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@andersio @mdiep @NachoSoto @ikesyo @Marcocanc
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import Foundation
import Dispatch
precedencegroup BindingPrecedence {
associativity: right
// Binds tighter than assignment but looser than everything else
higherThan: AssignmentPrecedence
}
infix operator <~ : BindingPrecedence
/// Describes a source which can be bound.
public protocol BindingSource: SignalProducerConvertible where Error == Never {}
extension Signal: BindingSource where Error == Never {}
extension SignalProducer: BindingSource where Error == Never {}
/// Describes an entity which be bond towards.
public protocol BindingTargetProvider {
associatedtype Value
var bindingTarget: BindingTarget<Value> { get }
}
extension BindingTargetProvider {
/// Binds a source to a target, updating the target's value to the latest
/// value sent by the source.
///
/// - note: The binding will automatically terminate when the target is
/// deinitialized, or when the source sends a `completed` event.
///
/// ````
/// let property = MutableProperty(0)
/// let signal = Signal({ /* do some work after some time */ })
/// property <~ signal
/// ````
///
/// ````
/// let property = MutableProperty(0)
/// let signal = Signal({ /* do some work after some time */ })
/// let disposable = property <~ signal
/// ...
/// // Terminates binding before property dealloc or signal's
/// // `completed` event.
/// disposable.dispose()
/// ````
///
/// - parameters:
/// - target: A target to be bond to.
/// - source: A source to bind.
///
/// - returns: A disposable that can be used to terminate binding before the
/// deinitialization of the target or the source's `completed`
/// event.
@discardableResult
public static func <~
<Source: BindingSource>
(provider: Self, source: Source) -> Disposable?
where Source.Value == Value
{
return source.producer
.take(during: provider.bindingTarget.lifetime)
.startWithValues(provider.bindingTarget.action)
}
/// Binds a source to a target, updating the target's value to the latest
/// value sent by the source.
///
/// - note: The binding will automatically terminate when the target is
/// deinitialized, or when the source sends a `completed` event.
///
/// ````
/// let property = MutableProperty(0)
/// let signal = Signal({ /* do some work after some time */ })
/// property <~ signal
/// ````
///
/// ````
/// let property = MutableProperty(0)
/// let signal = Signal({ /* do some work after some time */ })
/// let disposable = property <~ signal
/// ...
/// // Terminates binding before property dealloc or signal's
/// // `completed` event.
/// disposable.dispose()
/// ````
///
/// - parameters:
/// - target: A target to be bond to.
/// - source: A source to bind.
///
/// - returns: A disposable that can be used to terminate binding before the
/// deinitialization of the target or the source's `completed`
/// event.
@discardableResult
public static func <~
<Source: BindingSource>
(provider: Self, source: Source) -> Disposable?
where Value == Source.Value?
{
return provider <~ source.producer.optionalize()
}
}
extension Signal.Observer {
/// Binds a source to a target, updating the target's value to the latest
/// value sent by the source.
///
/// - note: Only `value` events will be forwarded to the Observer.
/// The binding will automatically terminate when the target is
/// deinitialized, or when the source sends a `completed` event.
///
/// - parameters:
/// - target: A target to be bond to.
/// - source: A source to bind.
///
/// - returns: A disposable that can be used to terminate binding before the
/// deinitialization of the target or the source's `completed`
/// event.
@discardableResult
public static func <~
<Source: BindingSource>
(observer: Signal<Value, Error>.Observer, source: Source) -> Disposable?
where Source.Value == Value
{
return source.producer.startWithValues { [weak observer] in
observer?.send(value: $0)
}
}
}
/// A binding target that can be used with the `<~` operator.
public struct BindingTarget<Value>: BindingTargetProvider {
public let lifetime: Lifetime
public let action: (Value) -> Void
public var bindingTarget: BindingTarget<Value> {
return self
}
/// Creates a binding target which consumes values on the specified scheduler.
///
/// If no scheduler is specified, the binding target would consume the value
/// immediately.
///
/// - parameters:
/// - scheduler: The scheduler on which the `action` consumes the values.
/// - lifetime: The expected lifetime of any bindings towards `self`.
/// - action: The action to consume values.
public init(on scheduler: Scheduler = ImmediateScheduler(), lifetime: Lifetime, action: @escaping (Value) -> Void) {
self.lifetime = lifetime
if scheduler is ImmediateScheduler {
self.action = action
} else {
self.action = { value in
scheduler.schedule {
action(value)
}
}
}
}
/// Creates a binding target which consumes values on the specified scheduler.
///
/// If no scheduler is specified, the binding target would consume the value
/// immediately.
///
/// - parameters:
/// - scheduler: The scheduler on which the key path consumes the values.
/// - lifetime: The expected lifetime of any bindings towards `self`.
/// - object: The object to consume values.
/// - keyPath: The key path of the object that consumes values.
public init<Object: AnyObject>(on scheduler: Scheduler = ImmediateScheduler(), lifetime: Lifetime, object: Object, keyPath: WritableKeyPath<Object, Value>) {
self.init(on: scheduler, lifetime: lifetime) { [weak object] in object?[keyPath: keyPath] = $0 }
}
}
extension Optional: BindingTargetProvider where Wrapped: BindingTargetProvider {
public typealias Value = Wrapped.Value
public var bindingTarget: BindingTarget<Wrapped.Value> {
switch self {
case let .some(provider):
return provider.bindingTarget
case .none:
return BindingTarget(lifetime: .empty, action: { _ in })
}
}
}
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