Как в рантайме заменить метод Objective-C класса

//  ExampleA.h
//

#import <Foundation/Foundation.h>

@interface ExampleA : NSObject

- (void)methodA;

@end

//
//  ExampleA.m
//

#import "ExampleA.h"

@implementation ExampleA

- (void)methodA
{
    NSLog(@"methodA");
}

@end

//
//  ExampleB.h
//

#import <Foundation/Foundation.h>

@interface ExampleB : NSObject

- (void)test;

@end

//
//  ExampleB.m
//

#import "ExampleB.h"
#import <objc/objc-class.h>
#import "ExampleA.h"

@implementation ExampleB

- (void)test
{
    ExampleA *theA = [ExampleA new];
    NSLog(@"First call:");
    [theA methodA];
    
    SEL theMethodASelector = @selector(methodA);
    Method theMethodA = class_getInstanceMethod([ExampleA class], theMethodASelector);
    
    SEL theMethodBSelector = @selector(methodB);
    Method theMethodB = class_getInstanceMethod([ExampleB class], theMethodBSelector);

    method_setImplementation(theMethodA, method_getImplementation(theMethodB));
    
    NSLog(@"Second call:");
    [theA methodA];
}

- (void)methodB
{
    NSLog(@"methodB");
}


@end

First call:
methodA
Second call:
methodB