Iterator Pattern

• Make a Class Iterable
• Use with For Each Loops
• Act Like a Collection

Iterator

• Class to Keep Track of Location
• Typically Includes next Method
• Defined Way To Find End
• Other Methods May Be Included

Iterable Interface

class CrayonBox implements Iterable[Crayon]:

    List[Crayon] contents

    function addCrayon(Crayon c):
        contents.add(c)

    function getIterator():
        return contents.getIterator()

    function get(int i):
        return contents[i]

    function contains(Crayon c):
        return contents.contains(c)

    function size():
        return contents.size()
    

Using an Iterable

class Main:

    function main():
        CrayonBox box = CrayonBoxFactorySingleton.getInstance().getBox(16)
        //get iterator and print
        for Crayon c in box:
            print(c.color)
    

Iterator Pattern

• Offload Most of Work to Underlying Collection
• Implement Helpful Collection Methods
• Don't Reinvent the Wheel

Template Method Pattern

• Define Method Structure in Parent
• Override Portions in Child
• Same Basic Steps, Different Details

Parent Class

abstract class Recipe:

    function bakeSomething():
        gatherIngredients()
        combineIngredients()
        putInOven()

    abstract function gatherIngredients()
    abstract function combineIngredients()
    abstract function putInOven()
    

Child Class

class Cake inherits Recipe:

    function gatherIngredients():
        getFlour()
        getSugar()
        getEggs()
        getButter()

    function combineIngredients()
        creamEggsAndButter()
        addSugar()
        addFlour()

    function putInOven()
        setOven(350)
        setTimer(30)