First example. Consider this example Ruby code. The test string contains 3 "a" characters. So the starting location of our search matters.
Part 1 We invoke index() to search from the start of the string. We immediately match the first letter "a," so 0 is returned.
Part 2 We call rindex to search from the end of the test string, and the last index 2 is returned.
test = "aaa"# Part 1: use index() to search from start.
left = test.index("a")
puts left
# Part 2: use rindex() to search from end.
right = test.rindex("a")
puts right0
2
No match. If no matching substring is found within the string, we get the special nil value. This can be tested in an if-statement.
Info Whenever we call index and rindex on a string, we should have code that checks for a nil result.
Part 1 We call index and the argument is not found in the string. The code detects this and prints a message.
Part 2 We invoke rindex and the argument is not found—the code prints a message to report this.
input = "test"# Part 1: test index() for nil result.
result1 = input.index("x")
puts "NOT FOUND 1" if result1 == nil
# Part 2: test rindex() for nil result.
result2 = input.rindex("x")
puts "NOT FOUND 2" if result2 == nilNOT FOUND 1
NOT FOUND 2
Between, before, after. In developing more complex Ruby methods, like a between method, we must use index() and rindex to search a string. And we should be careful with a nil result.
Searching a string is commonly done in Ruby programs. And with index and rindex we can specify the direction, and starting position, of our search.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
