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。