There’s an even simpler way to include values in strings: Write the value in parentheses, and write a backslash (\) before the parentheses. This is known as string interpolation.
let apples = 3let oranges = 5let appleSummary = "I have \(apples) apples."let fruitSummary = "I have \(apples + oranges) pieces of fruit."swift - use backslash to add the value in the string
原文：http://www.cnblogs.com/facial/p/5254033.html