Issue #12648 has been updated by Nobuyoshi Nakada.


Greg L wrote:
> Hence, a better solution might be adding a method like `sort_keys` or `sort_key`, where an array is returned by the block, and an array is used as the single parameter for ascending/descending info. 

Could you make clear what object these `sort_key`/`sort_keys` methods belong to?
The array to be sorted?
Or the returned object (it may not be an array) from the block?

> I might suggest, rather than true / false, or :asc / :desc, use 1 for ascending and -1 for descending.
> 
> If the parameter array is shorter, remaining keys could default to ascending, if it's longer, it's truncated.
> 
> Or (and maybe better), it could just raise an error if the arrays are different length.

Do you mean `enum.sort_by(-1) {...}` for descending?

----------------------------------------
Feature #12648: `Enumerable#sort_by` with descending option
https://bugs.ruby-lang.org/issues/12648#change-59962

* Author: Tsuyoshi Sawada
* Status: Open
* Priority: Normal
* Assignee: 
----------------------------------------
I would like to pass an optional argument to `Enumerable#sort_by` or `Enumerable#sort_by!` to allow descending sort. When the sort key is singular, this could be done by passing a single optinal boolean variable that represents ascending when `false` (default) and descending when `true`:

```ruby
[3, 1, 2].sort_by(&:itself)        # => [1, 2, 3]
[3, 1, 2].sort_by(false, &:itself) # => [1, 2, 3]
[3, 1, 2].sort_by(true, &:itself)  # => [3, 2, 1]
```

When there are multiple sort keys, corresponding numbers of arguments should be passed:

```ruby
[3, 1, 2, 0].sort_by{|e| [e % 2, e]}               # => [0, 2, 1, 3]
[3, 1, 2, 0].sort_by(false, false){|e| [e % 2, e]} # => [0, 2, 1, 3]
[3, 1, 2, 0].sort_by(false, true){|e| [e % 2, e]}  # => [2, 0, 3, 1]
[3, 1, 2, 0].sort_by(true, false){|e| [e % 2, e]}  # => [1, 3, 0, 2]
[3, 1, 2, 0].sort_by(true, true){|e| [e % 2, e]}   # => [3, 1, 2, 0]
```




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