UITableViewController
Anti-Patterns
Josh Bassett
@nullobject

A Few Thoughts

A Few Thoughts
• Learning Cocoa Touch is easy.

A Few Thoughts
• Learning Cocoa Touch is easy.
• Learning bad habits is easy.

A Few Thoughts
• Learning Cocoa Touch is easy.
• Learning bad habits is easy.
• There’s a lot of sample code out there
which teaches you bad habits.

A Few Thoughts
• Learning Cocoa Touch is easy.
• Learning bad habits is easy.
• There’s a lot of sample code out there
which teaches you bad habits.
• Some Apple samples apps are even guilty of
this.

Talking About Design

Talking About Design
• Design pattern: a reusable solution to a
common problem.

Talking About Design
• Design pattern: a reusable solution to a
common problem.
• Anti-pattern: an ineffective design pattern
which is often counterproductive.

Talking About Design
• Design pattern: a reusable solution to a
common problem.
• Anti-pattern: an ineffective design pattern
which is often counterproductive.
• Code smell: a symptom in the code which
indicates a deeper problem.

The Fat Controller

The Fat Controller
• A controller polluted with code which
belongs in the model or view.

The Fat Controller
• A controller polluted with code which
belongs in the model or view.
• Hard to understand.

The Fat Controller
• A controller polluted with code which
belongs in the model or view.
• Hard to understand.
• Very difficult to maintain.

The Fat Controller
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath
*)indexPath {
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
Animal *animal = [animals objectAtIndex:indexPath.row];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault
reuseIdentifier:CellIdentifier] autorelease];
// This is view code.
UILabel *nameLabel = [[UILabel alloc] init];
nameLabel.frame = CGRectMake(10, 5, 100, 30);
nameLabel.tag = NAME_LABEL_TAG;
[cell addSubview:nameLabel];
[nameLabel release];
}
...
}

The Fat Controller
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
...
UILabel *nameLabel = [cell viewWithTag:NAME_LABEL_TAG];
// This is model code.
NSString *name = [animal.name stringByTrimmingCharactersInSet:
[NSCharacterSet whitespaceCharacterSet]];
nameLabel.text = name;
...
return cell;
}

MVC

Tight Coupling
View
Model Controller
One big fat controller

Loose Coupling
View
Model Controller

Animal
Model

Animal
@interface Animal : NSManagedObject {
NSString *name;
}
@property (readwrite, assign) NSString *name;
@end

Animal
@implementation Animal
@synthesize name;
- (void)setName:(NSString *)value {
name = [value stringByTrimmingCharactersInSet:[NSCharacterSet
whitespaceCharacterSet]];
}
@end

AnimalTableViewCell
View

AnimalTableViewCell
@interface AnimalTableViewCell : UITableViewCell {
Animal *animal;
UIButton *speakButton;
UILabel *nameLabel;
}
@property (readwrite, assign) Animal *animal;
@end

AnimalTableViewCell
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {
if (self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]) {
speakButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
speakButton.frame = CGRectMake(200, 5, 100, 30);
[speakButton setTitle:@"Speak" forState:UIControlStateNormal];
[speakButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[speakButton addTarget:self action:@selector(speakPressed)
forControlEvents:UIControlEventTouchUpInside];
[self.contentView addSubview:speakButton];
nameLabel = [[UILabel alloc] init];
nameLabel.frame = CGRectMake(10, 5, 100, 30);
[self.contentView addSubview:nameLabel];
}
return self;
}

AnimalTableViewCell
- (void)setAnimal:(Animal *)value {
animal = value;
nameLabel.text = animal.name;
}

AnimalTableViewController
Controller

AnimalsTableViewController
- (UITableViewCell *)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath
*)indexPath {
static NSString *CellIdentifier = @"Cell";
AnimalTableViewCell *cell = (AnimalTableViewCell *)[tableView
dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[AnimalTableViewCell alloc] initWithFrame:CGRectZero
reuseIdentifier:CellIdentifier] autorelease];
}
cell.animal = [animals objectAtIndex:indexPath.row];
return cell;
}

Push To Speak
UIButton *speakButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
speakButton.frame = CGRectMake(200, 5, 100, 30);
[speakButton setTitle:@"Speak" forState:UIControlStateNormal];
[speakButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
// Where is this handled?
[speakButton addTarget:self action:@selector(speakHandler)
forControlEvents:UIControlEventTouchUpInside];
[self.contentView addSubview:speakButton];

AnimalsTableViewController
- (void)speakHandler {
NSIndexPath *indexPath = [self.tableView indexPathForCell:
(UITableViewCell*)[[sender superview] superview]];
AnimalTableViewCell *cell = (AnimalTableViewCell*)[tableView
cellForRowAtIndexPath:indexPath];
Animal *animal = cell.animal;
// Show alert “Hi I’m a monkey”.
}

Delegate

AnimalsTableViewDelegate
@protocol AnimalsTableViewDelegate <UITableViewDelegate>
- (void)tableView:(UITableView *)tableView didSpeakAtIndexPath:
(NSIndexPath *)indexPath;
@end

AnimalsTableViewController
@interface AnimalsTableViewController : UITableViewController
<UITableViewDataSource, AnimalsTableViewDelegate> {
NSArray *animals;
}
@end

AnimalTableViewCell
- (void)speakPressed {
UITableView *tableView = self.target;
NSIndexPath *indexPath = [tableView indexPathForCell:self];
[(id<AnimalsTableViewDelegate>)tableView.delegate
tableView:tableView didSpeakAtIndexPath:indexPath];
}

AnimalsTableViewController
- (void)tableView:(UITableView *)tableView didSpeakAtIndexPath:
(NSIndexPath *)indexPath {
AnimalTableViewCell *cell = (AnimalTableViewCell *)[tableView
cellForRowAtIndexPath:indexPath];
Animal *animal = cell.animal;
// Show alert “Hi I’m a monkey”.
}

Questions