177 lines
6.9 KiB
Ruby
177 lines
6.9 KiB
Ruby
# Copyright (c) 2004-2008 David Heinemeier Hansson
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#
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# Permission is hereby granted, free of charge, to any person obtaining
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# a copy of this software and associated documentation files (the
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# "Software"), to deal in the Software without restriction, including
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# without limitation the rights to use, copy, modify, merge, publish,
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# distribute, sublicense, and/or sell copies of the Software, and to
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# permit persons to whom the Software is furnished to do so, subject to
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# the following conditions:
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#
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# The above copyright notice and this permission notice shall be
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# included in all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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# Allows attributes to be shared within an inheritance hierarchy, but where
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# each descendant gets a copy of their parents' attributes, instead of just a
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# pointer to the same. This means that the child can add elements to, for
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# example, an array without those additions being shared with either their
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# parent, siblings, or children, which is unlike the regular class-level
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# attributes that are shared across the entire hierarchy.
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class Class
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# Defines class-level and instance-level attribute reader.
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#
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# @param *syms<Array> Array of attributes to define reader for.
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# @return <Array[#to_s]> List of attributes that were made into cattr_readers
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#
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# @api public
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#
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# @todo Is this inconsistent in that it does not allow you to prevent
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# an instance_reader via :instance_reader => false
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def cattr_reader(*syms)
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syms.flatten.each do |sym|
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next if sym.is_a?(Hash)
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class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
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unless defined? @@#{sym}
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@@#{sym} = nil
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end
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def self.#{sym}
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@@#{sym}
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end
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def #{sym}
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@@#{sym}
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end
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RUBY
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end
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end unless Class.respond_to?(:cattr_reader)
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# Defines class-level (and optionally instance-level) attribute writer.
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#
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# @param <Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to define writer for.
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# @option syms :instance_writer<Boolean> if true, instance-level attribute writer is defined.
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# @return <Array[#to_s]> List of attributes that were made into cattr_writers
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#
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# @api public
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def cattr_writer(*syms)
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options = syms.last.is_a?(Hash) ? syms.pop : {}
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syms.flatten.each do |sym|
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class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
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unless defined? @@#{sym}
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@@#{sym} = nil
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end
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def self.#{sym}=(obj)
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@@#{sym} = obj
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end
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RUBY
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unless options[:instance_writer] == false
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class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
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def #{sym}=(obj)
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@@#{sym} = obj
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end
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RUBY
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end
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end
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end unless Class.respond_to?(:cattr_writer)
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# Defines class-level (and optionally instance-level) attribute accessor.
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#
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# @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to define accessor for.
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# @option syms :instance_writer<Boolean> if true, instance-level attribute writer is defined.
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# @return <Array[#to_s]> List of attributes that were made into accessors
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#
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# @api public
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def cattr_accessor(*syms)
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cattr_reader(*syms)
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cattr_writer(*syms)
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end unless Class.respond_to?(:cattr_accessor)
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# Defines class-level inheritable attribute reader. Attributes are available to subclasses,
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# each subclass has a copy of parent's attribute.
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#
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# @param *syms<Array[#to_s]> Array of attributes to define inheritable reader for.
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# @return <Array[#to_s]> Array of attributes converted into inheritable_readers.
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#
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# @api public
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#
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# @todo Do we want to block instance_reader via :instance_reader => false
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# @todo It would be preferable that we do something with a Hash passed in
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# (error out or do the same as other methods above) instead of silently
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# moving on). In particular, this makes the return value of this function
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# less useful.
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def extlib_inheritable_reader(*ivars)
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instance_reader = ivars.pop[:reader] if ivars.last.is_a?(Hash)
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ivars.each do |ivar|
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self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
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def self.#{ivar}
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return @#{ivar} if self.object_id == #{self.object_id} || defined?(@#{ivar})
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ivar = superclass.#{ivar}
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return nil if ivar.nil? && !#{self}.instance_variable_defined?("@#{ivar}")
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@#{ivar} = ivar && !ivar.is_a?(Module) && !ivar.is_a?(Numeric) && !ivar.is_a?(TrueClass) && !ivar.is_a?(FalseClass) ? ivar.dup : ivar
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end
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RUBY
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unless instance_reader == false
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self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
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def #{ivar}
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self.class.#{ivar}
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end
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RUBY
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end
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end
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end unless Class.respond_to?(:extlib_inheritable_reader)
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# Defines class-level inheritable attribute writer. Attributes are available to subclasses,
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# each subclass has a copy of parent's attribute.
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#
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# @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to
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# define inheritable writer for.
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# @option syms :instance_writer<Boolean> if true, instance-level inheritable attribute writer is defined.
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# @return <Array[#to_s]> An Array of the attributes that were made into inheritable writers.
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#
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# @api public
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#
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# @todo We need a style for class_eval <<-HEREDOC. I'd like to make it
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# class_eval(<<-RUBY, __FILE__, __LINE__), but we should codify it somewhere.
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def extlib_inheritable_writer(*ivars)
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instance_writer = ivars.pop[:writer] if ivars.last.is_a?(Hash)
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ivars.each do |ivar|
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self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
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def self.#{ivar}=(obj)
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@#{ivar} = obj
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end
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RUBY
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unless instance_writer == false
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self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
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def #{ivar}=(obj) self.class.#{ivar} = obj end
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RUBY
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end
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end
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end unless Class.respond_to?(:extlib_inheritable_writer)
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# Defines class-level inheritable attribute accessor. Attributes are available to subclasses,
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# each subclass has a copy of parent's attribute.
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#
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# @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to
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# define inheritable accessor for.
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# @option syms :instance_writer<Boolean> if true, instance-level inheritable attribute writer is defined.
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# @return <Array[#to_s]> An Array of attributes turned into inheritable accessors.
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#
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# @api public
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def extlib_inheritable_accessor(*syms)
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extlib_inheritable_reader(*syms)
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extlib_inheritable_writer(*syms)
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end unless Class.respond_to?(:extlib_inheritable_accessor)
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end
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