How to pass a value while parsing a nested JSON in Swift - ios

Question

I would like to pass the parent area Id to it's children areas while parsing the nested JSON structure as per the attached response, Here I would like to insert 'parentId' for each children which will link to it's immediate parent area,
{
"areas": [
{
"id": "271341877549072423",
"name": "Breeze Office Tower",
"children": [
{
"id": "271341877549072424",
"name": "100 flinders street",
"position": 0,
"children": []
},
{
"id": "271341877549130929",
"name": "100 flinders street",
"position": 1,
"children": []
},
{
"id": "271341877549072425",
"name": "100 Flinder Stree",
"position": 2,
"children": [
{
"id": "271341877549072426",
"name": "Büro",
"position": 0,
"children": [
{
"id": "271341877549072427",
"name": "Dachgeschoß",
"position": 0,
"children": []
}
]
}
]
},
{
"id": "271341877549130931",
"name": "100 Flinder Stree",
"position": 3,
"children": [
{
"id": "271341877549130933",
"name": "Büro",
"position": 0,
"children": [
{
"id": "271341877549130935",
"name": "Dachgeschoß",
"position": 0,
"children": []
}
]
}
]
}
]
}
]
}
My JSON Codable model struct looks like,
struct AreaModel: Decodable {
var areas: [NestedAreaModel]?
}
struct NestedAreaModel: Codable {
let areaId: String
let areaName: String
let children: [NestedAreaModel]
let hasChildren: Bool
var areaPosition: Int16?
var parentId: String?
var projectId: String?
enum CodingKeys: String, CodingKey {
case areaId = "id"
case areaName = "name"
case areaPosition = "position"
case children
}
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
self.areaId = try values.decode(String.self, forKey: .areaId)
self.children = try values.decode([NestedAreaModel].self, forKey: .children)
self.areaName = try values.decode(String.self, forKey: .areaName)
self.projectId = ORAUserDefaults.selectedProjectId()
self.areaPosition = try values.decodeIfPresent(Int16.self, forKey: .areaPosition)
if !self.children.isEmpty {
self.hasChildren = true
self.parentId = self.areaId
} else {
self.hasChildren = false
}
}
}
Here I am not able to set the parent Id, its pointing its own id always.

Answer 1

As I allready pointed out in the comments you would need to iterate over the decoded children and set their respective parentId to the current areaId.
One possible Solution would be:
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
self.areaId = try values.decode(String.self, forKey: .areaId)
// decode the children to a local var
var children = try values.decode([NestedAreaModel].self, forKey: .children)
self.areaName = try values.decode(String.self, forKey: .areaName)
self.projectId = ORAUserDefaults.selectedProjectId()
self.areaPosition = try values.decodeIfPresent(Int16.self, forKey: .areaPosition)
// if there are children loop over them and assign your id
if !children.isEmpty {
self.hasChildren = true
for (index, _ ) in children.enumerated(){
children[index].parentId = areaId
}
} else {
self.hasChildren = false
}
// assign to self
self.children = children
}
Tested with the given JSON:
let decoded = try JSONDecoder().decode(AreaModel.self, from: data)
print(decoded.areas?[0].areaId)
print(decoded.areas?[0].children[0].parentId)
Result:
Optional("271341877549072423")
Optional("271341877549072423")
Remarks:
Regarding your comment on complexity:
children[index].parentId = areaId runs exactly once per child no matter of the level deapth. So this function is (O)n.