基于RAC的通用TableView

　　最近公司的一个新项目的1.0版本开发完了，但是对于这么一个初期的项目，部分VC的代码行数仍然超过300行。我也开始感觉到有种(Massive)MVC的趋势，而且部分界面控件的创建方法还是略略有点Magic。于是我开始寻求新的架构，来改善当前的状况。我想起了之前听说过的ReactiveCocoa，加上最近Ray神和Objcio.cn的介绍，我也开始了RAC的“修炼”。
　　不过，RAC的学习不但需要了解其API的作用，更重要的是用RAC的思维去思考。如果用传统的MVC架构思维，我可以很快速写出一个简单的框架，但是学习RAC和MVVM，就发现原来很多理所当然的东西也要仔细去思考。对于初学者而言，RAC并不是很友好，但掌握基本用法后，就已经可以感受到RAC的优势。
　　在学习的时候，我看到了Ray神上面用Signal和Command来代替UITableViewDataSource和UITableViewDelegate的helper。不过，本人还是觉得不太满意，毕竟需要额外的helper，而且限定cell必须来自xib。于是基于Ray神的基础上，我把这套模式搬到了UITableView层上，同时也支持多个section和cell的定制。这类相对常用的控件，我不想把API设计得过于复杂，所以对于有相对特殊的要求还是需要实现DataSource和Delegate。本人意在把Ray神的思路整合到控件层，并不打算写高大上的控件。

//
//  PINKBindCellProtocol.h
//

#import <Foundation/Foundation.h>

@protocol PINKBindCellProtocol <NSObject>

- (void)bindCellViewModel:(id)viewModel;

@end

//
//  PINKBindTableView.h
//

#import <UIKit/UIKit.h>

@protocol PINKBindCellProtocol;

typedef UITableViewCell *(^PINKBindTableViewCreateCellBlock)(NSIndexPath *indexPath);

@interface PINKBindTableView : UITableView

@property (nonatomic, getter = isAutoCheckDataSource) BOOL autoCheckDataSource;
@property (nonatomic, getter = isAutoDeselect) BOOL autoDeselect;

@property (nonatomic, readonly) id<UITableViewDataSource> realDataSource;
@property (nonatomic, readonly) id<UITableViewDelegate> realDelegate;

- (void)setDataSourceSignal:(RACSignal *)sourceSignal
           selectionCommand:(RACCommand *)selection
                  cellClass:(Class<PINKBindCellProtocol>)cellClass;

- (void)setDataSourceSignal:(RACSignal *)sourceSignal
           selectionCommand:(RACCommand *)selection
            createCellBlock:(PINKBindTableViewCreateCellBlock)createCellBlock;

@end

//以下是截获了的方法，继承子类时可以直接重写，但还是要调用super
@interface PINKBindTableView (UITableViewDataSourceIntercept)

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView;
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section;
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath;

@end

@interface PINKBindTableView (UITableViewDelegateIntercept)

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath;

@end

//
//  PINKBindTableView.m
//

#import "PINKBindTableView.h"

#import "MessageInterceptor.h"

#import "PINKBindCellProtocol.h"

typedef NS_OPTIONS(NSInteger, PINKBindTableView_DataSource_MethodType) {
    PINKBindTableView_DataSource_MethodType_numberOfSectionsInTableView  = 1 << 0,
    PINKBindTableView_DataSource_MethodType_numberOfRowsInSection        = 1 << 1,
    PINKBindTableView_DataSource_MethodType_cellForRowAtIndexPath        = 1 << 2,
};

@interface PINKBindTableView ()<UITableViewDataSource, UITableViewDelegate>
{
    MessageInterceptor *_dataSourceInterceptor;
    MessageInterceptor *_delegateInterceptor;
    
    PINKBindTableView_DataSource_MethodType _dataSourceMethodType;
}

/**
 *  tableData为nil时，若dataSource或delegate实现了对应方法，则调用。
 */
@property (nonatomic, strong) NSArray *tableData;
@property (nonatomic, strong) RACCommand *didSelectedCommand;
@property (nonatomic, unsafe_unretained) Class<PINKBindCellProtocol> cellClass;
@property (nonatomic, strong) NSString *cellReuseIdentifier;
@property (nonatomic, copy) PINKBindTableViewCreateCellBlock createCellBlock;

@end

@implementation PINKBindTableView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    
    if (self) {
        [self p_InitPINKBindTableView];
    }
    
    return self;
}

- (instancetype)initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];
    
    if (self) {
        [self p_InitPINKBindTableView];
    }
    
    return self;
}

#pragma mark - Private Initialize
- (void)p_InitPINKBindTableView
{
    _autoCheckDataSource = YES;
    _autoDeselect = YES;
    
    _dataSourceInterceptor = [[MessageInterceptor alloc] init];
    _dataSourceInterceptor.middleMan = self;
    _dataSourceInterceptor.receiver = [super dataSource];
    [super setDataSource:(id<UITableViewDataSource>)_dataSourceInterceptor];
    
    _delegateInterceptor = [[MessageInterceptor alloc] init];
    _delegateInterceptor.middleMan = self;
    _delegateInterceptor.receiver = [super delegate];
    [super setDelegate:(id<UITableViewDelegate>)_delegateInterceptor];
}

#pragma mark - Overwrite DataSource
- (void)setDataSource:(id<UITableViewDataSource>)dataSource
{
    if (_dataSourceInterceptor) {
        _dataSourceInterceptor.receiver = dataSource;
        //UITableViewDataSource有类似缓存机制优化，所以先设置nil
        [super setDataSource:nil];
        [super setDataSource:(id<UITableViewDataSource>)_dataSourceInterceptor];
        
