Deserializing an object with other objects in it - json

Question

I'm making a two-player game of chess played on the command line. I have a class for every type of chess piece and a board class. The board class looks like this:
class Board
attr_accessor :board, :choice
def initialize
#board = Array.new(8){Array.new(8," ")}
#choice = choice
end
end
My other classes look like this:
class Bishop
attr_accessor :x_position, :y_position, :piece, :color, :counter, :moves
def initialize(position,boolean)
#x_position = position[0]
#y_position = position[1]
#piece = boolean ? "♝" : "♗"
#color = boolean ? "white" : "black"
#counter = 0
#moves = [[+1,-1],
[+1,+1],
[-1,+1],
[-1,-1]]
end
I added my pieces to the board like this:
#board[0][0] = Rook.new([0,0],false)
These are my methods to serialize and deserialize the data:
def to_json
JSON.generate({board: #board})
end
def save_game(string)
File.open("saved.json", "w") do |game_file|
game_file.write(string)
end
end
def load_game
game_file = File.read("saved.json")
data = JSON.parse(game_file)
#board = data["board"]
end
After saving, the saved.json file looks like this:
{"board":[[" ","#<Knight:0x00000000e4fc28>","#<Bishop:0x00000000e4fa20>","#<Queen:0x00000000e4f890>","#<King:0x00000000e4f610>","#<Bishop:0x00000000e4f3e0>","#<Knight:0x00000000e4f278>","#<Rook:0x00000000e4e1c0>"],[" "," "," "," "," "," "," "," "],[" "," "," "," "," "," "," "," "],[" "," "," "," "," "," "," "," "],[" "," "," "," "," "," "," "," "],[" "," "," "," "," "," "," "," "],[" "," "," "," "," "," "," "," "],["#<Rook:0x00000000e4fd90>","#<Knight:0x00000000e4ed78>","#<Bishop:0x00000000e4eb70>","#<Queen:0x00000000e4ea08>","#<King:0x00000000e4e7b0>","#<Bishop:0x00000000e4e580>","#<Knight:0x00000000e4e3f0>"," "]]}
When I try to load back the data, the method that displays the board throws this error:
0 1 2 3 4 5 6 7
+----+----+----+----+----+----+----+----+
0|   /home/jacob/Desktop/chess/board.rb:30:in `block (2 levels) in display': undefined method `piece' for "#<Knight:0x00000000e4fc28>":String (NoMethodError)
from /home/jacob/Desktop/chess/board.rb:27:in `each'
from /home/jacob/Desktop/chess/board.rb:27:in `each_with_index'
from /home/jacob/Desktop/chess/board.rb:27:in `block in display'
from /home/jacob/Desktop/chess/board.rb:20:in `each'
from /home/jacob/Desktop/chess/board.rb:20:in `each_with_index'
It looks like my problem is that the objects come back as strings?
my display method:
def display
axis = 0
print " 0 1 2 3 4 5 6 7"
#board.each_with_index do |row,index|
print "\n"
#draw = " +----+----+----+----+----+----+----+----+"
puts #draw
print axis
axis +=1
if index.even?
row.each_with_index do|column,i|
if i.odd?
if column != " "
print "|"+" #{column.piece} ".bruno
else print "|"+" #{column} ".bruno
end
else
if column != " "
print "|"+" #{column.piece} "
else print "|"+" #{column} "
end
end
end
else
row.each_with_index do|column,j|
if j.even?
if column != " "
print "|"+" #{column.piece} ".bruno
else print "|"+" #{column} ".bruno
end
else
if column != " "
print "|"+" #{column.piece} "
else print "|"+" #{column} "
end
end
end
end
print "|"
end
print "\n"
print #draw
end

Answer 1

No, the problem is that your objects are saved as strings. Deserialization works fine, in this case. You'll have to explicitly specify what should be the json representation of your game pieces. Something like this:
class Rook
def to_json(*)
{ name: 'rook', position: 'A1', status: 'in_game' }.to_json
end
end
pieces = [Rook.new]
pieces.to_json # => "[{\"name\":\"rook\",\"position\":\"A1\",\"status\":\"in_game\"}]"
JSON.parse(pieces.to_json) # => [{"name"=>"rook", "position"=>"A1", "status"=>"in_game"}]
On deserialization you'll have to do the reverse. Construct proper game classes from plain ruby hashes, which you get from parsing JSON file.
Or if you don't actually care about JSON and just want to create some form of save file, then Marshal is your best friend. No need to override anything. Zero friction.
pieces = [Rook.new]
Marshal.dump(pieces) # => "\x04\b[\x06o:\tRook\x00" # write this to a file
# restore it later
Marshal.load("\x04\b[\x06o:\tRook\x00") # => [#<Rook:0x007fb50f825570>]