CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-3
user1493194
user1493194

Reputation: 343

What does % do in the following code?

I'm reading The "Rails 3 Way" and on page 39, it shows a code sample of the match :to => redirect method. In that method the following code exists. Whilst I know what modulo does with numbers, I'm unsure what the % is doing below because both path and params are clearly not numbers. If anyone can help me understand the use of % in this situation, I'd appreciate it. 

proc { |params| path % params }

Upvotes: 5

Views: 113

Answers (2)

tadman
tadman

Reputation: 211750

That's probably the String#% method which works a lot like sprintf does in other languages:

'%05d' % 10
# => "00010"

It can take either a single argument or an array:

'%.3f %s' % [ 10.341412, 'samples' ]
# => "10.341 samples"

Update: As Philip points out, this method also takes a hash:

'%{count} %{label}' % { count: 20, label: 'samples' }
# => "20 samples"

Of course, this is presuming that path is a String. In Ruby you never really know for sure unless you carefully read the code. It's unlikely, but it could be % meaning modulo.

The thing you can be sure of is it's calling method % on path.

Upvotes: 10

Todd A. Jacobs
Todd A. Jacobs

Reputation: 84453

It does string interpolation. In the simplest case, it's equivalent to:

"foo %s baz" % 'bar'
#=> "foo bar baz"

However, you can use more complex format specifiers to interpolate from Array or Hash objects too, such as the Rails params hash. See the String#% and Kernel#sprintf methods for details on how to construct a valid format specification.

Upvotes: 2

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