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gadams
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ruby

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[source,ruby]
----
require 'tempfile'
# bad
def with_tmp_dir
Dir.mktmpdir do |tmp_dir|
Dir.chdir(tmp_dir) { |dir| yield dir } # block just passes arguments
end
end
# good
def with_tmp_dir(&block)
Dir.mktmpdir do |tmp_dir|
Dir.chdir(tmp_dir, &block)
end
end
with_tmp_dir do |dir|
puts "dir is accessible as a parameter and pwd is set: #{dir}"
end
----
=== Trailing Comma in Block Parameters [[no-trailing-parameters-comma]]
Avoid comma after the last parameter in a block, except in cases where only a single argument is present and its removal would affect functionality (for instance, array destructuring).
[source,ruby]
----
# bad - easier to move/add/remove parameters, but still not preferred
[[1, 2, 3], [4, 5, 6]].each do |a, b, c,|
a + b + c
end
# good
[[1, 2, 3], [4, 5, 6]].each do |a, b, c|
a + b + c
end
# bad
[[1, 2, 3], [4, 5, 6]].each { |a, b, c,| a + b + c }
# good
[[1, 2, 3], [4, 5, 6]].each { |a, b, c| a + b + c }
# good - this comma is meaningful for array destructuring
[[1, 2, 3], [4, 5, 6]].map { |a,| a }
----
=== Nested Method Definitions [[no-nested-methods]]
Do not use nested method definitions, use lambda instead.
Nested method definitions actually produce methods in the same scope (e.g. class) as the outer method.
Furthermore, the "nested method" will be redefined every time the method containing its definition is called.
[source,ruby]
----
# bad
def foo(x)
def bar(y)
# body omitted
end
bar(x)
end
# good - the same as the previous, but no bar redefinition on every foo call
def bar(y)
# body omitted
end
def foo(x)
bar(x)
end
# also good
def foo(x)
bar = ->(y) { ... }
bar.call(x)
end
----
=== Multi-line Lambda Definition [[lambda-multi-line]]
Use the new lambda literal syntax for single-line body blocks.
Use the `lambda` method for multi-line blocks.
[source,ruby]
----
# bad
l = lambda { |a, b| a + b }
l.call(1, 2)
# correct, but looks extremely awkward
l = ->(a, b) do
tmp = a * 7
tmp * b / 50
end