Time for action – updating and drawing shots

1. Add the Update() method to the ShotManager class:

   Public Sub Update(gameTime As GameTime)
       For x As Integer = Shots.Count - 1 to 0 Step -1
           Shots(x).Update(gameTime)
           If Not _screenBounds.Intersects(Shots(x).Destination) Then
               Shots.RemoveAt(x)
           End If
       Next
   End Sub

2. Add the Draw() method to the ShotManager class:

   Public Sub Draw(spriteBatch As SpriteBatch)
       For Each shot As Sprite in Shots
           shot.Draw(spriteBatch)
       Next
   End Sub

What just happened?

Since we may be removing shots from the list, we cannot use a For Each loop to process the list during the Update() method—as we saw in Flood Control, items cannot be deleted from a List, while a For Each loop is processing the List. Looping backwards through the list, allows us to process all of the shots, removing ones that have expired, without the need to track separate removal lists or restart the iteration after each removal.

After an individual shot...