我只是在学习Ruby，并且很难解决这个错误，我读了一些帖子，所有人都说要定义这样的方法......
def self.methodname
我这样做但无济于事。这是我的代码希望这是一个我很想念的简单的事情。谢谢你的帮助。
class Cannibals
@VEGANS = 3
@CANNIBALS = 3
@VEGAN_ID = 0
@CANNIBAL_ID = 1
@EMPTY_ID = 2
@CROSSED_ID = 0
@SHORE_ID = 1
@vegansCrossed=0
@cannibalsCrossed=0
@vegansLeft = @VEGANS
@cannibalsLeft = @CANNIBALS
@boat = [@EMPTY_ID,@EMPTY_ID]
@boatLocation = @SHORE_ID
#/* take an integer as argument1,
# * 0- load 2 cannibals
# * 1- load 2 vegans
# * 2- load one of each.
# * 3- load 1 cannibal
# * 4- load 1 vegan
# * argument 2 is destionation
# * 0- crossed
# * 1- shore*/
def self.populateBoat (choice,destination )
message = "Invalid arguments delivered"
boatDestination
validChoice = false
case choice
when 0
validChoice = true
if destination == @CROSSED_ID
@cannibalsLeft -= 2
elsif destination == @SHORE_ID
@cannibalsCrossed -=2
end
@boat[0] = @CANNIBAL_ID
@boat[1] = @CANNIBAL_ID
when 1
validChoice = true
if destination == @CROSSED_ID
@vegansLeft -= 2
elsif destination == @SHORE_ID
@vegansCrossed -= 2
end
@boat[0] = @VEGAN_ID
@boat[1] = @VEGAN_ID
when 2
validChoice = true
if destination == @CROSSED_ID
--@vegansLeft
--@cannibalsLeft
elsif destination == @SHORE_ID
--@vegansCrossed
--@cannibalsCrossed
end
@boat[0] = @VEGAN_ID
@boat[1] = @CANNIBAL_ID
when 3
validChoice = true
if destination == @CROSSED_ID
--@cannibalsLeft
elsif destination == @SHORE_ID
--@cannibalsCrossed
end
@boat[0] = @CANNIBAL_ID
@boat[1] = @EMPTY_ID
when 4
validChoice = true
if destination == @CROSSED_ID
--@vegansLeft
elsif destination == @SHORE_ID
--@vegansCrossed
end
@boat[0] = @VEGAN_ID
@boat[1] = @EMPTY_ID
else
message = "Invalid choice"
end
if validChoice
if destination == @SHORE_ID
boatDestination = "the starting point."
elsif destination == @CROSSED_ID
boatDestination = "the ending point."
else
boatDestination = "a place unknown, they're off track."
message = @getBoatOccupants + "heading to " + boatDestination +"\n"
end
end
return message
end
#/*Unload the boat, takes an integer for an argument
# * 0- unload crossed
# * 1- unload at shore */
def unloadBoat (where)
#create message
String message = "They sunk the boat. \n"
if @boatLocation == @SHORE_ID
message = "Boat unloaded at ending point. \n"
elsif @boatLocation == @CROSSED_ID
message = "Boat unloaded at starting point. \n"
end
i = 0
if where == @CROSSED_ID
for i in 0..1
if @boat[i] == @VEGAN_ID
@vegansCrossed += 1
end
if @boat[i] == @CANNIBAL_ID
@cannibalsCrossed += 1
end
@boat[i]=@EMPTY_ID
end
@boatLocation = @CROSSED_ID
elsif where == @SHORE_ID
for i in 0..1
if @boat[i] == @VEGAN_ID
@vegansLeft += 1
elsif @boat[i] == @CANNIBAL_ID
@cannibalsLeft+= 1
end
@boat[i]=@EMPTY_ID
end
@boatLocation = @SHORE_ID
end
return message
end
#build a string describing boat's occupants.
def getBoatOccupants
message = ""
occupants = Array.new(2)
#Get names for occupants
i = 0
for i in 0..2
occupants[i] = ""
if @boat[i] == @VEGAN_ID
occupants[i] = "vegan"
end
if @boat[i] == @CANNIBAL_ID
occupants[i] = "cannibal"
end
end
#if boat is full start building string
if @boat[1] != @EMPTY_ID
if @boat[0] == @boat[1]
message = "Two " + occupants[0]
message += "s are "
else
message = "One "+occupants[0]
message += " and one " + occupants[1] + " are "
end
#if boat is empty start building string
elsif @boat[1] == @EMPTY_ID
message = "One "+occupants[0]
message += " is "
end
message += "in the boat "
return message
end
def getBoatPosition
String location = ""
if @boatLocation == @SHORE_ID
location = "at the starting position."
elsif @boatLocation == @CROSSED_ID
location = "across the river."
end
return location
end
#/*Check to see if game is over and i programmed it wrong perfectGameLogic or if user got eaten. */
def eaten
boolean gameOver = false
if @cannibalsLeft > @vegansLeft and @vegansLeft != 0 || @cannibalsCrossed > @vegansCrossed and @vegansCrossed != 0
gameOver = true
return gameOver
end
#/*Used for gamLogic playable only
# * decides if a users choice is valid given the circumstances.
# */
def isValid
validChoices = [true, true, true, true, true]
if @boatLocation == @SHORE_ID
case @cannibalsLeft
when 0
validChoices[0] = false
validChoices[2] = false
validChoices[3] = false
when 1
validChoices[0] = false
else #//do nothing.
