You want to use NSObject performSelector with multiple parameters, but you can't ? (1)

part1.m

- ( id ) methodWithOneParam:( id ) theParam {
    // Do amazing stuff
    return @"Srsly, Amazing!";
}


- ( id ) methodWithFirst:( id ) firstParam
               andSecond:( id ) secondParam
{
    // Do doubly amazing stuff
    return @"Even Amazinger";
}


- ( id ) methodWithFirst:( id ) firstParam
               andSecond:( id ) secondParam
                andThird:( id ) thirdParam
{
    // Do thricely amazing stuff that will certainly rock.
    return @"MOAR AMAZINGER-ER!";
}

part2.m

id first  = nil;
id second = nil;
id third  = nil;

id result = nil;

// easy peasy to do the first one.

SEL singleParamSelector = @selector(methodWithOneParam:);

result = [self performSelector:singleParamSelector // https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Protocols/NSObject_Protocol/Reference/NSObject.html
                    withObject:first];

NSLog(@"%@", result);

/*
 Let's get a bit trickier and get the selector signature
 from a string this tine
 */

SEL doubleParamSelector
    = NSSelectorFromString(@"methodWithFirst:andSecond:");

result = [self performSelector: doubleParamSelector
                    withObject: first
                    withObject: second];

NSLog(@"%@", result);

part3.m

- ( id ) boringMethod:( NSDictionary *) args {
    
    id first  = [args objectForKey:@"first" ];
    id second = [args objectForKey:@"second"];
    id third  = [args objectForKey:@"third" ];
    
    return @"Whatever";
}

part4.m

NSInvocation      * invocation;         // https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/DistrObjects/Tasks/invocations.html#//apple_ref/doc/uid/20000744-CJBBACJH
NSMethodSignature * methSig;            // http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSMethodSignature_Class/Reference/Reference.html
SEL                 triParamSelector;

/*
 We need both a selector and a method signature,
 they are different. A method signature contains
 information about the number and types of arguments
 a method takes, whereas a selector is just a name.
 */
triParamSelector = @selector(methodWithFirst:andSecond:andThird:);
methSig          = [self methodSignatureForSelector: triParamSelector];
invocation       = [NSInvocation invocationWithMethodSignature: methSig];


/*
 Set the target (the object to invoke the
 selector on) and the selector to invoke
 */

[invocation setSelector: triParamSelector];
[invocation setTarget: self];

/*
 Now we have to set up the arguments. Note that we
 have to start from 2, because there are two 'hidden'
 arguments, which we'll get to shortly
 */

[invocation setArgument: &first  atIndex: 2];
[invocation setArgument: &second atIndex: 3];
[invocation setArgument: &third  atIndex: 4];

/*
 Now make the call and get the returned value.
 */
[invocation invoke];
[invocation getReturnValue: &result];

NSLog(@"NSInvocation      : %@", result);

part5.m

SEL betterWaySelector
    = NSSelectorFromString(@"methodWithFirst:andSecond:andThird:");

IMP methodImplementation                              // https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSObject_Class/Reference/Reference.html
    = [self methodForSelector: betterWaySelector];

result = methodImplementation( self,
                              betterWaySelector,
                              first,
                              second,
                              third );

NSLog(@"methodForSelector : %@", result);

part6.m

SEL evenBetterWay
    = NSSelectorFromString(@"methodWithFirst:andSecond:andThird:");

result = objc_msgSend( self,
                      evenBetterWay,
                      first,
                      second,
                      third    );

NSLog(@"objc_msgSend      : %@", result);

part7.m

- ( void ) beware:( float ) whoops {
    NSLog(@"%f", whoops);
}


- ( float ) incrementFloat:( float ) digits {
    return digits + 1.0;
}

- ( void ) carefulNow {
    
    SEL    selector = @selector(beware:);
    IMP    method   = [self methodForSelector: selector];
    float  test     = 123.456;
    
    /* works, obvs */
    [self beware: test];
    /*
     123.456001
     */
    
    
    /* bork */
    objc_msgSend( self, selector, test);
    /*
     0.000000
     */
    
    
    /* bork */
    method( self, selector, test );
    /*
     0.000000
     */
    
    
    /* works */
    ((void (*) (id, SEL,float))method)(self,selector,test);
    /*
     123.456001
     */
    
    /* works */
    ((void (*) (id, SEL, float))objc_msgSend)(self,selector,test);
    /*
     123.456001
     */
    
    
    
    selector     = @selector(incrementFloat:);
    
    float result 
        = ((float (*)(id,SEL,float))objc_msgSend)(self,selector,test);
    
    NSLog(@"%f", result);
    /*
     124.456001
     */

    
    method = [self methodForSelector:selector];
    
    result = ((float (*) (id, SEL, float))method)(self,selector,test);
    
    NSLog(@"%f", result);
    /*
     124.456001
     */
}

Cool, thanks for sharing. By the way, the blog link seems broken.

One thing to notice when you call getReturnValue to get an object under ARC is that you need to either qualify result with __unsafe_unretained or change result to void* and __bridge cast result, otherwise the program may crash. See NSInvocation getReturnValue: called inside forwardInvocation: makes the returned object call dealloc:
.