Swift3错误：无法将类型'（）'的值分配给类型[[customObject]？

Question

I have a custom class containing 2 properties as below

class CustomObjectClass: NSObject {

    override init() {
        //AppointmentsDetails
    }

    var customName:String?
    var customDate:Date?
}

I am try to create group object of custom class by date using dictionary like Date:[CustomObjectClass]

While trying to iterate through object and add to the dictionary I get error : Cannot assign value of type () to type [CustomObjectClass]?

code is below

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    override func viewWillAppear(_ animated: Bool) {

        var tempCustObj = CustomObjectClass()
        var tempCustList = [CustomObjectClass]()

        for obj in customlist{
            dateDict[obj.customDate!] = tempCustList.append(obj)
            //error :  Cannot assign value of type '()' to type '[CustomObjectClass]?'
        }
    }

    var custObj = CustomObjectClass()
    var customlist = [CustomObjectClass]()
    var dateDict = [Date:[CustomObjectClass]]()
}

can some one suggest a solution for this

Answer 1

Swift 3

tempCustList.append(obj) returns Void ("nothing") so you can't add it to the dictionary

If you want to add obj , first you'd need to check if there's an array or not (create a new one otherwise), append the element to the array and finally set the value of the dictionary.

for obj in customlist {
    if classesByDate[obj.customDate!] == nil {
        classesByDate[obj.customDate!] = [obj]
    } else {
        classesByDate[obj.customDate!]!.append(obj)
    }
}

---

Swift 4

Thanks to the new Dictionary API, you can simply use an initializer:

let classesByDate = Dictionary(grouping: customlist) { $0.customDate! }