How do I create a class with a constructor and methods in EK9?

← Classes and OOP · Ref: Q874

Classes have private fields (initialised with '<-'), constructors, and methods. Fields are always private in classes. Use ':=:' (copy) to assign constructor parameters to fields. Add 'default operator ?' at the end for the isSet check.

See Q93 for class basics. See Q94 for constructors. See Q96 for operators. Use 'ek9 -h class' for syntax.

Example

defines module qa.classes.with.methods

  defines class

    BankAccount
      ownerName <- String()
      balance <- 0.0

      BankAccount()
        ->
          owner as String
          initialBalance as Float
        ownerName :=: owner
        balance :=: initialBalance

      deposit()
        -> amount as Float
        balance += amount

      getBalance()
        <- rtn as Float: Float(balance)

      describe()
        <- rtn as String: `${ownerName}: balance ${balance}`

      default operator ?

  defines program

    BankDemo()
      stdout <- Stdout()

      account <- BankAccount("Steve", 100.0)
      account.deposit(50.0)

      if account?
        stdout.println(account.describe())
        stdout.println(`Balance: ${account.getBalance()}`)

Other ways to ask this

Show me a basic EK9 class with state and behaviour
How do I define a class with fields and methods?
EK9 class example with constructor

Coming from another language?

Java: public/private fields. Python: self.field. Kotlin: data class. EK9: fields always private, '<-' initialises, ':=:' copies.

Keywords: private, class, behaviour, field, constructor, state, method