Not sure why My greeting Variable is not working

Hi Christopher,

As of Swift 2, the println function is no longer available and the print function should be used instead. That said, the online code editor for the challenges is still expecting the use of println. If you are using the latest version of Xcode, you will have to use the print function in the playground (use of println will give an error). For the online challenges you will have to use println until Treehouse makes the necessary updates.

As for string interpolation: It basically allows you to substitute the current value of a constant or variable within string.

For example:

var firstName = "John"
var greeting = "Hello \(firstName)"
print(greeting)

The above code would output "Hello John".

Without string interpolation, you would have to do the following:

var firstName = "John"
var greeting = "Hello " + "firstName"
print(greeting)

You would still get the same result, but string interpolation makes strings easier to format and your code easier to read.

Hope this helps.

-- Ryan