I'm relatively new to Swift. I wanted to capitalize the first letter of each word in a title. To learn from an example, I used the following code from Hacking with Swift. It seems straight forword but I'm receiving the error "Value of type String has no member 'capitalized'".

What could be causing this error?

let str = "sunday, monday, happy days"
print(str.capitalized)

I figured it out. I needed to use import Foundation.

Does anyone have an explanation why some string methods need the Foundation class while others, such as lowercased don't require it?

Probably because capitalized is a property of NSString, which is only available through the Foundation framework. So, apparently, the NSString stuff will be available throught String only when you import Foundation, otherwise, it's standard String.

Thanks for your reply! I'll compare the two classes.