Perform any operation for each of all updates

Using Middleware, you can perform any operation for each of all updates. ‌ For example,

• Manage Index according to updated entities, for each of all updates

Register Middleware

In DatabaseType protocol, we can return the set of middlewares. This property would be called for each update.

struct Database: DatabaseType {

  ...

  var middlewares: [AnyMiddleware<RootState.Database>] {
    [
      // Here
    ]
  }
}

We can return MiddlewareType object here. However since it’s a generic protocol, it needs to wrap up with AnyMiddleware object to return as an array.

struct AnyMiddleware

public struct AnyMiddleware<Database> : MiddlewareType where Database : VergeORM.DatabaseType {

    public init<Base>(_ base: Base) where Database == Base.Database, Base : VergeORM.MiddlewareType

    public init(performAfterUpdates: @escaping (DatabaseBatchUpdateContext<Database>) -> ())

    public func performAfterUpdates(context: DatabaseBatchUpdateContext<Database>)
}

To wrap your middleware up with AnyMiddleware

public struct MyMiddleware<Database: DatabaseType>: MiddlewareType {
  ...
}

let middleware = MyMiddleware()
AnyMiddleware<Database>(middleware)

To create anonymous middleware using AnyMiddleware

AnyMiddleware<Database>(performAfterUpdates: { (context) in

  // ... any operation

})

What middleware handles

• performs any operation with context after updating of batch-updates completed.
  • MiddlewareType.performAfterUpdates

Create Middleware

let autoIndex = AnyMiddleware<RootState.Database>(performAfterUpdates: { (context) in

  let ids = context.insertsOrUpdates.author.all().map { $0.id }
  context.indexes.bookMiddleware.append(contentsOf: ids)

})

This sample code adds identifier of Author that added on batch-updates. This means it manages Index automatically. Finally, returns this object on middlewares property.

let autoIndex = ...

struct Database: DatabaseType {

  ...

  var middlewares: [AnyMiddleware<RootState.Database>] {
    [
      autoIndex
    ]
  }
}