Passing arguments to functions in ruby using variables - ruby

Question

Following the tutorial Zed A. Shaw, I'm writing a soccer game. My code so far is as follows:
$team_a_players = ["Basar", "Mehmet", "Abdullah", "Alpaslan", "Salih", "Recep", "Ibrahim", "Orhan", "Hakki", "Yakup", "Serdar"]
$team_a_substitutes = ["Hasan", "Turgay", "Umit"]
$team_b_players = ["Habib", "Erkan", "Sahin", "Cemal", "Ahmet", "Fikret", "Yucel", "Pergel", "Ali", "Sabri", "Yilmaz"]
$team_b_substitutes = ["Abdulkadir", "Gokhan", "Mustafa"]
$yellow = []
$red = []
$reasons = ["corner", "direct attack", "free kick", "side attack", "speed kick"]
$team_a_attack = 90.0
$team_a_defense = 80.0
$team_b_attack = 70.0
$team_b_defense = 60.0
$team_a_goals = 0
$team_b_goals = 0
def prompt()
print "> "
end
def dice()
if rand(2) == 0
round_team_a()
else
round_team_b()
end
end
def fauls()
if rand(0) > 0.95 and rand(10) % 2 == 0
faul_player = $team_a_players[rand(11)]
if $yellow.include?(faul_player)
$red.push(faul_player)
$team_a_players.delete("faulplayer")
puts "#{faul_player} of Team A gets a red card in #{$i}. minute!"
puts "Who would you like to substitute in place of #{faul_player}?"
list_subs_a()
prompt()
substitute = STDIN.gets.chomp()
$team_a_players.push("substitute")
$yellow.delete(faul_player)
else
$yellow.push(faul_player)
puts "#{faul_player} of Team A gets a yellow card in #{$i}. minute!"
end
elsif rand(0) > 0.95 and rand(10) % 2 == 1
faul_player = $team_b_players[rand(11)]
if $yellow.include?(faul_player)
$red.push(faul_player)
$team_b_players.delete("faulplayer")
puts "#{faul_player} of Team B gets a red card in #{$i}. minute!"
puts "Who would you like to substitute in place of #{faul_player}?"
list_subs_b()
prompt()
substitute = STDIN.gets.chomp()
$team_b_players.push("substitute")
$yellow.delete(faul_player)
else
$yellow.push(faul_player)
puts "#{faul_player} of Team B gets a yellow card in #{$i}. minute!"
end
else
faul_player = nil
end
end
def list_subs_a()
$team_a_substitutes.each {|p| puts p}
end
def list_subs_b()
$team_b_substitutes.each {|p| puts p}
end
def list_yellow()
$yellow.each {|p| puts p}
end
def list_red()
$red.each {|p| puts p}
end
def round_team_a()
score = $team_a_attack / $team_b_defense * rand(0)
if score > 1
goal = 1
$team_a_goals += 1
reason = $reasons[rand(5)]
puts "Team A scored #{goal} goal through a #{reason} in #{$i}. minute!"
else
goal = 0
end
end
def round_team_b()
score = $team_b_attack / $team_a_defense * rand(0)
if score > 1
goal = 1
$team_b_goals += 1
reason = $reasons[rand(5)]
puts "Team B scored #{goal} goal through a #{reason} in #{$i}. minute!"
else
goal = 0
end
end
def match()
$i = 0
until $i > 59 do
dice()
fauls()
$i += 1
end
puts "Team A scored a total of #{$team_a_goals} goals and Team B scored a total of #{$team_b_goals} goals."
if $team_a_goals > $team_b_goals
puts "Team A won against Team B by #{$team_a_goals}:#{$team_b_goals}!"
elsif $team_b_goals > $team_a_goals
puts "Team B won against Team A by #{$team_b_goals}:#{$team_b_goals}!"
else
puts "It's a tie!"
end
if $yellow.length > 0
puts "Players shown a yellow card are:"
list_yellow()
else
puts "No yellow cards in the end of the game"
end
if $red.length > 0
puts "Players shown a red card are:"
list_red()
else
puts "No red cards in the end of the game"
end
end
match()
From here, I would like to do the following:
Replace the arrays $yellow and $red with hashes so that I can also report minutes and teams of yellow- and red-cards.
Replace the arrays starting with the name $team_ with hashes so that I can add individualized attack- and defense-powers to players so that substitutions mean sth. but before the code gets any more complex, I have to solve sth. This looks similar to this question concerning php.
Define the functions list, round and faul in a way that can be used common to a_players and b_players . I tried doing team_#{team}_players instead of team_a_players etc, but cannot achieve it.
What I seek is a guide to that problem, not a solution, so that I can fix this myself. A link or long explanation in clear words is very much more welcome than a fixed code. And please note that the tutorial has not mentioned classes yet, so this is not an option yet.

Answer 1

The basic idea you haven't seemed to grasp is passing arguments to functions.
Assume we have two global variables and we wish to perform identical operations on them - say multiply elements of arrays by 2.
You write:
$a = [1,2,3]
$b = [2,3,4]
def multiply_a
result = []
for element in $a do
result << element * 2
end
result
end
def multiply_b
result = []
for element in $b do
result << element * 2
end
result
end
But this code is very bad. First of all, you should note that in Ruby $a is a special variable - a global variable. You should never need to use them - writing code containing them means that there is something wrong with it. So how to fix it?
The basic idea is to pass an argument to a function, instead of hard coding the variable, the function operates on. So you can transform the code as follows:
a = [1, 2, 3]
b = [2, 3, 4]
def multiply(argument)
result = []
for element in argument do
result << element * 2
end
result
end
# and then call
multiply(a) # instead of multiply_a
multiply(b) # instead of multiply_b
This is the way you should fix your code.