Question

I have rows of hashes imported from several different XML database dumps that look like this (but with varying keys):

{"Id"=>"1", "Name"=>"Cat", "Description"=>"Feline", "Count"=>"123"}

I tried using #to_i but it converts a non-number string to 0:

"Feline".to_i
# => 0

But what I’d like is a way for "Feline" to remain a string, while Id and Count in the above example become integers 1 and 123.

Is there an easy way to convert only the strings values that are numbers into integers?

Answer 1

use Kernel#Integer:

my_hash = {"Id"=>"1", "Name"=>"Cat", "Description"=>"Feline", "Count"=>"123"}
Hash[ my_hash.map{ |a, b| [ a,
                            begin
                              Integer b
                            rescue ArgumentError
                              b
                            end ] } ]

ADDED LATER: With my y_support gem, you can make hash operations even more concise.

require 'y_support/core_ext/hash'
my_hash.with_values { |v| begin
                            Integer b
                          rescue ArgumentError
                            b
                          end }

YSupport can be installed by gem install y_support and also offers Hash#with_keys, Hash#with_values!, Hash#with_keys! that do what you expect they do, and Hash#modify that expects a binary block returning a pair of values, modifying the hash in place. There have been proposals to add such methods directly to the Ruby core in the future.