Finding a Struct in nested struct

Question

I have been trying to find a struct inside the list of nested structs. Can anyone help me on this?

struct Places: PlacesProtocol {
    private(set) var id: String
    private(set) var name: String
    private(set) var childPlaces: [PlacesProtocol]?

    init(json: JSON) {
        self.name = json[“Name”]
        self.id = json[“Id”]
        self. childPlaces = json[“ChildPlaces”].arrayValue.map { Places(json: $0) }
    }

JSON:

{
    "Id": "1",
    "Name": "Place 1",
    "ChildPlaces": [{
        "Id": "12",
        "Name": "Place 2",
        "ChildPlaces": [{
            "Id": "123",
            "Name": "Place 3",
            "ChildPlaces": [{
                "Id": "1234",
                "Name": "Place 4",
                "ChildPlaces": null
            }]
        }, {
            "Id": "13",
            "Name": "Place 5",
            "ChildPlaces": null
        }]
    }]
}

I have tried this:

nestedStruct.filter { $0.id == "13" }

I am able to parse this JSON in to the nested structure and I am trying to find a struct with Id. I have tried filter but it just filters only the first layer of the nested struct. Is there a way I can build recursive filter to find the struct which is deep inside the nested struct.

I would advise against an optional array property in this case. If there are no places, just use an empty array. It doesn't allocate a buffer on the heap until it needs to store any elements, so it doesn't take up any extra resources. It's easier to work with (e.g. can be iterated directly) — Alexander
– Alexander, Commented Jan 7, 2018 at 3:47
What is private(set) for? If you want a constant declare the members as let — vadian
– vadian, Commented Jan 7, 2018 at 6:03

rmaddy · Accepted Answer · 2018-01-07 04:01:14Z

2

You could use a recursive function to perform a depth first search. Here's a rough example:

extension Place {

    depthFirstSearch(where closure: (Place) -> Bool) -> Place? {
        if closure(self) { return self }
        else {
            return self.chlidPlaces.first(where: { 
                $0.depthFirstSearch(where: closure)
            })
        }
    }
}


let placeID13 = mainPlace.depthFirstSearch(where: { $0.id == "13" })

edited Jan 7, 2018 at 4:01

rmaddy

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answered Jan 7, 2018 at 3:43

Alexander

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2 Comments

Vijay Over a year ago

I have tried this and getting this error. Cannot convert value of type 'Place?' to closure result type 'Bool' @Alexander

Alexander Over a year ago

@Vijay Not sure how you expect us to be able to help you without a concrete test case to work with.

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