refactor: find 리턴값 수정

app/src/main/java/woowacourse/shopping/data/CartDbRepository.kt

@@ -11,14 +11,14 @@ class CartDbRepository(context: Context) : CartRepository {
         return dbHelper.selectAll()
     }
 
-    private fun find(id: Int): List<CartProduct> {
+    private fun find(id: Int): CartProduct? {
         return dbHelper.selectWhereId(id)
     }
 
     override fun add(id: Int, count: Int) {
-        val cardProducts = find(id)
-        if (cardProducts.isNotEmpty()) {
-            dbHelper.update(id, count + cardProducts[0].count)
+        val cardProduct = find(id)
+        if (cardProduct != null) {
+            dbHelper.update(id, count + cardProduct.count)
             return
         }
         dbHelper.insert(id, count)

app/src/main/java/woowacourse/shopping/data/RecentViewedDbRepository.kt

@@ -13,7 +13,7 @@ class RecentViewedDbRepository(context: Context) :
     }
 
     override fun add(id: Int) {
-        if (find(id).isNotEmpty()) {
+        if (find(id) != null) {
             dbHelper.remove(id)
         }
         if (findAll().size == 10) {
@@ -22,7 +22,7 @@ class RecentViewedDbRepository(context: Context) :
         dbHelper.insert(id)
     }
 
-    private fun find(id: Int): List<Int> {
+    private fun find(id: Int): Int? {
         return dbHelper.selectWhereId(id)
     }
 

app/src/main/java/woowacourse/shopping/data/db/CartDBHelper.kt

@@ -49,16 +49,15 @@ class CartDBHelper(context: Context) : SQLiteOpenHelper(context, "cart", null, 1
         return products
     }
 
-    fun selectWhereId(id: Int): List<CartProduct> {
-        val products = mutableListOf<CartProduct>()
+    fun selectWhereId(id: Int): CartProduct? {
         val sql = "select * from ${CartConstract.TABLE_NAME} where ${CartConstract.TABLE_COLUMN_ID}=$id"
         val cursor = readableDatabase.rawQuery(sql, null)
         while (cursor.moveToNext()) {
             val id = cursor.getInt(cursor.getColumnIndexOrThrow(CartConstract.TABLE_COLUMN_ID))
             val count = cursor.getInt(cursor.getColumnIndexOrThrow(CartConstract.TABLE_COLUMN_COUNT))
-            products.add(CartProduct(id, count))
+            cursor.close()
+            return CartProduct(id, count)
         }
-        cursor.close()
-        return products
+        return null
     }
 }

app/src/main/java/woowacourse/shopping/data/db/RecentViewedDBHelper.kt

@@ -29,16 +29,15 @@ class RecentViewedDBHelper(context: Context) : SQLiteOpenHelper(context, "recent
         writableDatabase.execSQL("DELETE FROM ${RecentViewedContract.TABLE_NAME} WHERE ${RecentViewedContract.TABLE_COLUMN_ID}=$id")
     }
 
-    fun selectWhereId(id: Int): List<Int> {
-        val viewedProducts = mutableListOf<Int>()
+    fun selectWhereId(id: Int): Int? {
         val sql = "select * from ${RecentViewedContract.TABLE_NAME} WHERE ${RecentViewedContract.TABLE_COLUMN_ID}=$id"
         val cursor = readableDatabase.rawQuery(sql, null)
         while (cursor.moveToNext()) {
             val id = cursor.getInt(cursor.getColumnIndexOrThrow(RecentViewedContract.TABLE_COLUMN_ID))
-            viewedProducts.add(id)
+            cursor.close()
+            return id
         }
-        cursor.close()
-        return viewedProducts
+        return null
     }
 
     fun selectAll(): List<Int> {