the even darker art of rails engines

The

Even-Darker Artof

Rails Engines

@lazyatom

github.com/lazyatom/engines

Rails 2.3

history

November 2005

it’s distracting!

reuse is overrated!

Evil!Evil!

Evil!Evil!

Evil!Evil!

Evil!

Evil!Shit!

eek!

appable_plugins

desert

merb slices?

engines

!"#$%&!"#$'#(%&$#)&!"#$%&*$+,#-.!)

!"#$%&'()$$*%&'()$++,$-'%!.%&'()./0#'12%)/'0"0!

3$405/0"6$%1"$7-(5/06$8/)9$%0$%77:$!/1";)'1<=!"#$"05/0">$$9%6.%77.!/1";)'1<>"0!

3$?")(106$)1("$/#$)9"$"05/0"$69/76$8/)9$%$1'()/05$#/-"!"#$1'()"!>$$@/-"="A/6)>B1'()/05.#/-"C"0!

!"#$D/"8.7%)9$$@/-"=E'/0B!/1";)'1<F$G%77GF$GD/"86GC"0!

app/controllers/models/helpers/views/metal/

*$+,#-&"**&23-'!3$$(!&*$+,#-523-'!3$$(!.!)

;-%66$H-(5/0I'0)1'--"1/0/1**$#2"'#3-43-'!3$$(!$$!"#$/0!"A$$$$1"0!"1$J)"A)$,K$LM"--'F$H-(5/0NL$$"0!"0!

9"-7"1$J%--won’t load from your plugin

Ticket #1905

config/routes.rb

O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+

$$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L7-(5/0LF$$$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL

"0!

*$+,#-&23-6#,&!3+'(%.!)

top precedence

O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+$$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L7-(5/0LF$$$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL"0!

O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+$$3$===$')9"1$1'()"6$===$$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L%77LF$$$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL$$3$===$')9"1$1'()"6$==="0!

in your plugin:

in your app:

O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+$$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L7-(5/0LF$$$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL"0!

O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+$$3$===$')9"1$1'()"6$===$$2%7=;'00";)$G:7%)9GF$J;'0)1'--"1$,K$L%77LF$$$$$$$$$$$$$$$$$$$$$$$$J%;)/'0$,K$L/0!"AL$$3$===$')9"1$1'()"6$==="0!

in your plugin:

in your app:

Ticket #2592(also Ticket #329)

785*$+,#-&$#)&785*$+,#-.!)

2'!(-"$P<H-(5/0$$!"#$6"-#=%!!.1'()"6B7"*C$$$$2%7=;'00";)$L:6)(##LF$J;'0)1'--"1$,K$L)9/056L$$"0!"0!

O;)/'0I'0)1'--"1JJ?'()/05JJ?'()"6=!1%8$!'$+2%7+$$3$<'(1$%77$1'()"6===

$$P<H-(5/0=%!!.1'()"6B2%7C

$$3$");==="0!

what’s missing?

public assets

copy

file clash

83+!5*$+,#-&#-%'"$$.!)

2<./2%5"6$,$H%)90%2"=0"8B@/-"=!/10%2"B..@QR4..CC$S$$$$$$$$$$$$$$$L%66")6:/2%5"6L)%15")$,$?%/-6=1'')$S$L7(&-/;:/2%5"6:2<.7-(5/0L

@/-"T)/-6=2U!/1.7B)%15")C

2<./2%5"6=;9/-!1"0="%;9$!'$+"+$$$$$@/-"T)/-6=;7.1B"F$)%15")$S$"=&%6"0%2"C$"0!

83+!5*$+,#-&#-%'"$$.!)

2<./2%5"6$,$H%)90%2"=0"8B@/-"=!/10%2"B..@QR4..CC$S$$$$$$$$$$$$$$$L%66")6:/2%5"6L)%15")$,$?%/-6=1'')$S$L7(&-/;:/2%5"6:2<.7-(5/0L

)%15")=2%U".6<2-/0UB2<./2%5"6C$(0-"66$)%15")="A/6)>

migrations

simple DSL

rollback

!&:2/51%)":$$VWWXWYWYYVYVZ[.%-79%=1&

version

20090101121234

20090102142345

2008123123456

VWWXWYWVY[VZ[\.&")%=1&

7-(5/0:!&:2/51%)":$$VWW]YVZYZ[\^.5%22%=1&

version

20090101121234

20090102142345

2008123123456

1%U"$!&J1'--&%;U

P/51%)'1=1'--&%;U

P/51%)'13;(11"0).D"16/'0

P/51%)'132/51%)"!=-%6)

