Spawning a object on touch position when area is free.

Currently im trying to make it so i can Instatiate a object on the screen where i click on the screen that i have manage do do. Now im wondering how would i go about saying "If this object is in the way .. or if this gui button is being pressed don't create a object) some kind of collision in code that detects this. Its hard to explain but i hope you get what i mean.

Code (CSharp):

1. public void AddSquare(){
2.         //Find the vector 3 of the postion in the world of the screen for finding mouse input location
3.         Vector3 a = Camera.main.ScreenToWorldPoint (new Vector3 (Input.mousePosition.x,Input.mousePosition.y,10));
4.         //Creates a instantiate of the game prefab Square and applys the location from above to its location and sets rotation to default.
5.         SquareInstance = (GameObject) Instantiate (Square, a, Quaternion.identity);
6.         //Increment increase
7.         increase++;
8.         //add's the instance and increments each time by increase to the list
9.         squares.Add (new Squares (increase, "Square" + " " +increase, SquareInstance));
10.         //Sorts the items by there ID
11.         squares.Sort ();
12.      
13.         foreach (Squares square in squares) {
14.             //Prints a list in to the console of the ID and name of a object in list.
15.             print ("ID: " + square.id + " Name: " + square.name);
16.         }
17.     }

Code (CSharp):

1.         if (Input.touchCount==1){
2.  
3. //Do some kinda of collision checking for gui buttons in the way or the ground is in the way? howww?
4.  
5.             //Excutes Add Square
6.             AddSquare();
7.         }

Would it be somthing like

Code (CSharp):

1.         if (Input.touchCount==1){
2.             if (!collider.CompareTag("GUI") && !collider.CompareTag ("Ground")){
3.             //Excutes Add Square
4.             AddSquare();
5.             }

And add the tags to the gui and ground?

 

Look up Raycasts.

 

Ive been thinking about how to check for colisions before placing buildings as well. So i'll use you post, if im allowed to.

Doing 4 vertical top to bottom raycasts in the position of each corner of where the building would be placed, based on mouse position, and checking for map is a good solution? Is there a better way?

 

I should of also mentioned it was a 2D game but will look in to raycasting now and try and understand how it works.

 

How are you placing the objects and are they square?