Design Pattern - Objective-C - MVC Model View Controller

Question

Hi I already read tutorials around the web on MVC and already read the topics on here. I think i got the concept of the MVC but i'm not sure of its implementation.

I've tried to apply it to a simple program, a window that have a label and a button. The button increase a counter and the label shows the value of it.

I tried in 2 different ways.

In the first case ( the example works ) i melt the View and the Controller. As i said, the example works, but i want you guys to tell me if it's a correct implementation for MVC or it's not following the right design.

The second example has Model View and Controller as 3 separated class, but the example doesnt work because the V and the C import itself, so i would love you guys to tell me where i'm doing wrong.

first version: model, view-controller

//Model.h
#import <Foundation/Foundation.h>

@interface Model : NSObject {
    int _counter;
}

-(void)setCounter:(int)valueCounter;
-(int)getCounter;
-(void)increaseCounter;
@end

//Model.m
#import "Model.h"
@implementation Model {}

-(void)setCounter:(int)valueCounter { _counter = valueCounter; }
-(int)getCounter { return _counter; }
-(void)increaseCounter{ _counter ++; }
@end


//ViewController.h
#import <UIKit/UIKit.h>
#import "Model.h"

@interface ViewController : UIViewController {
    IBOutlet UIButton *_button;
    IBOutlet UILabel *_label;
    Model *myModel;
}

-(IBAction)send:(id)sender;
@end

//ViewController.m
#import "ViewController.h"
@interface ViewController ()
@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
     myModel = [[Model alloc]init];
    _label.text = [NSString stringWithFormat:@"%d",[myModel getCounter]];
}

- (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; }

- (IBAction)send:(id)sender{
    [myModel increaseCounter];
    _label.text = [NSString stringWithFormat:@"%d",[myModel getCounter]];
}

@end

Is this way a correct Pattern for MVC ? The code works, but before i start more complex apps i want to make sure i code it in a good way. This is how i would do this app, my way of MVC. is it bad? good? how to change or fix it?

Second Version: Model, View, Controller separated

----> This is the Model

//Model.h
#import <Foundation/Foundation.h>

@interface Model : NSObject {
    int _count;
}

-(void)setCount:(int)value;
-(int)getCount;
-(void)increaseCount;

@end

//Model.m
#import "Model.h"

@implementation Model

-(void)setCount:(int)value { _count = value; }
-(int)getCount { return _count; }
-(void)increaseCount { _count = _count++; }

@end

----> This is the View

//View.h
#import <UIKit/UIKit.h>
#import "Controller.h"

@interface ViewController : UIViewController{
    IBOutlet UILabel *label;
    IBOutlet UIButton *button;
    Controller *myController;
}

@end

//View.m
#import "ViewController.h"
#import "Controller.h"

@interface ViewController ()
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    myController = [[Controller alloc]init];
}

- (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; }


-(IBAction)pressButton:(id)sender{
    label.text = [NSString stringWithFormat:@"%d",[myController actionIncrease]];
}

@end

----> This is the Controller

//Controller.m
#import <Foundation/Foundation.h>

@class "Model.h"
@class  "ViewController.h"

@interface Controller : NSObject {
    Model *_mymodel;
    UIViewController *_myviewController;
}

-(int)actionIncrease;

@end

//Controller.m
#import "Controller.h"
#import "Model.h"

@implementation Controller

-(id)init{
    _mymodel = [[Model alloc]init];
}

-(int)actionIncrease {
    [_mymodel increaseCount];
    return [_mymodel getCount];    
}

@end

this version doesn't work because the classes view and controller import each other and the compiler gives me a warning

Answer 1

Simply: UIViewController is not your view, it's your controller

Think of the UIViewController as a puppeteer and the UIView as the puppet.

• UIViewController controls WHAT is displayed on the UIView
• UIView's main purpose is to contain subviews.
• NSObject can be used by any class, but should be used by the UIViewController.

Admittedly, I understood it much better after completing codeschool's tutorial http://www.codeschool.com/courses/try-ios. I highly recommend this simple hands-on approach.

Let's break it down:

Note: Here we utilize @property declarations instead. These will save you from writing your own setter and getter methods. (unless you need to override them for custom functionality)

NSObject (model):

//MyModelObject.h
#import <Foundation/Foundation.h>

@interface MyModelObject : NSObject

@property (nonatomic) int count; 

@end

UIView (view):

//MyView.h
#import <UIKit/UIKit.h>

@interface MyView : UIView

// holds it's own subviews
@property (strong, nonatomic) UIView *anotherView;
@property (strong, nonatomic) UIImageView *myImageView;

@end

UIViewController (controller, it all comes together here!):

//MyViewController.h
#import <Foundation/Foundation.h>

#import "MyView.h"  // your custom view
#import "MyModel.h" // your custom model

@interface MyViewController : UIViewController

@property (strong, nonatomic) MyView *myView 
// see how the view is "owned" by the view controller?

@end



//MyViewController.m

@implementation MyViewController 

@synthesize myView;


- (void) someMethod {

    [myView doSomething]; 

}

@end

Answer 2

For whose have any doubt about where put the UI elements, I often like put the UI elements in View.m

My strategy is make all methods to build UI elements in View.m, where I have a method that call all others methods in View.m. Thus, i call only one method in ViewController

For example :

TodayView.h

#import <UIKit/UIKit.h>

@interface TodayView : UIView
@property (strong, nonatomic) UIImageView *imageView;
@property (strong,nonatomic) UINavigationBar *navBar;


-(void) addAllElements:(UIView*) mainView addController:(UIViewController*) controller;
-(void) addImage:(UIImageView*) image view:(UIView*) todayView;
-(void) addNavBar:(UIViewController*) navController addView:(UIView*)view;
@end

TodayView.m

#import "TodayView.h"

@implementation TodayView


-(void) addImage:(UIImageView *)image view:(UIView *)todayView{
    image= [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
    image.image = [UIImage imageNamed:@"icone-apps"];

    [todayView addSubview:image];
}

-(void) addNavBar:(UIViewController *)navController addView:(UIView *)view{
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 80, 120, 50)];
       label.textAlignment = UITextAlignmentCenter;
       [label setFont:[UIFont boldSystemFontOfSize:40.0]];
       [label setBackgroundColor:[UIColor clearColor]];
       [label setTextColor:[UIColor blackColor]];
       [label setText:@"Hoje"];
       [navController.navigationController.navigationBar.topItem setTitleView:label];
       [view addSubview:label];

}

-(void) addAllElements:(UIView *)mainView addController:(UIViewController*)controller{
    [self addNavBar:controller addView:mainView];

}

@end

TodayViewController.m

#import "TodayViewController.h"
@interface TodayViewController ()


@end

@implementation TodayViewController
@synthesize myView;

-(void) blankMethod{

}

-(void) addImage:(TodayView*)todayView{
    todayView.imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 320, 460)];
    todayView.imageView.image = [UIImage imageNamed:@"icone-apps"];

    [self.view addSubview:todayView.imageView];
}


- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = UIColor.whiteColor;

    TodayView *todayView = [[ TodayView alloc] init];
     # Here I call the method that call all others methods to build UI elements
    [todayView addAllElements:self.view addController:self];




}
-(UITabBarItem*) tabBarItem{

    return [[UITabBarItem alloc] initWithTitle:@"Hoje" image:[UIImage imageNamed:@"icone-hoje"] tag:0];
}


@end