Created
April 22, 2022 08:09
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Property wrapper for changing published values when in SwiftUI Preview mode
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| import Foundation | |
| import Combine | |
| @propertyWrapper | |
| public class PreviewPublisher<Value> { | |
| let isPreview = ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] == "1" | |
| private var defaultValue: Value | |
| private var previewValue: Value | |
| private let innerSubject = PassthroughSubject<Value, Never>() | |
| public var wrappedValue: Value { | |
| get { | |
| return isPreview ? previewValue : defaultValue | |
| } | |
| set { | |
| if isPreview { | |
| previewValue = newValue | |
| } else { | |
| defaultValue = newValue | |
| } | |
| innerSubject.send(isPreview ? previewValue : defaultValue) | |
| } | |
| } | |
| private var asPublisher: AnyPublisher<Value, Never> { | |
| self.innerSubject.eraseToAnyPublisher() | |
| } | |
| public init(wrappedValue defaultValue: Value, _ previewValue: Value) { | |
| self.defaultValue = defaultValue | |
| self.previewValue = previewValue | |
| } | |
| public init(initialValue defaultValue: Value, _ previewValue: Value) { | |
| self.defaultValue = defaultValue | |
| self.previewValue = previewValue | |
| } | |
| } | |
| extension PreviewPublisher: Publisher { | |
| public typealias Output = Value | |
| public typealias Failure = Never | |
| public func receive<S>(subscriber: S) where S : Subscriber, Never == S.Failure, Value == S.Input { | |
| self.asPublisher.receive(subscriber: subscriber) | |
| } | |
| } |
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