Structures and classes | ZPE/YASS documentation

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A structure is a data type in which many inner values can be specified. It provides a framework for all variables and functions.

YASS

structure person

  $name = null
  $age = 0
  $email = null

  function set_values($n, $a, $e)
    $name = $n
    $age = $a
    $email = $e
  end function

end structure

Instead of the full word structure being used, the keyword struct may be used.

A structure must be declared using the new or copyof keywords.

Variables and internal functions can be accessed using the object pointer literal, ->, as shown below:

YASS

function main($args)
  $s = new person()
  $t = copyof person()

  //Run an internal function within a structure
  $t->set_values("Jack", 20, "[email protected]")
  //Obtain and print a variable from a structure
  print($t->$name)
  //Set a variable in a structure
  $t->$name = "Joseph"
end function

Prior to version 1.5.3, the object pointer literal was called the pointer literal and was represented by => (fat arrow). The fat arrow was moved to association using maps and associative arrays.

Structures may also be constructed with parameters as of version 1.5.2 of ZPE. The important thing is that they have a function named _construct:

YASS

structure person

  $name = null
  $age = 0
  $email = null

  function _construct($n, $a, $e)
    $name = $n
    $age = $a
    $email = $e
  end function

end structure

function main($args)
  $p = new person("John", 20, "[email protected]")
end function

YASS

structure Person

  $name = null
  $age = 0
  $email = null

  function _output()
    return $name & " " & $age
  end function

end structure

Remember, in ZPE, structures are templates or prototypes for new objects and objects are the instantiated versions of these structures.

There are other special functions that can be used within an object such as the _output or the _compare functions:

YASS

structure Person

  $name = null
  $age = 0
  $email = null

  function _construct($n, $a, $e)
    $name = $n
    $age = $a
    $email = $e
  end function

  function _output()
      return this->$name & "(" & this->$email & ")"
  end function

  function _compare($o)
    return $o->$name == this->$name
  end function

end structure

function main($args)
  $p1 = new Person("John", 20, "[email protected]")
  $p2 = new Person("John", 48, "[email protected]")

  //Will return true
  print($p1 == $p2)
end function

Version 1.6.4 of ZPE added ZPEObjectNativeFunctions as an option which allows functions defined within Java to add native Java-based function calls on objects.

Inheritance

Object inheritance is a major part of object oriented programming. ZPE performs late object inheritance in that it is done at runtime. This has a slight performance hit but saves over adding more properties to a single structure.

YASS

structure Animal

  $type = "Animal"

  function _output()
      return this->$type
  end function

end structure

structure Person inherits Animal

  $name = null

  //Using the name of the structure as the function turns the function into a constructor as of version 1.8.5
  function Person($n)
    $name = $n
    this->$type = "Human"
  end function

end structure

function main($args)
  $p1 = new Person("Johnny Baxter")
  $p2 = new Person("Nick Harding")

  //Will return Human both times
  print($p1)
  print($p2)
end function