objc:class

(objc:class "ClassName")

Answers the Objective-C class of that name, or signals when no loaded framework declares it. A class is a receiver like any other: send it a class method, or alloc it. Part of the macOS-only objc package -- the interpreter (java -jar, or the rontolisp native binary) and a compiled .class / .jar, never a .wasm; on a machine without the runtime it signals an error. See the macOS GUI guide.

CL-USER> (objc:class "NSString")
#<objc NSString>
CL-USER> (objc:send (objc:class "NSString") "stringWithUTF8String:" "hi")
#<objc NSTaggedPointerString>

objc:send also accepts a class name as the receiver, so (objc:send "NSString" ...) needs no objc:class.