Handler

The handler is a function that receives a RequestContext object, possibly a list of parameters, and returns an object.

The handler is responsible for processing the request and returning a response.

Creating a Handler

An handler can be defined in the following ways. You can either use an anonymous function or a named function with just one parameter of type RequestContext.

Anonymous Function (Context)

import 'package:serinus/serinus.dart';

class MyController extends Controller {
  MyController({super.path = '/'}) {
    on(Route.get('/'), (context) async {
      return 'Hello World!';
    });
  }
}

Named Function (Context)

import 'package:serinus/serinus.dart';

class MyController extends Controller {
  MyController({super.path = '/'}) {
    on(Route.get('/'), _helloWorld);
  }

  Future<String> _helloWorld(RequestContext context) async {
    return 'Hello World!';
  }
}

Or you can use a named function with the RequestContext and the list of parameters in case of parametric routes.

Anonymous Function (Context, Parameters)

import 'package:serinus/serinus.dart';

class MyController extends Controller {
  MyController({super.path = '/'}) {
    on(Route.get('/<name>'), (RequestContext context, String name) async {
      return 'Hello $name!';
    });
  }
}

Named Function (Context, Parameters)

import 'package:serinus/serinus.dart';

class MyController extends Controller {
  MyController({super.path = '/'}) {
    on(Route.get('/<name>'), _helloWorld);
  }

  Future<String> _helloWorld(RequestContext context, String name) async {
    return 'Hello World $name!';
  }
}

In the case of a parametric route, the handler must have the same number of parameters as the number of parameters in the route and they must follow the same order.

Static Handler

A static handler is a function that does not require a RequestContext object. It is useful when you need to return instant responses. It uses the onStatic method of the Controller class instead of the on method.

import 'package:serinus/serinus.dart';

class MyController extends Controller {
  MyController({super.path = '/'}) {
    onStatic(Route.get('/'), 'Hello World!');
  }
}

Typed body handler

TIP

Before using typed body handlers, make sure to read the Model Provider section.

The handler can also receive a body of a specific type. This is useful when you need to receive a JSON body and convert it to a Dart object.

import 'package:serinus/serinus.dart';

class MyObject {
  String name;

  MyObject({this.name});

  factory MyObject.fromJson(Map<String, dynamic> json) {
    return MyObject(name: json['name']);
  }
}

class MyController extends Controller {
  MyController({super.path = '/'}) {
    on(Route.get('/'), body: MyObject, (RequestContext context, MyObject body) async {
      return 'Hello ${body.name}!';
    });
  }
}

In this case, the handler will receive an instance of MyObject as the second parameter.

In the case of a parametric route, the body must be the second parameter after the context.

import 'package:serinus/serinus.dart';

class MyObject {
  String name;

  MyObject({this.name});

  factory MyObject.fromJson(Map<String, dynamic> json) {
    return MyObject(name: json['name']);
  }
}

class MyController extends Controller {
  MyController({super.path = '/'}) {
    on(Route.get('/<name>'), body: MyObject, (RequestContext context, MyObject body, String name) async {
      return 'Hello $name ${body.name}!';
    });
  }
}