Copying and filtering Ruby arrays

Question

I'm doing a Ruby exercise to create new arrays with a given filter.

Copy the values less than 4 in the array stored in the source variable into the array in the destination variable.

The editorial solution code is:

def array_copy(source)
 destination = []
 for number in source
 # Add number to destination if number
 # is less than 4
 destination << number if number < 4
 end
 return destination
end

But, as a beginner, I came up with this solution:

def array_copy(source)
 return source.select {|i| i < 4}
end

Is there any problems with my solution?

Answer 1

I think your answer is perfectly valid and much better than the editorial solution.

I only have two suggestions to improve it further:

• variable name i is commonly used for array indexes. Using it instead for array values can confuse the reader of the code.
• return is not needed - Ruby functions will implicitly return the value of the last evaluated expression.

Answer 2

I don't think you have any problems, but you can improve it:

1. In Ruby, you don't need to return explicitly:

   def array_copy(source)
    source.select {|i| i < 4}
   end
   

2. The exercise says copy the values, so you might prefer using select!:

   def array_copy(source)
    source.select! {|i| i < 4}
   end
   

• Rene Saarsoo: As select! modifies the array in-place, it's actually the opposite of copying the values.
• ogirginc: I understood it as replacing the current values rather than creating a new duplicate. That’s why recommended bang version. 😊