Class: Sequel::SQL::Expression

Inherits:
Object
  • Object
show all
Defined in:
lib/sequel/sql.rb,
lib/sequel/extensions/eval_inspect.rb

Overview

Base class for all SQL expression objects.

Direct Known Subclasses

AliasedExpression, ColumnAll, ComplexExpression, GenericExpression, JoinClause, OrderedExpression, Window

Class Attribute Summary (collapse)

Class Method Summary (collapse)

Instance Method Summary (collapse)

Class Attribute Details

+ (Object) comparison_attrs (readonly)

All attributes used for equality and hash methods.



80
81
82
# File 'lib/sequel/sql.rb', line 80

def comparison_attrs
  @comparison_attrs
end

Class Method Details

+ (Object) attr_reader(*args)

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.



87
88
89
90
# File 'lib/sequel/sql.rb', line 87

def attr_reader(*args)
  super
  comparison_attrs.concat(args)
end

+ (Object) inherited(subclass)

Copy the comparison_attrs into the subclass.



93
94
95
96
# File 'lib/sequel/sql.rb', line 93

def inherited(subclass)
  super
  subclass.instance_variable_set(:@comparison_attrs, comparison_attrs.dup)
end

Instance Method Details

- (Object) ==(other)

Alias of eql?



112
113
114
# File 'lib/sequel/sql.rb', line 112

def ==(other)
  eql?(other)
end

- (Boolean) eql?(other)

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

Returns:

  • (Boolean)


118
119
120
# File 'lib/sequel/sql.rb', line 118

def eql?(other)
  other.is_a?(self.class) && !self.class.comparison_attrs.find{|a| send(a) != other.send(a)}
end

- (Object) hash

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



123
124
125
# File 'lib/sequel/sql.rb', line 123

def hash
  ([self.class] + self.class.comparison_attrs.map{|x| send(x)}).hash
end

- (Object) inspect

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

eval(obj.inspect) == obj


129
130
131
# File 'lib/sequel/sql.rb', line 129

def inspect
  "#<#{self.class} #{instance_variables.map{|iv| "#{iv}=>#{instance_variable_get(iv).inspect}"}.join(', ')}>"
end

- (Object) lit

Returns self, because SQL::Expression already acts like LiteralString.



134
135
136
# File 'lib/sequel/sql.rb', line 134

def lit
  self
end

- (Object) sql_literal(ds)

Alias of to_s



139
140
141
142
143
# File 'lib/sequel/sql.rb', line 139

def sql_literal(ds)
  s = ''
  to_s_append(ds, s)
  s
end