Step 6 - Send messages

In this step, you learn how to send messages from a Lua script.

You first create a function that checks whether the puzzle is solved and then add the functionality to show a message when the puzzle is solved.

Detect a solved puzzle

To detect a solved puzzle:

1. Define a function that checks whether the puzzle is solved before you define the movePieceMessageHandler.

   -- Declare a function that checks for the victory condition.
   local function checkForVictory()
       -- Count the number of pieces in a wrong position.
       local misplacedCount = 0
       for i = 0,PieceCount-1 do
           local piece = grid:getChild(i)
           local row = piece:getProperty(GridLayout2D.RowProperty)
           local column = piece:getProperty(GridLayout2D.ColumnProperty)
           local expectedRow = i // ColumnCount
           local expectedColumn = i % ColumnCount
           if row ~= expectedRow or column ~= expectedColumn then
               misplacedCount = misplacedCount + 1
           end
       end
   
       if misplacedCount == 0 then
           print("Victory!")
       end
   end
   

2. Call the function at the end of the movePieceMessageHandler message handler.

   local function movePieceMessageHandler(args)
   
       ...
   
       checkForVictory()
   end
   

Now when you solve the puzzle, the script prints Victory! to the Log. Send a message ————–

To send a message:

1. Use the VictoryMessage message type that is defined in the Kanzi Studio project.

   In the script, initialize the variable next to other variables.

   

   -- Find the "fifteen_puzzle.VictoryMessage" custom message type.
   local VictoryMessage = MessageType:new("fifteen_puzzle.VictoryMessage")
   

2. Modify the checkForVictory function so that after it prints a message to the Log, the function sends the VictoryMessage to the Grid node.

   The Grid node uses a VictoryMessage trigger to set the Victory Overlay State Manager to the Visible state that shows the victory message.

   Create the message arguments with VictoryMessage:newMessageArguments() and send the message to a node with the dispatchMessage member function.

   local function checkForVictory()
   
   ...
   
       if misplacedCount == 0 then
           print("Victory!")
   
           -- Send a VictoryMessage to the grid node.
           local args = VictoryMessage:newMessageArguments()
           grid:dispatchMessage(VictoryMessage, args)
       end
   end
   

Now the Lua script contains the complete game logic that:

• Fills the grid with pieces in random order.

• Reacts to input messages by moving the pieces according to the puzzle logic.

• Detects when the puzzle is solved and reacts by sending a message that displays the victory message in the application.

Previous step

What’s next?

In this tutorial, you learned the basics of programming application logic in Kanzi with Lua.

To learn more about:

• Using Kanzi Engine Lua API in Kanzi Studio, see Using Lua.

• Kanzi functions that you can use in a Kanzi Lua script, see Kanzi Lua API reference.

• The Lua programming language, see https://www.lua.org/manual/5.4/.