中介者模式

基本理解

中介者模式又叫做调停者模式，其实就是中间人或者调停者的意思。
尽管将一个系统分割成许多对象通常可以增加可复用性，但是对象之间的连接又降低了可复用性。
如果两个类不必彼此直接通信，那么着两个类就不应当发生直接的相互作用。如果其中一个类需要调用另一个类的方法的话，可以用过第三者转发这个调用。而这个第三者就是中介者。
概念：中介者模式（Mediator）,用一个中介者对象来封装一系列的对象交互。中介者使各个对象不需要显式地相互引用，从而使其耦合松散，而且可以独立地改变他们之间的交互。
UINavigationViewController就是属于一个中介者。

中介者模式的优缺点

中介者模式很容易在系统中应用，也很容易在系统中误用。当系统出现了多对多交互复杂的对象群时，不要急于使用中介者模式，而要先反思你在系统上设计是否合理。

优点就是集中控制，减少了对象之间的耦合度。缺点就是太过于集中。

应用场景

对象间的交互虽定义明确然而非常复杂，导致一组对象彼此相互依赖而且难以理解。
因为对象引用了许多其他对象并与其通信，导致对象难以复用。
想要定制一个分布在多个类中的逻辑或者行为，又不想生成太多子类。

例子

CoordinatingViewController.h

//

//  CoordinatingViewController.h

//  CoordinateDemo

//

//  Created by zhanggui on 15/8/6.

//  Copyright (c) 2015年 zhanggui. All rights reserved.

//

#import <UIKit/UIKit.h>

typedef NS_ENUM(NSInteger,ButtonTag) {

    kButtontagOpenThree,

    kButtontagOpenThreeNext,

    kButtontagBackThree

};

@interface CoordinatingViewController : UIViewController

@property(nonatomic,strong)NSMutableArray *controllersArray;

@property(nonatomic,strong)UIViewController *activeController;

@property(nonatomic,strong)UIViewController *mainViewController;

+(instancetype)shareInstance;

- (void)requestViewChangeByObject:(id)sender;

@end

CoordinationgViewController.m

//

//  CoordinatingViewController.m

//  CoordinateDemo

//

//  Created by zhanggui on 15/8/6.

//  Copyright (c) 2015年 zhanggui. All rights reserved.

//

#import "CoordinatingViewController.h"

#import "ThirdViewController.h"

#import "Third2ViewController.h"

@interface CoordinatingViewController ()

{

//    UIStoryboard *storyboard;

}

@end

@implementation CoordinatingViewController

+(instancetype)shareInstance

{

    static CoordinatingViewController *coorVC;

    if (coorVC==nil) {

        coorVC = [[self alloc] init];

    }

    return coorVC;

}

- (void)viewDidLoad {

    [super viewDidLoad];

//    storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];

    // Do any additional setup after loading the view.

}

- (void)requestViewChangeByObject:(id)sender {

    UIStoryboard *storyboard =[UIStoryboard storyboardWithName:@"Main" bundle:nil];

    if ([sender isKindOfClass:[UIButton class]]) {

        switch ([sender tag]) {

            case kButtontagOpenThree:

            {

                ThirdViewController *thirdVC = [storyboard instantiateViewControllerWithIdentifier:@"ThirdViewController"];

                self.activeController = thirdVC;

                [self.controllersArray addObject:thirdVC];

//                UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:thirdVC];

                [self.mainViewController presentViewController:thirdVC animated:YES completion:nil];

            }

                break;

            case kButtontagOpenThreeNext:

            {

                Third2ViewController *third2VC = [storyboard instantiateViewControllerWithIdentifier:@"Third2ViewController"];

                [self.controllersArray addObject:third2VC];

                UIViewController *cvc = [self.controllersArray objectAtIndex:1];

                [cvc presentViewController:third2VC animated:YES completion:nil];

            }

                break;

            case kButtontagBackThree:

            {

                UIViewController *cvc = [self.controllersArray objectAtIndex:2];

                [cvc dismissViewControllerAnimated:YES completion:nil];

                [self.controllersArray removeObjectAtIndex:2];

            }

                break;

            default:

            {

                UIViewController *cvc = [self.controllersArray objectAtIndex:1];

                [cvc dismissViewControllerAnimated:YES completion:nil];

                [self.controllersArray removeObjectAtIndex:1];

            }

                break;

        }

    }

}

@end

上面这个就是中介类。

在ViewController.m

//

//  ViewController.m

//  CoordinateDemo

//

//  Created by zhanggui on 15/8/6.

//  Copyright (c) 2015年 zhanggui. All rights reserved.

//

#import "ViewController.h"

#import "CoordinatingViewController.h"

@interface ViewController ()

{

    CoordinatingViewController *coorController;

}

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    coorController = [CoordinatingViewController shareInstance];

    coorController.controllersArray = [[NSMutableArray alloc] initWithObjects:self, nil];

    _firstButton.tag = kButtontagOpenThree;

    coorController.activeController = self;

    coorController.mainViewController = self;

    // Do any additional setup after loading the view, typically from a nib.

}

- (IBAction)showAction:(id)sender {

    [coorController requestViewChangeByObject:_firstButton];

}

@end

ThirdViewController.m

//

//  ThirdViewController.m

//  CoordinateDemo

//

//  Created by zhanggui on 15/8/6.

//  Copyright (c) 2015年 zhanggui. All rights reserved.

//

#import "ThirdViewController.h"

#import "CoordinatingViewController.h"

@interface ThirdViewController ()

@end

@implementation ThirdViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view.

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

- (IBAction)forwardAction:(id)sender {

    if ([sender isKindOfClass:[UIButton class]]) {

        UIButton *btn = (UIButton *)sender;

        btn.tag = kButtontagOpenThreeNext;

        CoordinatingViewController *coor = [CoordinatingViewController shareInstance];

        [coor requestViewChangeByObject:btn];

    }

}

@end

Third2ViewController.m

//

//  Third2ViewController.m

//  CoordinateDemo

//

//  Created by zhanggui on 15/8/6.

//  Copyright (c) 2015年 zhanggui. All rights reserved.

//

#import "Third2ViewController.h"

#import "CoordinatingViewController.h"

@interface Third2ViewController ()

@end

@implementation Third2ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view.

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

/*

#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

    // Get the new view controller using [segue destinationViewController].

    // Pass the selected object to the new view controller.

}

*/

- (IBAction)backAction:(id)sender {

    if ([sender isKindOfClass:[UIButton class]]) {

        UIButton *btn = (UIButton *)sender;

        btn.tag = kButtontagBackThree;

        CoordinatingViewController *coor = [CoordinatingViewController shareInstance];

        [coor requestViewChangeByObject:btn];

    }

}

- (IBAction)forwardAction:(id)sender {

}

@end

上面的这两个就是视图迁移的中介处理ThirdViewController和Third2ViewController。

附：

项目源码：http://pan.baidu.com/s/1gdGWbeV

巴特西

iOS设计模式之中介者模式

中介者模式

基本理解

中介者模式的优缺点

应用场景

例子

附：

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