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30 lines
808 B
Markdown
30 lines
808 B
Markdown
# Write Reversible Migration To Set Default
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You can use the `change_column_default` method to alter the default value of a
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column. If the column doesn't have a default, then you'd essentially be
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changing the default from `nil` to _some value_.
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```ruby
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def up
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change_column_default :books, :published, false
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end
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def down
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change_column_default :books, :published, nil
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end
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```
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This is fine, but you can write the migration as a single, reversible `change`
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method using the `:from` and `:to` options.
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```ruby
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def change
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change_column_default :books, :published, from: nil, to: false
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end
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```
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When you migrate, the default will be set to `false`. When you rollback, the
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default will be removed.
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[source](https://blog.arkency.com/how-to-add-a-default-value-to-an-existing-column-in-a-rails-migration/)
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