函式這個概念也許承載了太多的資訊量。不過別擔心,只要堅持做這些練習題,對照上個練習中的檢查清單檢查這次練習的關聯,你最終會明白這些內容的。 有一個你可能沒有注意到的細節,我們現在強調一下,函式裡面的變數和腳本裡面的變數之間是沒有連接的。下面的這個練習可以讓你對這一點有更多的思考: ~~~ 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) ~~~ 通過這個練習,你看到我們給我們的函式 `cheese_and_crackers` 很多的參數,然後在函式裡把他們印出來。我們可以塞數字、塞變數進去函式,我們甚至可以將變數和數學運算結合在一起。 從一方面來說,函式的參數和我們生成變數時用的 `=` 賦值符號類似。事實上,如果一個物件你可以用 `=` 將其命名,你通常也可以將其作為參數傳給一個函式。 ## 你應該看到的結果 你應該研究一下腳本的輸出,和你想像的結果對比一下看有什麼不同。 ~~~ $ 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. $ ~~~ ## 加分習題 1. 倒著將腳本讀完,在每一行上面添加一行註解,說明這行程式的作用。 2. 從最後一行開始,倒著閱讀每一行,讀出所有重要的符號來。 3. 自己邊寫出至少一個函式出來,然後用十種方法運行這個函式。