Tries to find the relevant method, and returns its signature.
objc-class-method-signature class-spec method-name => arg-types, result-type, type-encoding
A foreign type descriptor.
objc-class-method-signature tries to find the relevant method, and returns its signature.
class-spec needs to be a string naming a class, an objc-object-pointer foreign pointer (which specifies its class), or an objc-class pointer.
method-name specifies the method name. It can be either a class method or an instance method.
The first return value is a list of the argument types (that is, foreign types). Note that the first and second arguments of all Objective-C methods are the object/class and the method selector (name). These are are typed as objc-object-pointer and sel, so the arg-types list always starts with these two symbols.
The second return value is the result type of the method.
The third return value is a string which is the type encoding of the signature of the method, as stored internally by the Objective-C runtime system.
objc-class-method-signature fails to locate the method, it returns
LispWorks Objective-C and Cocoa Interface User Guide and Reference Manual - 21 Mar 2017