Question

我有一个scala特征如下 -

trait Mytrait {
   def saveData : Boolean = {
      //make database calls to store
      true
   }
    def getData : Integer = {
        //get data from database
        return i
    }

}

现在我听说过蛋糕模式，但我无法弄清楚如何应用蛋糕模式来模拟这样的特征。

有人能指出如何做到这一点吗？

Answer 1

你会这样做：

trait Mytrait { this: DbConnectionFactory => // Require this trait to be mixed with a DbConnectionFactory
  def saveData : Boolean = {
    val connection = getConnection // Supplied by DbConnectionFactory 'layer'
    //use DB connection to make database calls to store
    true
  }

  def getData : Integer = {
    val connection = getConnection // Supplied by DbConnectionFactory 'layer'
    val i: Integer = ... // use DB connection to get data from database
    return i
  }

}

trait DbConnection

trait DbConnectionFactory {
  def getConnection: DbConnection
}

// --- for prod:

class ProdDbConnection extends DbConnectionFactory {
  // Set up conn to prod Db - say, an Oracle DB instance
  def getConnection: DbConnection = ???
} // or interpose a connection pooling implementation over a set of these, or whatever

val myProdDbWorker = new ProdDbConnection with Mytrait

// --- for test:

class MockDbConnection extends DbConnectionFactory {
  // Set up mock conn
  def getConnection: DbConnection = ???
}

val myTestDbWorker = new MockDbConnection with Mytrait

你可以从合适的DbConnectionFactory和你的特质中形成'layers'或'cake'。

这只是一个简单的例子，您可以扩展所涉及的组件数量，有多个MyTrait实现，您希望在不同的环境下使用它们等等。例如，参见Dependency Injection in Scala: Extending the Cake Pattern

Junits使用Mocks scala特征和蛋糕模式

1 个答案: