我试图了解如何使用对象列表和UICollectionView实现MVVM。我不了解如何实现用户迭代->模型流程。
我已经设置了一个test application,Model只是一个带有Int的类,而View是一个UICollectionViewCell,它显示带有相应Int值的文本,并具有加,减和删除按钮以进行增,减并分别删除一个元素。 每个条目看起来像: 我想知道使用MVVM和RxSwift更新/删除单元格的最佳方法。
我有一个随机生成的Int值列表
let items: [Model]
仅具有Int值的模型
class Model {
var number: Int
init(_ n: Int = 0) {
self.number = n
}
}
仅包含模型并具有Observable的ViewModel类
class ViewModel {
var value: Observable<Model>
init(_ model: Model) {
self.value = Observable.just(model)
}
}
还有细胞
class Cell : UICollectionViewCell {
class var identifier: String { return "\(self)" }
var bag = DisposeBag()
let label: UILabel
let plus: UIButton
let minus: UIButton
let delete: UIButton
....
var viewModel: ViewModel? = nil {
didSet {
....
viewModel.value
.map({ "number is \($0.number)" })
.asDriver(onErrorJustReturn: "")
.drive(self.label.rx.text)
.disposed(by: self.bag)
....
}
}
}
我不清楚该怎么做,是如何将按钮连接到相应的动作,然后再更新模型和视图。
Cell的ViewModel负责吗?应该是接收tap事件,更新Model然后更新视图的人吗?
在删除情况下,单元格的删除按钮需要从数据列表中删除当前模型。如何在不将所有内容混合在一起的情况下完成此操作?
答案 0 :(得分:3)
以下是GitHub中具有以下更新的项目:https://github.com/dtartaglia/RxCollectionViewTester
我们要做的第一件事是概述所有输入和输出。输出应该是视图模型结构的成员,输入应该是输入结构的成员。
在这种情况下,我们从单元格中获得了三个输入:
struct CellInput {
let plus: Observable<Void>
let minus: Observable<Void>
let delete: Observable<Void>
}
单元格本身的一个输出(标签),单元格父级的两个输出(可能是视图控制器的视图模型)。
struct CellViewModel {
let label: Observable<String>
let value: Observable<Int>
let delete: Observable<Void>
}
我们还需要设置单元格以接受工厂功能,以便它可以创建视图模型实例。该单元还需要能够重置自身:
class Cell : UICollectionViewCell {
var bag = DisposeBag()
var label: UILabel!
var plus: UIButton!
var minus: UIButton!
var delete: UIButton!
// code to configure UIProperties omitted.
override func prepareForReuse() {
super.prepareForReuse()
bag = DisposeBag() // this resets the cell's bindings
}
func configure(with factory: @escaping (CellInput) -> CellViewModel) {
// create the input object
let input = CellInput(
plus: plus.rx.tap.asObservable(),
minus: minus.rx.tap.asObservable(),
delete: delete.rx.tap.asObservable()
)
// create the view model from the factory
let viewModel = factory(input)
// bind the view model's label property to the label
viewModel.label
.bind(to: label.rx.text)
.disposed(by: bag)
}
}
现在,我们需要构建视图模型的init方法。这是所有实际工作发生的地方。
extension CellViewModel {
init(_ input: CellInput, initialValue: Int) {
let add = input.plus.map { 1 } // plus adds one to the value
let subtract = input.minus.map { -1 } // minus subtracts one
value = Observable.merge(add, subtract)
.scan(initialValue, accumulator: +) // the logic is here
label = value
.startWith(initialValue)
.map { "number is \($0)" } // create the string from the value
delete = input.delete // delete is just a passthrough in this case
}
}
您会注意到,视图模型的init方法比工厂功能提供的更多。视图控制器在创建工厂时将提供额外的信息。
视图控制器将在其viewDidLoad
中添加它:
viewModel.counters
.bind(to: collectionView.rx.items(cellIdentifier: "Cell", cellType: Cell.self)) { index, element, cell in
cell.configure(with: { input in
let vm = CellViewModel(input, initialValue: element.value)
// Remember the value property tracks the current value of the counter
vm.value
.map { (id: element.id, value: $0) } // tell the main view model which counter's value this is
.bind(to: values)
.disposed(by: cell.bag)
vm.delete
.map { element.id } // tell the main view model which counter should be deleted
.bind(to: deletes)
.disposed(by: cell.bag)
return vm // hand the cell view model to the cell
})
}
.disposed(by: bag)
对于上述示例,我假设:
counters
类型为Observable<[(id: UUID, value: Int)]>
,来自视图控制器的视图模型。values
类型为PublishSubject<(id: UUID, value: Int)>
,并输入到视图控制器的视图模型中。deletes
类型为PublishSubject<UUID>
,并输入到视图控制器的视图模型中。视图控制器的视图模型的构建遵循与单元格相同的模式:
输入:
struct Input {
let value: Observable<(id: UUID, value: Int)>
let add: Observable<Void>
