如何在多维数组中按字母顺序排序？

Question

I'm an intermediate Ruby developer. I'm working on some puzzles to brush up on Ruby and I'm trying to figure out how to go about sorting a multidimensional array. Here's my code:

myArray = [['Jones', 'Layla'], ['Smith', 'Gary'], ['Williams', 'Nick'] ,['Brown', 'Kyle']]

So I need to iterate through the array and through the sub-arrays, identify the last names, and alphabetize them. For some reason nothing I've been trying for the last two hours seems to be working. I've been searching high and low online. Can anyone help out? I've been trying variations of the following, below. Any pointers?

myArray.each { |sub_array| 
sub_array.sort_by! { |x|
x[0].downcase #the x[0] element being the last name, which is the first element in each of the sub-arrays
    }
return sub_array
}

edit: forgot to clarify, the end result should look like this:

myArray = [['Brown', 'Kyle']['Jones', 'Layla'], ['Smith', 'Gary'], ['Williams', 'Nick']]

Answer 1

If you want sort the array by the lastname (the first element of each sub array) you could do easily with this:

myArray.sort { |x,y| x[0] <=> y[0] }

myArray = [['Jones', 'Layla'], ['Smith', 'Gary'], ['Williams', 'Nick'], ['Brown', 'Kyle']]
 => [["Jones", "Layla"], ["Smith", "Gary"], ["Williams", "Nick"], ["Brown", "Kyle"]] 
myArray.sort { |x,y| x[0] <=> y[0] }
 => [["Brown", "Kyle"], ["Jones", "Layla"], ["Smith", "Gary"], ["Williams", "Nick"]]  

sort documentation here

Answer 2

Just use Array#sort without a block:

my_array = [['Jones', 'Layla'], ['Smith', 'Gary'], ['Williams', 'Nick'],
            ['Brown', 'Kyle']]
my_array.sort
   #=> [["Brown", "Kyle"], ["Jones", "Layla"], ["Smith", "Gary"], ["Williams", "Nick"]]

See the doc for the method Array#<=> (the spaceship operator ) to learn how Ruby orders each pair of arrays within the sorting algorithm.

If two people have the same last name, sort will order them by their first name (ie, first names are used to break ties):

my_array = [['Jones', 'Layla'], ['Smith', 'Gary'], ['Williams', 'Nick'],
            ['Brown', 'Kyle'], ['Jones', 'Zack']]

my_array.sort
  #=> [["Brown", "Kyle"], ["Jones", "Layla"], ["Jones", "Zack"],
  #    ["Smith", "Gary"], ["Williams", "Nick"]] 

I used my_array instead of myArray because the Ruby convention is to use "snake-case" for names of variables and methods. You don't have to follow that convention, but 99%+ of Rubiests do.