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Module: Comparable

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Included In:
::Bignum, ::Complex, ::File::Stat, ::Fixnum, ::Float, ::Integer, ::Numeric, ::Rational, ::String, ::Symbol, ::Time
Defined in: compar.c

Overview

The Comparable mixin is used by classes whose objects may be ordered. The class must define the <=> operator, which compares the receiver against another object, returning -1, 0, or +1 depending on whether the receiver is less than, equal to, or greater than the other object. If the other object is not comparable then the <=> operator should return nil. Comparable uses <=> to implement the conventional comparison operators (#<, #<=, #==, #>=, and #>) and the method #between?.

class SizeMatters
  include Comparable
  attr :str
  def <=>(anOther)
    str.size <=> anOther.str.size
  end
  def initialize(str)
    @str = str
  end
  def inspect
    @str
  end
end

s1 = SizeMatters.new("Z")
s2 = SizeMatters.new("YY")
s3 = SizeMatters.new("XXX")
s4 = SizeMatters.new("WWWW")
s5 = SizeMatters.new("VVVVV")

s1 < s2                       #=> true
s4.between?(s1, s3)           #=> false
s4.between?(s3, s5)           #=> true
[ s3, s2, s5, s4, s1 ].sort   #=> [Z, YY, XXX, WWWW, VVVVV]

Instance Method Summary

Instance Method Details

#<(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns -1.

#<=(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns -1 or 0.

#==(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns 0. Also returns true if obj and other are the same object.

Even if obj <=> other raised an exception, the exception is ignored and returns false.

#>(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns 1.

#>=(other) ⇒ Boolean

Compares two objects based on the receiver's <=> method, returning true if it returns 0 or 1.

#between?(min, max) ⇒ Boolean

Returns false if obj <=> min is less than zero or if anObject <=> max is greater than zero, true otherwise.

3.between?(1, 5)               #=> true
6.between?(1, 5)               #=> false
'cat'.between?('ant', 'dog')   #=> true
'gnu'.between?('ant', 'dog')   #=> false