Blog: ObservableObjects and Protocols - Protocol with Published properties

blog--observableobject+protocols--protocol-published.swift

// Copyright 2021 Expedia, Inc.
// SPDX-License-Identifier: Apache-2.0

import Combine

protocol PriceRequesting: ObservableObject {
    
    var price: Price? { get }
    
    var priceValue: Published<Price?> { get }
    
    var pricePublisher: Published<Price?>.Publisher { get }
    
    func fetch()
}

class PricingProvider: PriceRequesting {
    
    @Published private(set) var price: Price?
    
    var priceValue: Published<Price?> {
        return _price
    }
    
    var pricePublisher: Published<Price?>.Publisher {
        return $price
    }
    
    init(price initialValue: Price? = nil) {
        self.price = initialValue
    }
    
    func fetch() {
        // TODO: fetch pricing from a service
        let price = Int.random(in: 42...150)
        self.price = Price(amount: "$\(price)", description: "avg/night")
    }
}