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Services

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Services are a set of reusable functions. They are particularly useful to respect the "don’t repeat yourself" (DRY) programming concept and to simplify controllers logic.

Implementation​

Services can be generated or added manually. Strapi provides a createCoreService factory function that automatically generates core services and allows building custom ones or extend or replace the generated services.

Adding a new service​

A new service can be implemented:

To manually create a service, export a factory function that returns the service implementation (i.e. an object with methods). This factory function receives the strapi instance:

./src/api/restaurant/services/restaurant.js

const { createCoreService } = require('@strapi/strapi').factories;

module.exports = createCoreService('api::restaurant.restaurant', ({ strapi }) =>  ({
  // Method 1: Creating an entirely new custom service
  async exampleService(...args) {
    let response = { okay: true }

    if (response.okay === false) {
      return { response, error: true }
    }

    return response
  },

  // Method 2: Wrapping a core service (leaves core logic in place)
  async find(...args) {  
    // Calling the default core controller
    const { results, pagination } = await super.find(...args);

    // some custom logic
    results.forEach(result => {
      result.counter = 1;
    });

    return { results, pagination };
  },

  // Method 3: Replacing a core service
  async findOne(entityId, params = {}) {
    return strapi.entityService.findOne('api::restaurant.restaurant', entityId, this.getFetchParams(params));
  }
}));
🤓 Entity Service API

To get started creating your own services, see Strapi's built-in functions in the Entity Service API documentation.

Example of a custom email service (using Nodemailer)

The goal of a service is to store reusable functions. A sendNewsletter service could be useful to send emails from different functions in our codebase that have a specific purpose:

./src/api/restaurant/services/restaurant.js


const { createCoreService } = require('@strapi/strapi').factories;
const nodemailer = require('nodemailer'); // Requires nodemailer to be installed (npm install nodemailer)

// Create reusable transporter object using SMTP transport.
const transporter = nodemailer.createTransport({
  service: 'Gmail',
  auth: {
    user: 'user@gmail.com',
    pass: 'password',
  },
});

module.exports = createCoreService('api::restaurant.restaurant', ({ strapi }) => ({
  sendNewsletter(from, to, subject, text) {
    // Setup e-mail data.
    const options = {
      from,
      to,
      subject,
      text,
    };

    // Return a promise of the function that sends the email.
    return transporter.sendMail(options);
  },
}));

The service is now available through the strapi.service('api::restaurant.restaurant').sendNewsletter(...args) global variable. It can be used in another part of the codebase, like in the following controller:

./src/api/restaurant/controllers/restaurant.js

module.exports = createCoreController('api::restaurant.restaurant', ({ strapi }) =>  ({
  // GET /hello
  async signup(ctx) {
    const { userData } = ctx.body;

    // Store the new user in database.
    const user = await strapi.service('plugin::users-permissions.user').add(userData);

    // Send an email to validate his subscriptions.
    strapi.service('api::restaurant.restaurant').sendNewsletter('welcome@mysite.com', user.email, 'Welcome', '...');

    // Send response to the server.
    ctx.send({
      ok: true,
    });
  },
}));
✏️ Note

When a new content-type is created, Strapi builds a generic service with placeholder code, ready to be customized.

Extending core services​

Core services are created for each content-type and could be used by controllers to execute reusable logic through a Strapi project. Core services can be customized to implement your own logic. The following code examples should help you get started.

💡 Tip

A core service can be replaced entirely by creating a custom service and naming it the same as the core service (e.g. find, findOne, create, update, or delete).

Collection type examples
async find(params) {
  // some logic here
  const { results, pagination } = await super.find(params);
  // some more logic

  return { results, pagination };
}
Single type examples
async find(params) {
  // some logic here
  const entity = await super.find(params);
  // some more logic

  return entity;
}

Usage​

Once a service is created, it's accessible from controllers or from other services:

// access an API service
strapi.service('api::apiName.serviceName').FunctionName();
// access a plugin service
strapi.service('plugin::pluginName.serviceName').FunctionName();

In the syntax examples above, serviceName is the name of the service file for API services or the name used to export the service file to services/index.js for plugin services.

💡 Tip

To list all the available services, run yarn strapi services:list.