Ruby知识积累1

• 书写风格：

  •   Bad:    if ! tweets.empty?      puts "Timeline:"      puts tweets    end  Good:    unless tweets.empty?      puts "Timeline:"      puts tweets    end  Bad:    unless tweets.emtpy?      puts "Timeline:"      puts tweets    else      puts "No tweets found - better follow some people."    end  Good:    if tweets.empty?      puts "Timeline:"      puts tweets    else      puts "No tweets found - better follow some people."    end  Bad:    if attachment.file_path != nil      attachment.post    end  Good:    if attachment.file_path      attachment.post    end  Bad:    if password.length < 8      fail "Password too short"    end    unless username      fail "No user name set."    end  Good:    fail "Password too short" if password.length < 8    fail "No user name set." unless username  Bad:    if user      if user.signed_in?        ...      end    end  Good:    if user && user.signed_in?      ...    end  Bad:    if list_name      options[:path] = "/#{user_name}/#{list_name}"    else      options[:path] = "/#{user_name}"    end  Good:    options[:path] = if list_name      "/#{user_name}/#{list_name}"    else      "/#{user_name}"    end  Bad:    def list_url(user_name, list_name)      if list_name        url = "https://twitter.com//#{user_name}/#{list_name}"      else        url = "https://twitter.com//#{user_name}"      end      url    end  Good:    def list_url(user_name, list_name)      if list_name        "https://twitter.com//#{user_name}/#{list_name}"      else        "https://twitter.com//#{user_name}"      end    end  Bad:(对于可选参数)    def tweet(message, lat, long)      #...    end    tweet("Practicing Ruby-Fu!", nil, nil)  Good:    def tweet(message, lat=nil, long=nil)      #...    end    tweet("Practicing Ruby-Fu!")  Bad:(Hash参数)    def tweet(message, lat=nil, long=nil, reply_id=nil)      #...    end    tweet("Practicing Ruby-Fu!", nil, nil, 227946)  Good:    def tweet(message, options={})      status = Status.new      status.lat = options[:lat]      status.long = options[:long]      status.body = message      status.reply_id = options[:reply_id]    end    tweet("Practicing Ruby-Fu!", :lat => 28.55, :long => -81.33, :reply_id => 227946)    Ruby>1.9      tweet("Practicing Ruby-Fu!", lat: 28.55, long: -81.33, reply_id: 227946)  Bad:(异常)    def get_tweets(list)      if list.authorized?(@user)        list.tweets      else        []      end    end    tweets = get_tweets(my_list)    if tweets.empty?      alert "No tweets were found!" + "Are you authorized to access this list?"    end  Good:    def get_tweets(list)      unless list.authorized?(@user)        raise AuthorizationException.new      end      list.tweets    end    begin      tweets = get_tweets(my_list)    rescue AuthorizationException      warn "You are not auhorized to access this list."    end  Bad:(类)    user_names = [["Ashton", "Kutcher"],["Wil", "Wheaton"],["Madonna"]]    user_names.each { |n| puts "#{n[1]},#{n[0]}" }  Good:    class Name      def initialize(first, last = nil)        @first = first        @last = last      end      def format        [@last, @first].compact.join(', ')      end    end    user_names = []    user_names << Name.new("Ashton", "Kutcher")    user_names << Name.new("Wil", "Wheaton")    user_names << Name.new("Madonna")    user_names.each{ |n| puts n.format }  Bad:(勿过度开放属性权限)    class Tweet      attr_accessor :status, :created_at      def initialize(status)        @status = status        @created_at = Time.now      end    end  Good:    class Tweet      attr_accessor :status      attr_reader :created_at      def initialize(status)        @status = status        @created_at = Time.now      end    end  Bad:(累的继承)    class Image      attr_accessor :title, :size, :url      def to_s        "#{@title}, #{@size}"      end    end    class Video      attr_accessor :title, :size, :url      def to_s        "#{@title}, #{@size}"      end    end      Good:    class Attachment      attr_accessor :title, :size, :url      def to_s        "#{@title}, #{@size}"      end    end    class Image < Attachment    end    class Video < Attachment    end  Bad:    class User      def tweet_header        [@first_name, @last_name].join(' ')      end      def profile        [@first_name, @last_name].join(' ') + @description      end    end  Good:    class User      def display_name        title = case @gender        when :female  then married? ? "Mrs." : "Miss"        when :male    then "Mr."        end        [title, @first_name, @last_name].join(' ')      end      def tweet_header        display_name      end      def profile        display_name + @description      end    end

• 类:

  •   class UserList    attr_accessor :name    def initialize(name)      self.name = name    end  end  list = UserList.new('Andy')  list.name----------->Andy

• 平板型参数:

  •   def metion(status, *names)    tweet("#{names.join(',')} #{status}")  end  metion('Your courses rocked!', 'eallam', 'greggpollack','jasonvanlue')

• CASE语句：

  •  client_url = case client_name  when "web"    "http://twitter.com"  else    nil  end  popularity = case tweet.retweet_count  when 0..9    nil  else    "hot"  end  tweet_type = case tweet.status  when /\A@\w+/    :mention  when /\Ad\s+\w+/    :direct_message  else    :public  end  tweet_type = case tweet.status  when /\A@\w+/     then  :mention  when /\Ad\s+\w+/  then  :direct_message  else                    :public  end

