CODEWITHSUNDEEP
ruby-on-railsrubylambda
Gav
Gav

Reputation: 11460

Rails: named_scope, lambda and blocks

I thought the following two were equivalent:

named_scope :admin, lambda { |company_id| {:conditions => ['company_id = ?', company_id]} }

named_scope :admin, lambda do |company_id| 
  {:conditions => ['company_id = ?', company_id]}
end

but Ruby is complaining:

ArgumentError: tried to create Proc object without a block

Any ideas?

Upvotes: 55

Views: 21028

Answers (4)

Kelvin
Kelvin

Reputation: 20912

If you're on ruby 1.9 or later 1, you can use the lambda literal (arrow syntax), which has high enough precedence to prevent the method call from "stealing" the block from the lambda.

named_scope :admin, ->(company_id) do 
  {:conditions => ['company_id = ?', company_id]}
end

1 The first stable Ruby 1.9.1 release was 2009-01-30.

Upvotes: 10

khelll
khelll

Reputation: 24010

It's something related to precedence as I can tell

1.upto 3 do # No parentheses, block delimited with do/end
  |x| puts x 
end

1.upto 3 {|x| puts x } # Syntax Error: trying to pass a block to 3!

Upvotes: 7

Martin DeMello
Martin DeMello

Reputation: 12346

it's a parser problem. try this

named_scope :admin, (lambda do |company_id| 
  {:conditions => ['company_id = ?', company_id]}
end)

Upvotes: 78

Mike Woodhouse
Mike Woodhouse

Reputation: 52326

I think the problem may be related to the difference in precedence between {...} and do...end

There's some SO discussion here

I think assigning a lambda to a variable (which would be a Proc) could be done with a do ... end:

my_proc = lambda do 
  puts "did it"
end
my_proc.call #=> did it

Upvotes: 19

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