Binding to a datasource using RxDatasources - swift

Question

I have a list of models that I fetch from a server, and basically I get array of these:
struct ContactModel: Codable, Equatable {
static func == (lhs: ContactModel, rhs: ContactModel) -> Bool {
return lhs.name == rhs.name &&
lhs.avatar == rhs.avatar &&
lhs.job == rhs.job &&
lhs.follow == rhs.follow
}
let id: Int
let name: String
let avatar:String?
let job: JobModel?
let follow:Bool
enum CodingKeys: String, CodingKey {
case id, name, avatar, job, follow
}
}
So I want to show a list of contacts in my tableview.
Now I have this struct as well which is wrapper around this model:
struct ContactCellModel : Equatable, IdentifiableType {
static func == (lhs: ContactCellModel, rhs: ContactCellModel) -> Bool {
return lhs.model == rhs.model
}
var identity: Int {
return model.id
}
var model: ContactModel
var cellIdentifier = ContactTableViewCell.identifier
}
What I am trying to do, is to create datasource using RxDatasources, and bind to it, like this(ContactsViewController.swift):
let dataSource = RxTableViewSectionedAnimatedDataSource<ContactsSectionModel>(
configureCell: { dataSource, tableView, indexPath, item in
if let cell = tableView.dequeueReusableCell(withIdentifier: item.cellIdentifier, for: indexPath) as? BaseTableViewCell{
cell.setup(data: item.model)
return cell
}
return UITableViewCell()
})
but I am not sure what I should do right after. I tried something like this:
Observable.combineLatest(contactsViewModel.output.contacts, self.contactViewModel.changedStatusForContact)
.map{ (allContacts, changedContact) -> ContactsSectionModel in
//what should I return here?
}.bind(to: dataSource)
I use combineLatest, cause I have one more observable (self.contactViewModel.changedStatusForContact) that notifies when certain contact has been changed (this happens when you tap a certain button on a contact cell).
So what should I return from .map above in order to successfully bind to previously created dataSource?

Answer 1

You have to replace the contacts that have changed; all the contacts that were changed, but you can't do that because you aren't tracking all of them, only the most recent one. So you can't do it in a map. You need to use scan instead.
I made a lot of assumptions about code you didn't post, so the below is a compilable example. If your types are different, then you will have to make some changes:
func example(contacts: Observable<[ContactModel]>, changedStatusForContact: Observable<ContactModel>, tableView: UITableView, disposeBag: DisposeBag) {
let dataSource = RxTableViewSectionedAnimatedDataSource<ContactsSectionModel>(
configureCell: { dataSource, tableView, indexPath, item in
if let cell = tableView.dequeueReusableCell(withIdentifier: item.cellIdentifier, for: indexPath) as? BaseTableViewCell {
cell.setup(data: item.model)
return cell
}
return UITableViewCell() // this is quite dangerious. Better would be to crash IMO.
})
let contactsSectionModels = Observable.combineLatest(contacts, changedStatusForContact) {
(original: $0, changed: $1)
}
.scan([ContactsSectionModel]()) { state, updates in
// `state` is the last array handed to the table view.
// `updates` contains the values from the combineLatest above.
var contactModels = state.flatMap { $0.items.map { $0.model } }
// get all the contactModels out of the state.
if contactModels.isEmpty {
contactModels = updates.original
}
// if there aren't any, then update with the values coming from `contacts`
else {
guard let index = contactModels
.firstIndex(where: { $0.id == updates.changed.id })
else { return state }
contactModels[index] = updates.changed
}
// otherwise find the index of the contact that changed.
// and update the array with the changed contact.
return [ContactsSectionModel(
model: "",
items: updates.original
.map { ContactCellModel(model: $0) }
)]
// rebuild the section model and return it.
}
contactsSectionModels
.bind(to: tableView.rx.items(dataSource: dataSource))
.disposed(by: disposeBag)
}
typealias ContactsSectionModel = AnimatableSectionModel<String, ContactCellModel>
struct ContactCellModel: Equatable, IdentifiableType {
var identity: Int { model.id }
let model: ContactModel
let cellIdentifier = ContactTableViewCell.identifier
}
struct ContactModel: Equatable {
let id: Int
let name: String
let avatar: String?
let job: JobModel?
let follow: Bool
}
struct JobModel: Equatable { }
class BaseTableViewCell: UITableViewCell {
func setup(data: ContactModel) { }
}
class ContactTableViewCell: BaseTableViewCell {
static let identifier = "Cell"
}