mirror of
https://github.com/jbranchaud/til
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43 lines
1.5 KiB
Markdown
43 lines
1.5 KiB
Markdown
# Mark For Destruction
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Do you have some complicated logic or criteria for deleting associated
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records? [ActiveRecord's
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`#mark_for_destruction`](http://api.rubyonrails.org/classes/ActiveRecord/AutosaveAssociation.html#method-i-mark_for_destruction) may come in handy.
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Let's say we have _users_ who author _articles_. We want to delete some of
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the user's articles based on some criteria -- those articles that have odd
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`id`s.
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```ruby
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> user = User.first
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#=> #<User...>
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> user.articles.each { |a| a.mark_for_destruction if a.id.odd? }
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#=> [#<Article...>, ...]
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> user.articles.find(1).marked_for_destruction?
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#=> true
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> user.articles.find(2).marked_for_destruction?
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#=> false
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```
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We've marked our articles for destruction and confirmed as much with the
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[`#marked_for_destruction?`](http://api.rubyonrails.org/classes/ActiveRecord/AutosaveAssociation.html#method-i-marked_for_destruction-3F) method. Now, to go through with the destruction, we just have to save the parent record -- the user.
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```ruby
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> user.save
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(0.2ms) BEGIN
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User Exists (0.8ms) SELECT 1 AS one FROM "users" WHERE ("users"."email" = 'person1@example.com' AND "users"."id" != 1) LIMIT 1
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SQL (3.0ms) DELETE FROM "articles" WHERE "articles"."id" = $1 [["id", 1]]
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SQL (0.2ms) DELETE FROM "articles" WHERE "articles"."id" = $1 [["id", 3]]
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(2.1ms) COMMIT
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=> true
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```
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Note: the parent record must have `autosave: true` declared on the
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association.
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```ruby
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class User < ActiveRecord::Base
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has_many :articles, autosave: true
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end
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```
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