What is Enumerator object? (Created with String#gsub)
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14-03-2021 - |
Question
I have an attributes array as follows,
attributes = ["test, 2011", "photo", "198.1 x 198.1 cm", "Photo: Manu PK Full Screen"]
When i do this,
artist = attributes[-1].gsub("Photo:")
p artist
i get the following output in terminal
#<Enumerator: "Photo: Manu PK Full Screen":gsub("Photo:")>
Wondering why am I getting an enumerator object as output? Thanks in advance.
EDIT:
Please note that instead of attributes[-1].gsub("Photo:", ""), I am doing attributes[-1].gsub("Photo:")
So would like to know why enumerator object has returned here( I was expecting an error message) and what is going on.?
Ruby - 1.9.2
Rails - 3.0.7
Solution
An Enumerator
object provides some methods common to enumerations -- next
, each
, each_with_index
, rewind
, etc.
You're getting the Enumerator
object here because gsub
is extremely flexible:
gsub(pattern, replacement) → new_str
gsub(pattern, hash) → new_str
gsub(pattern) {|match| block } → new_str
gsub(pattern) → enumerator
In the first three cases, the substitution can take place immediately, and return a new string. But, if you don't give a replacement string, a replacement hash, or a block for replacements, you get back the Enumerator
object that lets you get to the matched pieces of the string to work with later:
irb(main):022:0> s="one two three four one"
=> "one two three four one"
irb(main):023:0> enum = s.gsub("one")
=> #<Enumerable::Enumerator:0x7f39a4754ab0>
irb(main):024:0> enum.each_with_index {|e, i| puts "#{i}: #{e}"}
0: one
1: one
=> " two three four "
irb(main):025:0>
OTHER TIPS
When neither a block nor a second argument is supplied, gsub returns an enumerator. Look here for more info.
To remove it, you need a second parameter.
attributes[-1].gsub("Photo:", "")
Or
attributes[-1].delete("Photo:")
Hope this helps!!