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annotate 1-Ruby/code-blocks.rb @ 29:9c7af76fdbd0

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Print isn't PrinLn, so add some \n characters to the output
author IBBoard <dev@ibboard.co.uk>
date Wed, 06 Sep 2017 18:36:02 +0100
parents e58952c15e5e
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 #! /usr/bin/env ruby
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2
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3 # Simple passing of code block
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4 3.times { puts 'Repeated string' }
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5
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6 # Extending a class
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7 class Fixnum
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8 def my_times
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9 # We're in a number, so store it as an iterator
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10 i = self
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11 until i == 0
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12 i = i - 1
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13 # Magic happens here!
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14 # Yield normally yields a value, but somehow we're executing a block…
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15 yield
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16 end
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17 end
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18 end
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19
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20 3.my_times { puts 'My repeated string' }
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21
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22 # Blocks are objects, if you do it right - https://www.ruby-forum.com/topic/49018
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23 my_block = proc { puts 'I am a block' }
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24 puts my_block.class
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25
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26 # Blocks can be passed around - "&var" says "this is a block"
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27 def call_block(&block)
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28 block.call
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29 end
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30 def pass_block(&block)
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31 call_block(&block)
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32 end
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33 pass_block { puts 'Inline block' }
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34 pass_block &my_block
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35
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36 # Without the "&" we get "wrong number of arguments (1 for 0)" because
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37 # a block and an argument are different somehow. This is *not*
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38 # because we were trying to call "my_block" and pass what it returned (nil).
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39 # I tried. Calling a block definitely needs ".call"
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40 #
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41 # This page (https://mixandgo.com/blog/mastering-ruby-blocks-in-less-than-5-minutes)
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42 # makes it clearer: ANY method can take a block independent of its arguments.
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43 #
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44 # That means that this works, because we're taking an argument then treating it like
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45 # a block:
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46 def pass_var_block(block)
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47 call_block(&block)
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48 end
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49
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50 pass_var_block my_block