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?

Rene Saarsoo · Accepted Answer · 2017-11-18 15:14:52Z

2

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.

answered Nov 18, 2017 at 15:14

Rene Saarsoo

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Sᴀᴍ Onᴇᴌᴀ · Accepted Answer · 2017-11-18 15:25:34Z

1

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

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

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

The exercise says copy the values, so you might prefer using select!:
```
def array_copy(source)
  source.select! {|i| i < 4}
end
```

edited Nov 18, 2017 at 15:25

Sᴀᴍ Onᴇᴌᴀ♦

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answered Nov 18, 2017 at 15:18

ogirginc

1667 bronze badges

1

\$\begingroup\$ As select! modifies the array in-place, it's actually the opposite of copying the values. \$\endgroup\$

Rene Saarsoo
– Rene Saarsoo

2017-11-18 16:41:00 +00:00
Commented Nov 18, 2017 at 16:41
\$\begingroup\$ I understood it as replacing the current values rather than creating a new duplicate. That’s why recommended bang version. 😊 \$\endgroup\$

ogirginc
– ogirginc

2017-11-18 17:50:34 +00:00
Commented Nov 18, 2017 at 17:50

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