Ruby基础

1、数组和散列表

a = ['ant', 'bee', 'cat', 'dog']

a = %w{ant bee cat dog}

inst_section = {
    'cello'    => 'string',
    'clarinet'  => 'woodwind',
    'drum'      => 'percussion',
    'oboe'      => 'woodwind'
}

$greeting = "Hello world" #全局变量

2.block的使用

['cat', 'dog', 'horse'].each {|name| print name}

3.times {print 'i'} # 0,1,2

3.upto(6) {|i| print i} #3,4,5,6

('a'..'e').each {|char| print char}
##############如何调用block#####################
def call_block
  puts "begin the method"
  yield("hello", 1)
  yield("hello", 2)
  puts "end the method"
end

call_block {|greet, time| puts "#{greet}, #{time}"}
#begin the method
#hello, 1
#hello, 2
#end the method
################################################

def block_test
  if block_given? #函数后面给block了
    yield "give the block"
  else
    puts "give no block"
  end
end 

##############block其他方式########################
def call_block(&block)
  block.call
end
#&代表的是块转变为Proc(block to proc conversion)
call_block {puts "block的另一种调用"}

p = Proc.new {puts "block的其他调用"}
call_block(&p)

##################map函数用法#####################
name_list = ["chareice", "angel"]
name_list.map(&:upcase)  # => ["CHAREICE", "ANGEL"]

3.类

class Song
  def initialize(name, artist, duration)
    @name = name
    @artist = artist
    @duration = duration
  end
  def to_s
    "Song : #{@name}--#{@artist} (#{@duration})"
  end
end

song = Song.new("Bicy", "Fleck", 260)
puts song.to_s

继承

class KaraokeSong < Song
  def initialize(name, artist, duration, lyrics)
    super(name, artist, duration)
    @lyrics = lyrics
  end

  def to_s
    super + "[#@artist]"
  end
end

get方法

  def name
    @name
  end
  def artist
    @artist
  end
  def duration
    @duration
  end

get更简单的方式

  attr_reader :name, :artist, :duration

set方法

  def duration=(new_duration)
    @duration = new_duration
  end

set更简单的方法

  attr_writer :duration

4.类方法

class SongList
  MAX_TIME = 5 * 60
  
  def SongList.is_too_long(song)
    return song.duration > MAX_TIME
  end
end

5.单例模式

class MyLogger
  private_class_method :new  #private的类方法
  @@logger = nil
  def Mylogger.create  #def self.create
    @@logger = new unless @@logger
    @@logger
  end
  
  class <<self #类方法的第三种方式
    def create
      @@logger = new unless @@logger
      @@logger
    end
  end
end

---

⬆对比private_class_method

class MyTest
  def print_hello
    puts "hello"
  end

  private :print_hello #private实例方法
end

6.类的访问控制

在Ruby中对象的方法默认是public，Ruby中一切都是对象，对象之间赋值采用的是引用传递

7.容器类

数组

a = [1, 3, 5, 7, 9]

a[1, 3]  ->[3, 5, 7]

a[1..3]  ->[3, 5, 7]

a[1...3]  ->[3, 5]

8.实现管理song的容器

class SongList
  def initialize
    @songs = Array.new
  end

  def append(song)
    @songs.push song
    self
  end

  def delete_first
    @songs.shift
  end

  def delete_last
    @songs.pop
  end
  
  def [](index)
    @songs[index]
  end
end

实现查找

def with_title
    @songs.find {|song| title == song.name}
end
#查找到第一个就返回

inject方法

[1, 3, 5, 7].inject(0) {|sum, element| sum+element}

[1, 3, 5, 7].inject(1) {|product, element| product * element]

block做闭包回调

class Button
  def initialize(label, &action)
    @action = action
    @label = label
  end

  def button_pressed
    @action.call(self)
  end
end

button = Button.new("play") {puts 'play the music'}
#将后面的block传给&action

常见的迭代器

3.times {print "X "}
1.upto(5) {|x| print x, " "}
(1..5) {|x| print x}
99.downto(90) {|x| print x, " "}
50.step(80, 5) {|x| print x, " "}

document生成字符串

string = <<END_OF_STRING
  The body of the string
  is the input lines up to
  one ending with the same text '<<'
END_OF_STRING

字符串处理

#chomp去除行末的换行符
file, length, name, title= string.chomp.split(/\s*\|\s*/)
name.squeeze!(" ") #去除多余的空格，留一个(!)，不带!空格全去除

区间

digits = 0..9
puts digits.include?(5)
puts digits.min
puts digits.max
puts digits.reject {|i| i<5}
digits.each {|digit| print digit}

(0..9).to_a

正则表达式

a = Regexp.new('^\s*[a-z]')

if line =~ /perl|python/
  puts "Scripting language mentioned:#{line}"
end
匹配之后Ruby会设置一些变量
$& ->模式匹配的那部分字符串
$` -> 匹配之前的那部分字符串
$' -> 匹配之后的那部分字符串

不定参数

def log(*infos)
  infos.each {|info| puts info}
end

符号和字符串

"name".to_sym()       #:name
:name.to_s()             #"name"

类型判断

:name.is_a?(Symbol) #true
"name".is_a?(String) #true

重磅方法

带"!"方法返回的对象本身，普通方法返回的是对象的拷贝

9. 对象的内存

per1 = "Tim"
per2 = per1 #别名
per1[0] = 'J'    #per2 == "Jim"

per1 = "Tim"
per2 = per1.dup #复制
per1[0] = 'J'
per1  -> "Jim"
per2 -> "Tim"

per = "Tim"
per.freeze
per[0] = 'J'  #raise a TypeError

10. 计算数组的维度

module ObjectExtension
  refine Object do
    def dimension
      return 0 if self.class != Array || self.empty?
      max = 0
      self.each do |a|
        t = a.dimension
        max = [max, t].max
      end
      max + 1
    end
  end
end

using ObjectExtension

puts [1,[124,4], [1,2,3]].dimension

11. 技巧

songDuration = "2:58"
mins, secs = songDuration.split(/:/)
mins, secs = songDuration.scan(/\d+/)

12. 可选参数

#params={}可以替换成**params
def advance_search(key_words, params={})
  default_params = {
    page: 1,
    paging_size: 20,
    mode: 'text'
  }
  params = default_params.merge params

  puts params
end