MTMigration

Manages blocks of code that only need to run once on version updates in iOS apps. This could be anything from data normalization routines, "What's New In This Version" screens, or bug fixes.

Installation

MTMigration can be installed one of two ways:

• Add pod "MTMigration" to your Podfile, import as necessary with: #import <MTMigration/MTMigration.h>.
• Add MTMigration.{h,m} to your project, import as necessary with: #import "MTMigration.h".

Usage

By giving a version number and block of code to migrateToVersion:block:, MTMigration will ensure that the block of code is only ever run once.

[MTMigration migrateToVersion:@"1.1" block:^{
    [obj doSomeDataStuff];
}];

You would want to run this code in your app delegate or similar.

Because MTMigration inspects your *-info.plist file for your actual version number and keeps track of the last migration, it will migrate all un-migrated blocks inbetween. For example, let's say you had the following migrations:

[MTMigration migrateToVersion:@"0.9" block:^{
    // Some 0.9 stuff
}];

[MTMigration migrateToVersion:@"1.0" block:^{
    // Some 1.0 stuff
}];

If a user was at version 0.8, skipped 0.9, and upgraded to 1.0, then both the 0.9 and 1.0 blocks would run.

For debugging/testing purposes, you can call reset to clear out the last migration MTMigration remembered, causing all migrations to run from the beginning:

[MTMigration reset];

Notes

MTMigration assumes version numbers are incremented in a logical way, i.e. 1.0.1 -> 1.0.2, 1.1 -> 1.2, etc. MTMigration uses NSString#compare:options: to do the comparison, passing NSNumericSearch to options: so that 1.10 comes after 1.9.

Version numbers that are past the version specified in your app will not be run. For example, if your *-info.plist file specifies 1.2 as the app's version number, and you attempt to migrate to 1.3, the migration will not run.

Blocks are executed on the thread the migration is run on. Background/foreground situations should be considered accordingly.

Contributing

This library does not handle some more intricate migration situations, if you come across intricate use cases from your own app, please add it and submit a pull request. Be sure to add test cases.

Contributors

Parker Wightman (@parkerwightman)
Good Samaritans