Question

I’m trying to reverse words in an array of string variables, but split doesn’t seem to be working.

Testing in IRB I get “NoMethodError: private method `split’ called for Array”, which I’m assuming has something to do with my program quietly doing nothing.

For example, I have:

nameList = ["Joe Blow", "Mary Sue", "Alice Mallory"].

I expect to return:

["Blow Joe", "Sue Mary", "Mallory Alice"].

So I iterate through the array, splitting, reversing and joining. This is where nothing happens:

nameList.each { |x| 
  x.to_s.split(' ').reverse!.join(' ')
  puts x   #testing here
}

This outputs:

Joe Blow
Mary Sue
Alice Mallory

I must be missing something extremely simple, as this can’t be too difficult.

Answer 1

You’re splitting, reversing and discarding the result. Check this out.

nameList = ["Joe Blow", "Mary Sue", "Alice Mallory"]

nameList.each { |x| 
  puts x.to_s.split(' ').reverse.join(' ')
  puts x
  puts '' # for easier reading   
}
# >> Blow Joe
# >> Joe Blow
# >> 
# >> Sue Mary
# >> Mary Sue
# >> 
# >> Mallory Alice
# >> Alice Mallory
# >> 

If you want to apply some transformation to every element of array, get new value and construct a new array of these values, it is idiomatic to use Array#map function.

nameList = ["Joe Blow", "Mary Sue", "Alice Mallory"]

newList = nameList.map { |x| 
  x.to_s.split(' ').reverse.join(' ')
}

Also, here you shouldn’t use bang version of reverse (reverse!). It has destructive semantics. reverse creates a new reversed array, while reverse! updates source array in place. In this case source array is a temp variable, so it makes no difference result-wise. But I consider it confusing and distracting.