Question

当我想在CoreData中存储标量时，我已经阅读了很多文章，他们说要明确地转换为NSNumber：

@property (nonatomic, assign) NSInteger value;

- (NSInteger)value
{
    return [value integerValue];
}

- (void)setValue:(NSInteger)val
{
    value = [NSNumber numberWithInteger:val];
}

但是在我们的旧项目中，我们有很多属性，我们不进行这些操作（并且它们没有自定义访问器）！为什么会这样？

示例代码

宣言。标量值不是短暂的。

@interface ProductProperty : NSManagedObject

@property (nonatomic, strong, readonly) NSString * propertyID;
@property (nonatomic, strong, readonly) NSString * title;
@property (nonatomic, strong, readonly) NSSet * values;
@property (nonatomic, assign, readonly) BOOL filter;
@property (nonatomic, strong, readonly) NSDate *update;
@property (nonatomic, strong, readonly) NSNumber *index;
@property (nonatomic, assign, readonly) BOOL system;

@end


#import "ProductProperty.h"

@implementation ProductProperty

@dynamic propertyID;
@dynamic title;
@dynamic values;
@dynamic filter;
@dynamic update;
@dynamic index;
@dynamic system;

@end

映射到对象。如果收到的JSON与现有JSON不同，则调用。否则它从CoreData存储中获取。

- (void)updateProperties:(NSArray*)properties
{
    for (NSDictionary *_property in properties) {
        NSString *propertyID = [_property objectForKey:@"id"];

        ProductProperty *property = [state.productPropertiesWithIDs objectForKey:propertyID];
        if (!property) {
            property = [state.ctx newObjectWithEntityName:ProductProperty.entityName];
            property.propertyID = propertyID;
            [state.productPropertiesWithIDs setObject:property forKey:propertyID];
        }

        property.update = state.update;
        property.title = [_property objectForKey:@"title"];
        property.filter = [_property objectForKey:@"filter"] ? [[_property objectForKey:@"filter"] boolValue] : YES;
        property.index = [propertyIndexes objectForKey:propertyID] ? [propertyIndexes objectForKey:propertyID] : [NSNumber numberWithInt:propertyIndex++];
        property.system = [SYSTEM_PROPERTY_IDS containsObject:propertyID] ? YES : NO;

        [self updatePropertyValues:[_property objectForKey:@"values"] forProperty:property];
    }
}

- (ProductProperty*)productPropertyWithID:(NSString*)propertyId error:(NSError**)error
{
    NSFetchRequest *req = [ProductProperty request];
    req.predicate = [NSPredicate predicateWithFormat:@"propertyID == %@", propertyId];
    return [[ctx executeFetchRequest:req error:error] lastObject];
}

Answer 1

答案是，因为iOS 5 CoreData支持为标量自动生成访问器，所以我不需要手动实现它们。

在CoreData中存储标量值（NSInteger，BOOL，double）而不转换为NSNumber

示例代码

1 个答案: