Is there any built in way to require that a block be passed to a Ruby method? I realize I can just raise an exception if block_given? is false, but is there some nicer way to do it?
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niton
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Kyle Slattery
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3 Answers
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Simply by using yield.
If you include yield in a method, and a block is not given, it throws an error.
Put this in a file and run it:
def needs_block
yield
end
needs_block
It will throw an error like this:
LocalJumpError: no block given
from (irb):14:in `needs_block'
from (irb):16
Doug Neiner
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1Well that was way too easy :) Thanks! – Kyle Slattery Feb 22 '10 at 05:18
17
raise 'need block' unless block_given?
Baldrick
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rogerdpack
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2This is the best answer, since it has no side effects (i.e. calling the block). – Per Lundberg Jul 07 '16 at 10:03
1
If your method required a block, Ruby will prompt it. The raise keyword doesn't require a block, it only prompts a message for handling an Exception.
It could be a method like the above example
def needs_block
yield
end
needs_block
Or you could require a Proc
def needs_block(&Proc)
proc.call
end
Anyway, adding raise block_given? would be nice.
"The raise method is from the Kernel module. By default, raise creates an exception of the RuntimeError class. To raise an exception of a specific class, you can pass in the class name as an argument to raise".
