FOLDER_PATH']}/#{ENV['DWARF_DSYM_FILE_NAME']}/Contents/Info.plist"
puts "Updating dSYM at #{filepath}"
`/usr/libexec/PlistBuddy -c "Set :CFBundleVersion #{ver}" "#{filepath}"`

The first line counts the number of commits in your local repository. It’s safe to use as long as your builds are done on the same machine. Repositories on other computers may have different commit counts. For Git, you can count your commits using a similar command.

Steps

  1. Select your project in the Project Navigator
  2. Select your target
  3. Select the Build Phases tab
  4. Choose “Add Build Phase”
  5. Select “Add Run Script”
  6. Change the Shell to “/usr/bin/ruby”
  7. Copy and paste the script

Within your app, you can grab the version and build number with this code:

NSDictionary *appInfo = [[NSBundle mainBundle] infoDictionary];
NSString *appVersion = [NSString stringWithFormat:@"%@ (%@)", appInfo[@"CFBundleShortVersionString"], appInfo[@"CFBundleVersion"]];

This will give you a string like 2.2 (134) that you can display in your app. I’m using the new object subscripting syntax in Objective-C, but it’s not too hard to switch back to using objectForKey:.

Follow Up

Jared Sinclair has a nice example of how to do this with Git. I really like the idea of using the branch name as a build suffix for Debug builds. I’m going to update my code to match.

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