Class: Class

Inherits:
Object show all
Defined in:
lib/gems/extlib-0.9.9/lib/extlib/class.rb,
lib/mack-facets/extensions/class.rb,
lib/gems/activesupport-2.2.2/lib/active_support/core_ext/duplicable.rb,
lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/removal.rb,
lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/attribute_accessors.rb,
lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/delegating_attributes.rb,
lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb

Overview

Allows attributes to be shared within an inheritance hierarchy, but where each descendant gets a copy of their parents’ attributes, instead of just a pointer to the same. This means that the child can add elements to, for example, an array without those additions being shared with either their parent, siblings, or children, which is unlike the regular class-level attributes that are shared across the entire hierarchy.

Constant Summary collapse

EMPTY_INHERITABLE_ATTRIBUTES =

Prevent this constant from being created multiple times

{}.freeze

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.new_instance_of(klass_name) ⇒ Object

Returns a new Object instance of the class name specified.

Examples:

Class.new_instance_of("Orange") => #<Orange:0x376c0c>
Class.new_instance_of("Animals::Dog") => #<Animals::Dog:0x376a2c>



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# File 'lib/mack-facets/extensions/class.rb', line 8

def self.new_instance_of(klass_name)
  klass_name.constantize.new
end

Instance Method Details

#cattr_accessor(*syms) ⇒ Array[#to_s]

Defines class-level (and optionally instance-level) attribute accessor.

Parameters:

  • *syms (Array[*#to_s, Hash{:instance_writer => Boolean}]) —

    Array of attributes to define accessor for.

  • syms (Hash) —

    a customizable set of options

Options Hash (*syms):

  • :instance_writer (Boolean) —

    if true, instance-level attribute writer is defined.

Returns:

  • (Array[#to_s]) —

    List of attributes that were made into accessors



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# File 'lib/gems/extlib-0.9.9/lib/extlib/class.rb', line 94

def cattr_accessor(*syms)
  cattr_reader(*syms)
  cattr_writer(*syms)
end

#cattr_reader(*syms) ⇒ Array[#to_s]

TODO:

Is this inconsistent in that it does not allow you to prevent an instance_reader via :instance_reader => false

Defines class-level and instance-level attribute reader.

Parameters:

  • *syms (Array) —

    Array of attributes to define reader for.

Returns:

  • (Array[#to_s]) —

    List of attributes that were made into cattr_readers



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# File 'lib/gems/extlib-0.9.9/lib/extlib/class.rb', line 38

def cattr_reader(*syms)
  syms.flatten.each do |sym|
    next if sym.is_a?(Hash)
    class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
      unless defined? @@#{sym}
        @@#{sym} = nil
      end

      def self.#{sym}
        @@#{sym}
      end

      def #{sym}
        @@#{sym}
      end
    RUBY
  end
end

#cattr_writer(*syms) ⇒ Array[#to_s]

Defines class-level (and optionally instance-level) attribute writer.

Parameters:

  • Array (Array[*#to_s, Hash{:instance_writer => Boolean}]) —

    of attributes to define writer for.

  • syms (Hash) —

    a customizable set of options

Options Hash (*syms):

  • :instance_writer (Boolean) —

    if true, instance-level attribute writer is defined.

Returns:

  • (Array[#to_s]) —

    List of attributes that were made into cattr_writers



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# File 'lib/gems/extlib-0.9.9/lib/extlib/class.rb', line 64

def cattr_writer(*syms)
  options = syms.last.is_a?(Hash) ? syms.pop : {}
  syms.flatten.each do |sym|
    class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
      unless defined? @@#{sym}
        @@#{sym} = nil
      end

      def self.#{sym}=(obj)
        @@#{sym} = obj
      end
    RUBY

    unless options[:instance_writer] == false
      class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
        def #{sym}=(obj)
          @@#{sym} = obj
        end
      RUBY
    end
  end
end

#class_inheritable_accessor(*syms) ⇒ Array[#to_s]

Defines class-level inheritable attribute accessor. Attributes are available to subclasses, each subclass has a copy of parent’s attribute.

Parameters:

  • *syms (Array[*#to_s, Hash{:instance_writer => Boolean}]) —

    Array of attributes to define inheritable accessor for.

  • syms (Hash) —

    a customizable set of options

Options Hash (*syms):

  • :instance_writer (Boolean) —

    if true, instance-level inheritable attribute writer is defined.

