对不起,接下来的新颖性。非常感谢您的耐心配合。
将新对象添加到核心数据时,正确的初始化器是这样的:
- (id)initWithEntity:(NSEntityDescription *)entity insertIntoManagedObjectContext: (NSManagedObjectContext *)context
好的,所以我理解了initWithEntity部分。我的核心数据模型中只有一个实体,因此将其放置在那里。上下文是我感到困惑的地方。首先,在哪里声明上下文,或者我什至需要声明它?简单地输入self.ManagedObjectContext无效,也不会自动完成。也许是因为我试图从我的AddViewController调用此方法的原因,所以即使我键入Car.ManagedObjectContext或AppDelegate.ManagedObjectContext,也会发生相同的事情。我猜我可以在我的护理数据生成的模型类(Car.h)中声明它,但它实际上有什么作用?
我在这里不明白什么?对不起,新问题。我真的一直在努力弄清楚这个问题。
这是我的代码。
car.h:
@interface Car : NSManagedObject
@property (nonatomic, retain) NSString * brand;
@property (nonatomic, retain) NSString * model;
@property (nonatomic, retain) NSString * year;
@property (nonatomic, retain) NSString * color;
@property (nonatomic, retain) NSNumber * engineSize;
@property (nonatomic, retain) NSNumber * weight;
@property (nonatomic, retain) id image;
@end
car.m:
#import "Car.h"
@implementation Car
@dynamic brand;
@dynamic model;
@dynamic year;
@dynamic color;
@dynamic engineSize;
@dynamic weight;
@dynamic image;
@end
addViewController.h(不包含AppDelegate,因为它几乎都是标准的并且似乎可以正常工作。我所做的所有编码都在addview控制器中):
#import <Cocoa/Cocoa.h>
@interface AddViewController : NSWindowController{
}
@property (weak) IBOutlet NSTextField *brandField;
@property (weak) IBOutlet NSTextField *modelField;
@property (weak) IBOutlet NSTextField *yearField;
@property (weak) IBOutlet NSTextField *weightField;
@property (weak) IBOutlet NSTextField *engineSizeField;
@property (weak) IBOutlet NSTextField *colorField;
@property (weak) IBOutlet NSImageView *imageField;
- (IBAction)saveCar:(id)sender;
@end
AddViewController.m:
#import "AddViewController.h"
#import "AppDelegate.h"
#import "Car.h"
@interface AddViewController ()
@end
@implementation AddViewController
@synthesize brandField;
@synthesize modelField;
@synthesize yearField;
@synthesize engineSizeField;
@synthesize weightField;
@synthesize colorField;
@synthesize imageField;
- (id)initWithWindow:(NSWindow *)window
{
self = [super initWithWindow:window];
if (self) {
// Initialization code here.
}
return self;
}
- (void)windowDidLoad
{
[super windowDidLoad];
// Implement this method to handle any initialization after your window controller's window has been loaded from its nib file.
}
- (IBAction)saveCar:(id)sender {
NSManagedObjectContext *context = [Car managedObjectContext]; //This doesn't work here "no known class method"
Car *newCar = [[Car alloc] initWithEntity:@"Car" insertIntoManagedObjectContext:Car.managedObjectContext]; //compiler complains about this, property not found.
newCar.brand = [brandField stringValue];
newCar.model = [modelField stringValue];
newCar.year = [yearField stringValue];
newCar.weight = [weightField objectValue];
newCar.engineSize = [engineSizeField objectValue];
newCar.color = [colorField stringValue];
newCar.image = imageField;
}
@end
最佳答案
您需要创建一个managedObjectContext。
通常在appDelegate中完成。
苹果有一篇很好的文章:Apple documentation
关于objective-c - NSManagedObjectContext,声明在哪里?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/11894143/