Class: Class

Inherits:
Object show all
Defined in:
lib/extlib/class.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.

Instance Method Summary collapse

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



96
97
98
99
 
# File 'lib/extlib/class.rb', line 96

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] (*syms<Array] Array of attributes to define reader for.) —

    Array of attributes to define reader for.

Returns:

  • (Array<#to_s>) —

    List of attributes that were made into cattr_readers



40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
 
# File 'lib/extlib/class.rb', line 40

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



66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
 
# File 'lib/extlib/class.rb', line 66

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.



175
176
177
178
 
# File 'lib/extlib/class.rb', line 175

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

#class_inheritable_reader(*ivars) ⇒ Array<#to_s>

TODO:

Do we want to block instance_reader via :instance_reader => false

TODO:

It would be preferable that we do something with a Hash passed in (error out or do the same as other methods above) instead of silently moving on). In particular, this makes the return value of this function less useful.

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

Parameters:

  • *syms (Array[#to_s]) —

    Array of attributes to define inheritable reader for.

Returns:

  • (Array<#to_s>) —

    Array of attributes converted into inheritable_readers.



114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
 
# File 'lib/extlib/class.rb', line 114

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 defined?(@#{ivar})
        return nil      if self.object_id == #{self.object_id}
        ivar = superclass.#{ivar}
        return nil if ivar.nil?
        @#{ivar} = ivar.try_dup
      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(*ivars) ⇒ 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

Returns:

  • (Array<#to_s>) —

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



150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
 
# File 'lib/extlib/class.rb', line 150

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