What does %i or %I do in Ruby?

What's the meaning of %i or %I in ruby?

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"%i or %I" ruby 

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3 Answers

%i[ ] # Non-interpolated Array of symbols, separated by whitespace %I[ ] # Interpolated Array of symbols, separated by whitespace 

The second link from my search results

Examples in IRB:

%i[ test ] # => [:test] str = "other" %I[ test_#{str} ] # => [:test_other] 

It can be hard to find the official Ruby documentation (it's here). At the time of writing the current version is 2.5.1, and the documentation for the %i construct is found in the documentation for Ruby's literals.

There are some surprising (to me at least!) variants of Ruby's % construct. There are the often used %i %q %r %s %w %x forms, each with an uppercase version to enable interpolation. (see the Ruby literals docs for explanations.

But you can use many types of delimiters, not just []. You can use any kind of bracket () {} [] <>, and you can use (quoting from the ruby docs) "most other non-alphanumeric characters for percent string delimiters such as “%”, “|”, “^”, etc."

So %i% bish bash bosh % works the same as %i[bish bash bosh]

It's like %w and %W which work similar to ' and ":

x = :test # %w won't interpolate #{...} style strings, leaving as literal %w[ #{x} x ] # => ["\#{x}", "x"] # %w will interpolate #{...} style strings, converting to string %W[ #{x} x ] # => [ "test", "x"] 

Now the same thing with %i and %I:

# %i won't interpolate #{...} style strings, leaving as literal, symbolized %i[ #{x} x ] # => [:"\#{x}", :x ] # %w will interpolate #{...} style strings, converting to symbols %I[ #{x} x ] # => [ :test, :x ]