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Redesign of decorator pattern #12

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6b956fa
Redesign of decorator pattern
srgtrujillo Mar 15, 2017
45f69a1
Remove unnecessary asserts
srgtrujillo Mar 15, 2017
5be0c75
Using `by` keyword with IngredientDecorator
Cotel Mar 15, 2017
b31714e
Improve Decorator Pattern design
srgtrujillo Mar 15, 2017
12ba9ba
Extract the variable COST from the constructor to an immutable constant
srgtrujillo Mar 21, 2017
9177395
Remove unnecessary override of function calculateTotalCost() in Ingre…
srgtrujillo Mar 21, 2017
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10 changes: 6 additions & 4 deletions src/main/kotlin/Command/base/Cart.kt
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@@ -1,14 +1,12 @@
package Command.base

import Decorator.littlekai.base.IngredientDecorator
import Decorator.littlekai.base.Noodles
import Decorator.littlekai.base.SauceDecorator
import Decorator.littlekai.ingredients.Chicken
import Decorator.littlekai.ingredients.Peanuts
import Decorator.littlekai.ingredients.Pork
import Decorator.littlekai.ingredients.Tuna
import Decorator.littlekai.noodles.EggNoodles
import Decorator.littlekai.noodles.UdonNoodles
import Decorator.littlekai.noodles.WheatNoodles
import Decorator.littlekai.sauces.BittersweetSauce
import Decorator.littlekai.sauces.RedPepperSauce
import Decorator.littlekai.sauces.SateSauce
Expand Down Expand Up @@ -79,7 +77,11 @@ open class Cart(private val scanner: Scanner) {
}

fun showPrice() {
println("> Your order is: ${noodles.calculateCost()} $")
var totalCost = noodles.calculateCost()
if (noodles is IngredientDecorator) {
totalCost = (noodles as IngredientDecorator).calculateTotalCost()
}
println("> Your order is: $totalCost $")
if (noodles is SauceDecorator) {
println("> Spiciness is: ${(noodles as SauceDecorator).SPICINESS} out of 4")
} else {
Expand Down
6 changes: 2 additions & 4 deletions src/main/kotlin/Decorator/littlekai/base/IngredientDecorator.kt
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@@ -1,7 +1,5 @@
package Decorator.littlekai.base

abstract class IngredientDecorator (private val noodles: Noodles) : Noodles by noodles {
protected abstract val COST : Double

override fun calculateCost(): Double = noodles.calculateCost() + this.COST
abstract class IngredientDecorator (private val noodles: Noodles): Noodles by noodles {
override fun calculateTotalCost(): Double = noodles.calculateTotalCost()
}
3 changes: 2 additions & 1 deletion src/main/kotlin/Decorator/littlekai/base/Noodles.kt
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@@ -1,5 +1,6 @@
package Decorator.littlekai.base

interface Noodles {
fun calculateCost() : Double
fun calculateCost(): Double
fun calculateTotalCost(): Double
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Then IngredientDecorator is not adding any behaviour 😵

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I think with the fact of implementing the decorator function in each concrete case, it's already adding behaviour. What do you think about it?

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But If Noodles already has a method calculateTotalCost() then, every child that implements it modifies its behaviour. Noodles shouldn't have that method, it belongs to IngredientDecorator and the concrete decorators which will add that behaviour to Noodles.

}
2 changes: 1 addition & 1 deletion src/main/kotlin/Decorator/littlekai/base/SauceDecorator.kt
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@@ -1,5 +1,5 @@
package Decorator.littlekai.base

abstract class SauceDecorator(private val noodles: Noodles) : Noodles by noodles {
abstract class SauceDecorator(private val noodles: Noodles): Noodles by noodles {
abstract val SPICINESS: Int
}
4 changes: 2 additions & 2 deletions src/main/kotlin/Decorator/littlekai/ingredients/Chicken.kt
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Expand Up @@ -4,6 +4,6 @@ import Decorator.littlekai.base.IngredientDecorator
import Decorator.littlekai.base.Noodles


class Chicken(noodles: Noodles) : IngredientDecorator(noodles) {
override val COST: Double = 3.50
class Chicken(noodles: Noodles, val COST: Double = 3.50): IngredientDecorator(noodles) {
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COST is a constant. It shouln't go in the constructor because you are opening it to change and we are not interested in that.

