RubyonRails的当前年份-CurrentyearinRubyonRails

10  

In your example Date.today.year is evaluated only once - when the class is loaded and therefore doesn't change anymore.

在您的示例中,Date.today.year仅被评估一次 - 当类加载时因此不再更改。

When you use a lambda in your validator declaration then it re-evaluates the block each time when it runs the validation for that attribute:

在验证器声明中使用lambda时,每次运行该属性的验证时,它都会重新计算该块:

validates :year, numericality: { 
  only_integer: true, 
  less_than_or_equal_to: ->(_brewery) { Date.current.year }
}

Furthermore, I suggest using Date.current instead of Date.today, because the current method pays attention to timezone settings.

此外,我建议使用Date.current而不是Date.today,因为当前方法会关注时区设置。

1  

Actually, it's better to use Time.current instead of Time.now in Rails, because the first one adopts current time zone. http://edgeguides.rubyonrails.org/active_support_core_extensions.html#time-current

实际上,最好在Rails中使用Time.current而不是Time.now,因为第一个采用当前时区。 http://edgeguides.rubyonrails.org/active_support_core_extensions.html#time-current

1  

@spickermann's recipe seems to be correct, I'll just try to explain why it works.

@ spickermann的配方似乎是正确的,我只是试着解释它为什么有效。

The code you write inside your class is executed at compile time, when Ruby compiles to the VM bytecode. Therefore, the Date.today.year in your validator is calculated exactly once, when the class is compiled.

你在类中编写的代码是在编译时执行的,当Ruby编译为VM字节码时。因此,在编译类时,验证程序中的Date.today.year只计算一次。

By introducing the lambda you enable ActiveRecord to use the return value of said lambda. The lambda itself will be executed with each validation.

通过引入lambda,您可以使ActiveRecord使用所述lambda的返回值。 lambda本身将在每次验证时执行。

Hope that made the situation clearer!

希望使情况更加清晰!

1  

<%= Time.zone.now.year %> -- factors in time zone

<%= Time.zone.now.year%> - 时区中的因素