Question

我上课

Collections *tempLocalCollection = [[Collections alloc] init];

问题在于，当我尝试以后续方式提升属性时

 tempLocalCollection.id = [f numberFromString:[NSString stringWithFormat:@"%@", @"0"]];            
 tempLocalCollection.action = @"client_insert";

我应该是错误的

- [Collections setId：]：无法识别的选择器发送到实例0xff8afb0 2015-09-16 10：25：14.235 App [1042：128375] *** 由于未捕获的异常而终止应用程序 'NSInvalidArgumentException'，原因：' - [Collections setId：]：无法识别的选择器发送到实例0xff8afb0'

我哪里错了？

Collections.h

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

@class Items;

@interface Collections : NSManagedObject

@property (nonatomic, retain) NSNumber * datetime_creation;
@property (nonatomic, retain) NSNumber * datetime_last_update_client;
@property (nonatomic, retain) NSNumber * datetime_last_update_server;
@property (nonatomic, retain) NSString * local_delete;
@property (nonatomic, retain) NSNumber * id;
@property (nonatomic, retain) NSString * action;
@property (nonatomic, retain) NSString * label;
@property (nonatomic, retain) NSString * labelServer;
@property (nonatomic, retain) NSNumber * ref_user;
@property (nonatomic, retain) NSNumber * sorting;
@property (nonatomic, retain) NSNumber * system;
@property (nonatomic, retain) NSSet *collection_item;
@end

@interface Collections (CoreDataGeneratedAccessors)

@end

Collections.m

#import "Collections.h"
#import "Items.h"


@implementation Collections

@dynamic datetime_creation;
@dynamic datetime_last_update_client;
@dynamic datetime_last_update_server;
@dynamic local_delete;
@dynamic action;
@dynamic id;

@dynamic label;
@dynamic labelServer;
@dynamic ref_user;
@dynamic sorting;
@dynamic system;
@dynamic collection_item;

@end

这是使用类及其出错的方法。我认为上下文是一样的吗？

-(Collections *) upgrateListCollection:(NSDictionary *) coll{
    NSNumberFormatter *f = [[NSNumberFormatter alloc] init];
    f.numberStyle = NSNumberFormatterDecimalStyle;
    NSNumber *id = [f numberFromString:[NSString stringWithFormat:@"%@", coll[@"id"]]];
    Collections *tempLocalCollection = [[Collections alloc] init];
    NSArray *tmp = [Collections MR_findByAttribute:@"id" withValue:id];
    if(tmp.count != 0){
        tempLocalCollection = tmp[0];
    }
        if(!tempLocalCollection.isAccessibilityElement){
            tempLocalCollection.id = [f numberFromString:[NSString stringWithFormat:@"%@", @"0"]];

            tempLocalCollection.action = @"client_insert";
        }else{
            if([tempLocalCollection.local_delete isEqual: @"1"]){
                tempLocalCollection.action = @"client_delete";
            }else{
                if([tempLocalCollection.label isEqual:coll[@"label"]]){
                    if(tempLocalCollection.datetime_last_update_client < coll[@"datetime_last_update_server"]){
                        tempLocalCollection.action = @"client_update";
                    }else{
                        tempLocalCollection.action = @"server_update";
                    }
                }
            }
    }
    if(tempLocalCollection != nil){
        tempLocalCollection.labelServer = coll[@"label"];
        tempLocalCollection.datetime_last_update_server = coll[@"datetime_last_update_server"];
        tempLocalCollection.datetime_creation = coll[@"creation_utc_server"];
    }

    return tempLocalCollection;
}

Answer 1

NSManagedObject子类（Collections）属性是动态的，它们的setter和getter是generated at runtime

因此，在这种情况下使用Collections创建alloc/init的对象时，不会创建动态属性，因此会出现异常unrecognized selector sent to instance

创建NSManagedObject的正确方法是

NSEntityDescription *entity = [NSEntityDescription entityForName:@"Collections" inManagedObjectContext:myMOC];
Collections *collection = (Collections *)[[NSManagedObject alloc] initWithEntity:entity insertIntoManagedObjectContext:myMOC];

如果你想创建Collections的临时对象，那么将nil作为管理对象上下文传递

NSEntityDescription *entity = [NSEntityDescription entityForName:@"Collections" inManagedObjectContext:myMOC];
Collections *tempObj = (Collections *)[[NSManagedObject alloc] initWithEntity:entity insertIntoManagedObjectContext:nil];

Answer 2

这是一个托管对象，需要在其管理环境中创建。

初始化错误的类

2 个答案: