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)

4000
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/ }