用AFHTTPClient解析JSON

Question

我使用AFNetworking库通过AFHTTPClient解析json。我可以验证json是否在客户端块中被解析，并将该数据发送到我的json模型。但是，当我尝试从块外部访问json模型时，我没有得到任何数据。如何将解析后的json数据传递给json模型，然后在应用程序中的其他位置访问该模型数据？

AFHTTPClient子类/单例：

#import <Foundation/Foundation.h>
#import "AFHTTPClient.h"

@interface JsonClient : AFHTTPClient

+ (JsonClient *)sharedClient;

@end

#import "JsonClient.h"
#import "AFJSONRequestOperation.h"

static NSString *const kJsonBaseURLString = @"https://alpha-api.app.net/";

@implementation JsonClient

+ (JsonClient *)sharedClient {
    static JsonClient *_sharedClient = nil;

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _sharedClient = [[JsonClient alloc] initWithBaseURL:[NSURL URLWithString:kJsonBaseURLString]];
    });

    return _sharedClient;
}

- (id)initWithBaseURL:(NSURL *)url {
    self = [super initWithBaseURL:url];

    if (!self) {
        return nil;
    }

    [self registerHTTPOperationClass:[AFJSONRequestOperation class]];
    [self setDefaultHeader:@"Accept" value:@"application/json"];

    return self;
}

@end

JSON模型数据：

#import <Foundation/Foundation.h>

@interface TheJson : NSObject

@property (nonatomic, copy) NSString *createdAt;
@property (nonatomic, copy) NSString *userText;

- (id)initWithDictionary:(NSDictionary *)dict;

@end

#import "TheJson.h"

@implementation TheJson

- (id)initWithDictionary:(NSDictionary *)dict {
    self = [super init];

    if (self) {
        self.createdAt = [dict objectForKey:@"created_at"];
        self.userText = [dict objectForKey:@"text"];
    }

    return self;
}

@end

用于更新用户界面的ViewController：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@end

#import "ViewController.h"
#import "JsonClient.h"
#import "TheJson.h"

@interface ViewController ()

@property (weak) IBOutlet UILabel *createdLabel;
@property (weak) IBOutlet UILabel *textLabel;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

- (IBAction)fetchJsonData:(id)sender {

    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];

    [[JsonClient sharedClient] getPath:@"stream/0/posts/stream/global" parameters:nil
                               success:^(AFHTTPRequestOperation *operation, id JSON) {
                                   NSArray *postsFromResponse = [JSON valueForKeyPath:@"data"];
                                   NSDictionary *dictFromArray = postsFromResponse[0];

                                   TheJson *jsonObject = [[TheJson alloc] initWithDictionary:dictFromArray];
                                   NSLog(@"createdAt is %@", jsonObject.createdAt);
                                   NSLog(@"text from user is %@", jsonObject.userText);

                                   [self updateInterface];
                                   [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];

                               } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
                                   NSLog(@"Error is %@", [error description]);
                               }
     ];
}

- (void)updateInterface {
    TheJson *thejson;
    [_createdLabel setText:thejson.createdAt];
    [_textLabel setText:thejson.userText];
}

@end

Answer 1

您还没有将新的jsonObject传递到块之外，也没有将它存储在任何地方。短期的答案是声明updateInterface以jsonObject作为参数。

所以你的updateInterface变成了updateInterface:，就像这样：

- (void)updateInterface:(TheJson*)thejson {
    [_createdLabel setText:thejson.createdAt];
    [_textLabel setText:thejson.userText];
}

...and然后在你的代码块中，你像这样调用这个方法：

[self updateInterface:jsonObject];

从长远来看，如果您的应用程序有许多这样的对象，并且/或者需要在任意时间内保留它们，那么您可能需要考虑如何在下载时存储和组织这些对象。