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__END__
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Overriding #to_s changes #inspect
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# My Ruby is: ruby 1.9.2p180 (2011-02-18) [i386-mingw32]
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# sample codes 1:
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class Foo # subclass of Object, inherits #inspect and #to_s
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def initialize(bar,baz)
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@bar, @baz = bar, baz
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end
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end
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obj = Foo.new(:cat, :dog)
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puts "\n== #inspect ====="
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p obj #<Foo:0xb44398 @bar=:cat, @baz=:dog>
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puts obj.inspect #<Foo:0xb44398 @bar=:cat, @baz=:dog>
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printf "%p", obj #<Foo:0xb44398 @bar=:cat, @baz=:dog>
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puts "\n== #to_s ========"
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puts obj.to_s #<Foo:0xb44398>
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printf "%s", obj #<Foo:0xb44398>
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# Yes, #inspect and #to_s are not synonyms, they return different strings.
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# sample codes 2, add 'def to_s':
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class Foo
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def initialize(bar,baz)
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@bar, @baz = bar, baz
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end
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def to_s # override #to_s method
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"has @bar = #{@bar}, @baz = #{@baz}."
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end
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end
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obj = Foo.new(:cat, :dog)
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puts "\n== #inspect ====="
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p obj # has @bar = cat, @baz = dog.
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puts obj.inspect # has @bar = cat, @baz = dog.
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printf "%p", obj # has @bar = cat, @baz = dog.
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puts "\n== #to_s ========"
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puts obj.to_s # has @bar = cat, @baz = dog.
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printf "%s", obj # has @bar = cat, @baz = dog.
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# However, overriding #to_s makes #inspect do the identical thing. I don't think it's perfect.
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# In fact, the problem was reported in 2009. http://redmine.ruby-lang.org/issues/1786
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# At the bottom of the page, Matz said:
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# "Redefining #to_s should not affect inspect, if they are totally different."
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# I agree with Matz. #to_s and #inspcet should not be synonyms:
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# #to_s maybe for the user of the application, they want a readable message;
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# but #inspect maybe for the programmer, they want a debug information.
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# So, if this is a bug, maybe it should be fixed. If it's a feature in 1.9.2, I think it's not a good one,
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# because I lose a quick and convenient debug method to know an object's class the its instance variables.
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# I may want to show something readable to user of my app, as well as something usable for myself.
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# The feature (or bug) doesn't satisfy both.
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