前一段項(xiàng)目中用到了ReactiveCocoa.今天做一下簡(jiǎn)單的總結(jié),當(dāng)然項(xiàng)目還在不斷嘗試ReactiveCocoa的最佳實(shí)踐,希望自己還會(huì)有后續(xù)的文章 :)

<h4>MVC</h4>
一切要從我們熟悉的MVC架構(gòu)開始,這個(gè)被戲稱為Massive View Controller(臃腫的視圖控制器)的軟件架構(gòu)如下:

MVC架構(gòu)

• Model:Encapsulate the data specific to an application and define the logic and computation that manipulate and process that data.
• View:Is an object in an application that users can see.
• Controller: Acts as an intermediary between one or more of an application’s view objects and one or more of its model objects.
  From:Cocoa Core Competencies

簡(jiǎn)單來說Model用于程序的基本數(shù)據(jù)對(duì)象,View用于UI控件展示,Controller用于粘合View和Model,將Model里的數(shù)據(jù)內(nèi)容展示到UI上.
CS193p上有幅圖來表示MVC之間的關(guān)系及如何來進(jìn)行通訊:

MVC

• Model層無法與View層進(jìn)行通信的.
• Controller能直接讀寫調(diào)用Model,Model通過Notification&KVO來和Controller進(jìn)行通信
• Controller可以直接和View層通信,通過outlet控制View上的控件,View可以通過action來射向Controller里的target來告訴Controller View中某個(gè)控件被點(diǎn)擊等的操作.Controller還可以通過Protocol(delegate,datasource等)來對(duì)View進(jìn)行控制.

MVC在iOS開發(fā)中被廣泛應(yīng)用,然而慢慢你會(huì)發(fā)現(xiàn)他有些弊端,那就是大量的處理邏輯都塞進(jìn)了ViewController里面，會(huì)使其代碼行數(shù)變得不可控,于是就有人引入了MVVM.

<h5>MVVM</h5>
引用ReactiveCocoa and MVVM,an Introduction中的一幅圖來說明MVVM與MVC之間的聯(lián)系:

MVVM & MVC

簡(jiǎn)單來說ViewModel是將Controller里面的邏輯代碼分離出來,使Controller只用于將處理好的數(shù)據(jù)與View對(duì)應(yīng)起來.這就會(huì)產(chǎn)生一個(gè)問題:ViewModel如何與Controller進(jìn)行通信呢？想到的最簡(jiǎn)單的就是delegate.然而笨重寫法會(huì)使代碼變得難看,而拯救我們的super man就是ReactiveCocoa.

<h6>ReactiveCocoa的簡(jiǎn)單使用</h6>

• 對(duì)值的監(jiān)聽

    [self.usernameTextField.rac_textSignal subscribeNext:^(id x) {
        NSLog(@"username = %@", x);
    }];

• 對(duì)值的過濾

    [[self.usernameTextField.rac_textSignal
      filter:^BOOL(NSString *text) {
          return text.length > 5;
    }]
     subscribeNext:^(id x) {
         NSLog(@"filter x = %@", x);
    }];

• 對(duì)值的處理轉(zhuǎn)換

    [[[self.usernameTextField.rac_textSignal map:^id(NSString *text) {
        return @(text.length);
    }]
     filter:^BOOL(NSNumber *length) {
         return [length integerValue] > 5;
     }]
     subscribeNext:^(id x) {
         NSLog(@"username x = %@", x);
     }];
 
 RACSignal *validUsernameSignal = [self.usernameTextField.rac_textSignal
                                      map:^id(NSString *text) {
                                          return @([self isValidUsername:text]);
                                      }];
  - (BOOL)isValidUsername:(NSString *)username {
         return username.length > 5;
    }

• 對(duì)值的監(jiān)聽

    RAC(self.passwordTextfield, backgroundColor) = [validPasswordSignal map:^id(NSNumber *passwordValid) {
        return [passwordValid boolValue] ? [UIColor clearColor] : [UIColor yellowColor];
    }];

• 信號(hào)的融合

    RACSignal *validUsernameSignal = [self.usernameTextField.rac_textSignal
                                      map:^id(NSString *text) {
                                          return @([self isValidUsername:text]);
                                      }];
    
    RACSignal *validPasswordSignal = [self.passwordTextfield.rac_textSignal
                                      map:^id(NSString *text) {
                                          return @([self isValidPassword:text]);
                                      }];
    RACSignal *signUpActiveSignal = [RACSignal combineLatest:@[validUsernameSignal,  validPasswordSignal]
                                                      reduce:^id(NSNumber *usernameValid, NSNumber *passwordValid){
                                                          return @([usernameValid boolValue] && [passwordValid boolValue]);
                                                      }];
    
    [signUpActiveSignal subscribeNext:^(NSNumber *signupActive) {
        self.loginButton.enabled = [signupActive boolValue];
    }];

• 對(duì)事件的監(jiān)聽

    [[[self.loginButton rac_signalForControlEvents:UIControlEventTouchUpInside]
     map:^id(id value) {
         return [self loginSignal];
     }]
     subscribeNext:^(id x) {
         NSLog(@"login result: %@", x);
     }];
- (RACSignal *)loginSignal {
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        [self.loginService loginWithUsername:self.usernameTextField.text password:self.passwordTextfield.text complete:^(BOOL success) {
            [subscriber sendNext:@(success)];
            [subscriber sendCompleted];
        }];
        return nil;
    }];
}

Demo地址
<h3>參考</h3>

• ReactiveCocoa and MVVM,an Introduction 中文版
• Introduction to MVVM
• ReactiveCocoa Tutorial