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函数这个概念也许包含了太多的信息量。不过别担心,只要坚持做这些练习题,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,函数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数 `cheese_and_crackers` 很多的参数,然后在函数里把他们输出。我们可以塞数字、塞变量进去函数,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,函数的参数和我们生成变量时用的 `=` 赋值符号类似。事实上,如果一个东西你可以用 `=` 将其命名,你通常也可以将其作为参数传给一个函数。 # 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. $ ~~~ # 加分习题 * * * * * 1. 倒着将脚本读完,在每一行上面添加一行注释,说明这行程序的作用。 2. 从最后一行开始,倒着阅读每一行,读出所有重要的符号来。 3. 自己边写出至少一个函数出来,然后用十种方法运行这个函数。