blocks.m

@interface ViewController(Refactor)
@property (nonnull, readonly) NSArray *cellInfo;
@end

@implementation ViewController (Refactor)

- (NSArray *)cellInfo {
    return @[ @{ @"text": @"Awful code", @"block": ^{ [self showAlert]; } },
              @{ @"text": @"Really awful code", @"block": ^{ [self segue]; } } ];
}

- (void)showAlert {
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Bad"
                                                                   message:@"Terrible"
                                                            preferredStyle:UIAlertControllerStyleAlert];
    
    [alert addAction:[UIAlertAction actionWithTitle:@"Please stop"
                                              style:UIAlertActionStyleCancel
                                            handler:NULL]];
    
    [self presentViewController:alert animated:YES completion:NULL];
}

- (void)segue {
    [self performSegueWithIdentifier:@"Unforgivable" sender:self];
}

@end

@implementation ViewController

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.cellInfo.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];
    
    cell.textLabel.text = self.cellInfo[indexPath.row][@"text"];
    
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    void (^operation)() = self.cellInfo[indexPath.row][@"block"];
    operation();
}

@end

hardcoded-cells.m

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];
    
    if (indexPath.row == 0) {
        cell.textLabel.text = @"Awful code";
    }
    else if (indexPath.row == 1) {
        cell.textLabel.text = @"Really awful code";
    }
    else if (indexPath.row == 2) {
        cell.textLabel.text = @"Make it stop";
    }
    else if (indexPath.row == 3) {
        cell.textLabel.text = @"Ohmygodwereallgoingtodie";
    }
    else {
        cell.textLabel.text = @"You don't do this, do you?";
    }
    
    return cell;
}

initial-code.m

@implementation ViewController

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return 2;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];
    
    if (indexPath.row == 0) {
        cell.textLabel.text = @"Awful code";
    }
    else {
        cell.textLabel.text = @"Really awful code";
    }
    
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    if (indexPath.row == 0) {
        UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Bad"
                                                                       message:@"Terrible"
                                                                preferredStyle:UIAlertControllerStyleAlert];
        
        [alert addAction:[UIAlertAction actionWithTitle:@"Please stop"
                                                  style:UIAlertActionStyleCancel
                                                handler:NULL]];
        
        [self presentViewController:alert animated:YES completion:NULL];
    }
    else {
        [self performSegueWithIdentifier:@"Unforgivable" sender:self];
    }
}

@end

invocation.m

@implementation NSInvocation (Apokrupto)

+ (instancetype)invocationForSelector:(SEL)selector target:(id)target {
    NSMethodSignature *signature  = [target methodSignatureForSelector:selector];
    NSInvocation      *invocation = [NSInvocation invocationWithMethodSignature:signature];
    
    invocation.selector = selector;
    invocation.target   = target;
    
    return invocation;
}

@end

@interface ViewController(Refactor)
@property (nonnull, readonly) NSArray *cellInfo;
@end

@implementation ViewController (Refactor)

- (NSArray *)cellInfo {
    return @[ @{ @"text": @"Awful code",
                 @"selector": [NSInvocation invocationForSelector:@selector(showAlert) target:self] },
              @{ @"text": @"Really awful code",
                 @"selector": [NSInvocation invocationForSelector:@selector(segue) target:self] } ];
}

- (void)showAlert {
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Bad"
                                                                   message:@"Terrible"
                                                            preferredStyle:UIAlertControllerStyleAlert];
    
    [alert addAction:[UIAlertAction actionWithTitle:@"Please stop"
                                              style:UIAlertActionStyleCancel
                                            handler:NULL]];
    
    [self presentViewController:alert animated:YES completion:NULL];
}

- (void)segue {
    [self performSegueWithIdentifier:@"Unforgivable" sender:self];
}

@end

@implementation ViewController

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.cellInfo.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];
    
    cell.textLabel.text = self.cellInfo[indexPath.row][@"text"];
    
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    NSInvocation *invocation = self.cellInfo[indexPath.row][@"selector"];
    [invocation invoke];
}

@end

NSInvocation.md

This gist contains all the code snippets for the blog post "NSInvocation" at http://www.apokrupto.com/blog-1/2016/3/14/ogbhxwpj9n4qh79edsvpdyvbpklr3w

refactor-1.m

@implementation ViewController (Refactor)

- (void)showAlert {
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Bad"
                                                                   message:@"Terrible"
                                                            preferredStyle:UIAlertControllerStyleAlert];
    
    [alert addAction:[UIAlertAction actionWithTitle:@"Please stop"
                                              style:UIAlertActionStyleCancel
                                            handler:NULL]];
    
    [self presentViewController:alert animated:YES completion:NULL];
}

- (void)segue {
    [self performSegueWithIdentifier:@"Unforgivable" sender:self];
}

@end

@implementation ViewController

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return 2;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];
    
    if (indexPath.row == 0) {
        cell.textLabel.text = @"Awful code";
    }
    else {
        cell.textLabel.text = @"Really awful code";
    }
    
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    if (indexPath.row == 0) {
        [self showAlert];
    }
    else {
        [self segue];
    }
}

@end

refactor-2.m

@interface ViewController(Refactor)
@property (nonnull, readonly) NSArray *cellInfo;
@end

@implementation ViewController (Refactor)

- (NSArray *)cellInfo {
    return @[ @{ @"text": @"Awful code", @"selector": @selector(showAlert) },
              @{ @"text": @"Really awful code", @"selector": @selector(segue) } ];
}

- (void)showAlert {
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Bad"
                                                                   message:@"Terrible"
                                                            preferredStyle:UIAlertControllerStyleAlert];
    
    [alert addAction:[UIAlertAction actionWithTitle:@"Please stop"
                                              style:UIAlertActionStyleCancel
                                            handler:NULL]];
    
    [self presentViewController:alert animated:YES completion:NULL];
}

- (void)segue {
    [self performSegueWithIdentifier:@"Unforgivable" sender:self];
}

@end

@implementation ViewController

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.cellInfo.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell"];
    
    cell.textLabel.text = self.cellInfo[indexPath.row][@"text"];
    
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [self performSelector:self.cellInfo[indexPath.row][@"selector"]];
}

@end