Traverse nsdictionary in swift - ios

Question

I am new to swift.
I have my dictionary as
monthData =
{
"2018-08-10" = {
accuracy = 71;
attempted = 7;
correct = 5;
reward = Bronze;
};
"2018-08-12" = {
accuracy = 13;
attempted = 15;
correct = 2;
reward = "";
};
"2018-08-13" = {
accuracy = 33;
attempted = 15;
correct = 5;
reward = "";
};
"2018-08-14" = {
accuracy = 100;
attempted = 15;
correct = 15;
reward = Gold;
};
"2018-08-16" = {
accuracy = 73;
attempted = 15;
correct = 11;
reward = Silver;
};
"2018-08-21" = {
accuracy = 26;
attempted = 15;
correct = 4;
reward = "";
};
"2018-08-23" = {
accuracy = 46;
attempted = 15;
correct = 7;
reward = "";
};
}
I want to get all the dates for which reward is Gold
Can anyone please help me do that?
What I have tried 'till now is:
for (key,value) in monthData{
let temp = monthData.value(forKey: key as! String) as! NSDictionary
for (key1,value1) in temp{
if((value1 as! String) == "Gold"){
print("keyFINAL \(key)")
}
}
but it outputs the error Could not cast value of type '__NSCFNumber' to 'NSString'

Answer 1

The error occurs because when you are iterating the dictionary you force cast the Int values to String which is not possible
The (highly) recommended Swift way is to use the filter function. This is much more efficient than a loop.
In the closure $0.1 represents the value of the current dictionary ($0.0 would be the key). The result is an array of the date strings.
let data : [String:Any] = ["monthData" : ["2018-08-10": ["accuracy" : 71, "attempted" ... ]]]
if let monthData = data["monthData"] as? [String:[String:Any]] {
let goldData = monthData.filter { $0.1["reward"] as? String == "Gold" }
let allDates = Array(goldData.keys)
print(allDates)
}
The code safely unwraps all optionals.
However if there is only one Gold entry the first function is still more efficient than filter
if let monthData = data["monthData"] as? [String:[String : Any]] {
if let goldData = monthData.first( where: {$0.1["reward"] as? String == "Gold" }) {
let goldDate = goldData.key
print(goldDate)
}
}
In Swift avoid the ObjC runtime (value(forKey:)) and Foundation collection types (NSDictionary) as much as possible.

Answer 2

From the first for in loop, you are getting the NSDictionary in temp variable
"2018-08-16" = {
accuracy = 73;
attempted = 15;
correct = 11;
reward = Silver;
};
So, you should directly check .value(forKey:) on temp and get the value for reward.
You should try it like this
for (key,value) in monthData {
let temp = monthData.value(forKey: key as! String) as! NSDictionary
if(((temp.value(forKey: "reward")) as! String) == "Gold"){
print("keyFINAL \(key)")
}
}
Try and share results
EDIT
Please checkout the answer from vadian for in-depth explanation and pure swift approach to achieve the same.
Thanks