end
case @vegansLeft
when 0
validChoices[1] = false
validChoices[2] = false
validChoices[4] = false
when 1
validChoices[1] = false
else #//do nothing.
end
elsif @boatLocation == @CROSSED_ID
case @cannibalsCrossed
when 0
validChoices[0] = false
validChoices[2] = false
validChoices[3] = false
when 1
validChoices[0] = false
default:# //do nothing.
end
case @vegansCrossed
when 0
validChoices[1] = false
validChoices[2] = false
validChoices[4] = false
when 1
validChoices[1] = false
else #//do nothing.
end
end
return validChoices
end
#/*This is for a preset game where rules are strict.
#no user input is required.
#game must move all cannibals across first,
#then 2 humans across
#then bring back one of each
#then save last human.
#base case: everyone crossed */
def self.perfectGameLogic (run)
message = ""
if run == false
message = "Game Over"
else
if (@cannibalsLeft == 3 || @cannibalsLeft == 2 and @vegansLeft == 3)
message = message + populateBoat(0, @CROSSED_ID)
message +=unloadBoat(@CROSSED_ID)
message +=populateBoat(3, @SHORE_ID)
message +=unloadBoat(@SHORE_ID)
elsif @vegansLeft == 3 and @cannibalsLeft == 1
message +=populateBoat(1, @CROSSED_ID)
message +=unloadBoat(@CROSSED_ID)
message +=populateBoat(2, @SHORE_ID)
message +=unloadBoat(@SHORE_ID)
elsif @vegansLeft == 2 and @cannibalsLeft == 2
message +=populateBoat(1, @CROSSED_ID)
message +=unloadBoat(@CROSSED_ID)
elsif @vegansCrossed == 3 and @cannibalsCrossed < 3
i = 0
for i in 0..2
message +=populateBoat(3, @SHORE_ID)
message +=unloadBoat(@SHORE_ID)
message +=populateBoat(0, @CROSSED_ID)
message +=unloadBoat(@CROSSED_ID)
end
elsif @vegansCrossed == 3 and @cannibalsCrossed == 3
message = "You Win!"
run = false
end
puts message
if @eaten == true
puts "you lose"
run = false
end
perfectGameLogic(run)
end
end
#/* this is a game the user gets to interact with.
# * if you get eaten, game is over, or if you win, game is over.
# */
def self.gameLogic(run)
message = ""
error = ""
choice
destination = @CROSSED_ID
choiceOk = false
isValid = @isValid
if run == false
message = "Game Over"
else
if @vegansCrossed == 3 and @cannibalsCrossed == 3
puts "You Win!"
run = false
else
begin
putsln error+"\n"
message = "The boat is " + @getBoatPosition + "\n" +
@vegansCrossed+ " vegans have crossed and \n"+
@cannibalsCrossed + " cannibals have crossed. \n"
+"Please make a choice, who goes on the boat?: \n" +
"0 - load 2 cannibals \n" +
"1 - load 2 vegans \n" +
"2 - load one of each \n" +
"3 - load 1 cannibal \n" +
"4 - load 1 Vegan \n"
puts message
choice = scan.nextInt
if choice < 5 and choice >= 0
if isValid[choice]
#//this is the only case where a choice is acceptable.
choiceOk = true
else
error = "You can't move people who aren't there."
end
else
error= "You must choose a number between 0 and 4."
end
end
end while choiceOk == false
if @boatLocation == @SHORE_ID
destination = @CROSSED_ID
elsif @boatLocation == @CROSSED_ID
destination = @SHORE_ID
end
end
populateBoat(choice, destination)
unloadBoat(destination)
end
if @eaten == true
puts "You Lose, those poor vegans! : "
run = false
end
gameLogic run
end
end
end
Game = Cannibals.new
#/#perfectGameLogic just runs.
#//gameLogic is playable.
#Game.perfectGameLogic(true);
puts "***********************************Cannibals and vegan river crossing******************************** \n" +
"the object of the game is to get all the vegans across the river safetly. If the cannibals out number \n " +
"the vegans, they will be eaten alive and you lose the game, so try to avoid that!"
Game.populateBoat(0,0)
#Game.gameLogic(true)
这是我第一次尝试ruby，之前这是用java编码的，所以请原谅我，如果我错过了代码中的java特定内容。并给我一些指示，谢谢！
答案 0 :(得分：1)
在类的内部，使用：
声明的方法class MyClass
def self.my_method
# some stuff...
end
end
是一种“类方法”。这意味着您可以像这样调用它：
MyClass.my_method
拥有一个与该类的成员相关联的“实例方法”也是有效的，而不是类本身：
class MyClass
def my_method
# some stuff
end
end
在你的情况下，我认为你的代码在“这里的一些其他代码........”中可能有语法错误和额外的end语句，过早地关闭了类并导致def self.gameLogic(...)无效，因为它在课堂之外。
在使用def self.gameLogic创建类方法（如上所述）的逻辑中存在可见错误，但您将其称为具有类实例的实例方法。您应该将类方法调用为Cannibals.gameLogic(...)，或将gameLogic声明为实例方法：def gameLogic(...)在类中。