姚翔的部落格

VIPER实践（下）

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上一篇文章我们设计好了View和Interactor，现在我们来做Presenter。

Presenter在这个用例里面的主要作用就是接受View提交过来的“提问”请求，然后向Interactor获取“答案”，最后把结果更新到View上，以下是实现部分的代码片段：

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    @interface HumanComputerCommunicatePresenter : NSObject <AIRobotInteractorDelegate>

    @property (nonatomic, weak) id<ProgressViewInterface> progressView;
    @property (nonatomic, weak) id<MessageBoardViewInterface> messageBoard;
    @property (nonatomic, strong) AIRobotInteractor *aiRobotInteractor;

    - (void)wantSendMessage:(NSString *)message;

    @end


    @implementation HumanComputerCommunicatePresenter

    - (void)wantSendMessage:(NSString *)message {
      [self.progressView beginProgress];
      [self.aiRobotInteractor askQuestion:message]
    }

    - (void)aiRobotInteractor:(AIRobotInteractor *)aiRobotInteractor didResponseToQuestion:(NSString *)question response:(NSString *)response {
      [self.progressView endProgress];
      [self.messageBoard showMessage:response];
    }

    @end

可以发现，Presenter就是承担了一个中间者的角色，它才是传统意义上MVC机构中的C(Controller)。其中有一点要注意的是，对应ViewInterface的reference，我们采用了weak的定义来防止Strong reference cycle ，在我自己的设计当中，我偏向于如下的reference关系：

  • View –strong-> Presenter
  • Presenter –strong-> Interactor
  • Presenter –weak-> View

最后我们来看一下Routing，objc.io那片文章中的Routing做的很散，通过多个wireframe来实现，我个人的设计中偏向用一个大的wireframe结合Assembling Factory来实现Routing，废话不多说看代码比较直观，以下只是我个人目前的一种实现方案，仅供参考：

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@implementation AssemblingFactory

+ (UIViewController *)assembleChatroomView {
  ChatroomViewController *viewController = [[UIStoryboard genericStoryboard] instantiateViewControllerWithIdentifier:ChatroomViewIdentifier];
  HumanComputerCommunicatePresenter *presenter = [HumanComputerCommunicatePresenter new];
  AIRobotInteractor *interactor = [AIRobotInteractor new];

  viewController.presenter = presenter;
  presenter.progressView = viewController;
  presneter.messageBoard = viewController
  presenter.interactor = interactor;
  interactor.delegate = presenter;

  return viewController;
}

@end


@implementation Wireframe

+ (void)moveToNextPageOfViewController:(UIViewController *)viewController messenger:(PageMessenger *)messenger {
  SEL selector = [self selectorOfClass:[viewController class] messengerName:[messenger name]];
  IMP imp = [[self class] methodForSelector:selector];
  void (*func)(id, SEL, UIViewController*, NSDictionary*) = (void *)imp;
  func([self class], selector, viewController, [messenger params]);
}

+ (SEL)selectorOfClass:(Class)class messengerName:(NSString *)messengerName {
  static NSDictionary *selectorMap = nil;
  if (!selectorMap) {

    selectorMap = @{
                    @"SplashViewControllerDefault" : [NSValue valueWithPointer:@selector(moveToChatroomViewController:params:)]
                    // add more nav configuration here...
                    };
  }
  NSValue *value = [selectorMap valueForKey:[[class description] conj:messengerName]];
  return value ? [value pointerValue] : @selector(emptyMove:params:);
}

+ (void)moveToChatroomViewController:(UIViewController *)viewController params:(NSDictionary *)params {
  UIViewController *viewController = [AssemblingFactory assembleChatroomView];
  [(BaseViewController *)viewController setParams:params]; // I defined a base view controller to allow pass params
  [viewController.navigationController pushViewController:viewController animated:YES];
}

@end

以上大致就是我个人目前实践VIPER的一些心得，肯定非常不成熟，有很多地方可以改进，只想抛砖引玉让大家广思集益共同改进我们代码的架构方案，从而最终帮助提高开发效率。

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