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标题: objective-c - 尝试访问特定对象属性时出现无法识别的选择器错误 [打印本页]

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作者: 菜鸟教程小白    时间: 2022-12-11 22:18
标题: objective-c - 尝试访问特定对象属性时出现无法识别的选择器错误

我有一个小问题，对你来说可能很容易。我正在使用核心数据。我有一个实体:Session，它具有三个属性:access_token、user_id 和 secret。

session .h:

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>

@interface Session : NSManagedObject

@property (nonatomic) NSString * access_token;
@property (nonatomic) NSNumber * user_id;
@property (nonatomic) NSString * secret;

@end

session .m:

#import "Session.h"

@implementation Session

@dynamic access_token;
@dynamic user_id;
@dynamic secret;

@end 

有一个代码，我在使用这个实体:

AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
    Session *newSession = [NSEntityDescription insertNewObjectForEntityForName"Session" inManagedObjectContext:managedObjectContext];
    if (newSession != nil) {
        NSLog(@"access_token: %@", [JSON objectForKey"access_token"]);
        NSLog(@"user_id: %@", [JSON objectForKey"user_id"]);
        NSLog(@"secret: %@", [JSON objectForKey"secret"]);
        newSession.access_token = [JSON objectForKey"access_token"];
        newSession.user_id = [JSON objectForKey"user_id"];
        newSession.secret = [JSON objectForKey"secret"];
    }
    NSError *savingError = nil;
    if ([managedObjectContext save:&savingError] == YES) {
        NSLog(@"Session saved");
    } else {
        NSLog(@"Session not saved");
    }
} failure:nil];

此代码异常:

newSession.secret = [JSON objectForKey"secret"];

MyProject[7678:bc03] -[Session setSecret:]: unrecognized selector sent to instance 0x4e572d0

这是 NSLog:

2012-03-25 15:17:33.987 MyProject[7730:bc03] access_token: <some_access_token>
2012-03-25 15:17:33.988 MyPriject[7730:bc03] user_id: <some_user_id>
2012-03-25 15:17:33.989 MyProject[7730:bc03] secret: <some_secret>

这是堆栈跟踪:

*** Call stack at first throw:
(
0   CoreFoundation                      0x010625a9 __exceptionPreprocess + 185
1   libobjc.A.dylib                     0x013e6313 objc_exception_throw + 44
2   CoreFoundation                      0x010640bb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187
3   CoreFoundation                      0x00fd3966 ___forwarding___ + 966
4   CoreFoundation                      0x00fd3522 _CF_forwarding_prep_0 + 50
5   MyProject                           0x00004c94 __42-[APIWrapper authWithLogin:andPassword:]_block_invoke_0 + 836
6   MyProject                           0x0000d452 __74+[AFJSONRequestOperation JSONRequestOperationWithRequest:success:failure:]_block_invoke_0 + 146
7   MyProject                           0x0000e229 __block_global_3 + 41
8   libdispatch_sim.dylib               0x014de289 _dispatch_call_block_and_release + 16
9   libdispatch_sim.dylib               0x014e1833 _dispatch_main_queue_callback_4CF + 312
10  CoreFoundation                      0x00fa1589 __CFRunLoopRun + 2521
11  CoreFoundation                      0x00fa0840 CFRunLoopRunSpecific + 208
12  CoreFoundation                      0x00fa0761 CFRunLoopRunInMode + 97
13  GraphicsServices                    0x0153a1c4 GSEventRunModal + 217
14  GraphicsServices                    0x0153a289 GSEventRun + 115
15  UIKit                               0x000ebc93 UIApplicationMain + 1160
16  MyProject                           0x0001b305 main + 181
17  MyProject                           0x000020d5 start + 53
)

我真的不明白这里有什么问题。

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Best Answer-推荐答案

在您的 .h 文件中定义您的属性，如下所示。

@property (nonatomic,retain) NSString * access_token;
@property (nonatomic,retain) NSNumber * user_id;
@property (nonatomic,retain) NSString * secret;

然后在你的 .m 文件中

@synthesize access_token;
@synthesize user_id;
@synthesize secret;

这基本上管理你的 getter 和 setter。

关于objective-c - 尝试访问特定对象属性时出现无法识别的选择器错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/9859792/

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