• Open Menu Close Menu
  • Apple
  • Shopping Bag
  • Apple
  • Mac
  • iPad
  • iPhone
  • Watch
  • TV
  • Music
  • Support
  • Search apple.com
  • Shopping Bag

Lists

Open Menu Close Menu
  • Terms and Conditions
  • Lists hosted on this site
  • Email the Postmaster
  • Tips for posting to public mailing lists
Re: Checking a method for parameter types via SEL
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Checking a method for parameter types via SEL


  • Subject: Re: Checking a method for parameter types via SEL
  • From: Tommy Nordgren <email@hidden>
  • Date: Mon, 31 Jul 2006 21:31:20 +0200


Jul 31, 2006 kl. 8:49 PM skrev Bill Bumgarner:


On Jul 31, 2006, at 11:23 AM, Tommy Nordgren wrote:

Can someone who have been using cocoa long please tell me how to do this?
The signature should be like this:
-(BOOL) aMethod: (id) owner;

What, exactly, are you trying to do?

	This, to be extended with further methods:
@implementation NSCoder (ConditionalCoding)

-(void) encodeObject:(id) obj onCondition:(SEL) cond withOwner: (id) owner
{
BOOL strongCode = NO;
NSMethodSignature * sign = [obj methodSignatureForSelector:cond];
if (sign == nil) {
strongCode = YES;
} else {
if ([sign numberOfArguments] == 3 &&
strcmp([sign getArgumentTypeAtIndex:2],@encode(id)) == 0 &&
strcmp([sign methodReturnType] , @encode(BOOL)) == 0) {
int i = (int) objc_msgSend(obj,cond,owner);
strongCode = i ? YES: NO;
}
}
if ( strongCode) {
[self encodeObject: obj];
} else {
[self encodeConditionalObject:obj];
}
}
@end
I welcome any comment on the code
The Obj-C runtime supports introspection and you can grab the method signature and then rip it apart to deduce parameter and return types. To a degree; you lose with complex C types and certain other parameter types.

I would suggest poking through the source code for one of the various Obj-C bridges to see the full details; PyObjC, F-Script (Smalltalk-esque), RubyCocoa, and CamelBones (Perl-ObjC) all introspect to do cross language method dispatches.

b.bum


------------------------------------------------------ "Home is not where you are born, but where your heart finds peace" - Tommy Nordgren, "The dying old crone" email@hidden


_______________________________________________ Do not post admin requests to the list. They will be ignored. Cocoa-dev mailing list (email@hidden) Help/Unsubscribe/Update your Subscription: This email sent to email@hidden
  • Follow-Ups:
    • Re: Re: Checking a method for parameter types via SEL
      • From: "Michael Ash" <email@hidden>
References: 
 >Checking a method for parameter types via SEL (From: Tommy Nordgren <email@hidden>)
 >Re: Checking a method for parameter types via SEL (From: Bill Bumgarner <email@hidden>)

  • Prev by Date: Re: NSMenuItem protocol and incompatible types.
  • Next by Date: Re: Keeping an App Alive
  • Previous by thread: Re: Checking a method for parameter types via SEL
  • Next by thread: Re: Re: Checking a method for parameter types via SEL
  • Index(es):
    • Date
    • Thread