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I think the keyword val make the constant COST inmutable.

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But you are placing the declaration in the constructor. You are giving the opportunity to set another COST when making a new instance.

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I've done some tests and you're right. I have extracted the COST variable from the constructor to an immutable constant.

override fun calculateTotalCost(): Double = super.calculateTotalCost() + COST
}
4 changes: 2 additions & 2 deletions src/main/kotlin/Decorator/littlekai/ingredients/Peanuts.kt
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Expand Up @@ -4,6 +4,6 @@ import Decorator.littlekai.base.IngredientDecorator
import Decorator.littlekai.base.Noodles


class Peanuts(noodles: Noodles) : IngredientDecorator(noodles) {
override val COST: Double = 2.50
class Peanuts(noodles: Noodles, val COST: Double = 2.50): IngredientDecorator(noodles) {
override fun calculateTotalCost(): Double = super.calculateTotalCost() + COST
}
4 changes: 2 additions & 2 deletions src/main/kotlin/Decorator/littlekai/ingredients/Pork.kt
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Expand Up @@ -4,6 +4,6 @@ import Decorator.littlekai.base.IngredientDecorator
import Decorator.littlekai.base.Noodles


class Pork(noodles: Noodles) : IngredientDecorator(noodles) {
override val COST: Double = 4.00
class Pork(noodles: Noodles, val COST: Double = 4.00): IngredientDecorator(noodles) {
override fun calculateTotalCost(): Double = super.calculateTotalCost() + COST
}
4 changes: 2 additions & 2 deletions src/main/kotlin/Decorator/littlekai/ingredients/Tuna.kt
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Expand Up @@ -4,6 +4,6 @@ import Decorator.littlekai.base.IngredientDecorator
import Decorator.littlekai.base.Noodles


class Tuna(noodles: Noodles) : IngredientDecorator(noodles) {
override val COST: Double = 2.75
class Tuna(noodles: Noodles, val COST: Double = 2.75): IngredientDecorator(noodles) {
override fun calculateTotalCost(): Double = super.calculateTotalCost() + COST
}
7 changes: 3 additions & 4 deletions src/main/kotlin/Decorator/littlekai/noodles/EggNoodles.kt
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Expand Up @@ -2,8 +2,7 @@ package Decorator.littlekai.noodles

import Decorator.littlekai.base.Noodles

class EggNoodles : Noodles {
private val COST : Double = 3.75

override fun calculateCost(): Double = this.COST
class EggNoodles(val COST: Double = 3.75): Noodles {
override fun calculateCost(): Double = COST
override fun calculateTotalCost(): Double = COST
}
7 changes: 3 additions & 4 deletions src/main/kotlin/Decorator/littlekai/noodles/UdonNoodles.kt
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Expand Up @@ -2,8 +2,7 @@ package Decorator.littlekai.noodles

import Decorator.littlekai.base.Noodles

class UdonNoodles : Noodles {
private val COST : Double = 4.00

override fun calculateCost(): Double = this.COST
class UdonNoodles(val COST: Double = 4.00): Noodles {
override fun calculateCost(): Double = COST
override fun calculateTotalCost(): Double = COST
}
7 changes: 3 additions & 4 deletions src/main/kotlin/Decorator/littlekai/noodles/WheatNoodles.kt
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Expand Up @@ -2,8 +2,7 @@ package Decorator.littlekai.noodles

import Decorator.littlekai.base.Noodles

class WheatNoodles : Noodles {
private val COST : Double = 3.50

override fun calculateCost(): Double = this.COST
class WheatNoodles(val COST: Double = 3.50): Noodles {
override fun calculateCost(): Double = COST
override fun calculateTotalCost(): Double = COST
}
2 changes: 1 addition & 1 deletion src/main/kotlin/Decorator/littlekai/sauces/BittersweetSauce.kt
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Expand Up @@ -3,7 +3,7 @@ package Decorator.littlekai.sauces
import Decorator.littlekai.base.Noodles
import Decorator.littlekai.base.SauceDecorator

class BittersweetSauce(noodles: Noodles) : SauceDecorator(noodles) {
class BittersweetSauce(noodles: Noodles): SauceDecorator(noodles) {
override val SPICINESS: Int = 1
}