• Ruby中的FALSE：nil

  ""--------->true
  0 --------->true
  []--------->true

• Ruby中赋值便捷方法：

  •   当result为nil时，赋值1    result ||= 1  若express1 || express2中，express1为False时，采用express2的值。    result = nil || 1 ......> 1    result = 1 || nil ......> 1    result = 1 || 2   ......> 1    def sign_in      current_ssession || sign_uer_in    end

• ActiveSupport:

  •   gem install activesupport  gem install i18n  require 'active_support/all'

•   对数组的扩展:

  •     array = [0,1,2,3,4,5,6]    array.from(4)    array.to(2)    添加nil元素补齐：      array.in_groups_of(3)---->[[0,1,2],[3,4,5],[6,nil,nil]]    以分隔元素为轴划分，并将分隔元素删除：      array.split(2)---->[[0,1],[3,4,5,6]]

•   对Date的扩展：

  •     apocalypse = DateTime.new(2014,7,6,12,49,30)    apocalypse.at_beginning_of_day    apocalypse.at_end_of_month    apocalypse.at_beginning_of_year    apocalypse.advance(years: 4, months: 3, weeks: 2, days: 1)    apocalypse.tomorrow    apocalypse.yesterday

•   对Hash的扩展：

  •     options = {user: 'codeschool', lang: 'fr'}    new_options = {user: 'codeschool', lang: 'fr', password: 'dunno'}    options.diff(new_options)    将键值转换成字符串：      options.stringify_keys    合并Hash，以options为主：      options.reverse_merge(new_options)    new_options.except(:password)    new_options.assert_valid_keys(:user, :lang)

•   对Integer的扩展：

  •     def background_class(index)      return 'white' if index.odd?      return 'grey' if index.even?    end    tweets.each_with_index do |tweet, index|      puts "<div class='#{background_class(index)}'>#{tweet}</div>"    end

•   inflector:

  •     1.ordinalize    "user".pluralize    "users".singularize    "ruby".titleize    "account_options".humanize

• 命名空间:

  •   Bad:(污染了全局方法，可能会和同名方法冲突。)    image_utils.rb      def preview(image)      end      def transfer(image, destination)      end    run.rb      require 'image_utils'      image = user.image      preview(image)  Good:    image_utils.rb      module ImageUtils        def self.preview(image)        end        def self.transfer(image, destination)        end      end    run.rb      require 'image_utils'      image = user.image      ImageUtils.preview(image)

•   MIXIN：

  •       module ImageUtils        def preview        end        def transfer(destination)        end      end      require 'image_utils'      class Image        include ImageUtils      end      image = user.image      image.preview(image)

• HOOKS:(self.include)

  •   未用self.include:    模块:      module ImageUtils        def preview        end        def transfer(destination)        end        module ClassMethods          def fetch_from_twitter(user)          end        end      end    类:      class Image        include ImageUtils        extend ImageUtils::ClassMethods      end    调用:      image = user.image      image.preview      Image.fetch_from_twitter('grege')  使用self.include：    模块:      module ImageUtils        def self.included(base)          base.extend(ClassMethods)        end        def preview        end        def transfer(destination)        end        module ClassMethods          def fetch_from_twitter(user)          end        end      end    类:      class Image        include ImageUtils      end    调用:      image = user.image      image.preview      Image.fetch_from_twitter('grege')  使用activesupport gem:    模块:      require 'active_support/concern'      module ImageUtils        extend ActiveSupport::Concern        included do          clean_up        end        def preview        end        def transfer(destination)        end        module ClassMethods          def fetch_from_twitter(user)          end          def clean_up          end        end      end    类:      class Image        include ImageUtils      end

• Blocks:

  •   e.g.    words = ['Had','eggs','for']    for index in 0..(words.length-1)      puts words[index]    end    words.each { |word| puts word }    or    words.each do |word|      puts word    end

• Yield:

  •   e.g.    def call_this_block      yield "tweet"    end    call_this_block { |arg| puts arg.upcase } #---->TWEET  e.g.    def call_this_block      block_result = yield "foo"      puts block_result    end    call_this_block { |arg| puts arg.reverse } #---->OOF        e.g.    def puts_this_block      puts yield    end    puts_this_block { "tweet" }  #---->tweet  e.g.    Bad:      class Timeline        def list_tweeks          @user.friends.each do |friend|            friend.tweets.each { |tweet| puts tweet }          end        end        def store_tweeks          @user.friends.each do |friend|            friend.tweets.each { |tweet| tweet.cache }          end        end      end    Good:      class Timeline        def each          @user.friends.each do |friend|            friend.tweets.each { |tweet| yield tweet }          end        end      end      timeline = Timeline.new(user)      timeline.each { |tweet| puts tweet }      timeline.each { |tweet| tweet.cache }  e.g.    Bad:      def update_status(user, tweet)        begin          sign_in(user)          post(tweet)        rescue ConnectionError => e          logger.error(e)        ensure          sign_out(user)        end      end      def get_list(user, list_name)        begin          sign_in(user)          retrieve_list(list_name)        rescue ConnectionError => e          logger.error(e)        ensure          sign_out(user)        end      end    Good:      def while_signed_in_as(user)        sign_in(user)        yield        rescue ConnectionError => e          logger.error(e)        ensure          sign_out(user)      end            while_signed_in_as(user) do        post(tweet)      end      tweets = while_signed_in_as(user) do        retrieve_list(list_name)      end

    
    
    

• Enumerable:

  •   class Timeline    def each      #...    end    include Enumerable  end  timeline.sort_by { |tweet| tweet.created_at }  timeline.map { |tweet| tweet.status }  timeline.find_all { |tweet| tweet.status =~ /\@csdn/ }