How to add a method_missing method into ActiveRecord

Ruby
1

i want to write a plugin
that support like following

Book.search_by_author_and_description(keyword)

i must hold method_missing to dynamic find books

but ActiveRecord already used method_missing .

how can i add onother method_misng method ?

2

I believe you can alias the original method_missing, and then add a
new method_missing which calls the original except when your version
is relevant. it would look something like this:

alias :original_method_missing :method_missing

def method_missing(*args)
case args
when /normal stuff/
original_method_missing(args)
when /new stuff/
# your code goes here
end
end

(please bear in mind this is just a sketch.)

–
Giles B.
http://www.gilesgoatboy.org

http://gilesgoatboy.blogspot.com

3

What Giles said, except:
when /new stuff/: #your code
else original_method_missing(*args,&blk)
Probably makes more sense.

4

On 13 Dec 2006, at 14:47, ao tianlong wrote:

11 end
missingmy method missintest.rb:9:in method_missing': stack level too deep (SystemStackError) from test.rb:9:inmethod_missing’
from test.rb:14

any idia?

You are calling a missing method from within your new method_missing.
Infinite recursion ensues.

The following seems to work:

irb(main):001:0> class Book
irb(main):002:1> def method_missing(mtd,*arg,&blk)
irb(main):003:2> puts “Original”
irb(main):004:2> end
irb(main):005:1> alias :original :method_missing
irb(main):006:1> def method_missing(mtd,*arg,&blk)
irb(main):007:2> puts “New”
irb(main):008:2> original(mtd,*arg,&blk)
irb(main):009:2> end
irb(main):010:1> end
=> nil
irb(main):011:0> Book.new.test
New
Original
=> nil

Alex G.

Bioinformatics Center
Kyoto University

5

thank you

i find the error

original_method_missing(method_id,*prams,&block)

it’s misspelled *params as prams

thank you again.

6

1 class Book
2 def method_missing(method_id,*params,&block)
3 print ‘original method missing’
4 end
5
6 alias :original_method_missing :method_missing
7 def method_missing(method_id,*params,&block)
8 C(params[:comment])print ‘my method missing’
9 original_method_missing(method_id,*prams,&block)
10 end
11 end
12
13 book = Book.new
14 book.tester

its looks like work , but output is
thod missingmy method missingmy method missingmy method missingmy method
missingmy method missingmy method missingmy method missingmy method
missingmy method missingmy method missingmy method missingmy method
missingmy method missingmy method missingmy method missingmy method
missingmy method missintest.rb:9:in method_missing': stack level too deep (SystemStackError) from test.rb:9:inmethod_missing’
from test.rb:14

any idia?

thank you for your help

7

ao tianlong wrote:

i want to write a plugin
that support like following

Book.search_by_author_and_description(keyword)
i must hold method_missing to dynamic find books
but ActiveRecord already used method_missing .
how can i add onother method_misng method ?

You could alias the existing method_missing, redefine it to capture the
cases you are interested in and forward the rest on to the aliased
method. Check out Module#alias_method_chain in Rails 1.2:

Tom