Generic paginator for scala

Provides pagination for any data provider: DB, remote API, memory, ...
Based on a simple adapter pattern.
Fully functional.

Example

import com.github.ornicar.paginator._

val adapter   = InMemoryAdapter('a' to 'z')

for {
  paginator <- Paginator(adapter, currentPage = 2, maxPerPage = 5).right
} {
  paginator.nbResults           // 26
  paginator.nbPages             // 6
  paginator.currentPageResults  // Vector('f', 'g', 'h', 'i', 'j')
  paginator.currentPage         // 2
  paginator.maxPerPage          // 5
  paginator.hasToPaginate       // True
  paginator.hasNextPage         // True
  paginator.hasPreviousPage     // True
  paginator.nextPage            // Some(3)
  paginator.previousPage        // Some(1)
}

Adapters

InMemoryAdapter

This basic implementation of the adapter paginates a Seq. Example:

val adapter = InMemoryAdapter('a' to 'z')

val paginator = Paginator(adapter)

paginator is an instance of Either[String, Paginator[A]] where the left part is a possible error message.

Paginator(adapter) // Right[Paginator[A]]

Paginator(adapter, 1, 10) // Right[Paginator[A]]

Paginator(adapter, 0, 10) // Left("Max per page must be greater than zero")

Paginator(adapter, 1, 0) // Left("Current page must be greater than zero")

MongoDB Salat adapter

Allows to paginate on any MongoDB query:

import com.github.ornicar.paginator.SalatAdapter                // I assume you also import the salat stuff

case class Person(name: String)                                 // Say we have a basic model class

object PersonDAO extends SalatDAO[Person, ObjectId](collection) // And a DAO for the model

val query     = MongoDBObject("name" -> "Joe")                    // This is a normal salat query

val adapter   = SalatAdapter(PersonDAO, query)                    // And a shiny mongodb paginator adapter

val paginator = Paginator(adapter)

The adapter will take care of adding the skip and limit options to the mongodb query. To use this adapter, you must include the salat-adapter project.

Create another adapter

To create a new adapter, just implement the 2 methods of this trait:

trait Adapter[A] {

  /**
   * Returns the number of results.
   */
  def nbResults: Int

  /**
   * Returns an slice of the results.
   *
   * @param   offset    The number of elements to skip, starting from zero
   * @param   length    The maximum number of elements to return
   */
  def slice(offset: Int, length: Int): Seq[A]
}

You may use the provided InMemoryAdapter and SalatAdapter as implementation examples.

FabienPennequin / scala-paginator