### Install Paranoia Gem for Rails

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Specifies the gem version to install for different Rails versions. Includes options for installing directly from GitHub. Requires running 'bundle install' afterwards.

```ruby
gem "paranoia", "~> 1.0"
```

```ruby
gem "paranoia", "~> 2.2"
```

```ruby
gem "paranoia", github: "rubysherpas/paranoia", branch: "rails3"
```

```ruby
gem "paranoia", github: "rubysherpas/paranoia", branch: "rails4"
```

```ruby
gem "paranoia", github: "rubysherpas/paranoia", branch: "rails5"
```

--------------------------------

### Paranoia Gem Callback Example for Search Engine Integration

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

This example illustrates how to use Paranoia's callbacks (`after_destroy`, `after_restore`, `after_real_destroy`) to integrate with a search engine. It defines methods to update search engine documents when records are marked as deleted, restored, or permanently removed.

```ruby
class Product < ActiveRecord::Base
  acts_as_paranoid

  after_destroy      :update_document_in_search_engine
  after_restore      :update_document_in_search_engine
  after_real_destroy :remove_document_from_search_engine
end

```

--------------------------------

### Shared Examples: Verify Paranoid Model Behavior in Ruby

Source: https://github.com/rubysherpas/paranoia/wiki/Testing-with-rspec

These shared examples provide a robust way to test that models are correctly implementing `acts_as_paranoid`. They check for the presence of the `deleted_at` column and index, and verify the behavior of the `deleted_at` where clause, including its exclusion when `unscoped` is used. This relies on the Shoulda Matchers gem.

```ruby
shared_examples_for 'a Paranoid model' do

  it { is_expected.to have_db_column(:deleted_at) }

  it { is_expected.to have_db_index(:deleted_at) }

  it 'adds a deleted_at where clause' do
    expect(described_class.all.where_sql).to include('`deleted_at` IS NULL')
  end

  it 'skips adding the deleted_at where clause when unscoped' do
    expect(described_class.unscoped.where_sql.to_s).not_to include('`deleted_at`')  # to_s to handle nil.
  end
end
```

--------------------------------

### RSpec Matcher: Test Acts As Paranoid in Ruby

Source: https://github.com/rubysherpas/paranoia/wiki/Testing-with-rspec

This RSpec matcher simplifies testing if a model correctly includes the `acts_as_paranoid` functionality. It requires the `rails_helper` and `RSpec` to be set up. The primary input is the model being tested.

```ruby
require 'rails_helper'

RSpec.describe Foo, type: :model do
  it { is_expected.to act_as_paranoid }
end
```

--------------------------------

### Access Soft-Deleted Associations

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Provides an example of how to override an association getter method to include soft-deleted records when accessing them, using 'unscoped'.

```ruby
def product
  Product.unscoped { super }
end
```

--------------------------------

### Restore Records with Paranoia

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Demonstrates various ways to restore soft-deleted records using the Paranoia gem. This includes restoring single records, multiple records, recursively restoring associated records, and restoring within a specified time window. It also shows how to trigger after_commit callbacks during restoration.

```ruby
Client.restore([id1, id2, ..., idN])
Client.restore(id, :recursive => true)
client.restore(:recursive => true)
Client.restore(id, :recursive => true, :recovery_window => 2.minutes)
client.restore(:recursive => true, :recovery_window => 2.minutes)
```

```ruby
class Client < ActiveRecord::Base
  acts_as_paranoid after_restore_commit: true

  after_commit          :commit_called, on: :restore
  # or
  after_restore_commit  :commit_called
  ...
end
```

--------------------------------

### Optimizing Database Indexes for Paranoia

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Provides guidance on adapting database indexes to work efficiently with Paranoia's soft deletion. It demonstrates how to replace existing `add_index` statements with `where` clauses to only index active (not deleted_at IS NULL) records, and offers alternatives for unique indexes using computed columns or a sentinel column.

```ruby
add_index :clients, :group_id, where: "deleted_at IS NULL"
add_index :clients, [:group_id, :other_id], where: "deleted_at IS NULL"
```

```ruby
add_index :clients, [:group_id, 'COALESCE(deleted_at, false)'], unique: true
```

```ruby
add_column :clients, :active, :boolean
add_index :clients, [:group_id, :active], unique: true

class Client < ActiveRecord::Base
  acts_as_paranoid column: :active, sentinel_value: true

  def paranoia_restore_attributes
    {
      deleted_at: nil,
      active: true
    }
  end

  def paranoia_destroy_attributes
    {
      deleted_at: current_time_from_proper_timezone,
      active: nil
    }
  end
end
```

