Today I discovered Merb, and it definitely is da bomb class stuff!

What is it? It's a rails like MVC framework without the sucky parts.

The problem with rails is, although convention over configuration is generally a good thing, but sometimes it's hard to draw the line where it is. Merb don't do lots of things for you automatically like rails, so you have the freedom to do things in your own unique way.

Notable features of merbs are:

Pluggable ORM

When you generate a new app, it doesn't assume you're using a DB. so merb can be used to create app without DB need, and server management frontend, cron job admin, etc. Even if you need to use ORM, you have the choice to use activereord, or other ORM I've never heard of, like Datamapper, Sequel.

Manual rendering

Rails' action automatically calls render method for you. This pose some problems, you can't render multiple times or you get double render exception; you can't have nested layout, although people did create nested_layout plugin to work it around.

In merb, you have to call render manually. which just returns the output text as result. want nested layout? then render with different layouts as many times as you want, in situations like you want to provide theme support. As said in ancient Chinese proverb, 进一步，山穷水尽；退一步，海阔天空。(One step forward, you're stuck in nowhere; one step back, there's world of possibilities).

Rails has something similar method called render_to_string, in merb, it's first class citizen.

Plugin dependency

If you've been working with rails for awhile, then you know how much rails plugin suck. There's no plugin dependency, I see people either copy all plugin B code into plugin A if A needs B, or rename plugins since rails loads plugins alphabetically. Note, rails do allow you to configure plugin loading order now.

In merb, plugin is just a gem, multiple versions and dependency are all built in.

Summary

To give credit to rails, merb did "steal" lot of code from rails, but the framwork has vastly different approach. Merb tries to stay agile, a micro framework, yet provides support to allow component builders to add functionality easily.

Merb's tool and coding syntax usage are very similar to rails, so rails developer should be able to learn and use it without much difficulty.

For all rails developers, it's definitely something to dive into.

trivia

One thing intrigues me is that merb is on the domain merbivore.com, not merb.com. After some poking around, then I found out merb.com's owner wanted either $25000 lum sum or $500 monthly rent for use of the domain. No love for open source. :(