goa

Goa

Goa is a very small, very simple MVCish framework for Node. I say "MVCish" because it's built on top of Express which already handles views. So it's more like an "MC" framework. Except it doesn't do much with models, either. Whatever. It does SOMETHING, I'm sure of it.

Installation

Install via NPM: npm install goa

Legacy Express (3.x)

If you need legacy support for Express, you should use a version < 1.0.0 from NPM. Source code is in the express3 branch.

Usage

Goa sits on top of Express. It's Express all the way down. Except for the top. Which is Goa.

Do the thing

Goa is a drop-in replacement for Express: all Goa apps are Express apps.

As of v3.0.0, the interface to create an application changed from goa(...) to goa.createApplication(...). Also, since v3.0.0 promises are supported in both controller actions and controller factories.

As of v2.0.0, express is now a peer dependency which means you must supply your own version of express to goa.

So, inside your sweet app, wherever you would normally initialize Express, do this instead:

const express = require('express');
const goa = require('goa');

const createController = (name, context, callback) => callback(null, {
	index: (params, send) => send(goa.action('yay!'))
});

// or, using a promise
const createControllerViaPromise = async (name, context) => {
	return await getMyController();
};

const app = goa.createApplication(createController, { express });

That will get your new Goa application up and running. Since it's just a normal Express app, you can still configure() and use() and whatnot to your heart's content (note that the express index is exposed on app.express):

app.set('views', __dirname + '/views');
app.set('view engine', 'pug');
// etc.

Adding routes and stuff

Routing is, literally, the same as Express. Because it delegates to the default Express routing. So literally any route you were using in your Express app you can use with Goa. Literally.

The only difference is that it does not use a route handler in the form of function(req, res, next). Instead, in its place, you specify the controller and action that you want to execute.

//the "action" is optional, and defaults to "index" if not given
app.get('/awesome', { controller: 'foo', action: 'bar' });

Controllers and factories

So you need a controller.

A controller factory is a function that creates controllers. It takes three arguments:

1. the name of the controller to create (dictated from your route handler up there)
2. a context, which contains stuff that might be useful (specifically, the req and res)
3. a callback in the normal convention: callback(err, yourSweetController)

The properties on your controller correspond to actions. So if your route handler looks like this: { controller: 'foo', action: 'bar' }, then your foo controller better look like this:

{
	bar: (params, send) => {
		// do stuff
	}
}

You can set up your controller factory however you want. Here's a sample one:

const controllerFactory = (name, context, callback) => {
	//"foo" => "FooController"
	const className = name.charAt(0).toUpperCase() + name.substring(1) + 'Controller';

	//assuming the file name is "controllers/FooController.js"
	const Controller = require('./controllers/' + className);
	callback(null, new Controller(context));
}

Action methods

Action methods are properties on controllers, like the "bar" thing we did up above. They should always return some kind of Result object. There are seven built-in Result objects:

1. ActionResult(content[, contentType, options]) - simply sends whatever content you give it
   • goa.action('foo bar', 'text/plain');
2. JsonResult(json[, options]) - sends JSON
   • goa.json({ foo: 'bar' });
3. FileResult(file[, options]) - sends a file (uses res.sendfile() and res.download())
   • goa.file('/path/to/file');
   • goa.file('/path/to/file', { maxAge: 60000 });
   • goa.file('/path/to/file', { fileName: 'foo.txt' }); - sets Content-Disposition header
   • goa.file('http://example.com/foo.txt'); - acts as reverse proxy
4. ViewResult(view[, params, options]) - renders a view with optional params
   • goa.view('index.jade', { message: 'Welcome!' });
   • goa.view('index.jade', { message: 'Welcome!' }, { contentType: 'text/xml' });
   • goa.view('index.jade', function() { return { message: 'Welcome!' });
5. ErrorResult(error[, options = 500]) - delegates to Express's error handler
   • goa.error(new Error('Verboten!'), 403);
6. RedirectResult(location[, options = 302]) - redirects to location
   • goa.redirect('/foo');
7. EmptyResult([contentType]) - sends an empty response with status 204

All result objects should have an execute(res, next) function, if you decide to implement your own.

Notice that each Result constructor has an options parameter. This can be used for setting the status code of any of the results (it may be used for additional things in the future). For all results except EmptyResult you can simply pass a number for the status code, or an object { status: 404 }: they are equivalent. EmptyResult always sets the status code to 204 No Content.

