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Discussion on: Yet Another Post About Ruby Blocks

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pinotattari profile image
Riccardo Bernardini •

Another curiosity is around the number of parameters passed to yield, which in turn are sent as block parameters to your block. Are they enforced/requested by Ruby or not? Give it a try using irb - you'll be surprised with the result!

Interesting, I never tried before (although I used Ruby fairly a lot). This also is interesting

a = [1, 2, 3]
a.each {|*x| p x}
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yagosansz profile image
Yago Santos • • Edited

Hi Riccardo,

Thanks for sharing! I couldn't understand how it works though. Would you mind explaining what is happening behind the scenes? =)

I thought the * (splat operator) was only used to "spread" elements of a collection when passing it as an argument to a function.

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pinotattari profile image
Riccardo Bernardini •

It works also the other way around, as the varargin in Matlab. For example, suppose I define

def foo(a, b, *c)
   p c;
end
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Here foo is a function that expects a number of arguments larger or equal than two. The first two arguments are assigned to a and b and all the remaining arguments (zero or more) are collected in an Array assigned to c. For example, if I call

foo(42, 33, 'x', nil 12)
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the function prints ["x", nil, 12], if I call

foo(42, 33)
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the function prints [ ], if I call

foo(42)
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I get an error

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yagosansz profile image
Yago Santos •

Hi Riccardo,

Thank you for taking to explain it - it is more clear to me now how it works!