I'm trying to use Ruby 1.9.1 for an embedded scripting language, so that "end-user" code gets written in a Ruby block. One issue with this is that I'd like the users to be able to use the 'return' keyword in the blocks, so they don't need to worry about implicit return values. With this in mind, this is the kind of thing I'd like to be able to do:
def thing(*args, &block)
value = block.call
puts "value=#{value}"
end
thing {
return 6 * 7
}
If I use 'return' in the above example, I get a LocalJumpError. I'm aware that this is because the block in question is a Proc and not a lambda. The code works if I remove 'return', but I'd really prefer to be able to use 'return' in this scenario. Is this possible? I've tried converting the block to a lambda, but the result is the same.
Simply use next
in this context:
$ irb
irb(main):001:0> def thing(*args, &block)
irb(main):002:1> value = block.call
irb(main):003:1> puts "value=#{value}"
irb(main):004:1> end
=> nil
irb(main):005:0>
irb(main):006:0* thing {
irb(main):007:1* return 6 * 7
irb(main):008:1> }
LocalJumpError: unexpected return
from (irb):7:in `block in irb_binding'
from (irb):2:in `call'
from (irb):2:in `thing'
from (irb):6
from /home/mirko/.rvm/rubies/ruby-1.9.1-p378/bin/irb:15:in `<main>'
irb(main):009:0> thing { break 6 * 7 }
=> 42
irb(main):011:0> thing { next 6 * 7 }
value=42
=> nil
return
always returns from method, but if you test this snippet in irb you don't have method, that's why you have LocalJumpError
break
returns value from block and ends its call. If your block was called by yield
or .call
, then break
breaks from this iterator toonext
returns value from block and ends its call. If your block was called by yield
or .call
, then next
returns value to line where yield
was called