swift nested dictionary sorted result error

Question

the below source code results error like this:

"cannot assign value of type '[Dictionary<Int, Double>.Element]' (aka 'Array<(key: Int, value: Double)>') to type '[Int : Double]?' dateAndDict[date] = sortedDict"

Well, basically, what I am trying to do is sorting the nested Dictionary by Value.

source code:

let date = Date()
var dict = [2:4.0, 4:12.0 ,6:3.0,7:45.0, 8:15.0]

var dateAndDict:[Date:[Int:Double]]


let sortedDict = dict.sorted { currentElement , nextElement in
    
    return currentElement.value < nextElement.value
}


dateAndDict[date] = sortedDict

thanks in advance.