Created
June 13, 2019 07:36
-
-
Save chriseidhof/9652a0d7144f8f1805ef72bdcffd0d88 to your computer and use it in GitHub Desktop.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
/// Similar to a `Binding`, but this is also observable/dynamic. | |
@propertyDelegate | |
@dynamicMemberLookup | |
final class Derived<A>: BindableObject { | |
let didChange = PassthroughSubject<A, Never>() | |
fileprivate var cancellables: [AnyCancellable] = [] | |
private let get: () -> (A) | |
private let mutate: ((inout A) -> ()) -> () | |
init(get: @escaping () -> A, mutate: @escaping ((inout A) -> ()) -> ()) { | |
self.get = get | |
self.mutate = mutate | |
} | |
var value: A { | |
get { get() } | |
set { mutate { $0 = newValue } } | |
} | |
subscript<U: Equatable>(dynamicMember keyPath: WritableKeyPath<A, U>) -> Derived<U> { | |
let result = Derived<U>(get: { | |
let value = self.get()[keyPath: keyPath] | |
return value | |
}, mutate: { f in | |
self.mutate { (a: inout A) in | |
f(&a[keyPath: keyPath]) | |
} | |
}) | |
let c = didChange.map { $0[keyPath: keyPath] }.removeDuplicates().sink { value in | |
result.didChange.send(value) | |
} | |
cancellables.append(AnyCancellable(c)) | |
return result | |
} | |
var binding: Binding<A> { | |
return Binding<A>(getValue: { self.value }, setValue: { self.value = $0 }) | |
} | |
deinit { | |
for c in cancellables { | |
c.cancel() | |
} | |
} | |
} | |
final class SimpleStore<A>: BindableObject { | |
let didChange = | |
PassthroughSubject<A, Never>() | |
init(_ value: A) { self.value = value } | |
var value: A { | |
didSet { | |
didChange.send(value) | |
} | |
} | |
var bindable: Derived<A> { | |
let result = Derived<A>(get: { | |
self.value | |
}, mutate: { f in | |
f(&self.value) | |
}) | |
let c = self.didChange.sink { [weak result] value in | |
result?.didChange.send(value) | |
} | |
result.cancellables.append(AnyCancellable(c)) | |
return result | |
} | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment