# Controllers
Controllers are JavaScript files that contain a set of methods, called actions, reached by the client according to the requested route. Whenever a client requests the route, the action performs the business logic code and sends back the response. Controllers represent the C in the model-view-controller (MVC) pattern.
In most cases, the controllers will contain the bulk of a project's business logic. But as a controller's logic becomes more and more complicated, it's a good practice to use services to organize the code into re-usable parts.
# Implementation
Controllers can be generated or added manually. Strapi provides a createCoreController
factory function that automatically generates core controllers and allows building custom ones or extend or replace the generated controllers.
# Adding a new controller
A new controller can be implemented:
- with the interactive CLI command
strapi generate
- or manually by creating a JavaScript file:
- in
./src/api/[api-name]/controllers/
for API controllers (this location matters as controllers are auto-loaded by Strapi from there) - or in a folder like
./src/plugins/[plugin-name]/server/controllers/
for plugin controllers, though they can be created elsewhere as long as the plugin interface is properly exported in thestrapi-server.js
file (see Server API for Plugins documentation)
- in
Each controller action can be an async
or sync
function.
Every action receives a context object (ctx
) as a parameter. ctx
contains the request context and the response context.
Example: GET /hello route calling a basic controller
A specific GET /hello
route is defined, the name of the router file (i.e. index
) is used to call the controller handler (i.e. index
). Every time a GET /hello
request is sent to the server, Strapi calls the index
action in the hello.js
controller, which returns Hello World!
:
✏️ NOTE
When a new content-type is created, Strapi builds a generic controller with placeholder code, ready to be customized.
# Extending core controllers
Default controllers and actions are created for each content-type. These default controllers are used to return responses to API requests (e.g. when GET /api/articles/3
is accessed, the findOne
action of the default controller for the "Article" content-type is called). Default controllers can be customized to implement your own logic. The following code examples should help you get started.
💡 TIP
An action from a core controller can be replaced entirely by creating a custom action and naming the action the same as the original action (e.g. find
, findOne
, create
, update
, or delete
).
Collection type examples
Single type examples
# Usage
Controllers are declared and attached to a route. Controllers are automatically called when the route is called, so controllers usually do not need to be called explicitly. However, services can call controllers, and in this case the following syntax should be used:
// access an API controller
strapi.controller('api::api-name.controller-name');
// access a plugin controller
strapi.controller('plugin::plugin-name.controller-name');
💡 TIP
To list all the available controllers, run yarn strapi controllers:list
.