我使用NSCoder。MyApplicationData
@synthesize categories;
- (void)encodeWithCoder:(NSCoderforKey:ITEMS_KEY];}
-(id)initWithCoder:(NSCoder'NSCoder' may not r
decodeDouble on NSCoder返回一个非可选的值,但我想确定一个值在编码之前是否为零。var optionalDouble: Double?= nil
if let optionalDouble { optionalDouble = aDecoder.decodeDouble(forKey: