NSInvocation addition to create instance by target, selector, and arguments

NSInvocation+PopcornyLu.h

#import <Foundation/Foundation.h>

@interface NSInvocation (PopcornyLu)
+ (NSInvocation*) invocationWithTarget:(id)target 
                              selector:(SEL)selector;

+ (NSInvocation*) invocationWithTarget:(id)target 
                              selector:(SEL)selector 
                             arguments:(id)firstArg, ... NS_REQUIRES_NIL_TERMINATION;
@end

NSInvocation+PopcornyLu.m

#import "NSInvocation+PopcornyLu.h"

@implementation NSInvocation (PopcornyLu)
+ (NSInvocation*) invocationWithTarget:(id)target 
                              selector:(SEL)selector 
{
    NSMethodSignature* sig = [[target class] instanceMethodSignatureForSelector:selector];
    NSInvocation* invocation = [NSInvocation invocationWithMethodSignature:sig];
    [invocation setTarget:target];
    [invocation setSelector:selector];
    return invocation;
}

+ (NSInvocation*) invocationWithTarget:(id)target 
                              selector:(SEL)selector 
                             arguments:(id)firstArg, ...
{
    NSMethodSignature* sig = [[target class] instanceMethodSignatureForSelector:selector];
    NSInvocation* invocation = [NSInvocation invocationWithMethodSignature:sig];
    [invocation setTarget:target];
    [invocation setSelector:selector];
    
    va_list args;
    id arg;
    va_start(args, firstArg);
    NSUInteger index = 2;
    for(arg  = firstArg;
        arg != nil;
        arg  = va_arg(args, id))
    {    
        [invocation setArgument:&arg atIndex:index++];
    }    
    va_end(args);        
   
    
    return invocation; 
}
@end