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62 lines
1.6 KiB
Markdown
62 lines
1.6 KiB
Markdown
# Add ActiveRecord Error Not Tied To Any Attribute
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Often the [errors on an ActiveRecord
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object](https://api.rubyonrails.org/v6.1.3.2/classes/ActiveModel/Errors.html)
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are tied to a specific attribute of that object. For instance, when this
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validation is violated
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```ruby
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validates :name, presence: true
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```
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Then the error will be tied to `:name`.
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With the
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[`ActiveModel::Errors#add`](https://api.rubyonrails.org/v6.1.3.2/classes/ActiveModel/Errors.html#method-i-add)
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method, we can write custom validation logic that ties an error to a specific
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attribute.
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```ruby
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validate :quantity_for_bulk_purchase
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def quantity_for_bulk_purchase
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return if purchase_type != :bulk
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if quantity < 12
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errors.add(:quantity, "must be greater than 12 for bulk purchases")
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end
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end
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```
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Errors don't have to be tied to specific attribute. They can be tied to the
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object as a whole. This can be better for validations, like the one above, that
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involve multiple attributes.
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```ruby
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validate :quantity_for_bulk_purchase
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def quantity_for_bulk_purchase
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return if purchase_type != :bulk
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if quantity < 12
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errors.add(:base, "Quantity must be greater than 12 for bulk purchases")
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end
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end
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```
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By using the `:base` symbol, we are ascribing this error to the object as a
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whole.
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```
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> my_object.errors
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#=> #<ActiveModel::Errors:0x00007fccaa5a8740
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@base=
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#<MyObject:0x00007fcc8a5e9238
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...
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@details={:base=>[{:error=>"Quantity must be greater than 12 for bulk purchases"}]},
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@messages={:base=>["Quantity must be greater than 12 for bulk purchases"]}>
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> my_object.errors.full_messages
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#=> ["Quantity must be greater than 12 for bulk purchases"]
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```
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