Ruby

This rule applies whenever an if statement is followed by one or more elsif statements; the final elsif should be followed by an else statement.

The requirement for a final else statement is defensive programming.
The else statement should either take appropriate action or contain a suitable comment as to why no action is taken. This is consistent with the requirement to have a final else clause in a case statement.

Noncompliant Code Example

if x == 0                                      
  doSomething
elsif x == 1
  doSomethingElse
end

Compliant Solution

if x == 0                                      
  doSomething
elsif x == 1
  doSomethingElse
else
  raise 'An error has occured'
end

Exceptions

When all branches of an if-else if end with return, break or throw, the code that comes after the if implicitly behaves as if it was in an else clause. This rule will therefore ignore that case.