Objective C - Get argument types of a method? - objective-c

Question

At runtime I need to be able to get the argument types of a method. The following is what gets printed:
I have read on other threads that at run-time time objective c treats all objects passed to a method as arguments as id. If this approach doesn't work any other suggestions on a way to read argument types?
Log
2014-02-07 15:47:08.962 OCInjection[55727:70b] #
2014-02-07 15:47:08.964 OCInjection[55727:70b] :
Code
Class class = NSClassFromString(injectionBinding);
unsigned int methodCount;
Method *methodList = class_copyMethodList(class, &methodCount);
for (int i = 0; i < methodCount; i++)
{
Method method = methodList[i];
SEL selector = method_getName(method);
NSMethodSignature *signature = [class instanceMethodSignatureForSelector:selector];
NSUInteger numberOfArguments = [signature numberOfArguments];
for (int i=0 ; i<numberOfArguments ; i++)
{
NSString *type = [NSString stringWithUTF8String:[signature getArgumentTypeAtIndex:i]];
NSLog(type);
}
}

Answer 1

According to
-getArgumentTypeAtIndex:
and
Decode Class from #encoded type string
I think there is no method to get the "real" argument type.

Answer 2

Doesn't seem like it's possible to do this. I ended up using a proxy object to send the message to, and capture it. Probably not the ideal way, but I haven't found a better solution.
#interface DIContructorInjectorProxy()
#property (nonatomic, strong) id realObject;
#end
#implementation DIContructorInjectorProxy
#define Inject(x) [DIContructorInjectorProxy _injectMacro:x]
- (id)initWithClass:(Class)class
{
self.realObject = [[class alloc] init];
}
+ (id)_injectMacro:(id)x
{
if ([x isKindOfClass:NSClassFromString(#"Protocol")])
return NSStringFromProtocol(x);
else
return NSStringFromClass(x);
}
- (id)withConstructor
{
// Just making the method call for defining a constructor more readable by a call to this method first
return self;
}
- (void)forwardInvocation:(NSInvocation *)anInvocation
{
NSMutableString *selectorName = [NSStringFromSelector(anInvocation.selector) mutableCopy];
NSUInteger numberOfColonsInMethodName = [selectorName replaceOccurrencesOfString:#":"
withString:#":"
options:NSLiteralSearch
range:NSMakeRange(0, selectorName.length)];
[anInvocation retainArguments];
NSMutableArray *argumentsPassedToSelector = [NSMutableArray array];
for (int i=2 ; i<numberOfColonsInMethodName+2 ; i++)
{
NSString *argument;
[anInvocation getArgument:&argument atIndex:i];
[argumentsPassedToSelector addObject:[NSString stringWithFormat:#"%#", argument]];
}
// Store arguments somewhere
return;
}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
return [self.realObject methodSignatureForSelector:aSelector];
}
#end
How the user uses this to define method arguments
[self bindProtocol:#protocol(DataStorage) toClass:[InMemoryDataStorage class]];
// withConstructor returns an appropriate proxy object
// Then when the init method is called, it calls forwardInvocation,
// and from there I save all the info I need about the method and arguments
(void)[[[self bindProtocol:#protocol(GoogleClient) toClass:[GoogleClientEngine class]] withConstructor]
initWithDataStorage:Inject(#protocol(DataStorage))];