函數(shù)后面的！和简识？

1.  問號
    方法名后面加問號是 Ruby 的編碼風(fēng)格規(guī)范赶掖，用來表示該方法會返回一個(gè) boolean 類型的值，但是并不會強(qiáng)制該方法一定要返回 boolean 值七扰。
2.  感嘆號
    方法名后面加感嘆號是 Ruby 的編碼風(fēng)格規(guī)范奢赂，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(xiǎn)的方法戳寸，因?yàn)槌绦蛑锌赡苡衅渌胤綍眠@個(gè)對象呈驶。但是并不會強(qiáng)制該方法一定要修改對象本身。

反轉(zhuǎn)

> "str".reverse
  => "rts"

轉(zhuǎn)化

str = 40
str.to_s!
str.to_i

數(shù)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."

拆分疫鹊，轉(zhuǎn)化袖瞻，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拆吆，send聋迎，map，each枣耀，collect霉晕，inject方法總結(jié)

字符串轉(zhuǎn)數(shù)組，數(shù)組轉(zhuǎn)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(diào)用的時(shí)候，當(dāng)使用圓括號包裹參數(shù)的時(shí)候牺堰，切記左括號要緊貼方法名不能留白

# 錯(cuò)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(gè)參數(shù)是 方法sum的結(jié)果