ios - 子类 NSManagedObject 以轻松初始化

Question

对于来自服务器 API 的模型，我使用这样的构造函数:

@implementation MenuAPIModel

-(instancetype)initWithServerData:(id)data{

    self = [super initWithServerData:data];
    return self;
}

-(void)performMapping{

    _basketId = self.serverData[@"basket_id"];
    _orderId = self.serverData[@"order_id"];
    _itemId = self.serverData[@"id"];
    _name = self.serverData[@"name"] == [NSNull null] ? @"" : self.serverData[@"persons"];
    _payedFrom = [self.dfDetail dateFromString:self.serverData[@"payed_from"]] == nil ? [self.dfBasic dateFromString:self.serverData[@"payed_from"]] : [self.dfDetail dateFromString:self.serverData[@"payed_from"]];
    _payedTill = [self.dfBasic dateFromString:self.serverData[@"payed_till"]] == nil ? [self.dfBasic dateFromString:self.serverData[@"payed_till"]] : [self.dfDetail dateFromString:self.serverData[@"payed_till"]];
    _persons = self.serverData[@"persons"] == [NSNull null] ? @"2-3" : self.serverData[@"persons"];
    _price = self.serverData[@"price"] == [NSNull null] ? @(0) : self.serverData[@"price"];
    _price3 = self.serverData[@"price3"] == [NSNull null] ? @(0) : self.serverData[@"price3"];
    _price12 = self.serverData[@"price12"] == [NSNull null] ? @(0) : self.serverData[@"price12"];
    _status = self.serverData[@"status"] == [NSNull null] ? @"not_payed" : self.serverData[@"persons"];
}

因此，我可以通过简单地编写来创建对象:[MenuAPIModel initWithServerData:data];

现在我将 NSManagedObject 子类化并想知道，我如何将 XCode 为我创建的这 4 个文件子类化，以使构造函数像上面的那样？

Answer 1

您可以创建一种可以具有以下实现的助手(这只是示例，所以我使用了 Swift):

static open func createObject <T : NSManagedObject> (_ objectType : T.Type, record : Dictionary<String, Any>? = nil, context : NSManagedObjectContext) -> (T)
{
    let newObject = NSEntityDescription.insertNewObject(forEntityName: String(describing: objectType), into: context)

    // Error never occured

    var typedNewObject = newObject as! T

    guard let trueRecord = record
    else
    {
        return typedNewObject
    }

    typedNewObject = updateObject(typedNewObject, record: trueRecord, context: context)

    return typedNewObject
}

static open func updateObject <T : NSManagedObject> (_ object : T, record : Dictionary<String, Any>, context : NSManagedObjectContext) -> (T)
{
    for (key, value) in record
    {
        setValue(value, key: key, object: object)
    }

    return object
}

static public func setValue (_ value : Any, key : String, object : NSManagedObject) -> (Void)
{
    object.setValue(value, forKey: key)
}

使用这些方法，您可以输入:

let myNewObject = Helper.createObject(YourClassName.self, record: yourDictionary, context: yourContext) // Helper, or any other class name you give it.

我希望它足够接近您的需要。