--------------------------------

### Restore a Soft-Deleted Record

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Demonstrates how to restore a soft-deleted record using its ID with the 'restore' class method.

```ruby
Client.restore(id)
```

--------------------------------

### Generate Migration for Deleted At Column

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Provides the Rails generator command to create a migration for adding the 'deleted_at' datetime column with an index. Also shows the Ruby code for the migration itself.

```shell
bin/rails generate migration AddDeletedAtToClients deleted_at:datetime:index
```

```ruby
class AddDeletedAtToClients < ActiveRecord::Migration
  def change
    add_column :clients, :deleted_at, :datetime
    add_index :clients, :deleted_at
  end
end
```

--------------------------------

### Enable Global `delete_all` in Paranoia Gem

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

This snippet shows how to globally enable the `delete_all` method for the Paranoia gem by setting a configuration flag in the Rails environment file. This allows for mass deletion of soft-deleted records.

```ruby
Paranoia.delete_all_enabled = true

```

--------------------------------

### Correct acts_as_paranoid on Concrete Class (Ruby)

Source: https://github.com/rubysherpas/paranoia/wiki/Inheriting-from-an-Abstract-Class

Illustrates the correct way to use `acts_as_paranoid` by applying it directly to the concrete inherited class, ensuring proper table name resolution in SQL queries.

```ruby
class BaseClass < ActiveRecord::Base
  self.abstract_class = true
end

class InheritedClass < BaseClass
  acts_as_paranoid
end

# This will produce the correct SQL query
>> InheritedClass.scoped.where_sql
# => "WHERE (`inherited_classes`.deleted_at IS NULL)"

```

--------------------------------

### Perform Soft and Permanent Deletion

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Illustrates how to perform a soft delete by calling 'destroy' on a model instance, which sets the 'deleted_at' timestamp. Also shows how to permanently delete a record using 'really_destroy!'.

```ruby
>> client.deleted_at
# => nil
>> client.destroy
# => client
>> client.deleted_at
# => [current timestamp]
```

```ruby
>> client.deleted_at
# => nil
>> client.really_destroy!
# => client
```

--------------------------------

### Enable Paranoia Soft Deletion in Model

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Demonstrates how to enable the paranoia soft-deletion functionality in an ActiveRecord model by including the 'acts_as_paranoid' macro.

```ruby
class Client < ActiveRecord::Base
  acts_as_paranoid

  # ...
end
```

--------------------------------

### Query Records Including Deleted Ones

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Demonstrates how to retrieve all records, including those that have been soft-deleted, by using the 'with_deleted' scope.

```ruby
Client.with_deleted
```

--------------------------------

### Enable `delete_all` for Specific Models in Paranoia Gem

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

This snippet demonstrates how to enable the `delete_all` method on a per-model basis when using the Paranoia gem. It's configured directly within the model definition using the `acts_as_paranoid` macro.

```ruby
class User < ActiveRecord::Base
  acts_as_paranoid(delete_all_enabled: true)
end

```

--------------------------------

### Incorrect acts_as_paranoid on Abstract Base Class (Ruby)

Source: https://github.com/rubysherpas/paranoia/wiki/Inheriting-from-an-Abstract-Class

Demonstrates the incorrect application of `acts_as_paranoid` on an abstract base class, leading to an empty table name in SQL queries. This pattern should be avoided.

```ruby
class BaseClass < ActiveRecord::Base
  self.abstract_class = true
  
  acts_as_paranoid
end

class InheritedClass < BaseClass
end

# This will produce an incorrect SQL query
>> InheritedClass.scoped.where_sql
# => "WHERE (``.deleted_at IS NULL)"

