Convert array to dictionary in Swift

Question

I am having trouble coming up with an algorithm to convert an array into a dictionary. The array has the following structure:

let array = [
    Parameter(type: "string", name: "name1", value: "bar", parent: nil),
    Parameter(type: "bool", name: "name2", value: true, parent: nil),
    Parameter(type: "array", name: "name3", value: [], parent: nil),
    Parameter(type: "bool", name: "name3.1", value: false, parent: "name3"),
    Parameter(type: "array", name: "name3.2", value: [], parent: "name3"),
    Parameter(type: "string", name: "name4.1", value: "baz", parent: "name3.2")
]

Parameter is a simple struct. Output should be a dictionary. In the example given above this should look something like this:

[
    "name1": "bar",
    "name2": true,
    "name3": [
        "name3.1": false,
        "name3.2": [
            "name4.1": "baz"
        ]
    ]
]

In the case a given struct does not have a parent it is pretty basic to implement but I am having trouble implementing the other case:

func makeDictionary(from array: [Parameter]) -> [String: Any] {
    var dictionary: [String: Any] = [:]
    for parameter in array {
        if let parent = parameter.parent {
            #warning("how to handle this case?")
        } else {
            dictionary[parameter.name] = parameter.value
        }
    }
    return dictionary
}

Since the array could be unordered how would I handle the case receiving the "name4.1" parameter before the array "name3.2" or the array "name3" is created and available in my dictionary?

Answer 1

To solve this we need to use recursion to connect parent objects with child objects. Here is a solution with one normal function that iterates over the top-level parents (that is objects without a parent) and then call a recursive function for any parent of type "array", that is a parent that might have children.

//Main function
func makeDictionary(from array: [Parameter]) -> [String: Any] {
    let parents = array.filter { $0.parent == nil }
    var dictionary = [String: Any]()

    for parent in parents {
        if parent.type == "array" {
            let child = allChildren(for: array.filter { $0.parent == parent.name }, in: array)
            dictionary[parent.name] = child
        } else {
            dictionary[parent.name] = parent.value
        }
    }
    return dictionary
}

//Recursive function
func allChildren(for children: [Parameter], in array: [Parameter]) -> [[String: Any]] {
    var result = [[String: Any]]()

    for child in children {
        if child.type == "array" {
            let children = allChildren(for: array.filter { $0.parent == child.name }, in: array)
            result.append([child.name: children])
        } else {
            result.append([child.name: child.value])
        }
    }
    return result
}

Example

let dictionary = makeDictionary(from: array)
print(dictionary)

["name3": [["name3.1": false], ["name3.2": [["name4.1": "baz"]]]], "name2": true, "name1": "bar"]