rails-concern

Name: rails-concern
Author: ThibautBaissac

47installs79forks

How to install rails-concern?

thibautbaissac/rails_ai_agents/rails-concern

$npx -y skills add ThibautBaissac/rails_ai_agents --skill rails-concern

Installs into the current project.

Summary

Creates Rails concerns for shared behavior across models or controllers with TDD. Use when extracting shared code, creating reusable modules, DRYing up models/controllers, or when user mentions concerns, modules, mixins, or shared behavior. WHEN NOT: Logic used by only one model

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SKILL.md

1	# Rails Concern Generator (TDD)
2
3	Creates concerns (ActiveSupport::Concern modules) for shared behavior with specs first.
4
5	## Quick Start
6
7	1. Write failing spec testing the concern behavior
8	2. Run spec to confirm RED
9	3. Implement concern in `app/models/concerns/` or `app/controllers/concerns/`
10	4. Run spec to confirm GREEN
11
12	## When to Use Concerns
13
14	Good use cases:
15	- Shared validations across multiple models
16	- Common scopes used by several models
17	- Shared callbacks (e.g., UUID generation)
18	- Controller authentication/authorization helpers
19	- Pagination or filtering logic
20
21	Avoid concerns when:
22	- Logic is only used in one place (YAGNI)
23	- Creating "god" concerns with unrelated methods
24	- Logic should be a service object instead
25
26	## TDD Workflow
27
28	### Step 1: Create Concern Spec (RED)
29
30	For Model Concerns, test via a model that includes it:
31
32	```ruby
33	# spec/models/concerns/[concern_name]_spec.rb
34	RSpec.describe [ConcernName] do
35	# Create a test class that includes the concern
36	let(:test_class) do
37	Class.new(ApplicationRecord) do
38	self.table_name = "events" # Use existing table
39	include [ConcernName]
40	end
41	end
42
43	let(:instance) { test_class.new }
44
45	describe "included behavior" do
46	it "adds the expected methods" do
47	expect(instance).to respond_to(:method_from_concern)
48	end
49	end
50
51	describe "#method_from_concern" do
52	it "behaves as expected" do
53	expect(instance.method_from_concern).to eq(expected_value)
54	end
55	end
56
57	describe "class methods" do
58	it "adds scope" do
59	expect(test_class).to respond_to(:scope_name)
60	end
61	end
62	end
63	```
64
65	Alternative: Test through an actual model that uses the concern:
66
67	```ruby
68	# spec/models/event_spec.rb
69	RSpec.describe Event, type: :model do
70	describe "[ConcernName] behavior" do
71	describe "#method_from_concern" do
72	let(:event) { build(:event) }
73
74	it "does something" do
75	expect(event.method_from_concern).to eq(expected)
76	end
77	end
78	end
79	end
80	```
81
82	For Controller Concerns, test via request specs:
