How to convert miles into km and vice versa? [closed] - ruby

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I cannot figure out how to create this conversion, something about math no matter how minute it is rattles my brain.
My class
class Distance
def convert(miles_to_km, km_to_miles)
miles_to_km = 1 * 1.60934
km_to_miles = 1 * 0.621371
end
end
or should it be something like
class Distance
def convert(value, unit)
some data i have yet to understand
end
end
my added input
puts "______________Adding: _____________"
d1 = Distance.new(1, "m")
d2 = Distance.new(1, "k")
puts d1 + d2
d1 = Distance.new(2, "M")
d2 = Distance.new(2, "m")
d3 = d1 + d2
puts d3
puts d3.value
puts d3.unit
d1 = Distance.new(3, "k")
d2 = Distance.new(3, "K")
puts d1 + d2
d1 = Distance.new(4, "k")
d2 = Distance.new(4, "m")
puts d1 + d2
puts "-" * 30 ############
Results should be
______________Adding _____________
1.621371 Miles
4 Miles
4
m
6 Kilometers
10.43736 Kilometers

Answer 1

Your methods need to be specific to your actions.
def convert(miles_to_km, km_to_miles)
miles_to_km = 1 * 1.60934
km_to_miles = 1 * 0.621371
end
Should be
def convert_miles_to_km(km)
return km * 1.60934
end
and vice versa

Answer 2

Parse String Arguments for Flexibility
There are lots of ways to solve this problem. A lot depends one what sort of input you expect from the caller, and what sort of result you want to pass back as your return values.
Sometimes it's useful to be less rigorous about how one expresses units of measurement while still being strict about the way the conversions are performed. Here is an example where a single method takes a string as input, and returns an appropriate floating-point value for predefined units such as kilometers or miles while remaining flexible about the way the distance units are expressed.
# Use constants for your conversion ratios.
MI_TO_KM = 1.60934
KM_TO_MI = 0.621371
# Make your method more flexible by accepting a string
# containing both a distance and a unit identifier.
def convert_distance str
dist, unit = str.scan(/([\d.]+)\s*(\S+)/).flatten
case unit
when /^k/i
dist.to_f * KM_TO_MI
when /^m/i
dist.to_f * MI_TO_KM
else
raise ArgumentError, "unknown unit: #{unit.inspect}"
end
end
This will provide you with the following sample outputs:
convert_distance '10 miles'
#=> 16.0934
convert_distance '10 kilometers'
#=> 6.21371
convert_distance '3mi'
#=> 4.82802
convert_distance '3km'
#=> 1.8641130000000001
convert_distance '1 cubit'
#=> ArgumentError: unknown unit: "cubit"
This type of method isn't necessarily the simplest way to get the job done, but it certainly prevents you from having to define different methods for "km", "kilometers", "klicks", and so forth. It's also easily expandable for other units of distance (e.g. "yards") simply by adding a new clause with the appropriate conversion ratio to the case statement.