view 1-Ruby/code-blocks.rb @ 17:61dfac9a058a

Add some initial experiments with blocks
author IBBoard <dev@ibboard.co.uk>
date Tue, 03 Jan 2017 20:58:19 +0000
parents
children e58952c15e5e
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#! /usr/bin/env ruby

# Simple passing of code block
3.times { puts 'Repeated string' }

# Extending a class
class Fixnum
	def my_times
		# We're in a number, so store it as an iterator
		i = self
		until i == 0
			i = i - 1
			# Magic happens here!
			# Yield normally yields a value, but somehow we're executing a blockā€¦
			yield
		end
	end
end

3.my_times { puts 'My repeated string' }

# Blocks are objects, if you do it right - https://www.ruby-forum.com/topic/49018
my_block = proc { puts 'I am a block' }
puts my_block.class

# Blocks can be passed around - "&var" says "this is a block"
def call_block(&block)
	block.call
end
def pass_block(&block)
	call_block(&block)
end
pass_block { puts 'Inline block' }
pass_block &my_block

# Without the "&" we get "wrong number of arguments (1 for 0)" because
# a block and an argument are different somehow. This is *not* 
# because we were trying to call "my_block" and pass what it returned (nil).
# I tried. Calling a block definitely needs ".call"
#
# This page (https://mixandgo.com/blog/mastering-ruby-blocks-in-less-than-5-minutes)
# makes it cleared: ANY method can take a block independent of its arguments.
# That means that this works:
def pass_var_block(block)
	call_block(&block)
end

pass_var_block my_block