examples.md

Hook examples

There are many ways in which hooks can be used. Below are some examples that show how to quickly add useful functionality to a service. The authentication chapter has more examples on how to use hooks for user authorization.

Setting Timestamps

If the database adapter does not support it already, timestamps can be easily added as a before hook like this:

app.service('todos').before({
  create(hook) {
    hook.data.created_at = new Date();
  },
  
  update(hook) {
    hook.data.updated_at = new Date();
  },
  
  patch(hook) {
    hook.data.updated_at = new Date();
  }
})

Fetching Related Items

Hooks can also be used to fetch related items from other services. The following hook checks for a related query parameter in get and if it exists, includes all todos for the user in the response. Because it is an after hook, hook.result will already be populated with data from the original query. In this case, it's on a service.get request, so hook.result will contain a user object. The hook fetches data from the todos service and creates a todos property on the user object in hook.result:

app.service('users').after({
  get(hook) {
    // The user id
    const id = hook.result.id;
    
    if(hook.params.query.related) {
      return hook.app.service('todos').find({
        query: { user_id: id }
      }).then(todos => {
        // Set the todos on the user property
        hook.result.todos = todos;
        // Always return the hook object or `undefined`
        return hook;
      });
    }
  }
});

Validation

For a production app you need to do validation. With hooks it's actually pretty easy and validation methods can easily be reused.

app.service('users').before({
  create(hook) {
    // Don't create a user unless they accept our terms
    if (!hook.data.acceptedTerms) {
      throw new errors.BadRequest(`Invalid request`, {
        errors: [
          {
            path: 'acceptedTerms',
            value: hook.data.acceptedTerms,
            message: `You must accept the terms`
          }
        ]
      });
    }
  }
});

Sanitization

You might also need to correct or sanitize data that is sent to your app. Also pretty easy and you can check out some of our bundled hooks that cover some common use cases.

app.service('users').before({
  update(hook) {
    // Convert the user's age to an integer
    const sanitizedAge = parseInt(hook.data.age, 10);

    if (isNaN(age)) {
      throw new errors.BadRequest(`Invalid 'age' value ${hook.data.age}`, {
        errors: [
          {
            path: 'age',
            value: hook.data.age,
            message: `Invalid 'age' value ${hook.data.age}`
          }
        ]
      });
    }

    hook.data.age = sanitizedAge;
  }
});

Soft Delete

Sometimes you might not want to actually delete items in the database but just mark them as deleted. We can do this by adding a remove before hook, marking the todo as deleted and then setting hook.result. That way we can completely skip the original service method.

app.service('todos').before({
  remove(hook) {
    // Instead of calling the service remote, call `patch` and set deleted to `true`
    return this.patch(hook.id, { deleted: true }, hook.params).then(data => {
      // Set the result from `patch` as the method call result
      hook.result = data;
      // Always return the hook or `undefined`
      return hook;
    });
  },
  
  find(hook) {
    // Only query items that have not been marked as deleted
    hook.params.query.deleted = { $ne: true };
  }
});

ProTip: Setting hook.result will only skip the actual method. after hooks will still run in the order they have been registered.