# 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. Just like all the other parts of the Strapi backend, controllers can be customized.

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

A new controller can be implemented:

// path: ./src/api/[api-name]/controllers/my-controller.js

module.exports = {
  exampleAction: async (ctx, next) => {
    try {
      ctx.body = 'ok';
    } catch (err) {
      ctx.body = err;
    }
  }
};

Each controller action can be an async or sync function. Every action receives a context object (ctx) as the first 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, which takes hello.index as a handler. 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!: 

// path: ./src/api/hello/routes/router.js

module.exports = {
  routes: [
    {
      method: 'GET',
      path: '/hello',
      handler: 'hello.index',
    }
  ]
}

// path: ./src/api/hello/controllers/hello.js

module.exports = {
  index: async (ctx, next) => { // called by GET /hello 
    ctx.body = 'Hello World!'; // we could also send a JSON
  },
};

When a new content-type is created, Strapi builds a generic controller for it and allows overriding and extending it in the generated files.

💡 TIP

Use the code for the default controller actions of collection types (opens new window) and single types (opens new window) in Strapi's Github repository to create custom controllers or extend the existing ones.

# Usage

Controllers are called different ways depending on their scope:

  • for API controllers, use:
    • strapi.api('api-name').controller('controller-name')
    • or strapi.controller('api::api-name.controller-name')
  • for plugin controllers, use:
    • strapi.plugin('plugin-name').controller('controller-name')
    • or strapi.controller('plugin::plugin-name.controller-name')

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