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
     */
}