Returns:

  • (Array[#to_s]) —

    An Array of attributes turned into inheritable accessors.



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# File 'lib/gems/extlib-0.9.9/lib/extlib/class.rb', line 171

def class_inheritable_accessor(*syms)
  class_inheritable_reader(*syms)
  class_inheritable_writer(*syms)
end

#class_inheritable_array(*syms) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 81

def class_inheritable_array(*syms)
  class_inheritable_reader(*syms)
  class_inheritable_array_writer(*syms)
end

#class_inheritable_array_writer(*syms) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 42

def class_inheritable_array_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval <<-EOS
      def self.#{sym}=(obj)
        write_inheritable_array(:#{sym}, obj)
      end

      #{"
      def #{sym}=(obj)
        self.class.#{sym} = obj
      end
      " unless options[:instance_writer] == false }
    EOS
  end
end

#class_inheritable_hash(*syms) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 86

def class_inheritable_hash(*syms)
  class_inheritable_reader(*syms)
  class_inheritable_hash_writer(*syms)
end

#class_inheritable_hash_writer(*syms) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 59

def class_inheritable_hash_writer(*syms)
  options = syms.extract_options!
  syms.each do |sym|
    class_eval <<-EOS
      def self.#{sym}=(obj)
        write_inheritable_hash(:#{sym}, obj)
      end

      #{"
      def #{sym}=(obj)
        self.class.#{sym} = obj
      end
      " unless options[:instance_writer] == false }
    EOS
  end
end

#class_inheritable_reader(*syms) ⇒ Object

:nodoc:



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# File 'lib/gems/extlib-0.9.9/lib/extlib/class.rb', line 112

def class_inheritable_reader(*ivars)
  instance_reader = ivars.pop[:reader] if ivars.last.is_a?(Hash)

  ivars.each do |ivar|
    self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
      def self.#{ivar}
        return @#{ivar} if self.object_id == #{self.object_id} || defined?(@#{ivar})
        ivar = superclass.#{ivar}
        return nil if ivar.nil? && !#{self}.instance_variable_defined?("@#{ivar}")
        @#{ivar} = ivar && !ivar.is_a?(Module) && !ivar.is_a?(Numeric) && !ivar.is_a?(TrueClass) && !ivar.is_a?(FalseClass) ? ivar.dup : ivar
      end
    RUBY
    unless instance_reader == false
      self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
        def #{ivar}
          self.class.#{ivar}
        end
      RUBY
    end
  end
end

#class_inheritable_writer(*syms) ⇒ Array[#to_s]

TODO:

We need a style for class_eval <<-HEREDOC. I’d like to make it class_eval(<<-RUBY, __FILE__, __LINE__), but we should codify it somewhere.

Defines class-level inheritable attribute writer. Attributes are available to subclasses, each subclass has a copy of parent’s attribute.

Parameters:

  • *syms (Array[*#to_s, Hash{:instance_writer => Boolean}]) —

    Array of attributes to define inheritable writer for.

  • syms (Hash) —

    a customizable set of options

Options Hash (*syms):

  • :instance_writer (Boolean) —

    if true, instance-level inheritable attribute writer is defined.

Returns:

  • (Array[#to_s]) —

    An Array of the attributes that were made into inheritable writers.



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# File 'lib/gems/extlib-0.9.9/lib/extlib/class.rb', line 146

def class_inheritable_writer(*ivars)
  instance_writer = ivars.pop[:instance_writer] if ivars.last.is_a?(Hash)
  ivars.each do |ivar|
    self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
      def self.#{ivar}=(obj)
        @#{ivar} = obj
      end
    RUBY
    unless instance_writer == false
      self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
        def #{ivar}=(obj) self.class.#{ivar} = obj end
      RUBY
    end
  end
end

#class_is_a?(klass_name) ⇒ Boolean

This will through the ancestor tree of object and tell you if that object is of the specified type.

Returns:

  • (Boolean) 


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# File 'lib/mack-facets/extensions/class.rb', line 14

def class_is_a?(klass_name)
  self.ancestors.each do |an|
    if an == klass_name
      return true
    end
  end
  return false
end

#duplicable? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/duplicable.rb', line 40

def duplicable?
  false
end

#inheritable_attributes ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 91

def inheritable_attributes
  @inheritable_attributes ||= EMPTY_INHERITABLE_ATTRIBUTES
end

#parents ⇒ Object

Returns an array of the classes parent classes.