```

--------------------------------

### Include Soft-Deleted Associated Objects

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Shows how to use a lambda with 'with_deleted' on a belongs_to association to ensure that soft-deleted associated objects are included in queries.

```ruby
class Person < ActiveRecord::Base
  belongs_to :group, -> { with_deleted }
end

Person.includes(:group).all
```

--------------------------------

### Skip Default Scope with Paranoia

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Demonstrates how to prevent Paranoia from automatically adding a default scope to queries, allowing direct access to all records regardless of their deletion status.

```ruby
class Client < ActiveRecord::Base
  acts_as_paranoid without_default_scope: true

  ...
end
```

--------------------------------

### Query Only Soft-Deleted Records

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Shows how to retrieve only the records that have been soft-deleted by applying the 'only_deleted' scope.

```ruby
Client.only_deleted
```

--------------------------------

### Use Custom Deletion Column with Paranoia

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Explains how to configure Paranoia to use a custom column name for storing the deletion timestamp instead of the default 'deleted_at'.

```ruby
class Client < ActiveRecord::Base
  acts_as_paranoid column: :destroyed_at

  ...
end
```

--------------------------------

### Paranoia Association Callback Behavior

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Explains how `dependent: :destroy` associations behave when the parent model uses Paranoia. If both parent and child models have `acts_as_paranoid`, `destroy` on the parent calls `destroy` on children, preserving them with `deleted_at`. If the child does not use Paranoia, `destroy` on the parent will truly destroy the children.

```ruby
class Client < ActiveRecord::Base
  acts_as_paranoid

  has_many :emails, dependent: :destroy
end

class Email < ActiveRecord::Base
  acts_as_paranoid

  belongs_to :client
end
```

```ruby
class Client < ActiveRecord::Base
  acts_as_paranoid

  has_many :emails, dependent: :destroy
end

class Email < ActiveRecord::Base
  belongs_to :client
end
```

--------------------------------

### Per-Model Sentinel Value Configuration in Paranoia

Source: https://github.com/rubysherpas/paranoia/wiki/Custom-sentinel-values

This Ruby code snippet demonstrates how to configure a specific sentinel value for the Paranoia gem on a per-model basis. This is useful for overriding the global default or when specific models require a different non-null value to represent a 'not deleted' state, thus avoiding potential issues with unique index constraints involving nullable columns.

```ruby
acts_as_paranoid sentinel_value: DateTime.new(0)
```

--------------------------------

### Association Validation with Paranoia

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Shows how to use the `association_not_soft_destroyed` validator provided by the Paranoia gem to prevent associations with soft-deleted records. If a soft-deleted record is associated, the main object will be marked as invalid with a validation error.

```ruby
validates :some_assocation, association_not_soft_destroyed: true
```

--------------------------------

### Query Records Excluding Deleted Ones

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Illustrates how to retrieve only records that have not been soft-deleted, useful when the default scope is disabled, using the 'without_deleted' scope.

```ruby
Client.without_deleted
```

--------------------------------

### Skip Timestamp Updates on Permanent Deletion

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Shows how to call 'really_destroy!' with the 'update_destroy_attributes: false' option to skip updating timestamps during a permanent deletion, affecting associated records as well.

```ruby
>> client.really_destroy!(update_destroy_attributes: false)
# => client
```

--------------------------------

### Global Sentinel Value Configuration in Paranoia

Source: https://github.com/rubysherpas/paranoia/wiki/Custom-sentinel-values

This Ruby code snippet shows how to set a global sentinel value for the Paranoia gem within a Rails application. This configuration is typically placed in an initializer file and affects all models using the gem, providing a consistent non-null value to represent 'not deleted' records and mitigate unique index constraint problems.

```ruby
Paranoia.default_sentinel_value = DateTime.new(0)
```

--------------------------------

### Check if a Record is Soft-Deleted

Source: https://github.com/rubysherpas/paranoia/blob/core/README.md

Provides two methods, 'paranoia_destroyed?' and 'deleted?', to check if an individual record instance has been soft-deleted.

```ruby
client.paranoia_destroyed?
```

```ruby
client.deleted?
```

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