How can I prevent or stop dictionary values from being nill? - swift

Question

I have a dictionary and a array of strings
The keys and values are generated with for loop
for some reason , all values in dictionary are nill.
Create a empty dictionary
Create a string array
Create for loop to generate keys and values
keys become i.e. KEY_15.
values would be a random number
Create for loop to check if the dictionary contains any of the elements in the array
For each existing key that matches arr element, check if that key value is even or not i.e if(arr[0] == dictionary key)
if even, change dictionary value to 0 i.e. if arr contains element with string "Key_12" and dictionary contains a key with the name "Key_12", then value becomes 0.]
Making 2 for loops to match but problem still occurs
//Code Starts Here
var arr : [String] = ["KEY_10", "Bear", "KEY_23", "KEY_12"] // string array
var dic: [String : Int] = [:] //default dic
let ran: Int? = Int.random(in: 0...10) //generate random value
for i in 10...24{ //create elements to dic
let iAsString = String(i)
let stringWithZero = "KEY_" + iAsString
dic[stringWithZero] = ran!
}
for x in arr{
let dickeys: [String] = [String](dic.keys) //store keys
let element = x
for y in 0...dickeys.count-1{
let dicKey = dickeys[y]
if dicKey == element{ //never runs
if dic[x]! % 2 == 0{
dic.updateValue(0, forKey: x) //update value to 0
}
}
}
}

Answer 1

Your code works, but it isn't efficient.
Here is a cleaned up version:
var arr = ["KEY_10", "Bear", "KEY_23", "KEY_12"] // string array
var dic: [String : Int] = [:] //default dic
for i in 10...24 { //create elements to dic
dic["KEY_\(i)"] = Int.random(in: 0...10)
}
print(dic)
for x in arr {
if let value = dic[x] {
if value % 2 == 0 {
dic[x] = 0
}
}
}
print(dic)
Output:
["KEY_19": 2, "KEY_22": 5, "KEY_11": 7, "KEY_21": 3, "KEY_15": 8, "KEY_14": 6, "KEY_12": 6, "KEY_17": 9, "KEY_23": 3, "KEY_16": 1, "KEY_18": 1, "KEY_24": 4, "KEY_10": 0, "KEY_13": 8, "KEY_20": 1]
["KEY_19": 2, "KEY_22": 5, "KEY_11": 7, "KEY_21": 3, "KEY_15": 8, "KEY_14": 6, "KEY_12": 0, "KEY_17": 9, "KEY_23": 3, "KEY_16": 1, "KEY_18": 1, "KEY_24": 4, "KEY_10": 0, "KEY_13": 8, "KEY_20": 1]
Notes:
You should move the generation of the random Int into the first loop so that each key potentially gets a different random value.
Let Swift infer types wherever possible (eg. use var array = ["KEY_10"] instead of var array: [String] = ["KEY_10"]).
Use string interpolation to create "KEY_10" through "KEY_24".
To check if a key exists in a dictionary, just look it up. There is no need to loop over all of the keys of the dictionary. The value returned is an optional that is nil if the key doesn't exist. Use optional binding to unwrap that value.
if let value = dic[x] {
// we only get here if key x exists
// value is then the unwrapped value corresponding to key x
}
dic.updateValue(0, forKey: x) is better written as dic[x] = 0.