Issue #15927 has been updated by luke-gru (Luke Gruber).


Whether it's YAML or another data format like JSON, I've found it useful on occasion to treat `sprintf()` like a mini templating from a runtime generated Hash like ashmaroli mentioned. Sometimes ERB seems like overkill in quick scripts or internal projects. I understand now that these are considered `names` in the format string and so must be symbols, and this makes sense. It has surprised me in the past, however, and I have run into this error in my own scripts a few times.

Thank you for your time and explanations :)

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Feature #15927: Allow string keys to be used for String#% and sprintf methods
https://bugs.ruby-lang.org/issues/15927#change-78623

* Author: luke-gru (Luke Gruber)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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Right now, in the methods sprintf() and String#%, only symbol keys can be used for named interpolation. For example (from the example documentation):

"foo = %{foo}" % { :foo => 'bar' }        #=> "foo = bar"

String keys do not work like this:

"foo = %{foo}" % { 'foo' => 'bar' }        #=> raises KeyError

I think string keys should work just the same as symbol keys here.

I've created a PR on github for this, perhaps misguidedly, but if can be found here: https://github.com/ruby/ruby/pull/2238

My argument for this feature is that String#gsub() and family works with string keys if given a Hash, for example:

"chocolate ice cream".gsub(/\bc/, { 'c' => 'C' }) #=> 'Chocolate ice Cream'

Also, I don't like having to symbolize keys in strings unnecessarily, but maybe that just goes back to when
Ruby couldn't GC some symbols.





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