class Sequel::SQL::Expression

Base class for all SQL expression objects.

Attributes

comparison_attrs[R]

All attributes used for equality and hash methods.

Public Class Methods

attr_reader(*args) click to toggle source

Expression objects are assumed to be value objects, where their attribute values can't change after assignment. In order to make it easy to define equality and hash methods, subclass instances assume that the only values that affect the results of such methods are the values of the object's attributes.

Calls superclass method
   # File lib/sequel/sql.rb
92 def attr_reader(*args)
93   super
94   comparison_attrs.concat(args)
95 end
inherited(subclass) click to toggle source

Copy the comparison_attrs into the subclass.

Calls superclass method
    # File lib/sequel/sql.rb
 98 def inherited(subclass)
 99   super
100   subclass.instance_variable_set(:@comparison_attrs, comparison_attrs.dup)
101 end

Public Instance Methods

==(other) click to toggle source

Alias of eql?

    # File lib/sequel/sql.rb
125 def ==(other)
126   eql?(other)
127 end
clone() click to toggle source

Make clone/dup return self, since Expression objects are supposed to be frozen value objects

    # File lib/sequel/sql.rb
119 def clone
120   self
121 end
Also aliased as: dup
dup()
Alias for: clone
eql?(other) click to toggle source

Returns true if the receiver is the same expression as the the other expression.

    # File lib/sequel/sql.rb
131 def eql?(other)
132   other.is_a?(self.class) && !self.class.comparison_attrs.find{|a| public_send(a) != other.public_send(a)}
133 end
hash() click to toggle source

Make sure that the hash value is the same if the attributes are the same.

    # File lib/sequel/sql.rb
136 def hash
137   ([self.class] + self.class.comparison_attrs.map{|x| public_send(x)}).hash
138 end
inspect() click to toggle source

Attempt to produce a string suitable for eval, such that:

eval(obj.inspect) == obj
   # File lib/sequel/extensions/eval_inspect.rb
61 def inspect
62   # Assume by default that the object can be recreated by calling
63   # self.class.new with any attr_reader values defined on the class,
64   # in the order they were defined.
65   klass = self.class
66   args = inspect_args.map do |arg|
67     if arg.is_a?(String) && arg =~ /\A\*/
68       # Special case string arguments starting with *, indicating that
69       # they should return an array to be splatted as the remaining arguments.
70       # Allow calling private methods to get inspect output.
71       send(arg.sub('*', '')).map{|a| Sequel.eval_inspect(a)}.join(', ')
72     else
73       # Allow calling private methods to get inspect output.
74       Sequel.eval_inspect(send(arg))
75     end
76   end
77   "#{klass}.#{inspect_new_method}(#{args.join(', ')})"
78 end

Private Instance Methods

inspect_args() click to toggle source

Which attribute values to use in the inspect string.

   # File lib/sequel/extensions/eval_inspect.rb
83 def inspect_args
84   self.class.comparison_attrs
85 end
inspect_new_method() click to toggle source

Use the new method by default for creating new objects.

   # File lib/sequel/extensions/eval_inspect.rb
88 def inspect_new_method
89   :new
90 end