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44 lines
1.2 KiB
Markdown
44 lines
1.2 KiB
Markdown
# Refer To Implicit Block Argument With It
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One of the key features of the Ruby 3.4 release is the `it` implicit block
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argument.
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The vast majority of inline blocks defined in Ruby code receive a single block
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argument. Typically we name and reference a block argument explictly like so:
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```ruby
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items.map { |item| item * item }
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```
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Ruby likes to cut away excess syntax when possible. To that end, the implicit
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`it` block argument has been added. This is an identifier we can reference in
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the context of a block and its value is the current
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```ruby
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items = [1,2,3,4,5]
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squares = items.map { it * it }
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pp squares
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#=> [1, 4, 9, 16, 25]
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```
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Note: we cannot mix numbered parameters (`_1`, `_2`) with the `it` parameter.
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If we do, we'll get the following error:
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```ruby
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def method_using_block(a, b)
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yield(a, b) if block_given?
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end
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puts method_using_block(4,5) { _2 ** _1 } #=> 625
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puts method_using_block(4,5) { _2 ** it }
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# it_block.rb:12: syntax error found (SyntaxError)
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# 10 |
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# 11 | puts method_using_block(4,5) { _2 ** _1 }
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# > 12 | ... it }
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# | ^~ `it` is not allowed when a numbered parameter is already used
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```
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[source](https://docs.ruby-lang.org/en/3.4/NEWS_md.html)
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