83
84	```ruby
85	# spec/requests/[feature]_spec.rb
86	RSpec.describe "[Feature]", type: :request do
87	describe "pagination (from Paginatable concern)" do
88	let(:user) { create(:user) }
89	before { sign_in user }
90
91	it "paginates results" do
92	create_list(:resource, 30, account: user.account)
93	get resources_path
94	expect(response.body).to include("page")
95	end
96	end
97	end
98	```
99
100	### Step 2: Run Spec (Confirm RED)
101
102	```bash
103	bundle exec rspec spec/models/concerns/[concern_name]_spec.rb
104	# OR
105	bundle exec rspec spec/models/[model]_spec.rb
106	```
107
108	### Step 3: Implement Concern (GREEN)
109
110	Model Concern:
111
112	```ruby
113	# app/models/concerns/[concern_name].rb
114	module [ConcernName]
115	extend ActiveSupport::Concern
116
117	included do
118	# Callbacks
119	before_validation :generate_uuid, on: :create
120
121	# Validations
122	validates :uuid, presence: true, uniqueness: true
123
124	# Scopes
125	scope :with_uuid, ->(uuid) { where(uuid: uuid) }
126	scope :recent, -> { order(created_at: :desc) }
127	end
128
129	# Class methods
130	class_methods do
131	def find_by_uuid!(uuid)
132	find_by!(uuid: uuid)
133	end
134	end
135
136	# Instance methods
137	def generate_uuid
138	self.uuid \|\|= SecureRandom.uuid
139	end
140
141	def short_uuid
142	uuid&.split("-")&.first
143	end
144	end
145	```
146
147	Controller Concern:
148
149	```ruby
150	# app/controllers/concerns/[concern_name].rb
151	module [ConcernName]
152	extend ActiveSupport::Concern
153
154	included do
155	before_action :set_locale
156	helper_method :current_locale
157	end
158
159	class_methods do
160	def skip_locale_for(*actions)
161	skip_before_action :set_locale, only: actions
162	end
163	end
164
165	private
166
167	def set_locale
168	I18n.locale = params[:locale] \|\| I18n.default_locale
169	end
170
171	def current_locale
172	I18n.locale
173	end
174	end
175	```
176
177	### Step 4: Run Spec (Confirm GREEN)
178
179	```bash
180	bundle exec rspec spec/models/concerns/[concern_name]_spec.rb
181	```
182
183	## Common Concern Patterns
184
185	### Pattern 1: UUID Generation
186
187	```ruby
188	# app/models/concerns/has_uuid.rb
189	module HasUuid
190	extend ActiveSupport::Concern
191
192	included do
193	before_validation :generate_uuid, on: :create
194	validates :uuid, presence: true, uniqueness: true
195	end
196
197	private
198
199	def generate_uuid
200	self.uuid \|\|= SecureRandom.uuid
201	end
202	end
203	```
204
205	### Pattern 2: Soft Delete
206
207	```ruby
208	# app/models/concerns/soft_deletable.rb
209	module SoftDeletable
210	extend ActiveSupport::Concern
211
212	included do
213	scope :active, -> { where(deleted_at: nil) }
214	scope :deleted, -> { where.not(deleted_at: nil)

