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55// Created by eric_horacek on 11/18/20.
// Copyright © 2020 Airbnb Inc. All rights reserved.
// MARK: - EpoxyModeled
/// A protocol that all concrete Epoxy declarative UI model types conform to.
///
/// This protocol should be conditionally extended to fulfill provider protocols and with chainable
/// setters for those providers that concrete model types can receive by declaring conformance to
/// provider protocols.
protocol EpoxyModeled {
/// The underlying storage of this model that stores the current property values.
var storage: EpoxyModelStorage { get set }
}
// MARK: Extensions
extension EpoxyModeled {
/// Stores or retrieves a value of the specified property in `storage`.
///
/// If the value was set previously for the given `property`, the conflict is resolved using the
/// `EpoxyModelProperty.UpdateStrategy` of the `property`.
subscript<Property>(property: EpoxyModelProperty<Property>) -> Property {
get { storage[property] }
set { storage[property] = newValue }
}
/// Returns a copy of this model with the given property updated to the provided value.
///
/// Typically called from within the context of a chainable setter to allow fluent setting of a
/// property, e.g.:
///
/// ````
/// internal func title(_ value: String?) -> Self {
/// copy(updating: titleProperty, to: value)
/// }
/// ````
///
/// If a `value` was set previously for the given `property`, the conflict is resolved using the
/// `EpoxyModelProperty.UpdateStrategy` of the `property`.
func copy<Value>(updating property: EpoxyModelProperty<Value>, to value: Value) -> Self {
var copy = self
copy.storage[property] = value
return copy
}
/// Returns a copy of this model produced by merging the given `other` model's storage into this
/// model's storage.
func merging(_ other: EpoxyModeled) -> Self {
var copy = self
copy.storage.merge(other.storage)
return copy
}
}