[악어] 장바구니 미션 제출합니다.

app/src/main/java/nextstep/shoppingcart/data/Cart.kt

@@ -1,52 +1,46 @@
 package nextstep.shoppingcart.data
 
+import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.runtime.snapshots.SnapshotStateList
+import androidx.compose.runtime.toMutableStateList
 import nextstep.shoppingcart.domain.model.CartItem
 import nextstep.shoppingcart.domain.model.Product
 
 object Cart {
-    private val _items: MutableList<CartItem> = mutableListOf()
-    val items: List<CartItem> get() = _items.toList()
+    val items: SnapshotStateList<CartItem> = emptyList<CartItem>().toMutableStateList()
 
-    val totalPrice: Int get() = _items.sumOf { it.totalPrice }
-
-    private var maxCartItemId: Long = 0L
-
-    fun addOne(product: Product): List<CartItem> {
-        val item = _items.find { it.product == product }
-        if (item == null) {
-            _items.add(
-                CartItem(
-                    id = fetchMaxCartItemId(),
-                    product = product,
-                    count = 1,
-                )
-            )
+    val totalPrice = mutableIntStateOf(0)
 
+    fun addOne(product: Product) {
+        val item = items.find { it.product == product }
+        if (item != null) {
+            val index = items.indexOf(item)
+            items[index] = item.copy(count = item.count + 1)
         } else {
-            val index = _items.indexOf(item)
-            _items[index] = item.copy(count = item.count + 1)
+            items.add(CartItem(product = product, count = 1))
         }
-        return items
+        updateState()
     }
 
-    private fun fetchMaxCartItemId(): Long = maxCartItemId++
-
-    fun removeOne(product: Product): List<CartItem> {
-        _items
-            .find { it.product == product }
-            ?.let { item ->
-                if (item.count > 1) {
-                    val index = _items.indexOf(item)
-                    _items[index] = item.copy(count = item.count - 1)
-                } else {
-                    _items.remove(item)
-                }
+    fun removeOne(product: Product) {
+        val item = items.find { it.product == product }
+        if (item != null) {
+            if (item.count > 1) {
+                val index = items.indexOf(item)
+                items[index] = item.copy(count = item.count - 1)
+            } else {
+                items.remove(item)
             }
-        return items
+            updateState()
+        }
+    }
+
+    fun removeAll(product: Product) {
+        items.removeAll { it.product == product }
+        updateState()
     }
 
-    fun removeAll(product: Product): List<CartItem> {
-        _items.removeAll { it.product == product }
-        return items
+    private fun updateState() {
+        totalPrice.value = items.sumOf { it.product.price * it.count }
     }
 }

app/src/main/java/nextstep/shoppingcart/domain/model/CartItem.kt

@@ -1,9 +1,11 @@
 package nextstep.shoppingcart.domain.model
 
 data class CartItem(
-    val id: Long,
+    val id: Long = maxCartItemId++,
     val product: Product,
     val count: Int
 ) {
-    val totalPrice: Int get() = product.price * count
+    companion object {
+        private var maxCartItemId: Long = 0L
+    }
 }

app/src/main/java/nextstep/shoppingcart/presentation/CartActivity.kt

@@ -6,51 +6,33 @@ import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
-import androidx.compose.runtime.setValue
 import nextstep.shoppingcart.data.Cart
-import nextstep.shoppingcart.domain.model.CartItem
+import nextstep.shoppingcart.domain.model.Product
 import nextstep.shoppingcart.presentation.components.screens.CartScreen
 
 class CartActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContent {
-            var cart by remember { mutableStateOf(Cart) }
-            var cartItems by remember { mutableStateOf(Cart.items) }
+            val cartItems = remember { Cart.items }
+            val totalPrice by Cart.totalPrice
             CartScreen(
                 navigation = { finish() },
                 cartItems = cartItems,
-                cart = cart,
-                onIncrease = {
-                    onIncrease(it)
-                    cartItems = Cart.items
-                },
-                onDecrease = {
-                    onDecrease(it)
-                    cartItems = Cart.items
-                },
-                onClear = {
-                    onRemove(it)
-                    cartItems = Cart.items
-                }
+                totalPrice = totalPrice,
+                onIncrease = { addItem(it.product) },
+                onDecrease = { subItem(it.product) },
+                onClear = { removeItem(it.product) }
             )
         }
     }
 
+    private fun addItem(item: Product) = Cart.addOne(item)
 
-    private fun onIncrease(item: CartItem) {
-        Cart.addOne(item.product)
-    }
-
-    private fun onDecrease(item: CartItem) {
-        Cart.removeOne(item.product)
-    }
+    private fun subItem(item: Product) = Cart.removeOne(item)
 
-    private fun onRemove(item: CartItem) {
-        Cart.removeAll(item.product)
-    }
+    private fun removeItem(item: Product) = Cart.removeAll(item)
 
     companion object {
         fun createIntent(context: Context): Intent = Intent(context, CartActivity::class.java)

app/src/main/java/nextstep/shoppingcart/presentation/components/CartItemList.kt

@@ -3,6 +3,7 @@ package nextstep.shoppingcart.presentation.components
 import androidx.compose.foundation.border
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxWidth
@@ -41,6 +42,7 @@ fun CartItemList(
 ) {
     LazyColumn(
         modifier = modifier,
+        contentPadding = PaddingValues(50.dp)
     ) {
         items(
             items = items,

app/src/main/java/nextstep/shoppingcart/presentation/components/screens/CartScreen.kt

@@ -25,13 +25,12 @@ import nextstep.signup.R
 fun CartScreen(
     navigation: () -> Unit,
     cartItems: List<CartItem>,
-    cart: Cart,
+    totalPrice: Int,
     onIncrease: (CartItem) -> Unit = {},
     onDecrease: (CartItem) -> Unit = {},
     onClear: (CartItem) -> Unit = {},
     modifier: Modifier = Modifier,
 ) {
-    val totalPrice = cartItems.sumOf { it.product.price * it.count }
     AndroidshoppingcartTheme {
         Scaffold(
             modifier = modifier,
@@ -93,5 +92,5 @@ private fun CartScreenPreview() {
                 count = 2,
             ),
         )
-    CartScreen(navigation = {}, cartItems = items, cart = Cart)
+    CartScreen(navigation = {}, cartItems = items, totalPrice = items.sumOf { it.product.price * it.count })
 }

app/src/main/java/nextstep/shoppingcart/presentation/components/screens/HomeScreen.kt

@@ -26,7 +26,7 @@ fun HomeScreen(
             ProductList(
                 items = products,
                 onItemClick = onItemClick,
-                modifier = Modifier.padding(top = 18.dp, start = 13.dp, end = 13.dp)
+                modifier = Modifier.padding(top = 8.dp, start = 13.dp, end = 13.dp)
             )
         }
     }