Expand Down
2 changes: 1 addition & 1 deletion src/main/kotlin/Decorator/littlekai/sauces/RedPepperSauce.kt
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Expand Up @@ -4,6 +4,6 @@ import Decorator.littlekai.base.Noodles
import Decorator.littlekai.base.SauceDecorator


class RedPepperSauce(noodles: Noodles) : SauceDecorator(noodles) {
class RedPepperSauce(noodles: Noodles): SauceDecorator(noodles) {
override val SPICINESS: Int = 4
}
2 changes: 1 addition & 1 deletion src/main/kotlin/Decorator/littlekai/sauces/SateSauce.kt
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Expand Up @@ -3,6 +3,6 @@ package Decorator.littlekai.sauces
import Decorator.littlekai.base.Noodles
import Decorator.littlekai.base.SauceDecorator

class SateSauce(noodles: Noodles) : SauceDecorator(noodles) {
class SateSauce(noodles: Noodles): SauceDecorator(noodles) {
override val SPICINESS: Int = 2
}
2 changes: 1 addition & 1 deletion src/main/kotlin/Decorator/littlekai/sauces/TeriyakiSauce.kt
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Expand Up @@ -4,6 +4,6 @@ import Decorator.littlekai.base.Noodles
import Decorator.littlekai.base.SauceDecorator


class TeriyakiSauce(noodles: Noodles) : SauceDecorator(noodles) {
class TeriyakiSauce(noodles: Noodles): SauceDecorator(noodles) {
override val SPICINESS: Int = 0
}
30 changes: 17 additions & 13 deletions src/test/kotlin/Decorator/littlekai/base/IngredientDecoratorTest.kt
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@@ -1,31 +1,35 @@
package Decorator.littlekai.base

import Decorator.littlekai.ingredients.Chicken
import Decorator.littlekai.ingredients.Peanuts
import Decorator.littlekai.ingredients.Pork
import Decorator.littlekai.ingredients.Tuna
import Decorator.littlekai.noodles.EggNoodles
import Decorator.littlekai.noodles.UdonNoodles
import Decorator.littlekai.noodles.WheatNoodles
import org.hamcrest.CoreMatchers.`is`
import org.junit.Assert.assertThat
import Decorator.littlekai.sauces.BittersweetSauce
import org.junit.Assert.assertTrue
import org.junit.Test

class IngredientDecoratorTest {

@Test
fun `check if decorated element is still Noodles`() =
assertTrue(Pork(UdonNoodles()) is Noodles) //:+1:
fun `has the same interface`() =
assertTrue(BittersweetSauce(Chicken(EggNoodles())) is Noodles)

@Test
fun `Ingredient Decorator should return ingredient cost plus base noodle cost`() =
assertThat(Pork(UdonNoodles()).calculateCost(), `is`(8.00))
fun `does not modify behavior`() =
assertTrue(EggNoodles().calculateCost() == BittersweetSauce(Chicken(EggNoodles())).calculateCost())

@Test
fun `check decorated Noodles is of type IngredientDecorator`() =
assertTrue(Tuna(UdonNoodles()) is IngredientDecorator)
fun `adds behavior`() =
assertTrue(Chicken(EggNoodles()).calculateTotalCost() == EggNoodles().calculateCost() + Chicken(EggNoodles()).COST)

@Test
fun `price of ingredient is calculated correctly`() =
assertThat(Tuna(Pork(UdonNoodles())).calculateCost(), `is`(10.75))

fun `is stackable`() =
assertTrue(
Tuna(Pork(Peanuts(Chicken(EggNoodles())))).calculateTotalCost() ==
EggNoodles().COST +
Chicken(EggNoodles()).COST +
Peanuts(EggNoodles()).COST +
Pork(EggNoodles()).COST +
Tuna(EggNoodles()).COST)
}