> 2+6
=> 8
> 4*10
=> 40
> 40/4
=> 10
> "Jimmy"
=> "Jimmy"
> "Jimmy".re­verse
=> "ymmiJ"
> "Jimmy".le­ngth
=> 5
> "Jimmy"*5
=> "JimmyJimmyJimmyJimmyJimmy"
>  

> 5.times { print­ "Odel­ay!" }
=> "Odelay!Odelay!Odelay!Odelay!Odelay!"

> [12,47,35]­.max
=> 47
> ticket=[12­,47,35]
=> [12, 47, 35]
> ticket.sor­t
=> [12, 35, 47]
> ticket
=> [12, 47, 35]
> ticket.sor­t!
=> [12, 35, 47]
> ticket
=> [12, 35, 47]
>  

5.2.2变换、过滤、删除

[1, 2, 3, 4, 5].map { |i| i + 1 }  #变换  输出[2, 3, 4, 5, 6]
[1,2,3,4,5,6].select {|number| number % 2 == 0}  #过滤 输出[2,4,6]
names = ['rock', 'paper', 'scissors', 'lizard', 'spock']
names.select {|word| word.length > 5}  #过滤 输出长度大于5的元素
[1,2,3,4,5,6,7].delete_if{|i| i < 4 }  #删除小于4的元素

5.3字符串替换、查找

> print 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."
Success!
> poem['toas­t']='honey­dew'
=> "honeydew"
Success!
> 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."
>  

> poem.inclu­de?"my hand"­
=> true

> poem.rever­se
=> ".ti tae ot tnaw I did llits eroM
,temoc s'yellaH no galf ruo gnitnalP
,noisivelet no ti was I nehw tuB
.noom eht ot enog sah tsaot ym dnA
dnah ym morf nwolf sah wedyenoh yM"
Success!
> poem.lines­.to_a.reve­rse
=> ["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!
> print poem.­lines.to_a­.reverse.j­oin
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!
> 

5.4Hash表(Directory字典)

> books={}
=> {}
> books['a']­=111
=> 111
> books['b']­='222'
=> "222"
> books['c']­=true
=> true
> books.keys­
=> ["a", "b", "c"]
>

> books["Gra­vity's Rainb­ow"] = :sple­ndid
=> :splendid
Success!
> books["Gra­vity's Rainb­ow"] = :quit­e_good
=> :quite_good
> books["Gra­vity's Rainb­ow"] = :medi­ocre
=> :mediocre
> books["Gra­vity's Rainb­ow"] = :quit­e_not_good­
=> :quite_not_good
> books["Gra­vity's Rainb­ow"] = :abys­mal
=> :abysmal
> books.leng­th
=> 1
> 

5.6条件和循环语句 

def check_sign(number)
  if number > 0
    "#{number} is positive"
  else
    "#{number} is negative"
  end        
end

def check_sign(number)
  number > 0 ? "#{number} is positive" : "#{number} is negative"
end

5.7目录文件操作

Dir.entrie­s "/"  #列出当前目录文件(夹)
Dir["/*.txt"]    #过滤
print File.read("/comics.txt")  #读取
FileUtils.cp('/comics.txt', '/Home/comics.txt') #复制
File.open(­"/Home/com­ics.txt", "a") do |f|    #写文件,append mode
    f << "Cat and Girl:­ http:­//catandgi­rl.com/"
end

> def load_­comics( path )
	comics = {}
	File.forea­ch(path) do |line­|       #每行读取
	   name, url = line.­split(': ')   #以": "分开每行字符串为两段,分别存入name和url
	   comics[nam­e] = url.s­trip   #去除空格
	end
	comics
end
=> nil
> comics = load_­comics('/c­omics.txt'­)
=> {"Achewood"=>"http://achewood.com/", "Dinosaur Comics"=>"http://qwantz.com/", "Perry Bible Fellowship"=>"http://cheston.com/pbf/archive.html", "Get Your War On"=>"http://mnftiu.cc/"}
> 

5.9类和函数的定义

class Rectangle
  def initialize(length, breadth)
    @length = length
    @breadth = breadth
  end

  def perimeter
    2 * (@length + @breadth)
  end

  #write the 'area' method here
end

<span style="color: rgb(68, 68, 68); font-family: monospace, sans-serif; line-height: 24px; background-color: rgb(248, 248, 255); ">Rectangle.new.perimeter</span>