设计模式 学习笔记 建造者模式

建造者模式使用多个简单的对象一步一步构建成一个复杂的对象。例如去肯德基，汉堡、可乐、炸鸡、薯条等是不会变，而其组合是经常变化的，生成出所谓的“套餐”，这种方式的优点是建造者独立，易扩展、便于控制细节风险。缺点是产品必须有共同点，范围有限制，如内部变化复杂，会有很多的建造类。这种模式与工厂模式的区别是：建造者模式更加关注与零件装配的顺序

例：

interface Item {
    fun name(): String
    fun Packing(): Packing
    fun price(): Float
}
interface Packing {
    fun pack(): String
}
class Wrapper : Packing{
    override fun pack(): String {
        return "Wrapper"
    }
}
class Bottle: Packing{
    override fun pack(): String {
        return "Bottle"
    }
}
abstract class Burger: Item{
    override fun Packing(): Packing {
        return Wrapper()
    }
}
abstract class ColdDrink: Item{
    override fun Packing(): Packing {
        return Bottle()
    }
}
class VegBurger: Burger() {
    override fun name(): String {
        return "Veg Burger"
    }

    override fun price(): Float {
        return 25.0f
    }

}
class ChickenBurger: Burger(){
    override fun name(): String {
        return "Chicken Burger"
    }

    override fun price(): Float {
        return 50.0f
    }
}
class Coke: ColdDrink(){
    override fun name(): String {
        return "Coke"
    }

    override fun price(): Float {
        return 30.0f
    }
}

class Pepsi: ColdDrink(){
    override fun name(): String {
        return "Pepsi"
    }

    override fun price(): Float {
        return 35.0f
    }

}
class Meal {
    private var items: MutableList = mutableListOf()
    fun addItem(item: Item){
        items.add(item)
    }
    fun getCosat(): Float{
        var cost = 0f
        for(item in items){
            cost += item.price()
        }
        return cost
    }
    fun showItems(){
        for(item in items){
            println("Item: ${item.name()},Packing: ${item.Packing().pack()},Price: ${item.price()}")
        }
    }
}

class MealBuilder{
    fun prepareVegMeal(): Meal{
        val meal = Meal()
        meal.addItem(VegBurger())
        meal.addItem(Coke())
        return meal
    }

    fun prepareNonVegMeal(): Meal{
        val meal = Meal()
        meal.addItem(ChickenBurger())
        meal.addItem(Pepsi())
        return meal
    }
}
fun main(){
    val mealBuilder = MealBuilder()
    val vegMeal = mealBuilder.prepareVegMeal()
    vegMeal.showItems()
    println(vegMeal.getCosat())
    val nonMeal = mealBuilder.prepareNonVegMeal()
    nonMeal.showItems()
    println(nonMeal.getCosat())
}