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Commit d7e868b

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refactored Strategy pattern
1 parent f4159fe commit d7e868b

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2 files changed

+124
-21
lines changed

2 files changed

+124
-21
lines changed

‎src/main/kotlin/design_patterns/Strategy.kt

Lines changed: 65 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -2,35 +2,83 @@ package design_patterns
22

33
/**
44
*
5-
* pattern: Strategy
5+
* Strategy is a behavioral design pattern used to define a family of algorithms,
66
*
7-
* using: used when we need to change the behavior of an object
7+
* encapsulate each one and make them interchangeable
88
*
99
*/
1010

11-
interface ExchangeStrategy {
12-
fun into(price: Double) : Double
11+
// encapsulates the filtering algorithm
12+
interface FoodFilterStrategy {
13+
fun filter(items: List<FoodEntity>): List<FoodEntity>
14+
}
15+
16+
class OnlyChipsFilterStrategy : FoodFilterStrategy {
17+
override fun filter(items: List<FoodEntity>): List<FoodEntity> {
18+
return items.filter { it.category == "chips" }
19+
}
20+
}
21+
22+
class OnlyChocolateFilterStrategy : FoodFilterStrategy {
23+
override fun filter(items: List<FoodEntity>): List<FoodEntity> {
24+
return items.filter { it.category == "chocolate" }
25+
}
26+
}
1327

14-
class Dollar : ExchangeStrategy {
15-
override fun into(price: Double): Double {
16-
return price / 70
17-
}
28+
class PriceFilterStrategy(private val price: Int) : FoodFilterStrategy {
29+
override fun filter(items: List<FoodEntity>): List<FoodEntity> {
30+
return items.filter { it.price >= price }
1831
}
32+
}
1933

20-
class Tenge : ExchangeStrategy {
21-
override fun into(price: Double): Double {
22-
return price * 6
23-
}
34+
class SearchWordFilterStrategy(private val search: String) : FoodFilterStrategy {
35+
override fun filter(items: List<FoodEntity>): List<FoodEntity> {
36+
return items.filter { it.title.contains(search, ignoreCase = true) }
2437
}
2538
}
2639

27-
class RubleExchangeRate {
28-
private var strategy : ExchangeStrategy = ExchangeStrategy.Dollar()
40+
data class FoodEntity(
41+
val title: String,
42+
val price: Int,
43+
val category: String
44+
)
45+
46+
// FoodStore returns a list of food filtered by strategy
47+
class FoodStore(private var filterStrategy: FoodFilterStrategy) {
2948

30-
fun changeStrategy(strategy: ExchangeStrategy) {
31-
this.strategy = strategy
49+
// we can change strategy
50+
fun changeStrategy(strategy: FoodFilterStrategy) {
51+
filterStrategy = strategy
3252
}
3353

34-
fun exchange(priceInRuble: Double) = strategy.into(priceInRuble)
54+
fun foodItems(): List<FoodEntity> {
55+
val foodItems = fetchFoodItems()
56+
return filterStrategy.filter(foodItems)
57+
}
58+
59+
private fun fetchFoodItems() =
60+
listOf(
61+
FoodEntity(
62+
"Lays Potato Chips Fried Crab Flavor",
63+
2,
64+
"chips"
65+
),
66+
FoodEntity(
67+
"Lay's Potato Chips, Classic",
68+
3,
69+
"chips"
70+
),
71+
FoodEntity(
72+
"Dove Chocolate",
73+
3,
74+
"chocolate"
75+
),
76+
FoodEntity(
77+
"Ritter Sport Chocolate",
78+
4,
79+
"chocolate"
80+
)
81+
)
82+
3583
}
3684

‎src/test/kotlin/design_patterns/StrategyTest.kt

Lines changed: 59 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -7,11 +7,66 @@ internal class StrategyTest {
77

88
@Test
99
fun test() {
10-
val exchange = RubleExchangeRate()
11-
assertEquals(1.0, exchange.exchange(70.0), 0.0)
10+
val strategy = OnlyChipsFilterStrategy()
11+
val foodStore =FoodStore(strategy)
1212

13-
exchange.changeStrategy(ExchangeStrategy.Tenge())
14-
assertEquals(60.0, exchange.exchange(10.0), 0.0)
13+
assertEquals(listOf(
14+
FoodEntity(
15+
"Lays Potato Chips Fried Crab Flavor",
16+
2,
17+
"chips"
18+
),
19+
FoodEntity(
20+
"Lay's Potato Chips, Classic",
21+
3,
22+
"chips"
23+
)
24+
), foodStore.foodItems())
25+
26+
foodStore.changeStrategy(OnlyChocolateFilterStrategy())
27+
28+
assertEquals(listOf(
29+
FoodEntity(
30+
"Dove Chocolate",
31+
3,
32+
"chocolate"
33+
),
34+
FoodEntity(
35+
"Ritter Sport Chocolate",
36+
4,
37+
"chocolate"
38+
)
39+
), foodStore.foodItems())
40+
41+
foodStore.changeStrategy(PriceFilterStrategy(3))
42+
43+
assertEquals(listOf(
44+
FoodEntity(
45+
"Lay's Potato Chips, Classic",
46+
3,
47+
"chips"
48+
),
49+
FoodEntity(
50+
"Dove Chocolate",
51+
3,
52+
"chocolate"
53+
),
54+
FoodEntity(
55+
"Ritter Sport Chocolate",
56+
4,
57+
"chocolate"
58+
)
59+
), foodStore.foodItems())
60+
61+
foodStore.changeStrategy(SearchWordFilterStrategy("Ritter Sport"))
62+
63+
assertEquals(listOf(
64+
FoodEntity(
65+
"Ritter Sport Chocolate",
66+
4,
67+
"chocolate"
68+
)
69+
), foodStore.foodItems())
1570
}
1671

1772
}

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