Ruby on rails 为什么TimeWithZone对象的行为会有所不同，这取决于它是如何创建的，特别是在“.offset”方面？ >DateTime.now.in_time_zone.class =>ActiveSupport:：TimeWithZone >>时区，现在，班级 =>ActiveSupport:：TimeWithZone >>DateTime.now.in_time_zone.offset => (0/1) >>Time.zone.now.offset 命名错误：2017年8月28日星期一17:34:46 CEST+02:00:Time的未定义方法“偏移量” from/Users/Magne/.rvm/gems/ruby-2.3.1/gems/activesupport-4.1.16/lib/active\u support/time\u with_zone.rb:364:in'method\u missing' 发信人（irb）：287 来自/Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/console.rb:90:in'start' 来自/Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/console.rb:9:in'start' from/Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/commands\u tasks.rb:69:在“控制台”中 from/Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/commands\u tasks.rb:40:in“run\u command！” 来自/Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands.rb:17:in`' 从箱子/轨道：4:in“require” 从箱子/轨道：4:in`'

ActiveSupport:：TimeWithZone

没有偏移量

方法。相反，呼叫由以下人员处理：

将缺少的方法发送到
time
实例，并用现有的
时区
将结果包装成新的TimeWithZone

它适用于
日期时间
，因为它响应
偏移量
：

>> DateTime.now.in_time_zone.class
=> ActiveSupport::TimeWithZone
>> Time.zone.now.class
=> ActiveSupport::TimeWithZone
>> DateTime.now.in_time_zone.offset
=> (0/1)
>> Time.zone.now.offset
NoMethodError: undefined method `offset' for Mon, 28 Aug 2017 17:34:46 CEST +02:00:Time
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/activesupport-4.1.16/lib/active_support/time_with_zone.rb:364:in `method_missing'
    from (irb):287
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/console.rb:90:in `start'
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/console.rb:9:in `start'
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/commands_tasks.rb:69:in `console'
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/commands_tasks.rb:40:in `run_command!'
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands.rb:17:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

并在
时间内失败，因为它没有：

DateTime.instance_methods.include? :offset
#=> true

ActiveSupport:：TimeWithZone
没有
offset
方法。相反，呼叫由以下人员处理：

将缺少的方法发送到
time
实例，并用现有的
时区
将结果包装成新的TimeWithZone

它适用于
日期时间
，因为它响应
偏移量
：

>> DateTime.now.in_time_zone.class
=> ActiveSupport::TimeWithZone
>> Time.zone.now.class
=> ActiveSupport::TimeWithZone
>> DateTime.now.in_time_zone.offset
=> (0/1)
>> Time.zone.now.offset
NoMethodError: undefined method `offset' for Mon, 28 Aug 2017 17:34:46 CEST +02:00:Time
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/activesupport-4.1.16/lib/active_support/time_with_zone.rb:364:in `method_missing'
    from (irb):287
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/console.rb:90:in `start'
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/console.rb:9:in `start'
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/commands_tasks.rb:69:in `console'
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands/commands_tasks.rb:40:in `run_command!'
    from /Users/Magne/.rvm/gems/ruby-2.3.1/gems/railties-4.1.16/lib/rails/commands.rb:17:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

并在
时间内失败，因为它没有：

DateTime.instance_methods.include? :offset
#=> true

所以，一个DateTime对象变成一个TimeWithZone对象实际上只是被强制转换，而不是重新创建？这就解释了为什么DateTime类中预先存在的.offset方法仍然存在。那么，一个DateTime对象变成了一个TimeWithZone对象，实际上只是强制转换，而不是重新创建？这可以解释为什么DateTime类中预先存在的.offset方法仍然存在。。