Ruby: Transform Hash-Keys
I Have a Hash: Urls = [{'Logs' => 'Foo'}, {'Notifications' => 'Bar'}] the Goal Is to Add a Prefix to the Keys: Urls = [{' => 'Foo'}, {' => 'Bar'}] My Attempt...
I have a Hash:
urls = [{'logs' => 'foo'},{'notifications' => 'bar'}]
The goal is to add a prefix to the keys:
urls = [{' => 'foo'},{' => 'bar'}]
My attempt:
urls.map {|e| e.keys.map { |k| "example.com#{k}" }}
Then I get an array with the desired form of the keys but how can I manipulate the original hash?
3 Answers
If you want to "manually" transform the keys, then you can first iterate over your array of hashes, and then over each object (each hash) map their value to a hash where the key is interpolated with "", and the value remains the same:
urls.flat_map { |hash| hash.map { |key, value| { "" => value } } }
# [{""=>"foo"}, {""=>"bar"}]
Notice urls are being "flat-mapped", otherwise you'd get an arrays of arrays containing hash/es.
If you prefer to simplify that, you can use the built-in method for for transforming the keys in a hash that Ruby has; Hash#transform_keys:
urls.map { |url| url.transform_keys { |key| "" } }
# [{""=>"foo"}, {""=>"bar"}]
Use transform_keys.
urls = [{'logs' => 'foo'}, {'notifications' => 'bar'}]
urls.map { |hash| hash.transform_keys { |key| "" } }
# => [{""=>"foo"}, {""=>"bar"}]
One question: are you best served with an array of hashes here, or would a single hash suit better? For example:
urls = { 'logs' => 'foo', 'notifications' => 'bar' }
Seems a little more sensible a way to store the data. Then, saying you did still need to transform these:
urls.transform_keys { |key| "" }
# => {""=>"foo", ""=>"bar"}
Or to get from your original array to the hash output:
urls = [{'logs' => 'foo'}, {'notifications' => 'bar'}]
urls.reduce({}, &:merge).transform_keys { |key| "" }
# => {""=>"foo", ""=>"bar"}
Much easier to work with IMHO :)
If you don't have access to Hash#transform_keys i.e. Ruby < 2.5.5 this should work:
urls.map{ |h| a = h.to_a; { ' + a[0][0] => a[0][1] } }
Sarah Jenkins is a veteran tech journalist with over 12 years of experience covering artificial intelligence, mobile innovations, and digital ethics. Her insights have appeared in leading technology publications worldwide.