The preferred way of using the built-in result objects is via their factory functions on the goa object, e.g. goa.view('myview'). But, if you like typing, you can also access their constructors directly off of the goa.results object: new goa.results.ViewResult('myview').

Action methods are passed a params object, which is a conglomeration of req.query, req.body and req.params, in that order. That is, req.query.foo will be overridden by req.body.foo, which will be overridden by req.params.foo.

If you need access to the raw request, you should make sure and inject the context object into your controller and then you can do things like var referrer = context.req.headers.referer; or something.

So your controller should do something like this:

class MyController {
	constructor(context, db) {
		this.context = context;
		this.db = db;
	}
	
	index(params, send) {
		send(goa.view('index.pug', {
			message: 'Welcome',
			referrer: this.context.req.headers.referer
		}));
	}
	
	save(params, send) {
		const record = { content: params.content };
		this.db.insert(record, (err, result) => {
			if (err) {
				send(goa.error(err));
				return;
			}
	
			send(goa.redirect(`/edit/${result.id}`));
		});
	}
	
	// also supports promises
	async savePromise(params, send) {
		try {
			const result = await this.db.insert(record);
			send(goa.redirect(`/edit/${result.id}`));
		} catch (e) {
			send(goa.error(e));
		}
	}
}

The same in TypeScript:

import * as goa from 'goa';

interface SaveParams {
	content: string;
}

class MyController {
	private readonly context: goa.ControllerContext;
	private readonly db: any;
	
	public constructor(context: goa.ControllerContext, db: any) {
		this.context = context;
		this.db = db;
	}
	
	index(params: goa.ActionParams, send: goa.Send) {
		send(goa.view('index.pug', {
			message: 'Welcome',
			referrer: this.context.req.headers.referer
		}));
	}
	
	save(params: goa.ActionParams<SaveParams>, send: goa.Send) {
		const record: any = { content: params.content };
		this.db.insert(record, (err, result) => {
			if (err) {
				send(goa.error(err));
				return;
			}
	
			send(goa.redirect(`/edit/${result.id}`));
		});
	}
	
	public async savePromise(params: goa.ActionParams<SaveParams>, send: goa.Send) {
		try {
			const record: any = { content: params.content };
			const result = await this.db.insert(record);
			send(goa.redirect(`/edit/${result.id}`));
		} catch (e) {
			send(goa.error(e));
		}
	}
}

Unknown Actions

If an action is attempting to be executed, that doesn't exist on the controller, goa will raise an error, which you can handle in your express error handler.

If you want more finegrained control over those errors, you can define a handleUnknownAction method on your controller.

{
	handleUnknownAction: (params, send) => {
		send(goa.view('errors/404', { message: 'That page does not exist' }, 404));
	}
}

Hooking into rendering process

The send argument also accepts an onComplete callback:

{
	myAction: (params, send) => {
		const renderStart = Date.now();
		send(goa.view('some/view', { hello: 'world' }), (err) => {
			if (err) {
				console.error(`rendering encountered an error: ${err.message}`);
			}
			const renderElapsed = Date.now() - renderStart;
			console.log(`rendering took ${renderElapsed}ms`);
		});
	}
}

Note that any errors thrown from the onComplete callback will be ignored.

The onComplete callback can return a promise. Note that the promise will resolve before sending the response back to the client, so it's not recommended to perform any heavy tasks inside the onComplete callback as it can hide slowness from the normal program flow. Errors resulting from a rejected promise are ignored.

{
	myAction: (params, send) => {
		const renderStart = Date.now();
		send(goa.view('some/view', { hello: 'world' }), async (err) => {
			const renderElapsed = Date.now() - renderStart;
			await db.execute('INSERT INTO render_times (timestamp, elapsed) VALUES (?, ?)', Date.now(), renderElapsed);
		});
	}
}

Putting it all together

So, to set up your routes to use the controller above, you would do something like this:

app.get('/', { controller: 'my' });
app.post('/save', { controller: 'my', action: 'save' });

As mentioned earlier, you can also use router parameters to define the controller and action:

// would handle requests like "/foo/bar" -> "foo" controller, "bar" action
app.get('/:controller/:action', {});

// "/post/edit/1" => "blog" controller, "edit" action; id would be in params.id
app.get('/post/:action/:id', { controller: 'blog' });