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[iOS]将DataSource分离并构建更轻量的UIViewController

在objccn.io中看到一篇文章,构建更轻量的View Controllers,在此自己实践一下加深理解。



新疆项目,learn--tableview,类前缀为LT,开始我们的实验。


首先需要在StoryBoard中拖拽一个UITableView,在头文件中申明tableView变量并建立连接:





新建ArrayDataSource类,作为TableView的DataSource。目的是将DataSource从原本的ViewController中分离出来:

//
//  ArrayDataSource.h
//  objc.io example project (issue #1)
//

#import <Foundation/Foundation.h>


typedef void (^TableViewCellConfigureBlock)(id cell, id item);


@interface ArrayDataSource : NSObject <UITableViewDataSource>

- (id)initWithItems:(NSArray *)anItems
     cellIdentifier:(NSString *)aCellIdentifier
 configureCellBlock:(TableViewCellConfigureBlock)aConfigureCellBlock;

- (id)itemAtIndexPath:(NSIndexPath *)indexPath;

@end

//
//  ArrayDataSource.h
//  objc.io example project (issue #1)
//

#import "ArrayDataSource.h"


@interface ArrayDataSource ()

@property (nonatomic, strong) NSArray *items;
@property (nonatomic, copy) NSString *cellIdentifier;
@property (nonatomic, copy) TableViewCellConfigureBlock configureCellBlock;

@end


@implementation ArrayDataSource

- (id)init
{
    return nil;
}

- (id)initWithItems:(NSArray *)anItems
     cellIdentifier:(NSString *)aCellIdentifier
 configureCellBlock:(TableViewCellConfigureBlock)aConfigureCellBlock
{
    self = [super init];
    if (self) {
        self.items = anItems;
        self.cellIdentifier = aCellIdentifier;
        self.configureCellBlock = [aConfigureCellBlock copy];
    }
    return self;
}

- (id)itemAtIndexPath:(NSIndexPath *)indexPath
{
    return self.items[(NSUInteger) indexPath.row];
}


#pragma mark UITableViewDataSource

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return self.items.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:self.cellIdentifier
                                                            forIndexPath:indexPath];
    id item = [self itemAtIndexPath:indexPath];
    self.configureCellBlock(cell, item);
    return cell;
}

@end

可以看得出来,这个DataSource的管理类接受三个变量进行初始化,分别是:

1.anItems,存储表格数据的对象,是一个NSArray,里面存储封装好的对象,我们并不知道它是什么类型的,所以在使用的时候用id取出其中的元素。

2.cellIdentifier,单元格的标示符,用来指定TableView使用的单元格,是单元格的唯一标识,在创建和设计Cell的时候可以指定。

3.configureCellBlock,一个用来设置每个单元格的block,因为具体的item格式我们并不知道,所以我们也就不知道该如何初始化一个cell里面的数据,需要用block进行设置,因为这个block的目的是为了将item的数据应用到cell上,所以block接受两个参数,cell和item。


接下来在添加一个LTMyCell类,作为自定义的单元格类。在xib中添加两个label用来显示数据:





将xib中的两个label与.h头文件建立连接,连接后的头文件如下:

+ (UINib *)nib;

@property (weak, nonatomic) IBOutlet UILabel *photoTitleLabel;
@property (weak, nonatomic) IBOutlet UILabel *photoDateLabel;


修改.m文件,实现相关方法如下:

+ (UINib *)nib
{
    return [UINib nibWithNibName:@"PhotoCell" bundle:nil];
}

- (void)setHighlighted:(BOOL)highlighted animated:(BOOL)animated
{
    [super setHighlighted:highlighted animated:animated];
    if (highlighted) {
        self.photoTitleLabel.shadowColor = [UIColor darkGrayColor];
        self.photoTitleLabel.shadowOffset = CGSizeMake(3, 3);
    } else {
        self.photoTitleLabel.shadowColor = nil;
    }
}



接着,新建LTPhoto的封装类,我们需要把用来展示的数据进行分装:

//
//  LTPhoto.h
//  learn-tableview
//
//  Created by why on 8/11/14.
//  Copyright (c) 2014 why. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface LTPhoto : NSObject <NSCoding>

