How to store and retrieve values using Ruby?

I am trying to build a "train game" based loosely on the old video game "Drug Wars." I am currently working my way through LRTHW, and I believe that I should be using OOP, b开发者_如何学JAVAut I'm not to that lesson yet.

The premise is that you have a set number of cars on your train and you can see what products are for sale in other cities (no limit on the amount you can buy or sale presuming you can fit them in your train). This code isn't complete, but I'm wondering if I'm even approaching this half way sanely in regard to creating and accessing the product prices in a reasonable manner.

#Initializing variables. Current_location should be changed to random 
#in the future.

current_location = 'omaha'
train = []
new_york = []
chicago = []
omaha = []
dallas = []
seattle = []

def prompt()
    print "> "
end 

#Here is the selection menu. It is possible to exploit this and
#buy, sell and move all within the same turn. 
#There needs to be a "safe selection" so that once you have moved you 
#can't move again, but you can get info, buy and sell
#as many times as you would like.

def selection()
    puts "Do you want to travel, buy, sell or get info?"

    prompt; selection = gets.chomp

    if selection.include? "travel"
        puts "Where would you like to travel?"
        prompt; city = gets.chomp
        return 'city', city
    elsif selection.include? "buy"
        puts "Current Prices Are:"
        puts "What would you like to Buy?"
    elsif selection.include? "sell"
        puts "Current Prices Are:"
        puts "What would you like to sell?"
    elsif selection.include? "info"
        puts "What city or train would you like info on?"
    else
        puts "Would you like to exit selection or start selection again?"
    end
end

#This generates a new cost for each good at the start of each turn.
def generate_costs(new_york, chicago, omaha, dallas, seattle)
    new_york[0] = rand(10)
    new_york[1] = rand(10) + 25
    new_york[2] = rand(5) + 10

    omaha[0] = rand(10)
    omaha[1] = rand(10) + 25
    omaha[2] = rand(5) + 10

    chicago[0] = rand(25) + 5
    chicago[1] = rand(5) + 10
    chicago[2] = rand(4)

    dallas[0] = rand(6) + 11
    dallas[1] = rand(3) + 10 
    dallas[2] = rand(8)

    seattle[0] = rand(6)
    seattle[1] = rand(10) + 24
    seattle[2] = rand(14) + 13


    return new_york, chicago, omaha, dallas, seattle

end


# This is my main() loop. It drives the game forward. 
for i in (0..5)
    new_york, chicago, omaha, dallas, seattle = generate_costs(new_york, chicago, omaha, dallas, seattle)

    turns = 5 - i
    puts "You are currently in #{current_location}. You have #{turns} remaining."

    puts "{ ___________________________ }"

    #Code Here evaluates and accesses pricing based on current_location. 
    #Is this the correct way to do this?
    fish = eval("#{current_location}[0]")
    coal = eval("#{current_location}[1]")
    cattle = eval("#{current_location}[2]")
    puts "Fish is worth #{fish}"
    puts "Coal is worth #{coal}"
    puts "Cattle is worth #{cattle}"
    puts "{ ___________________________ }"

    change, value = selection()
    if change == 'city'
        current_location = value
    elsif change == 'buy'
        puts 'So you want to buy?'
    else
        puts "I don't understand what you want to do"
    end

end

eval is a nasty way of accessing data ( When is `eval` in Ruby justified? ). You should consider moving things into an object.

I have improved the code slightly, storing the cities in a hash, which gets rid of the evals. I have stubbed out the generate_costs logic but you can assign it by doing:

cities[:new_york][0] = rand(10)

Ideally, the code should be re-written in an object-oriented syntax. If I get some time then I'll knock up an example for you.

Here is the code:

#Initializing variables. Current_location should be changed to random 
#in the future.

current_location = :omaha
train = []
cities = {
  :new_york => [],
  :chicago => [],
  :omaha => [],
  :dallas => [],
  :seattle => []
}

def prompt()
    print "> "
end 

#Here is the selection menu. It is possible to exploit this and
#buy, sell and move all within the same turn. 
#There needs to be a "safe selection" so that once you have moved you 
#can't move again, but you can get info, buy and sell
#as many times as you would like.

def selection()
    puts "Do you want to travel, buy, sell or get info?"

    prompt; selection = gets.chomp

    if selection.include? "travel"
        puts "Where would you like to travel?"
        prompt; city = gets.chomp
        return 'city', city
    elsif selection.include? "buy"
        puts "Current Prices Are:"
        puts "What would you like to Buy?"
    elsif selection.include? "sell"
        puts "Current Prices Are:"
        puts "What would you like to sell?"
    elsif selection.include? "info"
        puts "What city or train would you like info on?"
    else
        puts "Would you like to exit selection or start selection again?"
    end
end

#This generates a new cost for each good at the start of each turn.
def generate_costs(cities)
    cities.each do |key,city|
      0.upto(2) do |i|
        city[i] = rand(10)
      end
    end
end


# This is my main() loop. It drives the game forward. 
for i in (0..5)
    generate_costs(cities)

    turns = 5 - i
    puts "You are currently in #{current_location}. You have #{turns} remaining."

    p cities

    puts "{ ___________________________ }"
    fish = cities[current_location][0]
    coal = cities[current_location][1]
    cattle = cities[current_location][2]
    puts "Fish is worth #{fish}"
    puts "Coal is worth #{coal}"
    puts "Cattle is worth #{cattle}"
    puts "{ ___________________________ }"

    change, value = selection()
    if change == 'city'
        current_location = value
    elsif change == 'buy'
        puts 'So you want to buy?'
    else
        puts "I don't understand what you want to do"
    end

end