Making an NSMethodInvocation from the current method
Making an NSMethodInvocation from the current method
- Subject: Making an NSMethodInvocation from the current method
- From: Roland King <email@hidden>
- Date: Sun, 22 Aug 2010 13:03:32 +0800
Is there a built-in function to make an NSMethodInvocation from 'the current method I'm in with all current parameters', or does anyone have any code they've written to do this?
Motivation, I'm writing a display class which can get updated from a background thread, it has a whole load of methods, some of which don't lend themselves to performSelectorOnMainThread (some take more than two arguments, some take primitives and I don't really want to wrap and unwrap into NSNumbers all over the place). What I really would like is in each method to be able to write something like
if( ![ NSThread isMainThread ] )
[ NSMagicFunctionReturningAnInvocationForThisCurrentFunction() performSelectorOnMainThread:@selector( invoke ) withObject:nil waitUntilDone:NO ];
else
{
// method performing code here
}
but there is of course no such function I'm aware of nor can I easily think how I'd write such a thing.
I have a current solution for those methods which are properties using forwarding because forwardInvocation: is the only function I know of which gives me a pre-packaged invocation object but I find it a bit inelegant and it only works for properties. That method briefly works as follows, if I want a property 'foo', I declare it, then use @dynamic to suppress the compiler warnings. In the class continuation I declare the same property prepended with an given prefix (I'm using TS_ for threadsafe) and implement it. I then override forwardInvocation: and methodSignatureForSelector: to check for the existance of a method TS_<called selector> and if it exists I switch the selector in the NSInvocation forwardInvocation: gives me and invoke it if I'm on the main thread or forward it to the main thread if I'm not.
eg setFoo:123 is not implemented so methodSignatureForSelector: is called for setFoo: and I return the signature for TS_setFoo:. Then forwardInvocation: is called with a prepacked NSInvocation, I switch the selector to that for TS_setFoo: and invoke it.
This only works for properties because I can only use @dynamic to suppress the warnings on those, other declared methods in the interface need to be implemented (or is there a way to suppress that warning) and the whole TS_ prefix thing seems a bit hokey to me so I was looking for a more direct way to make an NSInvocation. _______________________________________________
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