The document shows code for retrieving an employee and their associated role from a database using Futures. It defines getEmployee and getRole methods that return Futures of type Employee and Role, respectively. It constructs a Future of type EmployeeWithRole by chaining a flatMap and map to call getEmployee, extract the employee, call getRole to get the role, and combine them into an EmployeeWithRole object. It initially passes an explicit ExecutionContext to the methods but then switches to an implicit global execution context to simplify the code.

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11. // `ExecutionContext`
def getEmployee(id: Int)(implicit e: ExecutionContext): Future[Employee] = ???
def getRole(employee :Employee)(implicit e: ExecutionContext): Future[Role] = ???

12. // `ExecutionContext`
def getEmployee(id: Int)(implicit e: ExecutionContext): Future[Employee] = ???
def getRole(employee :Employee)(implicit e: ExecutionContext): Future[Role] = ???

13. // `ExecutionContext`
def getEmployee(id: Int)(implicit e: ExecutionContext): Future[Employee] = ???
def getRole(employee :Employee)(implicit e: ExecutionContext): Future[Role] = ???
val ec: ExecutionContext = scala.concurrent.ExecutionContext.Implicits.global
val bigEmployee: Future[EmployeeWithRole] =
getEmployee(100)(ec).flatMap { e =>
getRole(e)(ec).map { r =>
EmployeeWithRole(e.id, e.name,r)
}(ec)
}(ec)

14. // `ExecutionContext`
def getEmployee(id: Int)(implicit e: ExecutionContext): Future[Employee] = ???
def getRole(employee :Employee)(implicit e: ExecutionContext): Future[Role] = ???
val ec: ExecutionContext = scala.concurrent.ExecutionContext.Implicits.global
val bigEmployee: Future[EmployeeWithRole] =
getEmployee(100)(ec).flatMap { e =>
getRole(e)(ec).map { r =>
EmployeeWithRole(e.id, e.name,r)
}(ec)
}(ec)

15. // `ExecutionContext`
def getEmployee(id: Int)(implicit e: ExecutionContext): Future[Employee] = ???
def getRole(employee :Employee)(implicit e: ExecutionContext): Future[Role] = ???
val ec: ExecutionContext = scala.concurrent.ExecutionContext.Implicits.global
val bigEmployee: Future[EmployeeWithRole] =
getEmployee(100)(ec).flatMap { e =>
getRole(e)(ec).map { r =>
EmployeeWithRole(e.id, e.name,r)
}(ec)
}(ec)
🤔🤔🤔

16. // `ExecutionContext`
def getEmployee(id: Int)(implicit e: ExecutionContext): Future[Employee] = ???
def getRole(employee :Employee)(implicit e: ExecutionContext): Future[Role] = ???
implicit val ec: ExecutionContext = scala.concurrent.ExecutionContext.Implicits.global
val bigEmployee: Future[EmployeeWithRole] =
getEmployee(100).flatMap { e =>
getRole(e).map { r =>
EmployeeWithRole(e.id, e.name,r)
}
}

17. // `ExecutionContext`
def getEmployee(id: Int)(implicit e: ExecutionContext): Future[Employee] = ???
def getRole(employee :Employee)(implicit e: ExecutionContext): Future[Role] = ???
implicit val ec: ExecutionContext = scala.concurrent.ExecutionContext.Implicits.global
val bigEmployee: Future[EmployeeWithRole] =
getEmployee(100).flatMap { e =>
getRole(e).map { r =>
EmployeeWithRole(e.id, e.name,r)
}
}

18. // `ExecutionContext`
def getEmployee(id: Int)(implicit e: ExecutionContext): Future[Employee] = ???
def getRole(employee :Employee)(implicit e: ExecutionContext): Future[Role] = ???
implicit val ec: ExecutionContext = scala.concurrent.ExecutionContext.Implicits.global
val bigEmployee: Future[EmployeeWithRole] =
getEmployee(100).flatMap { e =>
getRole(e).map { r =>
EmployeeWithRole(e.id, e.name,r)
}
}
😇😇😇

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