在一個(gè)ViewController中，這些職責(zé)可以被統(tǒng)一放在#pragma區(qū)域中。但是，我們其實(shí)應(yīng)該考慮將它拆分，并且放在更小的原件中。

數(shù)據(jù)源

數(shù)據(jù)源模式（Data Source Pattern）是一種用來(lái)隔離哪個(gè)對(duì)象對(duì)應(yīng)哪個(gè)引導(dǎo)路徑的邏輯的方式。尤其是在復(fù)雜的圖標(biāo)視圖中，這個(gè)模式非常實(shí)用，可以用來(lái)移除View Controller里所有“哪些cell在特定條件下可見(jiàn)”的邏輯。如果你曾經(jīng)寫過(guò)這樣的圖標(biāo)，經(jīng)常需要對(duì)row和section的整數(shù)進(jìn)行對(duì)比，那么數(shù)據(jù)源模式非常適合你。

數(shù)據(jù)源模式可以和UITableViewDataSource共存，但是我發(fā)現(xiàn)用這些對(duì)象對(duì)cell進(jìn)行配置，其發(fā)揮的作用于管理引導(dǎo)路徑時(shí)不太一樣，因此我比較喜歡將兩者分開(kāi)。

這個(gè)簡(jiǎn)單的數(shù)據(jù)源模式使用實(shí)例，可以幫你處理分段邏輯：

@implementation SKSectionedDataSource : NSObject

 

- (instancetype)initWithObjects:(NSArray*)objects sectioningKey:(NSString *)sectioningKey {

    self = [super init];

    if (!self) return nil;

 

    [self sectionObjects:objectswithKey:sectioningKey];

 

    return self;

}

 

-(void)sectionObjects:(NSArray *)objects withKey:(NSString *)sectioningKey {

    self.sectionedObjects = //section theobjects array

}

 

-(NSUInteger)numberOfSections {

    return self.sectionedObjects.count;

}

 

-(NSUInteger)numberOfObjectsInSection:(NSUInteger)section {

    return [self.sectionedObjects[section]count];

}

 

-(id)objectAtIndexPath:(NSIndexPath *)indexPath {

    returnself.sectionedObjects[indexPath.section][indexPath.row];

}

 

@end

標(biāo)準(zhǔn)合成（Standard Composition）

蘋果在發(fā)布iOS5的時(shí)候，一同推出了View Controller Containment API。你可以使用這個(gè)API對(duì)View Controller進(jìn)行合成。如果你的ViewController由多個(gè)邏輯單元所構(gòu)成，你可以考慮將其拆分。

在一個(gè)擁有header和grid視圖的屏幕上，我們可以加載兩個(gè)View Controller，然后將他們放在正確的位置上。

-(SKHeaderViewController *)headerViewController {

    if (!_headerViewController) {

        SKHeaderViewController*headerViewController = [[SKHeaderViewController alloc] init];

 

        [selfaddChildViewController:headerViewController];

        [headerViewControllerdidMoveToParentViewController:self];

 

        [self.viewaddSubview:headerViewController.view];

 

        self.headerViewController =headerViewController;

    }

    return _headerViewController;

}

 

-(SKGridViewController *)gridViewController {

    if (!_gridViewController) {

        SKGridViewController*gridViewController = [[SKGridViewController alloc] init];

 

        [selfaddChildViewController:gridViewController];

        [gridViewControllerdidMoveToParentViewController:self];

 

        [self.viewaddSubview:gridViewController.view];

 

        self.gridViewController =gridViewController;

    }

    return _gridViewController;

}

 

-(void)viewDidLayoutSubviews {

    [super viewDidLayoutSubviews];

 

    CGRect workingRect = self.view.bounds;

 

 CGRect headerRect = CGRectZero, gridRect =CGRectZero;

    CGRectDivide(workingRect, &headerRect,&gridRect, 44, CGRectMinYEdge);

 

   self.headerViewController.view.frame = tagHeaderRect;

    self.gridViewController.view.frame =hotSongsGridRect;

}

Smarter Views

如果你是在ViewController的類中對(duì)所有子視圖進(jìn)行分配，你可以考慮使用Smarter View。UIViewController默認(rèn)情況下會(huì)使用UIView來(lái)瀏覽屬性，但是你也可以用自己的視圖去取代它。你可以使用-loadView作為接入點(diǎn)，前提是你要在那個(gè)方法中設(shè)定了self.view。

@implementationSKProfileViewController

 

- (void)loadView {

    self.view = [SKProfileView new];

}

 

//...

