Objective-C Find all init (constructor methods)

using the "Method * class_copyMethodList(Class cls, unsigned int *outCount)" function one can get a list of all methods that exist on an objective-C class.

I would like to know how to find which of these methods are constructors as I am writing an IOC container. I would like to determine the constructors and their p开发者_如何学Pythonarameter types.

I would like to know how to find which of these methods are constructors as I am writing an IOC container. I would like to determine the constructors and their parameter types.

In short, you can't. Or, at the least, you'll find that down this path lies madness.

First, Objective-C does not have constructors. It has initializers, sometimes many, and -- for a properly written class -- only one of which is the designated initializer. There is no way to identify the designated initializer at compile time or run time.

How do I use this with a Method * and no instantiated member of the class?

You don't. First you allocate an instance of the class, then you initialize the instance.

Overall, this level of abstraction just isn't done in Objective-C outside of academic investigations. It can be done, but it is generally avoided because of the fragility of the resulting solution and the hairball of code-hell that is trying to dynamically support the underlying C ABI (go look at the source to libffi).

If you want to go down this path, then you are far better off either defining a custom abstract class that all of your containers will subclass that can provide the binding logic to the class behind it.

Or use protocols; i.e. a class could implement an IOCBean protocol and one method would be initIOCGoop that is the designated initializer goo.

Doing this generically for all classes is going to be rife with fragility, special cases, and will require a gigantic mess of code that will be difficult to maintain over time.

You can get the method signature by using the following method:

methodSignatureForSelector:

From the documentation:

An NSMethodSignature object records type information for the arguments and return value of a method. It is used to forward messages that the receiving object does not respond to—most notably in the case of distributed objects. You typically create an NSMethodSignature object using NSObject’s methodSignatureForSelector: instance method (on Mac OS X v10.5 and later you can also use signatureWithObjCTypes:). It is then used to create an NSInvocation object, which is passed as the argument to a forwardInvocation: message to send the invocation on to whatever other object can handle the message. In the default case, NSObject invokes doesNotRecognizeSelector:, which raises an exception. For distributed objects, the NSInvocation object is encoded using the information in the NSMethodSignature object and sent to the real object represented by the receiver of the message.