How to save to and read from a NSObject

问题

I have two NSObject's.

@interface Car : NSObject{
     @property (strong) NSSet *cars;
}

and

@interface Model : NSObject{
     @property (strong) UIImage *picture;
     @property (strong) NSString *name;
}

Basically the object Car has a NSSet cars and each object of the NSSet cars has the properties picture and name.

How can I relate this two NSObject's and how can I save a string or image to the Car NSSet using the properties of the Model NSObject. Thanks.

回答1:

For easy adding or removing, your "cars" property should be declared as a NSMutableSet.

And assuming your single Car object is named "listOfCars", here is one way to do what (I think) you are trying to do:

Model * newModel = [[Model alloc] init];
if(newModel)
{
    newModel.picture = [UIImage imageNamed: @"Edsel.jpg"];
    newModel.name = @"Ugly Car";

    [listOfCars.cars addObject: newModel];
}

And, in your Car .m file, do something like this:

- (id) init
{
    self = [super init];
    if(self)
    {
        _cars = [[NSMutableSet alloc] init];
    }
    return(self);
}

The init method is the only place you should be referring to the underlying variable for your "cars" property. Everywhere else it should be "listOfCars.cars" or "self.cars" if you're referring to the cars set from within the Car object.

来源：https://stackoverflow.com/questions/17244823/how-to-save-to-and-read-from-a-nsobject