函數后面的！和？

1.  問號
    方法名后面加問號是 Ruby 的編碼風格規范，用來表示該方法會返回一個 boolean 類型的值，但是并不會強制該方法一定要返回 boolean 值。
2.  感嘆號
    方法名后面加感嘆號是 Ruby 的編碼風格規范，用來表示該方法會去修改對象本身，Ruby 會把帶有感嘆號的方法稱為危險的方法，因為程序中可能有其他地方會引用這個對象。但是并不會強制該方法一定要修改對象本身。

反轉

> "str".reverse
  => "rts"

轉化

str = 40
str.to_s!
str.to_i

數組

> []

打印 賦值 替換

//  賦值
poem = "My toast has flown from my hand
And my toast has gone to the moon.
But when I saw it on television,
Planting our flag on Halley's comet,
More still did I want to eat it."
// 替換
poem['toas-t']='honey-dew'
=> "honeydew"
Success!
// 打印
> print poem
=> "My honeydew has flown from my hand
And my toast has gone to the moon.
But when I saw it on television,
Planting our flag on Halley's comet,
More still did I want to eat it."

拆分，轉化，排序

> poem.lines-.to_a.reve-rse
=> ["More still did I want to eat it.
", "Planting our flag on Halley's comet,
", "But when I saw it on television,
", "And my toast has gone to the moon.
", "My honeydew has flown from my hand
"]
Success!

ruby中的join，split，send，map，each，collect，inject方法總結

字符串轉數組，數組轉字符串

> print poem.lines-.to_a.reve-rse.join

哈希

> books = {}
=> {}
Success!

> books["Gra-vity's Rainb-ow"]
=> :splendid
Success!

> books.keys-
=> ["Gravity's Rainbow"]
// 初始化 
> ratings = Hash.-new(0)
=> {}
Success!
 
> books.valu-es.each{ |rate-| ratin-gs[rate] +=1 }
=> [:splendid, "sssss"]

> ratings
=> {:splendid=>1, "sssss"=>1}
> 

ruby 寫法注意

• ruby 方法調用的時候，當使用圓括號包裹參數的時候，切記左括號要緊貼方法名不能留白

# 錯誤的寫法
p (sum 2,3)   # 語意分歧 p (sum (2),3)  or p (sum(2,3)) ?
# 正確寫法
p sum(2,3) 
p (sum 2,2) # p方法后的空格指明后面一個參數是 方法sum的結果