@property (nonatomic, copy) NSString* name;
@property (nonatomic, strong) NSDate* creationDate;

@end



//
//  LTPhoto.m
//  learn-tableview
//
//  Created by why on 8/11/14.
//  Copyright (c) 2014 why. All rights reserved.
//

#import "LTPhoto.h"


static NSString * const IdentifierKey = @"identifier";
static NSString * const NameKey = @"name";
static NSString * const CreationDateKey = @"creationDate";
static NSString * const RatingKey = @"rating";


@implementation LTPhoto


- (void)encodeWithCoder:(NSCoder*)coder
{
    [coder encodeObject:self.name forKey:NameKey];
    [coder encodeObject:self.creationDate forKey:CreationDateKey];
}

- (BOOL)requiresSecureCoding
{
    return YES;
}

- (id)initWithCoder:(NSCoder*)coder
{
    self = [super init];
    if (self) {
        self.name = [coder decodeObjectOfClass:[NSString class] forKey:NameKey];
        self.creationDate = [coder decodeObjectOfClass:[NSDate class] forKey:CreationDateKey];
    }
    return self;
}

@end



在写完了LTPhoto这个封装对象之后,我们可以对原来的MyCell进行Category扩展。新建一个Category:



具体代码如下:

#import "LTMyCell.h"

@class LTPhoto;

@interface LTMyCell (ConfigureForPhoto)
- (void)configureForPhoto:(LTPhoto *)photo;

@end


//
//  LTMyCell+ConfigureForPhoto.m
//  learn-tableview
//
//  Created by why on 8/11/14.
//  Copyright (c) 2014 why. All rights reserved.
//

#import "LTMyCell+ConfigureForPhoto.h"
#import "LTPhoto.h"


@implementation LTMyCell (ConfigureForPhoto)

- (void)configureForPhoto:(LTPhoto *)photo
{
    self.photoTitleLabel.text = photo.name;
    self.photoDateLabel.text = [self.dateFormatter stringFromDate:photo.creationDate];
}

- (NSDateFormatter *)dateFormatter
{
    static NSDateFormatter *dateFormatter;
    if (!dateFormatter) {
        dateFormatter = [[NSDateFormatter alloc] init];
        dateFormatter.timeStyle = NSDateFormatterMediumStyle;
        dateFormatter.dateStyle = NSDateFormatterMediumStyle;
    }
    return dateFormatter;
}

@end




接下来就是在ViewController中指定TableView的DataSource。修改m文件代码如下:


//
//  LTViewController.m
//  learn-tableview
//
//  Created by why on 8/11/14.
//  Copyright (c) 2014 why. All rights reserved.
//

#import "LTViewController.h"
#import "ArrayDataSource.h"
#import "LTMyCell.h"
#import "LTMyCell+ConfigureForPhoto.h"
#import "LTPhoto.h"


static NSString * const PhotoCellIdentifier = @"LTMyCell";



@interface LTViewController ()<UITableViewDelegate>

@property (nonatomic, strong) ArrayDataSource *photosArrayDataSource;


@end

@implementation LTViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
    [self setupTableView];

}


- (void)setupTableView
{
    
    TableViewCellConfigureBlock configureCell = ^(LTMyCell *cell, LTPhoto *photo) {
        [cell configureForPhoto:photo];
    };
    
    NSMutableArray *photos = [[NSMutableArray alloc] init];
    for (int i = 0; i < 10; i++) {
        LTPhoto *photo = [[LTPhoto alloc] init];
        photo.name = @"Hello";
        photo.creationDate = [NSDate date];
        [photos addObject:photo];
    }
    
    self.photosArrayDataSource = [[ArrayDataSource alloc] initWithItems:photos
                                                         cellIdentifier:PhotoCellIdentifier
                                                     configureCellBlock:configureCell];
    
    _tableVIew.dataSource = self.photosArrayDataSource;
    
    [_tableVIew registerNib:[LTMyCell nib] forCellReuseIdentifier:PhotoCellIdentifier];
    
}

#pragma mark UITableViewDelegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSLog(@"Click!");
}




- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

这样就实现了基本的DataSource分离。


项目源码地址:learn-tableview