Ruby Tricks 大全

编程技术  /  houtizong 发布于 3年前   90

下面所有用法都是1.8.6里的，同时欢迎补充1.9和rails里面的tricks...

一.神奇的*
1.String#*

  "Hello!" * 2 #=> "Hello!Hello!" 

2.Array#*

   %w{one two three} * 2  #=> ["one", "two", "three", "one", "two", "three"] 

3.Shortcut for Array#join

   %w{one two three} * ", "  #=> "one, two, three" 

 

 %w{this is a test} * ", "                 # => "this, is, a, test" h = { :name => "Fred", :age => 77 } h.map { |i| i * "=" } * "&"              # => "age=77&name=Fred" 

4.explore to enumerator

  a = %w{a b}b = %w{c d}[a + b]                              # => [["a", "b", "c", "d"]][*a + b]                             # => ["a", "b", "c", "d"] 

 

 a = { :name => "Fred", :age => 93 }[a]                                  # => [{:name => "Fred", :age =>93}][*a]                                 # => [[:name, "Fred"], [:age, 93]]  

 

  a = %w{a b c d e f g h}b = [0, 5, 6]a.values_at(*b).inspect              # => ["a", "f", "g"] 

 

  fruit = ["apple","red","banana","yellow"]#=> ["apple", "red", "banana", "yellow"]Hash[*fruit]    #=> {"apple"=>"red", "banana"=>"yellow"} 

5.*arg作为参数

 def my_method(*args)  a, b, c, d = argsend 

6.Object#*

 match, text, number = *"Something 981".match(/([A-z]*) ([0-9]*)/)

 

  a, b, c = *('A'..'Z')Job = Struct.new(:name, :occupation)tom = Job.new("Tom", "Developer")name, occupation = *tom

二.默认返回值.
Array#[]在index超出array范围时会默认返回nil（如果不想要默认值或是要扩展默认值可以用Array#fetch）：

 irb(main):074:0> a = [1 ,2, 3]=> [1, 2, 3]irb(main):075:0> a[5]=> nilirb(main):076:0> a.fetch(8)IndexError: index 8 out of array        from (irb):76:in `fetch'        from (irb):76        from :0irb(main):077:0> a.fetch(8,nil)=> nilirb(main):078:0> a.fetch(8,"index out of array!")=> "index out of array!" 

Hash也是在key不存在的时候返回默认值nil，也可以自己设置默认值或default_proc

 irb(main):008:0> hash = Hash.new{|hash,key| hash[key] = key.upcase if key.kind_of? String}=> {}irb(main):009:0> hash[1]=> nilirb(main):010:0> hash["key"]=> "KEY"

Regex也可以有默认返回值：

 email = "Fred Bloggs <[email protected]>"email.match(/<(.*?)>/)[1]            # => "[email protected]"email[/<(.*?)>/, 1]                  # => "[email protected]"email.match(/(x)/)[1]                # => NoMethodError email[/(x)/, 1]                      # => nil

当然最强大的还是method_missing了....

三.习以为常的single line method
在ruby里一行代码完成一个方法是很常见的....这主要归功于enumerable模块里面定义的神奇方法,还有if，unless等

 queue = []%w{hello x world}.each do |word|  queue << word and puts "Added to queue" unless word.length <  2endputs queue.inspect# Output:#   Added to queue#   Added to queue#   ["hello", "world"]

三元操作符：

 def is_odd(x)  x % 2 == 0 ? false : trueend

 

 all?, any?, collect, detect, each_cons, each_slice, each_with_index, entries, enum_cons, enum_slice, enum_with_index, find, find_all, grep, include?, inject, inject, map, max, member?, min, partition, reject, select, sort, sort_by, to_a, to_set, zip

 

 

  p queue = %w{hello x world}.select { |word| word.length >= 2 }

四.其他
1.Format decimal amounts quickly

 money = 9.5"%.2f" % money                       # => "9.50"

2.Surround text quickly

"[%s]" % "same old drag"             # => "[same old drag]"

3.Delete trees of files

require 'fileutils'FileUtils.rm_r 'somedir'

4.Cut down on local variable definitions

 (z ||= []) << 'test'

5.Using non-strings or symbols as hash keys

 does = is = { true => 'Yes', false => 'No' }does[10 == 50]                       # => "No"is[10 > 5]                           # => "Yes"

6.Do something only if the code is being implicitly run, not required

 if __FILE__ == $0  # Do something.. run tests, call a method, etc. We're direct.end

7.Use ranges instead of complex comparisons for numbers

#让 if x > 1000 && x < 2000 歇菜吧 year = 1972puts  case year        when 1970..1979: "70后"        when 1980..1989: "80后"        when 1990..1999: "90后"      end

8.See the whole of an exception's backtrace

  def do_division_by_zero; 5 / 0; endbegin  do_division_by_zerorescue => exception  puts exception.backtraceend

9.Rescue blocks don't need to be tied to a 'begin'

 def x  begin    # ...  rescue    # ...  endend

 

 def x  # ...rescue  # ...end

10.Rescue to the rescue

 h = { :age => 10 }h[:name].downcase                         # ERRORh[:name].downcase rescue "No name"        # => "No name"

11.convert a Fixnum into any base up to 36

  >> 1234567890.to_s(2)=> "1001001100101100000001011010010">> 1234567890.to_s(8)=> "11145401322">> 1234567890.to_s(16)=> "499602d2">> 1234567890.to_s(24)=> "6b1230i">> 1234567890.to_s(36)=> "kf12oi"

12.module_function

#让module更class  module M  def not!    'not!'  end  module_function :not!endclass C  include M  def fun    not!  endendM.not!     # => 'not!C.new.fun  # => 'not!'C.new.not! # => NoMethodError: private method `not!' called for #<C:0x1261a00>

 

 module M  module_function  def not!    'not!'  end  def yea!    'yea!'  endendclass C  include M  def fun    not! + ' ' + yea!  endendM.not!     # => 'not!'M.yea!     # => 'yea!'C.new.fun  # => 'not! yea!'

13.use  here document and any character you want to delimit strings 

 message = "My message"contrived_example = "<div id=\"contrived\">#{message}</div>"contrived_example = %{<div id="contrived-example">#{message}</div>}contrived_example = %[<div id="contrived-example">#{message}</div>]sql = %{    SELECT strings     FROM complicated_table    WHERE complicated_condition = '1'}sql = <<-SQL    SELECT strings     FROM complicated_table    WHERE complicated_condition = '1'SQL

14.define_method

 ((0..9).each do |n|    define_method "press_#{n}" do      @number = @number.to_i * 10 + n    end  end

15.create Class at run time..

class Array#define Array#rand  def rand    self.fetch Kernel.rand(self.size)  endend

class RandomSubclass < [Array, Hash, String, Fixnum, Float, TrueClass].randendRandomSubclass.superclass # could output one of 6 different classes.

16.call private methods of class with send.

 class A  private  def my_private_method    puts 'private method called'  endenda = A.newa.my_private_method # Raises exception saying private method was calleda.send :my_private_method # Calls my_private_method and prints private method called'

16.__END__

p DATA #=>#<File:tt.rb>p DATA.read #=> "line1\nline2\nline3"__END__line1line2line3

17.FX和NS两位大神提供...目前不知道是做什么的.......

gets gets