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Rails 6.1 allows attribute's default to be configured but keeping its type

 3 years ago
source link: https://blog.saeloun.com/2020/11/15/rails-6-1-allows-attribute-default-to-be-configured-but-keeping-its-type
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Rails 6.1 allows attribute's default to be configured but keeping its type

Nov 15, 2020 , by Romil Mehta
1 minute read

Rails allows us to change the type and set the default value of the attribute.

Let’s consider Message class with sent_at attribute of type datetime.

class Message
end

> Message.type_for_attribute(:sent_at)
=> <ActiveRecord::Type::DateTime:0x00007fa01c1fd650 @precision=6, @scale=nil, @limit=nil>
> Message.new.sent_at
=> nil

We can change the sent_at attribute’s type to integer in the following way:

class Message
  attribute :sent_at, :integer
end

> Message.type_for_attribute(:sent_at)
=> <ActiveModel::Type::Integer:0x00007fa01bd86ba8 @precision=nil, @scale=nil, @limit=nil, @range=-2147483648...2147483648>

We can also set the default value by providing a default option:

class Message
  attribute :sent_at, default: -> { Time.now.utc }
end

> Time.now.utc
=> 2020-10-15 12:10:16 UTC
> Message.new.sent_at
=> 2020-10-15 12:10:16 UTC

But the problem with this is, Rails also changes the type of the attribute when setting the default value, and drops the proper type:

> Message.type_for_attribute(:sent_at)
=> <ActiveModel::Type::Value:0x00007fd16d255418 @precision=nil, @scale=nil, @limit=nil>

Rails 6.1

Rails 6.1 has now fixed this issue.

class Message
  attribute :sent_at, default: -> { Time.now.utc }
end

> Time.now.utc
=> 2020-10-15 12:10:16 UTC
> Message.new.sent_at
=> 2020-10-15 12:10:16 UTC
> Message.type_for_attribute(:sent_at)
=> <ActiveRecord::Type::DateTime:0x00007fa01c1fd650 @precision=6, @scale=nil, @limit=nil>

As we can see, the type here is set to ActiveRecord::Type::DateTime based on the default value, instead of dropping the type.

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