iOS 应该模型对象能够使用 NSURLSession 访问网络

Question

我正在重新设计应用程序，正在重构和扩展我的模型。

我的应用程序模型的一个方面是应用程序从网络服务检索数据并填充模型。

我的问题是:我的模型对象应该有能力实现 NSURLSession 还是应该依赖 VC 来提供连接？

我是从最佳实践的角度提问的。考虑这个问题的最佳方式是什么？该模型应该完全独立还是应该具有网络访问权限？

一个考虑因素是，如果没有来自网络的数据，这些模型对象基本上是无用的，这意味着来自 Internet 的数据是它们存在的一个基本方面。

Answer 1

如果我们取 SOLID — 特别是 Single Responsible Principle 的 S — 考虑到，很明显，无论是 VC 还是模型都不应该做网络:

• VC 的唯一职责是处理意见
• 模型的目的是保存数据
• 网络应该由第三类网络 Controller 完成。

这三点将实现 SOLID，但是如何将网络中的数据转换为 View 上显示的模型对象？

好吧，这取决于您在应用程序上的整体架构设计，但一种常见的方法是将回调(委托(delegate)协议(protocol)或 block )与您的网络 Controller 一起使用。
您在应用程序委托(delegate)中创建一个网络 Controller ，并将它从 View Controller 传递到 View Controller ，通过属性传递到应用程序中需要新获取数据的任何地方。我不会在这里使用单例，因为这违反了 SOLID 的 O、I 和 D。
将类方法添加到您的模型 +(NSArray *)modelObjectsFromDictionaries:(NSArray *) 或类似方法。
在 View Controller 中你现在可以做

-(void)viewDidLoad
{
    [super viewDidLoad];
    __weak typeof(self) weakSelf = self;
    [self.networkController fetchModels:^(NSArray *modelDictionaries, NSError *error){
        typeof(weakSelf) self = weakSelf;
        if(self) {
            if(!error){
              [self.dataSource addOrUpdateData:[Model modelObjectsFromDictionaries:modelDictionaries]];
            } else {
                // error handling
            }
        }
    }];
}

这只是一个起点。对于更复杂的 API，使用本身使用网络 Controller 和持久性 Controller 的 api Controller 可能会很有用。

虽然您可能想要使用某种映射和抽象工厂模式而不是模型类方法……但是所有这些都需要有关您的应用程序的更多信息，并且超出了这个问题的范围。

---

更新:

我创建了一个示例项目来演示这一点。
和我上面说的略有不同:
因为它使用 TableView ，所以我使用数据源类来填充它。数据源将代替 View Controller 告诉网络 Controller 获取新数据。

我正在使用 OFAPopulator为此，我编写了一个库，以符合 SOLID 的方式填充 TableView 和 Collection View ，或者“保持 View Controller 清洁和 MVC 智能”。

---

#import "AppDelegate.h"
#import "VSNetworkController.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [self.window.rootViewController setValue:[[VSNetworkController alloc] initWithBaseURL:[NSURL URLWithString:@"http://api.goeuro.com/api/v2/"]]
                                      forKey:@"networkController"];
    return YES;
}

@end

---

//  VSNetworkController.h

#import <Foundation/Foundation.h>

@interface VSNetworkController : NSObject
-(instancetype)initWithBaseURL:(NSURL *) baseURL;

-(void)suggestionsForString:(NSString *)suggestionString
            responseHandler:(void(^)(id responseObj, NSError *error))responseHandler;
@end

---

//  VSNetworkController.m


#import "VSNetworkController.h"

@interface VSNetworkController ()
@property (nonatomic, strong) NSURL *baseURL;

@end


@implementation VSNetworkController
-(instancetype)initWithBaseURL:(NSURL *)baseURL
{
    self = [super init];
    if (self) {
        _baseURL = baseURL;
    }
    return self;
}

-(void)suggestionsForString:(NSString *)suggestionString
            responseHandler:(void(^)(id responseObj, NSError *error))responseHandler
{
    NSURL *url = [self.baseURL URLByAppendingPathComponent:[NSString stringWithFormat:@"position/suggest/en/%@", suggestionString]];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    
    [NSURLConnection sendAsynchronousRequest:request
                                       queue:[NSOperationQueue mainQueue]
                           completionHandler:^(NSURLResponse *response,
                                               NSData *data,
                                               NSError *connectionError) {
                               responseHandler([NSJSONSerialization JSONObjectWithData:data options:0 error:nil], connectionError);
                           }];
}
@end

---

//  VSLocationSuggestion.h

#import <Foundation/Foundation.h>
@import CoreLocation;

@interface VSLocationSuggestion : NSObject
@property (nonatomic, copy, readonly) NSString *name;
@property (nonatomic, copy, readonly) NSString *country;
@property (nonatomic, strong, readonly) CLLocation *position;

+(NSArray *)suggestionsFromDictionaries:(NSArray *)dictionaries;
@end

---

//  VSLocationSuggestion.m

#import "VSLocationSuggestion.h"

@interface VSLocationSuggestion ()
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *country;
@property (nonatomic, strong) CLLocation *position;
@end

