I am using a data source -- think UITableViewDataSource -- that caches the real data for dynamic filtering purposes, but in such a way that client code only has to rely on the existence of a `count` property and a `subscript` element accessor.
But, as of Swift 2.x, Xcode 7.2, this fails to compile:
protocol Iterable {
typealias ItemType
var count: Int { get }
subscript(index: Int) -> ItemType
}=> .../Iterable.swift:20:38: Expected '{' for subscripting
If I cannot use protocols, maybe, sadly, a class will do?
class Iterable<Element> {
var count:Int = 0
subscript(index:Int) -> Element
}=> .../Iterable.swift:26:36: Expected '{' for subscripting
Hmmm ...
Assuming I were able to define such an Iterable(*) in some way, the intended use was something along the lines
class MyIterable<Element> : Iterable {
...
var items:[Element] = []
var cache:[Element] = []
...
func filter() {
...
cache = ...
}
...
var count:Int {
return cache.count
}
...
subscript(index:Int) -> Element {
return cache[index]
}
...
}and at the use site:
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return myIterable.count
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.dequeueReusableCellWithIdentifier(Parameters.productionCellId, forIndexPath: indexPath)
if indexPath.row >= myIterable.count {
return cell
}
let item = myIterable[indexPath.row]
...
return cell
}How could I achieve this?
(*) the `Indexable` name is already reserved by the standard Swift library, for a related, but different purpose.
The error message says: "Expected '{' for subscripting". That is to say, it expects this in the protocol:
subscript(index: Int) -> ItemType {...which should be a clue that the correct form is:
subscript(index: Int) -> ItemType { get } // or
subscript(index: Int) -> ItemType { get set }depending whether you want a setter too.
