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Ruby Ruby Foundations Arrays Working With Arrays

Christ khodabakhshi
Christ khodabakhshi
10,916 Points
Posted by Christ khodabakhshi
Christ khodabakhshi
10,916 Points

index vs rindex

I am wondering to know what is the difference of index and rindex methods in array object (I searched but i couldn't find something).

1 Answer

Geoff Parsons
Geoff Parsons
11,679 Points

index searches the array for the object starting at element 0 and working up, where rindex will start at the end of the array and work down searching for the object. They can both return the same result if the object you're searching for only exists in the array once. But if, however, it exists multiple times you'll get different indices when using index as it only returns the index first occurrence of the object you're searching for.

Some IRB output to help illustrate:

>> array = ['a', 'b', 'c', 'd', 'e', 'a']
=> ["a", "b", "c", "d", "e", "a"]
>> array.index('a')
=> 0
>> array.rindex('a')
=> 5
>> array.index('c')
=> 2
>> array.rindex('c')
=> 2
Christ khodabakhshi
Christ khodabakhshi
10,916 Points
Christ khodabakhshi
Christ khodabakhshi
10,916 Points

Thank you, very clear explanation :)