P/51%)'1=5").%--.D"16/'06

BL_4R4I`$D"16/'0$@?aP$$$$$6;9"2%.2/51%)/'06LC=2%7BbJ)'./C=6'1)

it gets worse

!&:2/51%)":$$WWY.%-79%=1&

version

001

002

WWV.&")%=1&

7-(5/0:!&:2/51%)":$$WWY.5%22%=1&

http://www.flickr.com/photos/bk2204/475332962/

single timeline

app migration 1

app migration 2

plugin migration 1

app migration 3

plugin migration 2

install

upgrade

You

Me

app migration 1

app migration 2

plugin migration 1

app migration 3

plugin migration 2

You

WW[.!"-)%=1&

!&:2/51%)":$$WWY.%-79%=1&

WWV.&")%=1&

7-(5/0:!&:2/51%)":$$WWY.5%22%=1&

WWZ.7-(5/0.)'.WWY=1&

WW[.!"-)%=1&

!&:2/51%)":$$WWY.%-79%=1&

WWV.&")%=1&

7-(5/0:!&:2/51%)":$$WWY.5%22%=1&

WWZ.7-(5/0.)'.WWY=1&

Copy & Retimestamp?

Reference?

Symlink?

Ticket #2058interblah.net/plugin-migrations

my recommendation?(for the moment, at least)

write a generator

c$6;1/7):5"0"1%)"$%;)6.%6.#(.2/51%)/'06$$$$$$$"A/6)6$$!&:2/51%)"$$$;1"%)"$$!&:2/51%)":VWWXW\W\YYYZZd.&-%9=1&

c$===

(within your plugin)

techniques

overriding functionality

views just work

controllers

straight override

module

namespaced

playing nice with the class cache

1/23*8/36/1**$#2"'#3-43-'!3$$(!/

9"%/)((-/!(73:(;/6!37/'9(/73;+$(/

'!((/)+'/#%/%'#$$/"2'#:(<<<<<<<<!

O;)/D"_(77'1)JJe"7"0!"0;/"6=-'%!.'0;".7%)96

ApplicationController

AppController PluginController

ApplicationController

PluginController

23-6#,&(-:#!3-7(-'.!)

?%/-6JJQ0/)/%-/f"1=1(0$!'$+;'0#/5+$$3$");===

$$;'0#/5=1"-'%!.7-(5/06$,$)1("$$"0!

83+!5*$+,#-&"**&23-'!3$$(!%&,33;523-'!3$$(!.!)

;-%66$g''!I'0)1'--"1$h$===$$(0-'%!%&-"$$$$3$");$===

"0!

init.rb woes

;'0#/5=)'.71"7%1"$!'

$$"0!

785*$+,#-&#-#'.!)

$$_'2"O77I-%66="A)"0!BP<i"9%D/'(1C

testing

ApplicationController

PluginControllerAppController

ApplicationController

PluginController

Their Code

Your Code

!"

#$

unit test?

test in your own rails environment?

plugin_test_helper

I care about testing my chunk

You care about testing your whole app

empower the developer

avoiding fail

;%6"$;'!"=;'06(2"1

$$89"0$;'!"=%()9'1$$$$1"(6"=2'6)-<$,j$:"##";)/D":

$$89"0$1%0!B!"D"-'7"1C$$$$1"(6"=)1/;U/"1.&().7'66/&-"B)1("C

$$"-6"$$$$1"(6"='D"11%)"!N

"0!

consume wisely

Serving Size 14 klocNutrition Facts

Amount Per Serving 1 bad engine

Calories 10,666

Long Methods 1578g 34%

God Objects 326g 7%

Stress 320mg 119%

Total Fat 2674g 98%

Hairloss 45g 45.8%

% Daily Value*

Technical Debt 13g 87%

Untested Code 1578mg 34%

Hidden Bugs 326mg 7%

Benefit 1mg 0.1%

you will not be able to write some engines.

you will not be able to use some engines.

extractspecific functionality

establish someclear integration points

you are customer #1

READ the CODE

james@lazyatom.com

lets@gofreerange.com

FIN