Hi David and all,
a google search for Objective-C runtime functions of course led to
https://developer.apple.com/documentation/objectivec/objective-c_runtime?language=objc
and I thought I just had to select the proper method from the list and am done.
But this does not seem to be that simple!? I found
NSMethodSignature *methodSig = [[self class]
instanceMethodSignatureForSelector:mySelector];
NSInvocation *invocation = [NSInvocation
invocationWithMethodSignature:methodSig];
for getting the method signature of an instance method for a known class. But
in my case I just have a protocol. What would be the replacement for
methodDescription = [_protocol descriptionForInstanceMethod:aSelector];
char *types = methodDescription->types;
NSMethodSignature *methodSig = [NSMethodSignature
signatureWithObjCTypes:types];
with current objective-C runtime functions? Is that still possible at all? My
search attempts for the proper runtime function so far led to
void method_getReturnType(Method m, char *dst, size_t dst_len);
void method_getArgumentType(Method m, unsigned int index, char *dst, size_t
dst_len);
unsigned int method_getNumberOfArguments(Method m);
So I might be able to construct
char *types = NULL;
from this and then do
NSMethodSignature *methodSig = [NSMethodSignature
signatureWithObjCTypes:types];
but how do I get a Method from a given selector and protocol??
I am lost! :-(
Thanks a lot,
Andreas
> On 18 Jun 2019, at 14:12, David Chisnall <[email protected]> wrote:
>
>> *SRProxy.m:419:29: **warning: **instance method
>> '-descriptionForInstanceMethod:' not found (return type defaults to 'id')
>> [-Wobjc-method-access]*
>> types = [_protocol descriptionForInstanceMethod:aSelector]->types;
>> * ^~~~~~~~~~~~~~~~~~~~~~~~~~~~*
>> */usr/include/objc/Protocol.h:45:12: note: *receiver is instance of class
>> declared here
>> @interface Protocol : NSObject
>> * ^*
>> *SRProxy.m:419:70: **error: **no member named 'types' in 'struct
>> objc_object'*
>> *
>> *
>
> With the 'Modern' Objective-C ABI (circa 2006) on Apple platforms, the only
> option on 64-bit and the default for a very long time on 32-bit, Protocol no
> longer has any methods exposed on it. This means:
>
> - descriptionForInstanceMethod: is gone. Don't use it, use the runtime
> functions instead. There is no point paying the overhead of an Objective-C
> message send for a function where all of the types are known at compile time.
>
> - The compiler assumes that the nonexistent method
> -descriptionForInstanceMethod: returns id, which is a typedef for struct
> objc_object, which has no fields other than isa (probably not even isa,
> because direct access to isa is also deprecated).
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