Swift: is it possible to iterate and call an array of functions?

Question

I am trying to simplify the following repetitive code:

var cells = [Cell]()
var modules = [Module]()
var fields = [Field]()

root.child("cells").observeSingleEvent(of: .value) { (snapshot) in
    guard let dict = snapshot.value as? [String: Any],
        let cell = Cell(dict: dict) else { return }
    cells.append(cell)
}

root.child("modules").observeSingleEvent(of: .value) { (snapshot) in
    guard let dict = snapshot.value as? [String: Any],
        let module = Module(dict: dict) else { return }
    modules.append(module)
}

root.child("fields").observeSingleEvent(of: .value) { (snapshot) in
    guard let dict = snapshot.value as? [String: Any],
        let field = Field(dict: dict) else { return }
    fields.append(field)
}

Cell, Module, Field are custom struct. I am thinking whether it's possible to put their initiators init?(dict: [String: Any]) in an array and pass in dict to each of them.

user2908517 · Accepted Answer · 2018-02-22 05:02:28Z

I think you will need to make your structs adopt one protocol for that:

protocol InitializableWithDictionary {
    init?(dict: [String : Any])
}

struct Cell: InitializableWithDictionary {

    //...

    init?(dict: [String : Any]){
        //...
    }
}

struct Module: InitializableWithDictionary {

   //...

    init?(dict: [String : Any]){
       //...
    }
}

struct Field: InitializableWithDictionary {

    //...

    init?(dict: [String : Any]){
        //...
    }
}

var cells: [InitializableWithDictionary] = [Cell]()
var modules: [InitializableWithDictionary] = [Module]()
var fields: [InitializableWithDictionary] = [Field]()

root.child("cells").observeSingleEvent(of: .value) { (snapshot) in

        guard let dict = snapshot.value as? [String: Any] else { return }

        let array: [InitializableWithDictionary.Type] = [Cell.self, Module.self, Field.self]

        array.forEach {

            if let element = $0.init(dict: dict) {

                switch element {

                case is Cell: cells.append(element)
                case is Module: modules.append(element)
                case is Field: fields.append(element)
                default: break
                }

            } else { return }
    }
}

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