@implementation VSLocationSuggestion
+(NSArray *)suggestionsFromDictionaries:(NSArray *)dictionaries
{
    NSMutableArray *array = [@[] mutableCopy];
    [dictionaries enumerateObjectsUsingBlock:^(NSDictionary *suggestionDict, NSUInteger idx, BOOL *stop) {
        [array addObject:[[self alloc] initWithDictionary:suggestionDict]];
    }];
    
    return [array copy];
}

-(instancetype)initWithDictionary:(NSDictionary *)dict
{
    self = [super init];
    if (self) {
        _name = dict[@"name"];
        _country = dict[@"country"];
        CLLocationDegrees latitude = [dict[@"geo_position"][@"latitude"] doubleValue];
        CLLocationDegrees longitude =[dict[@"geo_position"][@"longitude"] doubleValue];
        _position = [[CLLocation alloc] initWithLatitude:latitude longitude:longitude];
    }
    return self;
}
@end

---

//  VSSuggestionDataSource.h

#import <Foundation/Foundation.h>
#import <OFADataProvider.h>
@class VSNetworkController;
@interface VSSuggestionDataSource : NSObject <OFADataProvider>

-(instancetype)initWithNetworkController:(VSNetworkController *)networkController;
-(void)setNewSuggestions:(NSArray *)suggetsions;

-(void)enteredStringForSuggestions:(NSString *)suggestionString;
@end

---

//  VSSuggestionDataSource.m

#import "VSSuggestionDataSource.h"
#import "VSNetworkController.h"
#import "VSLocationSuggestion.h"

@interface VSSuggestionDataSource ()
@property (nonatomic, copy) void (^available)(void);
@property (nonatomic, strong) VSNetworkController *networkController;
@end


@implementation VSSuggestionDataSource
@synthesize sectionObjects;

-(instancetype)initWithNetworkController:(VSNetworkController *)networkController
{
    self = [super init];
    if (self) {
        _networkController = networkController;
    }
    return self;
}

-(void)dataAvailable:(void (^)(void))available
{
    _available = available;
}

-(void)setNewSuggestions:(NSArray *)suggetsions
{
    self.sectionObjects = suggetsions;
    self.available();
}

-(void)enteredStringForSuggestions:(NSString *)s
{
    __weak typeof(self) weakSelf = self;
    [self.networkController suggestionsForString:s responseHandler:^(NSArray *responseObj, NSError *error) {
        typeof(weakSelf) self = weakSelf;
        if (self) {
            if (!error && responseObj) {
                NSArray *suggestion = [VSLocationSuggestion suggestionsFromDictionaries:responseObj];
                [self setNewSuggestions:suggestion];
            }
        }
    }];
}


@end

---

//  ViewController.h

#import <UIKit/UIKit.h>
@class VSNetworkController;

@interface ViewController : UIViewController
@property (nonatomic, strong) VSNetworkController *networkController;

@end

---

//  ViewController.m

#import "ViewController.h"
#import "VSLocationSuggestion.h"
#import <OFAViewPopulator.h>
#import <OFASectionPopulator.h>
#import "VSSuggestionDataSource.h"


@interface ViewController ()
@property (weak, nonatomic) IBOutlet UITableView *tableView;
@property (strong, nonatomic) OFAViewPopulator *viewPopultor;
@property (strong, nonatomic) VSSuggestionDataSource *dataSource;
- (IBAction)textChanged:(UITextField *)sender;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.dataSource = [[VSSuggestionDataSource alloc] initWithNetworkController:self.networkController];
    
    OFASectionPopulator *sectionPopulator = [[OFASectionPopulator alloc] initWithParentView:self.tableView
                                                                               dataProvider:self.dataSource
                                                                             cellIdentifier:^NSString *(id obj, NSIndexPath *indexPath) {
        return @"Cell";
    } cellConfigurator:^(VSLocationSuggestion *obj, UITableViewCell *cell, NSIndexPath *indexPath) {
        cell.textLabel.text = obj.name;
    }];
    
    sectionPopulator.objectOnCellSelected = ^(VSLocationSuggestion *suggestion, UIView *cell, NSIndexPath *indexPath ){
        NSString * string =[NSString stringWithFormat:@"%@, %@ (%f %f)", suggestion.name, suggestion.country, suggestion.position.coordinate.latitude, suggestion.position.coordinate.longitude];
        
        UIAlertController *avc = [UIAlertController alertControllerWithTitle:@"Selected" message:string preferredStyle:UIAlertControllerStyleAlert];
        
        UIAlertAction *cancelAction = [UIAlertAction
                                       actionWithTitle:NSLocalizedString(@"Cancel", @"Cancel action")
                                       style:UIAlertActionStyleCancel
                                       handler:^(UIAlertAction *action)
                                       {
                                           ;
                                       }];
        [avc addAction:cancelAction];
        [self presentViewController:avc animated:YES completion:NULL];
    };
    self.viewPopultor = [[OFAViewPopulator alloc] initWithSectionPopulators:@[sectionPopulator]];

}


- (IBAction)textChanged:(UITextField *)sender
{
    NSString *s = sender.text;
    if ([s length]) {
        [self.dataSource enteredStringForSuggestions:s];
    }
}
@end;

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我在 github 上提供了这段代码:https://github.com/vikingosegundo/LocationSugesstion

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