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Filename : cdesc-Data.ri
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U:RDoc::NormalClass[iI"	Data:ET@I"Object;To:RDoc::Markup::Document:@parts[o;;[o:RDoc::Markup::Paragraph;[I"E\Class \Data provides a convenient way to define simple classes ;TI"for value-alike objects.;To:RDoc::Markup::BlankLine�o;	;[I"#The simplest example of usage:;T@o:RDoc::Markup::Verbatim;[I"+Measure = Data.define(:amount, :unit)
;TI"
;TI"4# Positional arguments constructor is provided
;TI"'distance = Measure.new(100, 'km')
;TI"/#=> #<data Measure amount=100, unit="km">
;TI"
;TI"1# Keyword arguments constructor is provided
;TI"2weight = Measure.new(amount: 50, unit: 'kg')
;TI".#=> #<data Measure amount=50, unit="kg">
;TI"
;TI"0# Alternative form to construct an object:
;TI" speed = Measure[10, 'mPh']
;TI"/#=> #<data Measure amount=10, unit="mPh">
;TI"
;TI"*# Works with keyword arguments, too:
;TI".area = Measure[amount: 1.5, unit: 'm^2']
;TI"0#=> #<data Measure amount=1.5, unit="m^2">
;TI"
;TI"(# Argument accessors are provided:
;TI"distance.amount #=> 100
;TI"distance.unit #=> "km"
;T:@format0o;	;[I"AConstructed object also has a reasonable definitions of #== ;TI"Koperator, #to_h hash conversion, and #deconstruct / #deconstruct_keys ;TI"$to be used in pattern matching.;T@o;	;[I"C::define method accepts an optional block and evaluates it in ;TI"Cthe context of the newly defined class. That allows to define ;TI"additional methods:;T@o;;[I".Measure = Data.define(:amount, :unit) do
;TI"  def <=>(other)
;TI"E    return unless other.is_a?(self.class) && other.unit == unit
;TI"!    amount <=> other.amount
;TI"  end
;TI"
;TI"  include Comparable
;TI"	end
;TI"
;TI"0Measure[3, 'm'] < Measure[5, 'm'] #=> true
;TI"(Measure[3, 'm'] < Measure[5, 'kg']
;TI"A# comparison of Measure with Measure failed (ArgumentError)
;T;0o;	;[	I"BData provides no member writers, or enumerators: it is meant ;TI"@to be a storage for immutable atomic values. But note that ;TI"Lif some of data members is of a mutable class, Data does no additional ;TI"immutability enforcement:;T@o;;[I"+Event = Data.define(:time, :weekdays)
;TI"1event = Event.new('18:00', %w[Tue Wed Fri])
;TI"D#=> #<data Event time="18:00", weekdays=["Tue", "Wed", "Fri"]>
;TI"
;TI"C# There is no #time= or #weekdays= accessors, but changes are
;TI"# still possible:
;TI"event.weekdays << 'Sat'
;TI"event
;TI"K#=> #<data Event time="18:00", weekdays=["Tue", "Wed", "Fri", "Sat"]>
;T;0o;	;[I"?See also Struct, which is a similar concept, but has more ;TI"Dcontainer-alike API, allowing to change contents of the object ;TI"and enumerate it.;T:
@fileI"
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