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.

Class Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Class Attribute Details

.comparison_attrs ⇒ Object (readonly)

All attributes used for equality and hash methods.



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# File 'lib/sequel/sql.rb', line 85

def comparison_attrs
  @comparison_attrs
end

Class Method Details

.attr_reader(*args) ⇒ Object

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.



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# File 'lib/sequel/sql.rb', line 92

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

.inherited(subclass) ⇒ Object

Copy the comparison_attrs into the subclass.



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# File 'lib/sequel/sql.rb', line 98

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

Instance Method Details

#==(other) ⇒ Object

Alias of eql?



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

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

#clone ⇒ Object Also known as: dup

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



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

def clone
  self
end

#eql?(other) ⇒ Boolean

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

Returns:

  • (Boolean) 


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

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

#hash ⇒ Object

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



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

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

#inspect ⇒ Object

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

eval(obj.inspect) == obj



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# File 'lib/sequel/sql.rb', line 141

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