Ruby 一些惯用的细节

1.try 永远不会抛出异常 在 没有的时候 返回 nil 

province_id = Province.find_by_name(prov).try(:id)

mobile_info = MobileInfo.find(:first, :conditions => ["mobile_num = ? ", mobile_num.to_i])

support_amount_a = ProvinceMerchantChangeValue.find(:all, :select => "DISTINCT change_value_id",                        :conditions => ["status = 1 and merchant_id = ? and province_id =? and channel_id in (select id from channels where status = 1)",                        merchant_id, province_id]).map { |cv| cv.change_value_id }.compactsupport_amount_s = ChangeValue.find(:all,:select => "price" ,:conditions => ["id in (?)", support_amount_a]) \                                  .map { |cv| cv.try(:price).to_i }.compact

 curl -d "channel=中信异度支付&action_type=娱人节-手机充值&user_indicate=13911731997&original_amount=10000" http://xx.xxx.xxx:3000/search.json

5.Ruby 中纯数据结构 ( Struct 与 OpenStruct )
讲一下它俩之间的区别:
Struct 需要开头明确声明字段; 而 OpenStruct 人如其名, 随时可以添加属性
Struct 性能优秀; 而 OpenStruct 差点, 具体的性能差距可看这里:http://stackoverflow.com/questions/1177594/ruby-struct-vs-openstruct
Struct 是 Ruby 解释器内置, 用 C 实现; OpenStruct 是 Ruby 标准库, Ruby 实现
API 不同: Struct API 与 OpenStruct
6. MIme::Type.register

Mime::Type.register "application/json", :ejson

ActiveSupport::CoreExtensions::Hash::Conversions::XML_PARSING.delete('symbol')ActiveSupport::CoreExtensions::Hash::Conversions::XML_PARSING.delete('yaml') 

if defined?(ActiveRecord)  # Include Active Record class name as root for JSON serialized output.  ActiveRecord::Base.include_root_in_json = true  # Store the full class name (including module namespace) in STI type column.  ActiveRecord::Base.store_full_sti_class = trueendActionController::Routing.generate_best_match = false# Use ISO 8601 format for JSON serialized times and dates.ActiveSupport.use_standard_json_time_format = true# Don't escape HTML entities in JSON, leave that for the #json_escape helper.# if you're including raw json in an HTML page.ActiveSupport.escape_html_entities_in_json = false

@_cache = ActiveSupport::Cache::MemCacheStore.new(                      CONFIG['host'], { :namespace => "#{CONFIG['namespace']}::[email protected]}" }                      )localhost::callback_lock@_cache.write(pay_channel.channel_id,'true’)v = @_cache.read(pay_channel.channel_id)if v.nil? || v != 'true'      return false    else      return true    endend

start_time = start_time.to_s.to_datetime.at_beginning_of_dayend_time = end_time.to_s.to_datetime.end_of_day

m_order[:merchant_id] = (merchant.instance_of? MplusMerchant) ? merchant.id : merchant

require 'will_paginate' 修改controller文件中的index方法： #    @products = Product.find(:all)     @products = Product.paginate  :page => params[:page],                                   :per_page => 2   .pagination    = will_paginate @mplus_orders, :class => 'digg_pagination'最好有个include

 PROVINCE = %w{ 安徽  北京  福建  甘肃  广东  广西  贵州  海南  河北  河南  黑龙江 湖北       湖南  吉林  江苏  江西  辽宁  内蒙古 宁夏  青海  山东  山西  陕西  上海       四川  天津  西藏   新疆  云南  浙江  重庆 }  MONTH = 1.upto(12).to_a  def self.total_to_xls(year = '2012', opts = {})    book = Spreadsheet::Workbook.new    sheet1 = book.create_worksheet    months = MONTH    months = opts[:month].to_s.split(/,/) if opts[:month]    fixed_row = months.collect{ |m| m.to_s + '月' }.insert(0, '')    sheet1.row(0).concat(fixed_row)    row1 = ['']    (months.size - 1).times { row1 << ['用户数', '金额', '订单数'] }    sheet1.row(1).concat(row1.flatten!)    row = 2    sheet1.row(row).insert(0, '全国')    months.each_with_index do |m, i|      sheet1.row(row).insert(i*3 + 1, self.monthly_users_count(m))      sheet1.row(row).insert(i*3 + 2, self.monthly_amount(m))      sheet1.row(row).insert(i*3 + 3, self.monthly_orders_count(m))         end    PROVINCE.each do |province|      row += 1      sheet1.row(row).insert(0, province)      months.each_with_index do |m, i|        sheet1.row(row).insert(i*3 + 1, self.monthly_users_count_by_province(m, province))        sheet1.row(row).insert(i*3 + 2, self.monthly_amount_by_province(m, province))        sheet1.row(row).insert(i*3 + 3, self.monthly_orders_count_by_province(m, province))      end       end    path = "tmp/phone_recharge.xls"    book.write path    path  end

selected_conditions = base_conditions.inject({}) do |hash, data|      hash[data.first] = data.last unless data.last.blank?      hash    end

return time_str if time_str.instance_of? Time

Person.instance_eval do    def species      "Homo Sapien"    end  end

class Foo  end  metaclass = (class << Foo; self; end)  metaclass.class_eval do      def species        "Homo Sapien"      end    end  end

21.
Ruby中 respond_to? 和 send 的用法
http://galeki.is-programmer.com/posts/183.html
因为obj对象没法响应talk这个消息，如果使用 respond_to? 这个方法，就可以实现判断对象能否响应给定的消息了
obj = Object.new
if obj.respond_to?("talk")
   obj.talk
else
   puts "Sorry, object can't talk!"
end
 
request = gets.chomp
 
if book.respond_to?(request)
  puts book.send(request)
else
  puts "Input error"
end

22.
method_missing，一个 Ruby 程序员的梦中情人 

    def method_missing(method, *args)      if method.to_s =~ /(.*)_with_cent$/        attr_name = $1        if self.respond_to?(attr_name)          '%.2f' % (self.send(attr_name).to_f / 100.00)        else          super        end      end    end

if bank_order.present?          data_hash.each_pair { |k, v| bank_order.send("#{k}=", v) }        else          bank_order = BankOrder.new data_hash        end