Bug #10612: Documentation: Document behaviour of Hash#invert

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.1.5p273 (2014-11-13 revision 48405) [i686-linux]
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN

[shevegen (Robert A. Heiler)]

Currently a hash loses data if an .invert is done:

{"hey"=>3, "there"=>3, "yippie"=>3, "ack"=>2, "ackack"=>9, "thore"=>3, "yippa"=>9}.invert

Result:

# {3=>"thore", 2=>"ack", 9=>"yippa"}

In the example, this is shown, but it is not documented at:

http://www.ruby-doc.org/core-2.1.5/Hash.html#method-i-invert

As the example already shows it, my suggestion is to extend the documentation
with a sentence such as this:

"If a key with the same name already exists in the Hash then the
last one defined will be used, the earlier key will be discarded."

Or something similar to this.

[shevegen (Robert A. Heiler)]

For those of you who don't want to click on the link above, here
is the copy paste of the official documentation of said method:

invert → new_hash

Returns a new hash created by using hsh’s values as keys, and the keys as values.

h = { "n" => 100, "m" => 100, "y" => 300, "d" => 200, "a" => 0 }
h.invert   #=> {0=>"a", 100=>"m", 200=>"d", 300=>"y"}"

The last two lines are the official example - the last line shows that one key
was lost (key at "n" => 100))

[nobu (Nobuyoshi Nakada)]

Robert A. Heiler wrote:

"If a key with the same name already exists in the Hash then the
last one defined will be used, the earlier key will be discarded."

"name" should be "value", I guess.

[ayumin (Ayumu AIZAWA)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

Applied in changeset r49126.

---

• hash.c: fix docs for Hash#invert. [ruby-core:66917] [Bug #10612]