String.Index does not have a member named advancedBy - swift

Question

This is the swift code I have as an exercise from my class, I am re-writing it(as I am new to it).
At the position of
let end = starIndex.advancedBy(position), I am getting an error message of String.Index does not have a member named advancedBy I am not sure what this means or how to correct it just yet, many thanks for any help in understanding what I am doing wrong.
//: Playground - noun: a place where people can play
import UIKit
var str : String = "Hello, playground"
str
let strFix = " Can not change"
str = "Good bye"
//strFix = "Testing"
var str2 = str + "F"
var townName = "NeverLand"
let population = 30000
let numOfStopLight : Int = 10
print("\(townName) has populations of \(population)
and has \ (numOfStopLight) Stop Lights")
for c in townName.unicodeScalars
{
print ("\(c)")
}
let starIndex = str.startIndex
let position = 3
let end = starIndex.advancedBy(position)
let charAt = str[end]
let range = starIndex...end
str[range]
let aChar: Character = "\u{1F60E}"
str.append(aChar)
let dollarSign = "\u{24}" //$, Unicode scalar U+0024
let blackHeart = "\u{2665}" // , Unicode scalar U+2665
let sparklingHeart = "\u{1F496}" // , Unicod scalar U=1F496
str.append(Character(sparklingHeart))
for c in str.characters
{
print("\(c)")
}
for c in str.unicodeScalars
{
print("\(c.value)")
}
/////////////////////
struct Car
{
var make : String = ""
var price : Double = 0.0
let color : String = "RED"
func getMske()->String
{
return make
}
mutating func setMake (m: String)
{
make = m
}
func showCar()->String
{
return "Make:\(make) Price=\(price) Color= \(color)"
}
}
//let us make some Car
var myCar = Car(make: "Nissan", price: 45000.0)
print(myCar.showCar())
myCar.setMake("Nissan2016")
print (myCar.showCar())
//show pass value
func doChange (var c: Car)
{
c.setMake("Toyota")
print (c.showCar())
}
doChange(myCar)
print (myCar.showCar())
//let us have a class
class Xcar
{
var make :String = ""
var price : Double = 0.0
var color : String = ""
init(m :String, p: Double, c: String)
{
self.make = m
self.price = p
self.color = c
}
func setMake(m: String)
{
self.make = m
}
func showXCar()->String
{
return "Make: \(make) Price=\(price) Color=\(color)"
}
}
func doChangex( c:Xcar)
{
c.setMake("BMW")
print("\(c.showXCar())")
}
var hisCar = Xcar(m: "Fiat", p: 15000.0, c: "Blue")
print ("\(hisCar.showXCar())")
doChangex(hisCar)
//notice the function did change
//because it was a class
print ("\(hisCar.showXCar())")
//What is optional
let a: Float?
let b: Float?
let c :Float?
a = 10
b = 20
c = 5
//this is implicit unrap
let ave = (a! + b! + c!)/3.0
if let x = a, y = b, z = c
{
print ("\((x + y + z) / 3.0)")
}
else
{
print ("missing value...")
}
// note Array, Double, Float, Int and Dictionary are all struct
var intArray = [Int] ()
intArray.append(50)
intArray.append(100)
intArray.append(600)
intArray.maxElement()
intArray.capacity
intArray.count
intArray.description
intArray.dropFirst()
intArray.first
intArray.description
intArray.removeFirst()
intArray.description
for c in intArray
{
print("\(c)")
}
var dict = [Int :String ] ()
dict = [235 :"Jack", 100: "Joe", 60: "Lisa"]
dict.description
for(key, value) in dict
{
print ("\(key)")
}
var name = dict[235]

Answer 1

Try doing it in one line
let startIndex = str.startIndex.advancedBy(3)

Answer 2

The code has a number of issues and we don't know what the expected output is, but here are a few items:
The line with just 'str' on it should be removed.
You may be running an older version of Xcode or OS (or both). This is Swift2 and you should be using Xcode 7 or higher.
Also, there are 'var' that should be 'let' (hisCar) and there are a number of unused variables.
The good news is once you fix the issues that, the code runs correctly (as far as I can tell)