Method signature in Objective-C - ios

Question

I'm trying to understand, how does method signature in Objective-C is look like.
INTRO:
At first, lets break misunderstandings about question, what is it, method signature?
Method signature it is something, that helps compiler unambiguously identifies subroutine.
Am i right? :)
So in the C language signature is roughly equivalent to its prototype definition:
For example, we have function int printf( const char *format, ... ); in stdlib.
Signature of this function is printf.
In this case, we can't overload in C language, because compiler can't identify function with different argument types, so people decide to do some tricky thing like this:
long int labs (long int n);
int abs (int n);
double fabs (double x);
In the C++ language, method signature is class name, method name and method arguments.
So in this language we can overload methods.
PROBLEM
I can't get simple answer, what is method signature in Objective-C?!
I'm trying to use my logic...
1)At first, we can't overloading in Objective-C => method arguments is not part of method signature.
2)I tried to compile code with different return value:
#interface Foo : NSObject
- (CGFloat)method;
- (NSInteger)method;
#end
I got error in this case => return value is not part of method signature.
I tested different cases and got the answer, method signature in Objective-C is class name, method type ('+' or '-') and selector.
For example, we have method in class Foo (code below):
#interface Foo : NSObject
+ (void)methodWithArgument:(NSInteger)argument;
#end
So the signature of this method is +[Foo methodWithArgument:]
But then, i look at apple's documentation of NSMethodSignature (http://bit.ly/1tGR8zt)
An NSMethodSignature object records type information for the arguments
and return value of a method
Arguments and return value?! Only using arguments and return value, we can unambiguously identify method? It's very strange.

Answer 1

First thing. Who said that compiler can differentiate between 2 methods on the basis or its return type
so
#interface Foo : NSObject
- (CGFloat)method;
- (NSInteger)method;
#end
is wrong. Even in C or C++ you cannot overload method on the basis of its return type. Overloading can be performed on the basis of type of argument or number of arguments for a methods or both.
so over loading can be performed in this way only
#interface Foo : NSObject
-(ReturnType)methodNameHere:(int)argument;
-(ReturnType)methodNameHere:(int)argument secondArgumentDescription:(BOOL)anotherArgument;
-(ReturnType)methodNameHere;
compiler identifies different methods on the basis for number of arguments and their data type

Answer 2

Method signature is for developers and for runtime,
Not for compiler. (Compiler uses another technique to understand signatures)

Answer 3

you cannot identify methods that have the same name but different return types. If you call it while discarding the return value, which one should be called?
#interface Foo : NSObject
- (CGFloat)method;
- (NSInteger)method;
#end
Foo *foo = [Foo new];
[foo method]; // no use for return value here. Which implementation to call?