Define an Employee record with name, hire date, and department, then sort employees by hire date.

← Classes and OOP · Ref: Q1204

Define a record with fields in the desired sort priority order. The 'default operator' generates <=> comparing fields in declaration order. Put hireDate first for chronological sorting.

FIELD ORDER MATTERS

  Employee
    hireDate as Date: Date()     first field = primary sort key
    employeeName as String: String()  second field = secondary sort key
    department as String: String()    third field = tertiary sort key

SORT BY HIRE DATE

  sorted <- cat employees | sort | collect as List of Employee

Since hireDate is declared first, the default <=> operator sorts chronologically. Stream pipelines use the type's <=> operator automatically.

See Q1199 for sorting by date+time. See Q1135 for record sort pipeline. See Q1195 for mixed-type record.

Example

defines module qa.classesandoop.employeehiredate

  defines record

    Employee
      hireDate as Date: Date()
      employeeName as String: String()
      department as String: String()

      Employee() as pure
        ->
          theHireDate as Date
          theName as String
          theDepartment as String
        this.hireDate :=: theHireDate
        this.employeeName :=: theName
        this.department :=: theDepartment

      default operator

  defines program

    EmployeeHireDateDemo()
      stdout <- Stdout()

      // === CREATE EMPLOYEES ===

      employees <- List() of Employee
      employees += Employee(2024-06-15, "Alice", "Engineering")
      employees += Employee(2023-01-10, "Bob", "Marketing")
      employees += Employee(2024-01-05, "Carol", "Engineering")
      employees += Employee(2022-09-20, "Dave", "Operations")

      // === SORT BY HIRE DATE (field declaration order) ===

      sorted <- cat employees | sort | collect as List of Employee
      stdout.println("Employees by seniority:")
      cat sorted > stdout

      // === MOST SENIOR (earliest hire date) ===

      mostSenior <- cat employees | sort | head 1 | collect as List of Employee
      stdout.println("Most senior:")
      cat mostSenior > stdout

      // === NEWEST HIRES ===

      newest <- cat employees | sort | tail 2 | collect as List of Employee
      stdout.println("Newest hires:")
      cat newest > stdout

      // === COMPARE TWO EMPLOYEES ===

      alice <- Employee(2024-06-15, "Alice", "Engineering")
      bob <- Employee(2023-01-10, "Bob", "Marketing")
      if bob < alice
        stdout.println("Bob was hired before Alice")

Common mistakes

E06820 — The 'default operator' must be the LAST declaration in the record body. Placing fields or methods after it triggers E06820. See ek9 -h E06820 for details.

Incorrect:

default operator
      department as String: String()

      (fields after default operator)

Correct:

      default operator

  defines program

Other ways to ask this

Create an Employee record with a Date field and sort a list of employees chronologically.
I need to define an employee type and order employees by when they were hired.
In Java I'd use Comparator.comparing(Employee::getHireDate). How does EK9 sort by a date field?
Build an Employee record with hire date and use a stream pipeline to sort by seniority.

Coming from another language?

Java: employees.stream().sorted(Comparator.comparing(Employee::getHireDate)). Python: sorted(employees, key=lambda e: e.hire_date). Rust: sort_by_key(|e| e.hire_date). Go: sort.Slice with custom less. EK9: declare hireDate first + default operator + cat | sort | collect.

Keywords: seniority, sort, default operator, hire date, chronological, stream, field order, employee, date, record