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 92 def attr_reader(*args) 93 super 94 comparison_attrs.concat(args) 95 end
Copy the comparison_attrs
into the subclass.
# 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
Alias of eql?
# File lib/sequel/sql.rb 125 def ==(other) 126 eql?(other) 127 end
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
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
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
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
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
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