Ruby - Methods - Keyword Arguments Discussions | Ruby

3 years ago+ 0 comments

I was wondering why nobody was trying to use objects since this problem is well suited for them. Maybe it is becauseHackerRank forces silly interfaces like convert_temp on us.

If you allow me some criticism, I'd say you are using obejcts but not taking the opportunity to benefit from designing with them im mind. Instead of writing a single class TemperatureConverter, here is how I'd write it:

class TemperatureConverter
    def initialize(degrees)
       @degrees = degrees
    end

    def value
        @degrees
    end
		
    def to(a_unit)
        a_unit.from(self)
    end
    
    def to_celsius
        subclass_responsibility
    end
    
    def to_fahrenheit
        subclass_responsibility
    end
    
    def to_kelvin
        subclass_responsibility
    end
    
    def subclass_responsibility
        raise 'Should be implemented by subclass'
    end
end

class Celsius < TemperatureConverter
    def to_celsius
        self
    end

    def to_fahrenheit
        Fahrenheit.new @degrees * 9/5r + 32
    end
    
    def to_kelvin
        Kelvin.new @degrees + 273.15
    end
    
    def self.from(a_temperature)
        a_temperature.to_celsius
    end
end

class Fahrenheit < TemperatureConverter
    def to_celsius
        Celsius.new (@degrees - 32) * 5/9r
    end

    def to_fahrenheit
        self
    end
    
    def to_kelvin
        Kelvin.new (@degrees + 459.67) * 5/9r
    end
    
    def self.from(a_temperature)
        a_temperature.to_fahrenheit
    end
end

class Kelvin < TemperatureConverter
    def to_celsius
        Celsius.new @degrees - 273.15
    end

    def to_fahrenheit
        Fahrenheit.new @degrees * 9/5r - 459.67
    end
    
    def to_kelvin
        self
    end
    
    def self.from(a_temperature)
        a_temperature.to_kelvin
    end
end

def convert_temp(degrees, input_scale:, output_scale: 'celsius')
    Object.const_get(input_scale.capitalize).new(degrees).to(Object.const_get(output_scale.capitalize)).value
    # or alternatively
    # Object.const_get(output_scale.capitalize).from(Object.const_get(input_scale.capitalize).new(degrees)).value
end

Look ma, no ifs!

I am pretty sure my design can be improved as well, and the naming is also suspiciuous. Why is a unit like Kelvin a sublclass of TemperatureConverter? Take a look at Aconcagua (Measures) If you'd like to study some production quality code.

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