        [self updateDataSourceMethodType];
    } else {
        [super setDataSource:dataSource];
    }
}

- (id<UITableViewDataSource>)realDataSource
{
    if (_dataSourceInterceptor) {
        return _dataSourceInterceptor.receiver;
    } else {
        return [super dataSource];
    }
}

#pragma mark - Overwrite Delegate
- (void)setDelegate:(id<UITableViewDelegate>)delegate
{
    if (_delegateInterceptor) {
        _delegateInterceptor.receiver = delegate;
        
        [super setDelegate:nil];
        [super setDelegate:(id<UITableViewDelegate>)_delegateInterceptor];
    } else {
        [super setDelegate:delegate];
    }
}

- (id<UITableViewDelegate>)realDelegate
{
    if (_delegateInterceptor) {
        return _delegateInterceptor.receiver;
    } else {
        return [super delegate];
    }
}

#pragma mark - UITableViewDataSource
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    if (!_tableData &&
        _dataSourceMethodType & PINKBindTableView_DataSource_MethodType_numberOfSectionsInTableView) {
        return [_dataSourceInterceptor.receiver numberOfSectionsInTableView:tableView];
    } else
        return _tableData.count;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if (!_tableData &&
        _dataSourceMethodType & PINKBindTableView_DataSource_MethodType_numberOfRowsInSection) {
        return [_dataSourceInterceptor.receiver tableView:tableView numberOfRowsInSection:section];
    } else
        return [_tableData[section] count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (!_tableData &&
        _dataSourceMethodType & PINKBindTableView_DataSource_MethodType_cellForRowAtIndexPath) {
        return [_dataSourceInterceptor.receiver tableView:tableView cellForRowAtIndexPath:indexPath];
    } else {
        UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:_cellReuseIdentifier];
        if (!cell) {
            if (_cellClass) {
                cell = [[(Class)_cellClass alloc] init];
            } else if (_createCellBlock) {
                cell = _createCellBlock(indexPath);
            }
        }
        [(id<PINKBindCellProtocol>)cell bindCellViewModel:_tableData[indexPath.section][indexPath.row]];
        
        return cell;
    }
}

#pragma mark - UITableViewDelegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (_autoDeselect) {
        [tableView deselectRowAtIndexPath:indexPath animated:YES];
    }
    
    if (_tableData && _didSelectedCommand) {
        [_didSelectedCommand execute:_tableData[indexPath.section][indexPath.row]];
    }
    
    if ([_delegateInterceptor.receiver respondsToSelector:@selector(tableView:didSelectRowAtIndexPath:)]) {
        [_delegateInterceptor.receiver tableView:tableView didSelectRowAtIndexPath:indexPath];
    }
}

#pragma mark - 缓存DataSource方法
- (void)updateDataSourceMethodType
{
    _dataSourceMethodType = 0;
    
    if ([_dataSourceInterceptor.receiver respondsToSelector:@selector(numberOfSectionsInTableView:)]) {
        _dataSourceMethodType |= PINKBindTableView_DataSource_MethodType_numberOfSectionsInTableView;
    }
    
    if ([_dataSourceInterceptor.receiver respondsToSelector:@selector(tableView:numberOfRowsInSection:)]) {
        _dataSourceMethodType |= PINKBindTableView_DataSource_MethodType_numberOfRowsInSection;
    }
    
    if ([_dataSourceInterceptor.receiver respondsToSelector:@selector(tableView:cellForRowAtIndexPath:)]) {
        _dataSourceMethodType |= PINKBindTableView_DataSource_MethodType_cellForRowAtIndexPath;
    }
}

#pragma mark - API
- (void)setDataSourceSignal:(RACSignal *)sourceSignal
           selectionCommand:(RACCommand *)selection
                  cellClass:(Class<PINKBindCellProtocol>)cellClass
{
    self.cellClass = cellClass;
    self.createCellBlock = nil;
    self.didSelectedCommand = selection;
    [self configCellReuseIdentifierAndCellHeight];
    
    @weakify(self);
    [sourceSignal subscribeNext:^(NSArray *source) {
        @strongify(self);
        self.tableData = source;
        [self reloadData];
    }];
}

- (void)setDataSourceSignal:(RACSignal *)sourceSignal
           selectionCommand:(RACCommand *)selection
            createCellBlock:(PINKBindTableViewCreateCellBlock)createCellBlock
{
    self.cellClass = nil;
    self.createCellBlock = createCellBlock;
    self.didSelectedCommand = selection;
    [self configCellReuseIdentifierAndCellHeight];
    
    @weakify(self);
    [sourceSignal subscribeNext:^(NSArray *source) {
        @strongify(self);
        self.tableData = source;
        [self reloadData];
    }];
}

- (void)configCellReuseIdentifierAndCellHeight
{
    UITableViewCell *oneCell = nil;
    if (_cellClass) {
        oneCell = [[(Class)_cellClass alloc] init];
    } else if (_createCellBlock) {
        oneCell = _createCellBlock([NSIndexPath indexPathForRow:0 inSection:0]);
    }
    _cellReuseIdentifier = oneCell.reuseIdentifier;
    self.rowHeight = oneCell.frame.size.height;
}

#pragma mark - Properties
- (void)setTableData:(NSArray *)tableData
{
    if (_autoCheckDataSource &&
        tableData.count &&
        ![tableData[0] isKindOfClass:[NSArray class]]) {
        _tableData = @[tableData];
    } else {
        _tableData = tableData;
    }
}

@end