函式这个概念也许承载了太多的数据量。不过别担心，只要坚持做这些练习，对照上个练习中的检查清单检查这次练习的关联，你最终会明白这些内容的。 有一个你可能没有注意到的细节，我们现在强调一下，函式里面的变量和脚本里面的变量之间是没有连接的。下面的这个练习可以让你对这一点有更多的思考：
def cheese_and_crackers(cheese_count, boxes_of_crackers)
puts "You have #{cheese_count} cheeses!"
puts "You have #{boxes_of_crackers} boxes of crackers!"
puts "Man that's enough for a party!"
puts "Get a blanket."
puts # a blank line
end
puts "We can just give the function numbers directly:"
cheese_and_crackers(20, 30)
puts "OR, we can use variables from our script:"
amount_of_cheese = 10
amount_of_crackers = 50
cheese_and_crackers(amount_of_cheese, amount_of_crackers)
puts "We can even do math inside too:"
cheese_and_crackers(10 + 20, 5 + 6)
puts "And we can combine the two, variables and math:"
cheese_and_crackers(amount_of_cheese + 100, amount_of_crackers + 1000)
通过这个练习，你看到我们给我们的函式cheese_and_crackers很多的参数，然后在函式里把他们打印出来。我们可以填数字、填变量进去函式，我们甚至可以将变量和数学运算结合在一起。
从一方面来说，函式的参数和我们生成变量时用的=赋值符号类似。事实上，如果一个物件你可以用=将其命名，你通常也可以将其作为参数传给一个函式。
你应该看到的结果
你应该研究一下脚本的输出，和你想像的结果对比一下看有什么不同。
$ ruby ex19.rb
We can just give the function numbers directly:
You have 20 cheeses!
You have 30 boxes of crackers!
Man that's enough for a party!
Get a blanket.
OR, we can use variables from our script:
You have 10 cheeses!
You have 50 boxes of crackers!
Man that's enough for a party!
Get a blanket.
We can even do math inside too:
You have 30 cheeses!
You have 11 boxes of crackers!
Man that's enough for a party!
Get a blanket.
And we can combine the two, variables and math:
You have 110 cheeses!
You have 1050 boxes of crackers!
Man that's enough for a party!
Get a blanket.
$
加分练习
- 倒着将脚本读完，在每一行上面添加一行注解，说明这行程式的作用。
- 从最后一行开始，倒着阅读每一行，读出所有重要的符号来。
- 自己边写出至少一个函式出来，然后用十种方法运行这个函式。