Swift return error that goes against what the Apple developer site says

func evaluateDate(nDate: Int!, rDate: Int!) -> Int{
    if(nDate < rDate) {
        return 1
    }
    if(nDate == rDate) {
        return 2
    }
    if(nDate > rDate) {
        return 3
    }
}

Every time I get an error that says: "Missing return in a function expected to return 'Int'" However on the apple developer website they give an example of this doing

func sayHello(personName: String, alreadyGreeted: Bool) -> String {
   if alreadyGreeted {
      return sayHelloAgain(personName)
   } else {
      return sayHello(personName)

   }
}
print(sayHello("Tim", alreadyGreeted: true))
// prints "Hello again, Tim!"

I don't understand what's going on because also in another place I try to change the value of a variable and it doesn't recognize the variable has changed outside the if-else block, however I don't ever remember this being an issue.