Examples:

Orange.parents # => [Citrus, Fruit, Object]
Citrus.parents # => [Fruit, Object]
Fruit.parents # => [Object]



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# File 'lib/mack-facets/extensions/class.rb', line 29

def parents
  ans = [self.superclass]
  until ans.last.superclass.nil?
    ans << ans.last.superclass
  end
  ans
end

#read_inheritable_attribute(key) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 112

def read_inheritable_attribute(key)
  inheritable_attributes[key]
end

#remove_class(*klasses) ⇒ Object

Removes the classes in klasses from their parent module.

Ordinary classes belong to some module via a constant. This method computes that constant name from the class name and removes it from the module it belongs to.

Object.remove_class(Integer) # => [Integer]
Integer                      # => NameError: uninitialized constant Integer

Take into account that in general the class object could be still stored somewhere else.

i = Integer                  # => Integer
Object.remove_class(Integer) # => [Integer]
Integer                      # => NameError: uninitialized constant Integer
i.subclasses                 # => ["Bignum", "Fixnum"]
Fixnum.superclass            # => Integer



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/removal.rb', line 36

def remove_class(*klasses)
  klasses.flatten.each do |klass|
    # Skip this class if there is nothing bound to this name
    next unless defined?(klass.name)
    
    basename = klass.to_s.split("::").last
    parent = klass.parent
    
    # Skip this class if it does not match the current one bound to this name
    next unless parent.const_defined?(basename) && klass = parent.const_get(basename)

    parent.instance_eval { remove_const basename } unless parent == klass
  end
end

#remove_subclasses ⇒ Object

Unassociates the class with its subclasses and removes the subclasses themselves.

Integer.remove_subclasses # => [Bignum, Fixnum]
Fixnum                    # => NameError: uninitialized constant Fixnum



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/removal.rb', line 8

def remove_subclasses
  Object.remove_subclasses_of(self)
end

#reset_inheritable_attributes ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 116

def reset_inheritable_attributes
  @inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
end

#subclasses ⇒ Object

Returns an array with the names of the subclasses of self as strings.

Integer.subclasses # => ["Bignum", "Fixnum"]



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/removal.rb', line 15

def subclasses
  Object.subclasses_of(self).map { |o| o.to_s }
end

#superclass_delegating_accessor(*names) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/delegating_attributes.rb', line 42

def superclass_delegating_accessor(*names)
  superclass_delegating_reader(*names)
  superclass_delegating_writer(*names)
end

#superclass_delegating_reader(*names) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/delegating_attributes.rb', line 8

def superclass_delegating_reader(*names)
  class_name_to_stop_searching_on = self.superclass.name.blank? ? "Object" : self.superclass.name
  names.each do |name|
    class_eval <<-EOS
    def self.#{name}
      if defined?(@#{name})
        @#{name}
      elsif superclass < #{class_name_to_stop_searching_on} && superclass.respond_to?(:#{name})
        superclass.#{name}
      end
    end
    def #{name}
      self.class.#{name}
    end
    def self.#{name}?
      !!#{name}
    end
    def #{name}?
      !!#{name}
    end
    EOS
  end
end

#superclass_delegating_writer(*names) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/delegating_attributes.rb', line 32

def superclass_delegating_writer(*names)
  names.each do |name|
    class_eval <<-EOS
      def self.#{name}=(value)
        @#{name} = value
      end
    EOS
  end
end

#write_inheritable_array(key, elements) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 102

def write_inheritable_array(key, elements)
  write_inheritable_attribute(key, []) if read_inheritable_attribute(key).nil?
  write_inheritable_attribute(key, read_inheritable_attribute(key) + elements)
end

#write_inheritable_attribute(key, value) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 95

def write_inheritable_attribute(key, value)
  if inheritable_attributes.equal?(EMPTY_INHERITABLE_ATTRIBUTES)
    @inheritable_attributes = {}
  end
  inheritable_attributes[key] = value
end

#write_inheritable_hash(key, hash) ⇒ Object 



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# File 'lib/gems/activesupport-2.2.2/lib/active_support/core_ext/class/inheritable_attributes.rb', line 107

def write_inheritable_hash(key, hash)
  write_inheritable_attribute(key, {}) if read_inheritable_attribute(key).nil?
  write_inheritable_attribute(key, read_inheritable_attribute(key).merge(hash))
end