class Sequel::SQL::Expression
Base class for all SQL expression objects.
Attributes
All attributes used for equality and hash methods.
Public Class Methods
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.
# File lib/sequel/sql.rb, line 105 def attr_reader(*args) super comparison_attrs.concat(args) end
Copy the ::comparison_attrs into the subclass.
# File lib/sequel/sql.rb, line 111 def inherited(subclass) super subclass.instance_variable_set(:@comparison_attrs, comparison_attrs.dup) end
Public Instance Methods
Alias of eql?
# File lib/sequel/sql.rb, line 130 def ==(other) eql?(other) end
Returns true if the receiver is the same expression as the the
other
expression.
# File lib/sequel/sql.rb, line 136 def eql?(other) other.is_a?(self.class) && !self.class.comparison_attrs.find{|a| send(a) != other.send(a)} end
Make sure that the hash value is the same if the attributes are the same.
# File lib/sequel/sql.rb, line 141 def hash ([self.class] + self.class.comparison_attrs.map{|x| send(x)}).hash end
Attempt to produce a string suitable for eval, such that:
eval(obj.inspect) == obj
# File lib/sequel/extensions/eval_inspect.rb, line 68 def inspect # Assume by default that the object can be recreated by calling # self.class.new with any attr_reader values defined on the class, # in the order they were defined. klass = self.class args = inspect_args.map do |arg| if arg.is_a?(String) && arg =~ /\A\*/ # Special case string arguments starting with *, indicating that # they should return an array to be splatted as the remaining arguments send(arg.sub('*', '')).map{|a| Sequel.eval_inspect(a)}.join(', ') else Sequel.eval_inspect(send(arg)) end end "#{klass}.#{inspect_new_method}(#{args.join(', ')})" end
Returns self
, because SQL::Expression
already
acts like LiteralString
.
# File lib/sequel/sql.rb, line 152 def lit self end
Alias of to_s
# File lib/sequel/sql.rb, line 157 def sql_literal(ds) s = String.new to_s_append(ds, s) s end
Private Instance Methods
Which attribute values to use in the inspect string.
# File lib/sequel/extensions/eval_inspect.rb, line 88 def inspect_args self.class.comparison_attrs end
Use the new method by default for creating new objects.
# File lib/sequel/extensions/eval_inspect.rb, line 93 def inspect_new_method :new end