https://github.com/krzysztofzablocki/Versionable

Migration for `Codable` objects.
https://github.com/krzysztofzablocki/Versionable

Last synced: 3 months ago
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Migration for `Codable` objects.

• Host: GitHub
• URL: https://github.com/krzysztofzablocki/Versionable
• Owner: krzysztofzablocki
• License: mit
• Created: 2020-06-10T13:20:14.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2021-01-08T08:22:52.000Z (almost 5 years ago)
• Last Synced: 2025-07-08T12:42:56.429Z (3 months ago)
• Language: Swift
• Size: 37.1 KB
• Stars: 85
• Watchers: 5
• Forks: 3
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# Versionable

Example showing 2 ways to implement migrations for `Codable` models.

[Related article](http://merowing.info/2020/06/adding-support-for-versioning-and-migration-to-your-codable-models./)

# Protocol conformance

Migrations in both ways are handled by conforming to `Versionable` protocol like so:

```swift

extension Object: Versionable {

    enum Version: Int, VersionType {

        case v1 = 1

        case v2 = 2

        case v3 = 3

    }

    static func migrate(to: Version) -> Migration {

        switch to {

        case .v1:

            return .none

        case .v2:

            return .migrate {  payload in

                payload["text"] = "defaultText"

            }

        case .v3:

            return .migrate { payload in

                payload["number"] = (payload["text"] as? String) == "defaultText" ? 1 : 200

            }

        }

    }

}

```

# Method 1

If you are only encoding flat structures you can use provided `VersionableDecoder` to get back your models, in this approach we rely on using a special decoder for the logic, instead of swift standards `JSONDecoder`.

- `+` Good for flat structures

- `+` Faster than container method

- `-` Won't work with composed tree hierarchy

# Method 2

If you want to encode whole tree's of objects (versionable object A containing other versionable objects via composition) then you want to be able to use regular system encoders, for this scenario you can wrap your objects into `VersionableContainer`, custom implementation of that container will deal with all migration logic.

- `+` Works with any encoder

- `+` Supports arbitrary model tree setup

- `-` Slower