You could replace `forEach` with a supped up `map` that also allowed `break`
and `continue`. The following library function gives `continue` and `break` and
also combines `repeat`, `times`, `forEach`, `filter`, `flatMap`, and `map` into
one:
public final class MapController<E, R> {
var results = [R]()
var isContinuing = true
init<C: CollectionType where C.Generator.Element == E>(_ collection: C,
sizeEstimate: Int = 0, @noescape mapper: (controller: MapController<E, R>,
element: E) throws -> R?) rethrows {
results.reserveCapacity(sizeEstimate)
for var generator = collection.generate(), element = generator.next();
element != nil && isContinuing; element = generator.next() {
let result = try mapper(controller: self, element: element!)
if let actualResult = result {
results.append(actualResult)
}
}
}
}
extension CollectionType {
/// Controllable `map`, additional controls beyond simple `map` are:
///
/// 1. Continue without returning a result (`return nil`)
/// 2. Return multiple results (`control.results += [...]` then `return
nil`)
/// 3. Break (`control.isContinuing = false` then `return nil`)
///
/// These additional controls allow this `map` to function like `repeat`,
`times`, `forEach`, `filter`, `flatMap`, and `map` combined into one as well as
providing an early termination (break).
@warn_unused_result func map<R>(sizeEstimate sizeEstimate: Int = 0,
@noescape mapper: (controller: MapController<Self.Generator.Element, R>,
element: Self.Generator.Element) throws -> R?) rethrows -> [R] {
return try MapController(self, sizeEstimate: sizeEstimate, mapper:
mapper).results
}
}
// Demonstration of full functionality including continue, break, and multiple
returns
var result = (0 ..< 5).map { (control, index) -> Int? in
switch index {
case 1:
return nil // Continue - skip 1 (`filter`)
case 2:
control.results.append(2) // Yield two results - this one and the
'return’ yield (`flatMap`)
case 3:
control.isContinuing = false // Break after next yield - which could be
`return nil` if there are no more results
default:
break
}
return index // Yield next result - except for case 1 all the above yield
`index`
}
print(result) // prints `[0, 2, 2, 3]` note missing "1", double "2", and last
is "3"
// Demonstration of `repeat`/`forEach`/`times` like usage - note `(_, _) ->
Void?`
result = [Int]()
(0 ..< 3).map { (_, _) -> Void? in
result.append(1) // Do whatever - in this case append to a global
return nil // Don't yield any results
}
print(result) // prints `[1, 1, 1]`
Would this be a superior alternative to both `forEach` and `times` in the
library and `repeat` as a language feature?
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