A blink into the “rails magic”The meta-programming in Rails / Rails as a code generator

Some rights reservedNikos Dimitrakopoulos, 2009http://blog.nikosd.com

The “classic” rails ingredientsMVCDRYCOC…

Not for today…MVCDRYCOC…

Rails as a code generator

PART I : 100% Static

The directory structure

Models + Tests

Controllers / views + tests

Resources (the whole set)

Even with *implemented* views & controllers (a.k.a. “scaffolds”)

Static(*) API

Nothing special so far…

PART II : 100% On-the-fly

This is where the actual fun begins!

Some basic stuff: ORM

How does Rails map the attributes???

The truth is in the source…

A blink into the “magic”

if we haven’t already generated the “dynamic” methods

if we haven’t already generated the “dynamic” methods generate them

generate them

if we haven’t already generated the “dynamic” methods generate themtry to call the method with the given name again!

generate them

try to call the method with the given name again!

for each column on the db table :

for each column on the db table : define a “read” method

define a “read” method

for each column on the db table : define a “read” method (for example the Guest#name)

define a “read” method

for each column on the db table : define a “read” method(for example the Guest#name) define a “write” method

define a “read” method

define a “write” method

for each column on the db table : define a “read” method(for example the Guest#name) define a “write” method(for example the Guest#name = …)

define a “read” method

define a “write” method

for each column on the db table : define a “read” method(for example the Guest#name) define a “write” method(for example the Guest#name = …) define a “question” method

define a “read” method

define a “write” method

define a “question” method

for each column on the db table : define a “read” method(for example the Guest#name) define a “write” method(for example the Guest#name = …) define a “question” method(for example the Guest#name?)

define a “read” method

define a “write” method

define a “question” method

PART III : Magic happens Everywhere

On the routes / Controllers

+ 3 more by default

+ 3 more by defaultMore info on “resources” : http://api.rubyonrails.org/classes/ActionController/Resources.html

On the ORM / Models

Dynamic finders

Dynamic finders

As said this is just a “blink”

Look for more in :ActiveRecordassociationsActiveRecordnamed_scopesActionControllerroutesActionControllerrenderingActionControllerformatetc…

ActiveRecordassociations

ActiveRecordnamed_scopes

ActionControllerroutes

ActionControllerrendering

ActionControllerformat

etc…

What do we get from this?

What do we get from this?Glue code

Glue code

What do we get from this?Glue codeDomain-aware code

Glue code

Domain-aware code

What do we get from this?Glue codeDomain-aware codeOut of the box

Glue code

Domain-aware code

Out of the box

What do we get from this?Glue codeDomain-aware codeOut of the boxEvery time

Glue code

Domain-aware code

Out of the box

Every time

What do we get from this?Glue codeDomain-aware codeOut of the boxEvery timeOn every app

Glue code

Domain-aware code

Out of the box

Every time

On every app

Compare it with Java or .Net “enterprise” solutions…

Compare it with Java or .Net “enterprise” solutions…© Rubyrags.com

Implement your own!!!

Implement your own!!!(Jim will give you a hint tomorrow at the Ruby Meetup)

Thanks for your time

Thanks for your timeAnd welcome to themagic world of Rubyand Ruby on Rails