Rails 4验证:进行包含时，将allow_nil放在哪里? [英] Rails 4 Validation: where to put the allow_nil when doing an inclusion?

问题描述

这两个实现在功能上是否等效?如果是这样，哪个更好?

Are these two implementations functionally equivalent? If so, which is "better?"

  # from a model
  WIDGET_COLORS = %w(red yellow green)
  validates :widget_color,
           inclusion: {in: WIDGET_COLORS, allow_nil: true}

或

  # from a model
  WIDGET_COLORS = %w(red yellow green)
  validates :widget_color,
           inclusion: {in: WIDGET_COLORS},
           allow_nil: true

更新:固定错字，因此示例读取 validates

UPDATE: fixed typo so example reads validates

推荐答案

首先validate和validates是不同的方法-在此处应为validates.

Firstly validate and validates are different methods - it should be validates here.

validates将在提供的哈希中搜索所谓的_validates_default_keys，它是内部数组[:if, :unless, :on, :allow_blank, :allow_nil , :strict].将此数组中传递给validates的所有参数视为该方法附加到模型的所有验证器的通用选项.因此，如果您这样做:

validates will search the supplied hash for so-called _validates_default_keys, which is an internal array [:if, :unless, :on, :allow_blank, :allow_nil , :strict]. All the arguments passed to validates being in this array are treated as common options for all the validators attached to the model with this method. So if you do:

validates :widget_color,
          inclusion: {in: WIDGET_COLORS},
          uniqueness: true,
          allow_nil: true

allow_nil将同时影响两个验证器，或等效于:

allow_nil will affect both of the validators, or is equivalent of:

validates :widget_color,
          inclusion: {in: WIDGET_COLORS, allow_nil: true},
          uniqueness: {allow_nil: true}

另一方面

validates :widget_color,
          inclusion: {in: WIDGET_COLORS, allow_nil: true},
          uniqueness: true

它只会影响为其定义的验证器(在本例中为InclusionValidator)

it will only affect the validator it is defined for (in this case InclusionValidator)

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