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9113aa2744
git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1455 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
43 lines
1.3 KiB
Ruby
43 lines
1.3 KiB
Ruby
# Extensions to nil which allow for more helpful error messages for
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# people who are new to rails.
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#
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# The aim is to ensure that when users pass nil to methods where that isn't
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# appropriate, instead of NoMethodError and the name of some method used
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# by the framework users will see a message explaining what type of object
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# was expected.
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class NilClass
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WHINERS = [ ActiveRecord::Base, Array ]
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@@method_class_map = Hash.new
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WHINERS.each do |klass|
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methods = klass.public_instance_methods - public_instance_methods
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methods.each do |method|
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@@method_class_map[method.to_sym] = klass
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end
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end
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private
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def method_missing(method, *args, &block)
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if @@method_class_map.include?(method)
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raise_nil_warning_for @@method_class_map[method]
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else
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super
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end
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end
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def raise_nil_warning_for(klass)
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raise NoMethodError, NIL_WARNING_MESSAGE % klass
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end
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NIL_WARNING_MESSAGE = <<-end_message unless const_defined?(:NIL_WARNING_MESSAGE)
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WARNING: You have a nil object when you probably didn't expect it! Odds are you
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want an instance of %s instead.
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Look in the callstack to see where you're working with an object that could be nil.
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Investigate your methods and make sure the object is what you expect!
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end_message
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end
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