I am trying to get a string name of a class from the class object itself.
// For instance
[NSArray className]; // @"NSArray"
I have found object_getClassName(id obj) but that requires an instance be passed to it, and in my case that is needless work.
So how can I get a string from a class object, and not an instance?
NSString *name = NSStringFromClass ([NSArray class]);
You can even go back the other way:
Class arrayClass = NSClassFromString (name);
id anInstance = [[arrayClass alloc] init];
NSStringFromClass implemented? Is it more performant to store the class name in a static NSString variable?
[NSArray class]) is actually a struct. The struct contains a lot of information about the class, including its name, the methods it implements, the superclass, etc. NSStringFromClass just pulls the name of the class from this struct and converts it to an NSString. Don't store the class name in a static NSString, it won't offer any performance advantage.NSClassFromString works a bit differently. Since all of the class names exist somewhere in the Objective-C runtime, NSClassFromString takes the string and explores the list of classes maintained by the runtime looking for the class that has the given name. If it finds it, it returns it, otherwise it returns Nil.
class_getName() in the runtime, which returns a C stringclassName is a method added by the scripting extensions which is only available on Mac OS X, even then it is finicky in how it works because it is not fully documented (or at least it wasn't the last time I checked). NSStringFromClass() is the correct way to go about it.Here's a different way to do it with slightly less typing:
NSString *name = [NSArray description];
+description, however, in theory, this is not the purpose for +description, and so this method is fragile for determining class names.Consider this alternative:
const char *name = class_getName(cls);
It's much faster, since it doesn't have to alloc NSString object and convert ASCII to whatever NSString representation is. That's how NSStringFromClass() is implemented.
