将NSDictionary转换为JSON

我有一个核心数据实体签出，它只有一个可转换的属性，并设置为[String:Any]：

 cart : [String:Any]

以下函数用于从核心数据中检索值：

 func getCheckOutItems()->  [NSDictionary]{
    let request : NSFetchRequest<Checkout> = Checkout.fetchRequest()
    request.propertiesToFetch = ["cart"]
    request.resultType = .dictionaryResultType
    var checkout : [NSDictionary]!
    var cart : [String:Any]!
    do{
        checkout = try context.fetch(request)
    }catch{
        print ("Error fetching data")
    }
    return checkout
}

这是为了产生如下json结果：

 {
    "fcm_token": "tokden",
    "cart": [{
            "entity": 1,
            "quantity": 1,
            "id": 428,
            "price": 80,
            "date": "30 Jan 2018",
            "seat_no": 20,
            "type": "bus",
            "item": "STANDARD",
            "schedule_id": 132
        },
        {
            "entity": 1,
            "quantity": 1,
            "id": 1539,
            "price": 110,
            "date": "30 Jan 2018",
            "seat_no": 7,
            "type": "bus",
            "item": "EXECUTIVE",
            "schedule_id": 131
        },
        {
            "entity": 1,
            "quantity": 1,
            "id": 282,
            "price": 40,
            "date": "30 Jan 2018",
            "seat_no": 1,
            "type": "bus",
            "item": "STANDARD",
            "schedule_id": 114
        }
    ],
    "telco": "something",
    "email": "email"
}

主要的问题是，我需要从核心数据中删除键，该键突出显示为cart:{以获得上述格式的JSON。但事实证明，这非常难以捉摸，很难实现

 {
    "fcm_token": "tokden",
    "cart": [{
        **"cart": {**
            "entity": 1,
            "quantity": 1,
            "id": 428,
            "price": 80,
            "date": "30 Jan 2018",
            "seat_no": 20,
            "type": "bus",
            "item": "STANDARD",
            "schedule_id": 132
        }
    }, {
        "cart": {
            "entity": 1,
            "quantity": 1,
            "id": 1539,
            "price": 110,
            "date": "30 Jan 2018",
            "seat_no": 7,
            "type": "bus",
            "item": "EXECUTIVE",
            "schedule_id": 131
        }
    }, {
        "cart": {
            "entity": 1,
            "quantity": 1,
            "id": 282,
            "price": 40,
            "date": "30 Jan 2018",
            "seat_no": 1,
            "type": "bus",
            "item": "STANDARD",
            "schedule_id": 114
        }
    }],
    "telco": "something",
    "email": "email"
}

如何格式化此结果，以消除cart键，从而按照前面的指示格式化json。我对swift非常陌生，似乎很难理解这个问题。

您可以使用flatMap。试试这个

let cartItems = getCheckOutItems() as? [[String:Any]]
var cart = [String:Any]()
cart["cart"] = cartItems?.flatMap({ $0.flatMap { $0.value } })
cart["telco"] = "something"
cart["fcm_token"] = "tokden"
cart["email"] = "email"
let jsonData = try? JSONSerialization.data(withJSONObject: cart, options: [])
let jsonString = String(data: jsonData!, encoding: .utf8)
print("Printing JSON \(jsonString)")

---

首先，使用Swift 4 Jain解析器

let cartItems = getCheckOutItems() as? [[String:Any]]
var cart = [String:Any]()
cart["cart"] = cartItems?.flatMap({ $0.flatMap { $0.value } })
cart["telco"] = "something"
cart["fcm_token"] = "tokden"
cart["email"] = "email"
let jsonData = try? JSONSerialization.data(withJSONObject: cart, options: [])
let jsonString = String(data: jsonData!, encoding: .utf8)
print("Printing JSON \(jsonString)")