 

@end

 

@implementationSKProfileView : NSObject

 

- (UILabel *)nameLabel {

    if (!_nameLabel) {

        UILabel *nameLabel = [UILabel new];

        //configure font, color, etc

        [self addSubview:nameLabel];

        self.nameLabel = nameLabel;

    }

    return _nameLabel;

}

 

- (UIImageView*)avatarImageView {

    if (!_avatarImageView) {

        UIImageView * avatarImageView =[UIImageView new];

        [self addSubview:avatarImageView];

        self.avatarImageView = avatarImageView;

    }

    return _avatarImageView

}

 

-(void)layoutSubviews {

    //perform layout

}

 

@end

你也可以重新定義@property(nonatomic) SKProfileView *view，因?yàn)樗且粋€(gè)比UIView更具體的類別，分析器會(huì)將self.view視為 SKProfileView，從而完成正確的處理。

Presenter模式

Presenter模式可以包裹模型對(duì)象，改變它的顯示屬性，并且公開(kāi)那些已被改變的屬性的消息。在其他一些情境中，它也被稱為Presentation Model、Exhibit模式和ViewModel等。

@implementation SKUserPresenter : NSObject

 

-(instancetype)initWithUser:(SKUser *)user {

    self = [super init];

    if (!self) return nil;

    _user = user;

    return self;

}

 

- (NSString *)name{

    return self.user.name;

}

 

- (NSString *)followerCountString{

    if (self.user.followerCount == 0) {

        return @"";

    }

    return [NSString stringWithFormat:@"%@followers", [NSNumberFormatterlocalizedStringFromNumber:@(_user.followerCount)numberStyle:NSNumberFormatterDecimalStyle]];

}

 

- (NSString*)followersString {

    NSMutableString *followersString =[@"Followed by " mutableCopy];

    [followersStringappendString:[self.class.arrayFormatter stringFromArray:[self.user.topFollowersvalueForKey:@"name"]];

    return followersString;

}

 

+(TTTArrayFormatter*) arrayFormatter {

    static TTTArrayFormatter *_arrayFormatter;

    static dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{

        _arrayFormatter = [[TTTArrayFormatteralloc] init];

       _arrayFormatter.usesAbbreviatedConjunction = YES;

    });

    return _arrayFormatter;

}

 

@end

最重要的是，模型對(duì)象本身不會(huì)被暴露。Presenter扮演了模型看門人的角色。這保證了View Controller無(wú)法繞開(kāi)Presenter而直接訪問(wèn)模型。

Binding模式

Binding模式在變化的過(guò)程中會(huì)使用模型數(shù)據(jù)對(duì)視圖進(jìn)行更新。Cocoa非常適合使用這個(gè)模式，因?yàn)镵VO能夠觀察模型，并且從模型中進(jìn)行讀取，在視圖中完成寫入。Cocoa Binding是這個(gè)模式的AppKit版本。Reactive Cocoa等第三方庫(kù)也非常適合這個(gè)模式。

@implementationSKProfileBinding : NSObject

 

-(instancetype)initWithView:(SKProfileView *)view presenter:(SKUserPresenter*)presenter {

    self = [super init];

    if (!self) return nil;

    _view = view;

    _presenter = presenter;

    return self;

}

 

- (NSDictionary*)bindings {

    return @{

              @"name":@"nameLabel.text",

              @"followerCountString":@"followerCountLabel.text",

            };

}

 

- (void)updateView{

    [self.bindingsenumerateKeysAndObjectsUsingBlock:^(id presenterKeyPath, id viewKeyPath, BOOL*stop) {

        id newValue = [self.presentervalueForKeyPath:presenterKeyPath];

        [self.view setObject:newvalueforKeyPath:viewKeyPath];

    }];

}

 

@end

Interaction模式

View Controller變得體量過(guò)大的重要原因之一，就是actionSheet.delegate= self的濫用。在Smaitalk中，Controller對(duì)象的整個(gè)角色，就是接受用戶輸入，并且更新試圖和模型。如今我們所使用的交互相對(duì)復(fù)雜，這些交互會(huì)要求我們?cè)赩iew Controller中寫下大量的代碼。

交互的過(guò)程通常開(kāi)始與用戶的最初輸入（例如點(diǎn)擊按鈕）、可選的用戶再次輸入（例如“你確定要繼續(xù)嗎？”），之后程序或產(chǎn)生活動(dòng)，例如網(wǎng)路請(qǐng)求和狀態(tài)改變。這個(gè)操作其實(shí)可以完全包裹在Interaction Object之中。

 @implementationSKProfileViewController

 

- (void)followButtonTapped:(id)sender{

    self.followUserInteraction =[[SKFollowUserInteraction alloc] initWithUserToFollow:self.user delegate:self];

    [self.followUserInteraction follow];

}

 

-(void)interactionCompleted:(SKFollowUserInteraction *)interaction {

    [self.binding updateView];

}

 

//...

