incorrect use of ruby's sort_by function

Question

My sort function is clearly not working, I am trying to sort ALL_VIEWS by @permalink.length:

ALL_VIEWS.sort_by {|view| view.permalink.length}

ALL_VIEWS[0..4].each do |view|
    puts view.inspect
    puts view.permalink.length
end

this produces:

#<View:0x1014da7b8 @permalink="xxxx">
4
#<View:0x1014da790 @permalink="yyyyy">
5
#<View:0x1014da718 @permalink="zzz">
3
#<View:0x1014da6a0 @permalink="aaaaaaa">
7
#<View:0x1014da628 @permalink="b">
1

I am expecting the following result:

#<View:0x1014da628 @permalink="b">
1
#<View:0x1014da718 @permalink="zzz">
3
#<View:0x1014da7b8 @permalink="xxxx">
4
#<View:0x1014da790 @permalink="yyyyy">
5
#<View:0x1014da6a0 @permalink="aaaaaaa">
7

Answer 1

Use

ALL_VIEWS.replace ALL_VIEWS.sort_by {|view| view.permalink.length }

for the first line. sort_by does not sort in place - it returns the sorted array and does not modify the original one.

Answer 2

The Problem

sort_by does not mutate the object, it is a method of Enumerable that returns an Array whose elements are the elements yielded by your object's each method. It then sorts that array by the criteria given in your block. But notice that it does not sort your array docs for Enumerable#sort_by

You could normally do what Adrian suggested, and assign the results back to the original variable, but your original is a constant, which is going to give you issues.

The Solution(s)

So you need to either make ALL_VIEWS something other than a constant (if you are wanting to change it, then it really shouldn't be a constant anyway). Perhaps a class variable?

---

Or you need to have these values sorted before they are assigned to ALL_VIEWS

ALL_VIEWS = view_paths.map do |path| 
  View.new 'views/pages' , path 
end.sort_by do |view| 
  view.permalink.length
end

---

Or you can sort in place with something other than the sort_by method

ALL_VIEWS.sort! do |view1,view2| 
  view1.permalink.length <=> view2.permalink.length
end

This will work, but again, if you are doing stuff like this, then should ALL_VIEWS really be a constant? docs for Array#sort and Array#sort!