started work on place obj

Assets/Scripts/Grid/GridBuildingSystem.cs

@@ -0,0 +1,57 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+public class GridBuildingSystem : MonoBehaviour
+{
+    [SerializeField] Transform testTransform;
+
+    Grid<GridObject> grid;
+    void Awake()
+    {
+        int gridWidth = 20;
+        int gridHeight = 20;
+        float cellSize = 2f;
+
+        grid = new Grid<GridObject>(gridWidth, gridHeight, cellSize, Vector3.zero, (Grid<GridObject> g, int x, int y) => new GridObject(g, x, y));
+    }
+    public class GridObject
+    {
+        int x, y;
+        Grid<GridObject> grid;
+        Transform transform;
+        public GridObject(Grid<GridObject> _grid, int _x, int _y)
+        {
+            grid = _grid;
+            x = _x;
+            y = _y;
+        }
+        public void SetTransform(Transform _transform) => transform = _transform;
+        public Transform GetTransform() => transform;
+        public void ClearTransform() => transform = null;
+
+        public bool CanBuild()
+        {
+            return transform == null;
+        }
+    }
+    void Update()
+    {
+        if (Input.GetMouseButtonDown(0))
+        {
+            Vector3 mousePosition = new Vector3(Camera.main.ScreenToWorldPoint(Input.mousePosition).x, Camera.main.ScreenToWorldPoint(Input.mousePosition).y);
+            grid.GetXY(mousePosition, out int x, out int y);
+
+            GridObject gridObject = grid.GetGridObject(x, y);
+            if (gridObject.CanBuild())
+            {
+                Transform builtTransform = Instantiate(testTransform, grid.GetWorldPosition(x, y), Quaternion.identity);
+                gridObject.SetTransform(builtTransform);
+            }
+            else
+            {
+                Debug.Log("Cannot build here!" + " " + mousePosition);
+            }
+        }
+    }
+}