Generic UITableView adapter with sections

SectionedTableViewAdapter.swift

//: Playground - noun: a place where people can play

import UIKit

protocol SectionModel {
    var count: Int { get }
    
    func cell(at: Int) -> UITableViewCell
    func selected(at: Int)
}

class Adapter: NSObject {
    let sections: [SectionModel]
    
    init(sections: [SectionModel]) {
        self.sections = sections
    }
}

extension Adapter: UITableViewDelegate, UITableViewDataSource {
    func numberOfSections(in tableView: UITableView) -> Int {
        return sections.count
    }
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return sections[section].count
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let section = sections[indexPath.section]
        return section.cell(at: indexPath.row)
    }
    
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let section = sections[indexPath.section]
        section.selected(at: indexPath.row)
    }
}

protocol Adaptable {
    associatedtype Model
    
    func adapt(model: Model)
}

class GenericSectionModel<Model, Cell>: SectionModel where Cell: UITableViewCell, Cell: Adaptable, Cell.Model == Model {
    typealias ModelCellClosure = (Model, Cell) -> ()
    
    private let items: [Model]
    private lazy var cells: [Cell] = self.createCells()
    
    var onSelected: ModelCellClosure? = nil
    
    var count: Int {
        return items.count
    }
    
    init(items: [Model]) {
        self.items = items
    }
    
    func cell(at: Int) -> UITableViewCell {
        return cells[at]
    }
    
    func createCells() -> [Cell] {
        return items.map { m in
            let c = Cell()
            c.adapt(model: m)
            return c
        }
    }
    
    func selected(at: Int) {
        let m = items[at]
        let c = cells[at]
        onSelected?(m, c)
    }
}

extension UITableView {
    func setAdapter(_ adapter: Adapter) {
        dataSource = adapter
        delegate = adapter
        reloadData()
    }
}


// Usage
struct User {
    let name: String
}
class UserCell: UITableViewCell, Adaptable {
    func adapt(model: User) {
        textLabel?.text = model.name
    }
}

struct Account {
    let id: String
}
class AccountCell: UITableViewCell, Adaptable {
    func adapt(model: Account) {
        textLabel?.text = model.id
        textLabel?.textColor = UIColor.red
    }
}

let users = [User(name: "Test User 0"),
             User(name: "Test User 1"),
             User(name: "Test User 2"),
             User(name: "Test User 3"),
             User(name: "Test User 4"),
             User(name: "Test User 5"),
             User(name: "Test User 6")]
let accs = [Account(id: "test_acc")]

let usersSection = GenericSectionModel<User, UserCell>(items: users)
usersSection.onSelected = { m, c in
    print(m)
    print(c)
}
let accountsSection = GenericSectionModel<Account, AccountCell>(items: accs)

let adapter = Adapter(sections: [usersSection, accountsSection])

let table = UITableView(frame: CGRect(x: 0, y: 0, width: 200, height: 400), style: .grouped)
table.setAdapter(adapter)