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Type

rails-concern

47installs79forks

View on GitHub

How to install rails-concern?

thibautbaissac/rails_ai_agents/rails-concern

$npx -y skills add ThibautBaissac/rails_ai_agents --skill rails-concern

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# Rails Concern Generator (TDD)
2
3	Creates concerns (ActiveSupport::Concern modules) for shared behavior with specs first.
4
5	## Quick Start
6
7	1. Write failing spec testing the concern behavior
8	2. Run spec to confirm RED
9	3. Implement concern in `app/models/concerns/` or `app/controllers/concerns/`
10	4. Run spec to confirm GREEN
11
12	## When to Use Concerns
13
14	Good use cases:
15	- Shared validations across multiple models
16	- Common scopes used by several models
17	- Shared callbacks (e.g., UUID generation)
18	- Controller authentication/authorization helpers
19	- Pagination or filtering logic
20
21	Avoid concerns when:
22	- Logic is only used in one place (YAGNI)
23	- Creating "god" concerns with unrelated methods
24	- Logic should be a service object instead
25
26	## TDD Workflow
27
28	### Step 1: Create Concern Spec (RED)
29
30	For Model Concerns, test via a model that includes it:
31
32	```ruby
33	# spec/models/concerns/[concern_name]_spec.rb
34	RSpec.describe [ConcernName] do
35	# Create a test class that includes the concern
36	let(:test_class) do
37	Class.new(ApplicationRecord) do
38	self.table_name = "events" # Use existing table
39	include [ConcernName]
40	end
41	end
42
43	let(:instance) { test_class.new }
44
45	describe "included behavior" do
46	it "adds the expected methods" do
47	expect(instance).to respond_to(:method_from_concern)
48	end
49	end
50
51	describe "#method_from_concern" do
52	it "behaves as expected" do
53	expect(instance.method_from_concern).to eq(expected_value)
54	end
55	end
56
57	describe "class methods" do
58	it "adds scope" do
59	expect(test_class).to respond_to(:scope_name)
60	end
61	end
62	end
63	```
64
65	Alternative: Test through an actual model that uses the concern:
66
67	```ruby
68	# spec/models/event_spec.rb
69	RSpec.describe Event, type: :model do
70	describe "[ConcernName] behavior" do
71	describe "#method_from_concern" do
72	let(:event) { build(:event) }
73
74	it "does something" do
75	expect(event.method_from_concern).to eq(expected)
76	end
77	end
78	end
79	end
80	```
81
82	For Controller Concerns, test via request specs:
83
84	```ruby
85	# spec/requests/[feature]_spec.rb
86	RSpec.describe "[Feature]", type: :request do
87	describe "pagination (from Paginatable concern)" do
88	let(:user) { create(:user) }
89	before { sign_in user }
90
91	it "paginates results" do
92	create_list(:resource, 30, account: user.account)
93	get resources_path
94	expect(response.body).to include("page")
95	end
96	end
97	end
98	```
99
100	### Step 2: Run Spec (Confirm RED)
101
102	```bash
103	bundle exec rspec spec/models/concerns/[concern_name]_spec.rb
104	# OR
105	bundle exec rspec spec/models/[model]_spec.rb
106	```
107
108	### Step 3: Implement Concern (GREEN)
109
110	Model Concern:
111
112	```ruby
113	# app/models/concerns/[concern_name].rb
114	module [ConcernName]
115	extend ActiveSupport::Concern
116
117	included do
118	# Callbacks
119	before_validation :generate_uuid, on: :create
120
121	# Validations
122	validates :uuid, presence: true, uniqueness: true
123
124	# Scopes
125	scope :with_uuid, ->(uuid) { where(uuid: uuid) }
126	scope :recent, -> { order(created_at: :desc) }
127	end
128
129	# Class methods
130	class_methods do
131	def find_by_uuid!(uuid)
132	find_by!(uuid: uuid)
133	end
134	end
135
136	# Instance methods
137	def generate_uuid
138	self.uuid \|\|= SecureRandom.uuid
139	end
140
141	def short_uuid
142	uuid&.split("-")&.first
143	end
144	end
145	```
146
147	Controller Concern:
148
149	```ruby
150	# app/controllers/concerns/[concern_name].rb
151	module [ConcernName]
152	extend ActiveSupport::Concern
153
154	included do
155	before_action :set_locale
156	helper_method :current_locale
157	end
158
159	class_methods do
160	def skip_locale_for(*actions)
161	skip_before_action :set_locale, only: actions
162	end
163	end
164
165	private
166
167	def set_locale
168	I18n.locale = params[:locale] \|\| I18n.default_locale
169	end
170
171	def current_locale
172	I18n.locale
173	end
174	end
175	```
176
177	### Step 4: Run Spec (Confirm GREEN)
178
179	```bash
180	bundle exec rspec spec/models/concerns/[concern_name]_spec.rb
181	```
182
183	## Common Concern Patterns
184
185	### Pattern 1: UUID Generation
186
187	```ruby
188	# app/models/concerns/has_uuid.rb
189	module HasUuid
190	extend ActiveSupport::Concern
191
192	included do
193	before_validation :generate_uuid, on: :create
194	validates :uuid, presence: true, uniqueness: true
195	end
196
197	private
198
199	def generate_uuid
200	self.uuid \|\|= SecureRandom.uuid
201	end
202	end
203	```
204
205	### Pattern 2: Soft Delete
206
207	```ruby
208	# app/models/concerns/soft_deletable.rb
209	module SoftDeletable
210	extend ActiveSupport::Concern
211
212	included do
213	scope :active, -> { where(deleted_at: nil) }
214	scope :deleted, -> { where.not(deleted_at: nil)

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Type