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| Decorator pattern | |
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class Printer
def initialize(path)
@file = File.open(path, 'w')
end
def write_line(line)
@file.print(line)
@file.print("\n")
end
def pos
@file.pos
end
def rewind
@file.rewind
end
def close
@file.close
end
end
class PrinterDecorator
def initialize(real_writer)
@real_writer = real_writer
end
def write_line(line)
@real_writer.write_line(line)
end
def pos
@real_writer.pos
end
def rewind
@real_writer.rewind
end
def close
@real_writer.close
end
end
class NumberPrinter < PrinterDecorator
def initialize(real_writer)
super(real_writer)
@line_number = 1
end
def write_line(line)
@real_writer.write_line("#{@line_number}: #{line}")
@line_number += 1
end
end
writer = NumberPrinter.new(Printer.new('final.txt'))
writer.write_line('Hello out there')
class StringPrinter < PrinterDecorator
attr_reader :check_sum
def initialize(real_writer)
@real_writer = real_writer
@check_sum = 0
end
def write_line(line)
@real_writer.write_line(line)
end
end
class TimeStampingWriter < PrinterDecorator
def write_line(line)
@real_writer.write_line("#{Time.new}: #{line}")
end
end
writer = StringPrinter.new(TimeStampingWriter.new(
NumberPrinter.new(Printer.new('final.txt'))))
writer.write_line('Hello out there')
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