let delete: Observable<UUID>
}
输出:
struct ViewModel {
let counters: Observable<[(id: UUID, value: Int)]>
}
逻辑:
extension ViewModel {
private enum Action {
case add
case value(id: UUID, value: Int)
case delete(id: UUID)
}
init(_ input: Input, initialValues: [(id: UUID, value: Int)]) {
let addAction = input.add.map { Action.add }
let valueAction = input.value.map(Action.value)
let deleteAction = input.delete.map(Action.delete)
counters = Observable.merge(addAction, valueAction, deleteAction)
.scan(into: initialValues) { model, new in
switch new {
case .add:
model.append((id: UUID(), value: 0))
case .value(let id, let value):
if let index = model.index(where: { $0.id == id }) {
model[index].value = value
}
case .delete(let id):
if let index = model.index(where: { $0.id == id }) {
model.remove(at: index)
}
}
}
}
}
答案 1 :(得分:2)
我正在这样做:
ViewModel.swift
import Foundation
import RxSwift
import RxCocoa
typealias Model = (String, Int)
class ViewModel {
let disposeBag = DisposeBag()
let items = BehaviorRelay<[Model]>(value: [])
let add = PublishSubject<Model>()
let remove = PublishSubject<Model>()
let addRandom = PublishSubject<()>()
init() {
addRandom
.map { _ in (UUID().uuidString, Int.random(in: 0 ..< 10)) }
.bind(to: add)
.disposed(by: disposeBag)
add.map { newItem in self.items.value + [newItem] }
.bind(to: items)
.disposed(by: disposeBag)
remove.map { removedItem in
self.items.value.filter { (name, _) -> Bool in
name != removedItem.0
}
}
.bind(to: items)
.disposed(by: disposeBag)
}
}
Cell.swift
import Foundation
import Material
import RxSwift
import SnapKit
class Cell: Material.TableViewCell {
var disposeBag: DisposeBag?
let nameLabel = UILabel(frame: .zero)
let valueLabel = UILabel(frame: .zero)
let removeButton = FlatButton(title: "REMOVE")
var model: Model? = nil {
didSet {
guard let (name, value) = model else {
nameLabel.text = ""
valueLabel.text = ""
return
}
nameLabel.text = name
valueLabel.text = "\(value)"
}
}
override func prepare() {
super.prepare()
let textWrapper = UIStackView()
textWrapper.axis = .vertical
textWrapper.distribution = .fill
textWrapper.alignment = .fill
textWrapper.spacing = 8
nameLabel.font = UIFont.boldSystemFont(ofSize: 24)
textWrapper.addArrangedSubview(nameLabel)
textWrapper.addArrangedSubview(valueLabel)
let wrapper = UIStackView()
wrapper.axis = .horizontal
wrapper.distribution = .fill
wrapper.alignment = .fill
wrapper.spacing = 8
addSubview(wrapper)
wrapper.snp.makeConstraints { make in
make.edges.equalToSuperview().inset(8)
}
wrapper.addArrangedSubview(textWrapper)
wrapper.addArrangedSubview(removeButton)
}
}
ViewController.swift
import UIKit
import Material
import RxSwift
import SnapKit
class ViewController: Material.ViewController {
let disposeBag = DisposeBag()
let vm = ViewModel()
let tableView = UITableView()
let addButton = FABButton(image: Icon.cm.add, tintColor: .white)
override func prepare() {
super.prepare()
view.addSubview(tableView)
tableView.snp.makeConstraints { make in
make.edges.equalToSuperview()
}
addButton.pulseColor = .white
addButton.backgroundColor = Color.red.base
view.layout(addButton)
.width(48)
.height(48)
.bottomRight(bottom: 16, right: 16)
addButton.rx.tap
.bind(to: vm.addRandom)
.disposed(by: disposeBag)
tableView.register(Cell.self, forCellReuseIdentifier: "Cell")
vm.items
.bind(to: tableView.rx.items) { (tableView, row, model) in
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell") as! Cell
cell.model = model
cell.disposeBag = DisposeBag()
cell.removeButton.rx.tap
.map { _ in model }
.bind(to: self.vm.remove)
.disposed(by: cell.disposeBag!)
return cell
}
.disposed(by: disposeBag)
}
}
请注意,常见的错误是在Cell内仅创建一次DisposeBag,这将在触发操作时引起混乱。
每次重新使用Cell时,都必须重新创建 DisposeBag 。
可以找到完整的工作示例here。