Select Case Not working as expected (Code specific)

Question

I have a while loop displaying an array of graphnodes (using a function that returns a char in the graphnodes to display) followed by a 'move' procedure that moves a "Creature" from one node to the other. The creature decides where to go by pressing 'W', 'A', 'S', or 'D' which then deoccupies (using a function called 'deoccupy') the graphnode from the creature and puts that creature into the graphnode in the direction the creature wants to move.

I've tried throwing some errors pretty much everywhere and using trycatch to interrupt code that isn't working and I didn't get any errors. I added a case else to the movement "Select Case" statement.

    While True
        Try
            Console.SetCursorPosition(0, 0)
            myMap.ShowMap()
            myMap.MoveCreatures()
        Catch ex As Exception
            Console.Clear()
            Console.WriteLine(ex.Message)
            Console.ReadKey(True)
        End Try
    End While

    Public Sub MoveCreatures()
        For y = 0 To tiles.GetLength(1) - 1
            For x = 0 To tiles.GetLength(0) - 1
                If tiles(x, y).IsOccupied Then
                    tiles(x, y).MoveCreature()
                End If
            Next
        Next

    Public Sub MoveCreature() Implements ITile.MoveCreature
        If Occupied = True Then
            Creature.Action(Me)
        Else
            Throw New Exception("No creature to move here.")
        End If
    End Sub

    Select Case Console.ReadKey(True).KeyChar
        Case "w"
            If currentTile.North IsNot Nothing Then
                currentTile.North.Occupy(currentTile.Deoccupy)
            Else
                Throw New Exception("Can't go in this direction!")
            End If
        Case "a"
            If currentTile.West IsNot Nothing Then
                currentTile.West.Occupy(currentTile.Deoccupy)
            Else
                Throw New Exception("Can't go in this direction!")
            End If
        ...

The code is the same for 'S' and 'D' minus the directions change. E.g. 'S' has

currentTile.South

When the creature moves in 'W' or 'D', it does not redisplay the map until I press another key, whereas when it moves in 'A' or 'S', it refreshes the map right away. I want it to refresh the map any time I press any of 'W', 'A', 'S', or 'D'.

P.S. Sorry for putting so much code.

You are testing a Char against strings. Change your strings to Chars: `"w"c`, `"a"c`, etc. — djv, Jul 09 '19 at 18:33
Thank you for the help, I'll try that asap and if it doesn't work I'll put more code up hopefully it'll help identify the error. — Kijilas, Jul 09 '19 at 18:44
Can you put a breakpoint on all places that calls ReadKey and see if it hangs somewhere. — the_lotus, Jul 09 '19 at 18:45

score 2 · Accepted Answer · answered Jul 09 '19 at 18:45

While True is a C# workaround as they cannot create endless loops. In VB simply use Do Loop instead:

    Do
        Try
            Console.SetCursorPosition(0, 0)
            myMap.ShowMap()
            myMap.MoveCreatures()
        Catch ex As Exception
            Console.Clear()
            Console.WriteLine(ex.Message)
            Console.ReadKey(True)
        End Try
    Loop

I guess the problem lies in method

Public Sub MoveCreatures()
    For y = 0 To tiles.GetLength(1) - 1
        For x = 0 To tiles.GetLength(0) - 1
            If tiles(x, y).IsOccupied Then
                tiles(x, y).MoveCreature()
            End If
        Next
    Next

as you do not exit the function when you have found the occupied cell, depending in what direction you move tiles(x, y).IsOccupied is true again before the method is finished and myMap.ShowMap() is called. It also looks quite inefficient to me - why don't you track the current position of the creature(s) instead of looping through the whole grid, e.g. within the creature object?

This was helpful, thank you I realised that I missed out the piece of code that actually checks if the creature has already moved and so I put that in and it was fixed. As for tracking the creatures, I couldn't think of an efficient method to do so that I knew of and I figured if I just looped through the grid, when I have 100 creatures in it I won't have to track all of them. However if it would be more efficient to do so even with 100 (or maybe more) creatures, I'll look into that more. — Kijilas, Jul 09 '19 at 20:22

Select Case Not working as expected (Code specific)

1 Answers1