Swift array map with comma before append new value - ios

Question

i have this following data structure in my Realm object
var tags = List<Tag>()
"tags": [
{
"tagId": "80069",
"tagName": "A"
},
{
"tagId": "80070",
"tagName": "B"
},
{
"tagId": "80071",
"tagName": "C"
},
{
"tagId": "80073",
"tagName": "D"
}
]
So what i want to achieve is, I map all my tag name into my new array
this is my code
let realmObject = self.realm.objects(MyDTO.self)
let array = Array(realmOutletList).map{Array($0.tags).map{$0.tagName!}.joined(separator: ",")}
it prints out this
["A,B,C", "A,C,D", "B,C,D"]
What I want to achieve is like
["A","B","C", "A","C","D", "B","C","D"]
I need that kind of array because I am going to create a Set from the array and then compare with another array
The compared array will be like
["A","B","C", "A","C","D", "B","C","D"]
because of the compared Array and the realmObject Array is different, it always shows false when i use
let subset = filterSet.isSubset(of: mySet)
Can anyone guide me please??
Thanks

Answer 1

Let's walk through solving the issue:
Consider that you have:
let originalArray = ["A,B,C", "A,C,D", "B,C,D"]
First, we need to separate each string in originalArray by "," character, so we could do:
let modifiedArray = originalArray.map { $0.components(separatedBy: ",") }
We map it to transform each string to a strings array (separation).
So far, the output of modifiedArray would be:
[["A", "B", "C"], ["A", "C", "D"], ["B", "C", "D"]]
which is an array of strings array.
Second, we need to spilt each -string- array in modifiedArray (having one reduced strings array instead), so we could do:
var final = [String]()
for array in modifiedArray {
for string in array {
final.append(string)
}
}
OR by using reduce
let finalArray = modifiedArray.reduce([], +)
Therefore, finalArray would be:
["A", "B", "C", "A", "C", "D", "B", "C", "D"]
which is the desired result.
Conclusion
For a fully one-lined answer (following the high-order functions approach):
let originalArray = ["A,B,C", "A,C,D", "B,C,D"]
let desiredArray = originalArray.map { $0.components(separatedBy: ",") }.reduce([], +)
print(desiredArray) // ["A", "B", "C", "A", "C", "D", "B", "C", "D"]

Answer 2

Well, it's quite easy:
This
let array = Array(realmOutletList).map{Array($0.tags).map{$0.tagName!}.joined(separator: ",")}
should be this
let array = Array(realmOutletList).flatMap{Array($0.tags).map{$0.tagName!}}
That's all. And you will get your ["A","B","C", "A","C","D", "B","C","D"].