How to require a block in Ruby?

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

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.

Here says:

"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".

raise 'need block' unless block_given?