Class: Bmg::Ordering

Inherits:
Object
  • Object
show all
Defined in:
lib/bmg/support/ordering.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(attrs) ⇒ Ordering

Returns a new instance of Ordering.



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# File 'lib/bmg/support/ordering.rb', line 4

def initialize(attrs)
  @attrs = if attrs.empty?
    []
  elsif attrs.first.is_a?(Symbol)
    attrs.map{|a| [a, :asc] }
  else
    attrs
  end
end

Instance Attribute Details

#attrs ⇒ Object (readonly)

Returns the value of attribute attrs.



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# File 'lib/bmg/support/ordering.rb', line 13

def attrs
  @attrs
end

Instance Method Details

#call(t1, t2) ⇒ Object 



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# File 'lib/bmg/support/ordering.rb', line 15

def call(t1, t2)
  comparator.call(t1, t2)
end

#comparator ⇒ Object 



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# File 'lib/bmg/support/ordering.rb', line 19

def comparator
  @comparator ||= ->(t1, t2) { compare_attrs(t1, t2) }
end

#compare_attrs(t1, t2) ⇒ Object 



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# File 'lib/bmg/support/ordering.rb', line 23

def compare_attrs(t1, t2)
  attrs.each do |(attr,direction)|
    a1, a2 = t1[attr], t2[attr]
    if a1.nil? && a2.nil?
      0
    elsif a1.nil?
      return direction == :desc ? -1 : 1
    elsif a2.nil?
      return direction == :desc ? 1 : -1
    elsif a1.respond_to?(:<=>)
      c = a1 <=> a2
      unless c.nil? || c==0
        return direction == :desc ? -c : c
      end
    end
  end
  0
end

#to_a ⇒ Object 



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# File 'lib/bmg/support/ordering.rb', line 42

def to_a
  attrs.to_a
end