Shortcut for getting ids for an ActiveRecord scope
You can use .ids on an ActiveRecord scope to pluck all the ids of the relation:
# Modern Rails
User.where("users.name LIKE 'Foo Bar'").ids
# Rails 3.2+ equivalent
User.where("users.name LIKE 'Foo Bar'").pluck(:id)
# Edge rider equivalent for Rails 2+
User.where("users.name LIKE 'Foo Bar'").collect_ids(:id)
Related cards:
Collect all values for a given column in an ActiveRecord scope
In modern Rails versions you can also use ActiveRecord's pluck method.
User.active.pluck(:id)
=> [1, 5, 23, 42]
If you are plucking from the id c...
Edge Rider: Power tools for ActiveRecord scopes
In our continued quest to extract proven code snippets from makandropedia into tested and upgradable gems, we have released Edge Rider.
Edge Rider was created with two intents:
- Provides a number of ut...
Security issues with hash conditions in Rails 2 and Rails 3
Find conditions for scopes can be given either as an array (:conditions => ['state = ?', 'draft']) or a hash (:conditions => { 'state' => 'draft' }). The later is nicer to read, but has horrible security implications in some versions of Ru...
How to generate GIDs from an ActiveRecord scope
ActiveRecord provides the ids method to pluck ids from a scope, but what if you need to pluck Global IDs?
While you could just call map(&:to_global_id) on your scope, this approach would instantiate each r...
Rails: When defining scopes with class methods, don't use `self`
Sometimes it is useful to define a named scope by implementing a static method with the scope's name on the scoped class. For instance, when a method should decide which existing scope should be the next link in the scope chain. Take this class fo...
Rails I18n scope for humanized attribute names
ActiveModel classes have a class method .human_attribute_name. This returns a human-readable form of the attribute:
Person.human_attribute_name(:first_name) # => "First name"
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Be careful when checking scopes for blankness
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Merging two arbitrary ActiveRecord scopes
(Rails has a method ActiveRecord::Relation#merge that can merge ActiveRecord scopes. However, its behavior has never been clear, and in Rails 7 it still discards conditions on the same column by the last condition. **We disco...
How to remove properties of ActiveRecord scopes
When dealing with AR scopes, you can remove conditions, order, etc by using the unscope method.
It is available on Rails 4+.
Examples
Consider an exemplary User class as follows. For the examples below, we will use a scope that ...
Check if an object is an ActiveRecord scope
Don't say is_a?(ActiveRecord::NamedScope::Scope) because that is no longer true in Rails 3 and also doesn't match unscoped ActiveRecord classes themselves (which we consider scopes for all practical purposes).
A good way is to say this instead:...