Created
October 13, 2012 15:53
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A Ruby quirk with include. Quite annoying.
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module A | |
module B | |
end | |
module Wrapper | |
module C | |
end | |
end | |
#Cite: | |
#When this module is included in another, Ruby calls append_features in this | |
#module, passing it the receiving module in mod. Ruby’s default | |
#implementation is to add the constants, methods, and module variables of | |
#this module to mod if this module has not already been added to mod or one | |
#of its ancestors. See also Module#include. | |
#But it's not that easy... | |
include Wrapper | |
end | |
p A.constants # => [:B, :Wrapper, :C] | |
p A::B # => A::B | |
p A::C # => A::Wrapper::C | |
module A | |
p B # => A::B | |
end | |
module A | |
p C # => A::Wrapper::C | |
end | |
module A | |
module Bracket | |
p B # => A::B | |
#p C (see bottom) | |
end | |
end | |
# Manual constant copying, from A::Wrapper | |
module X | |
A::Wrapper.constants.each do |sym| | |
const_set sym, A::Wrapper.const_get(sym) | |
end | |
p C # => A::Wrapper::C | |
# Quirk 1: | |
p defined?(B) # => nil | |
end | |
# Manual constant copying, from A. Works as well. | |
module Y | |
A.constants.each do |sym| | |
const_set sym, A.const_get(sym) | |
end | |
p B # => A::B | |
p C # => A::Wrapper::C | |
end | |
# This was a surprise to me: | |
module A | |
module Bracket | |
# Quirk 2: | |
p C #raises uninitialized constant A::Bracket::C (NameError) | |
end | |
end |
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