What is the different between NSCFString and NSConstantString?

Question

I declare the object variable as a NSString But when I use the XCode to look into my object, I saw there are two type of String, it seems that the system automa

Answer 1

It appears to be an optimization done by the compiler. I'm guessing that the string that is getting converted to an NSCFConstantString is equal to one of the constants that is cached for performance reasons. Your NSCFString is just a toll-free bridged string that can be an NSString or a CFString. See this article for more information.