 

@end

@implementationSKFollowUserInteraction : NSObject 

 

-(instancetype)initWithUserToFollow:userdelegate:(id)delegate {

    self = [super init];

    if !(self) return nil;

    _user = user;

    _delegate = delegate;

    return self;

}

 

- (void)follow {

    [[[UIAlertView alloc] initWithTitle:nil

                               message:@"Are you sure you want to follow this user?"

                               delegate:self

                     cancelButtonTitle:@"Cancel"

                     otherButtonTitles:@"Follow", nil] show];

}

 

-(void)alertView:(UIAlertView *)alertViewclickedButtonAtIndex:(NSInteger)buttonIndex {

    if ([alertView buttonTitleAtIndex:buttonIndex]isEqual:@"Follow"]) {

        [self.user.APIGatewayfollowWithCompletionBlock:^{

            [self.delegateinteractionCompleted:self];

        }];

    }

}

 

@end

Keyboard Manager

當(dāng)鍵盤狀態(tài)出現(xiàn)改變，視圖的更新也會(huì)在View Controller中出現(xiàn)卡頓，但是使用KeyboardManager模式可以很好的解決這個(gè)問(wèn)題。

@implementationSKNewPostKeyboardManager : NSObject

 

-(instancetype)initWithTableView:(UITableView *)tableView {

    self = [super init];

    if (!self) return nil;

    _tableView = tableView;

    return self;

}

 

- (void)beginObservingKeyboard{

    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardDidHide:)name:UIKeyboardDidHideNotification object:nil];

    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardWillShow:)name:UIKeyboardWillShowNotification object:nil];

}

 

-(void)endObservingKeyboard {

    [[NSNotificationCenter defaultCenter]removeObserver:self name:UIKeyboardDidHideNotification object:nil];

    [[NSNotificationCenter defaultCenter] removeObserver:selfname:UIKeyboardWillShowNotification object:nil];

}

 

-(void)keyboardWillShow:(NSNotification *)note {

    CGRect keyboardRect = [[note.userInfoobjectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

 

    UIEdgeInsets contentInsets = UIEdgeInsetsMake(self.tableView.contentInset.top,0.0f, CGRectGetHeight(keyboardRect), 0.0f);

    self.tableView.contentInset =contentInsets;

   self.tableView.scrollIndicatorInsets = contentInsets;

}

 

-(void)keyboardDidHide:(NSNotification *)note {

    UIEdgeInsets contentInset =UIEdgeInsetsMake(self.tableView.contentInset.top, 0.0f,self.oldBottomContentInset, 0.0f);

    self.tableView.contentInset =contentInset;

   self.tableView.scrollIndicatorInsets = contentInset;

}

 

@end

Navigator模式

通常情況下，視圖間的切換是通過(guò)調(diào)取to -pushViewController:animated:來(lái)實(shí)現(xiàn)的。隨著過(guò)渡效果越來(lái)越復(fù)雜，你可以將這個(gè)任務(wù)指定給Navigator對(duì)象來(lái)完成。尤其是在同時(shí)支持iPhone和iPad的應(yīng)用中，視圖切換需要根據(jù)設(shè)備屏幕尺寸的不同而改變。

@protocolSKUserNavigator 

 

-(void)navigateToFollowersForUser:(SKUser *)user;

 

@end

 

@implementationSKiPhoneUserNavigator : NSObject

 

-(instancetype)initWithNavigationController:(UINavigationController*)navigationController {

    self = [super init];

    if (!self) return nil;

    _navigationController =navigationController;

   return self;

}

 

- (void)navigateToFollowersForUser:(SKUser*)user {

    SKFollowerListViewController *followerList= [[SKFollowerListViewController alloc] initWithUser:user];

    [self.navigationControllerpushViewController:followerList animated:YES];

}

 

@end

 @implementationSKiPadUserNavigator : NSObject

 

-(instancetype)initWithUserViewController:(SKUserViewController*)userViewController {

    self = [super init];

    if (!self) return nil;

    _userViewController = userViewController;

    return self;

}

 

-(void)navigateToFollowersForUser:(SKUser *)user {

    SKFollowerListViewController *followerList= [[SKFollowerListViewController alloc] initWithUser:user];

   self.userViewController.supplementalViewController = followerList;

}

總結(jié)

從歷史來(lái)看，蘋果的SDK只包含最小數(shù)量的原件，但是隨著越來(lái)越多的API使用，我們經(jīng)常會(huì)讓View Controller的體量變得越來(lái)越大。將ViewController的職責(zé)指定給其他方式去完成，我們可以更好的控制View Controller的體積。

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