CakePattern.playground

//: Playground - noun: a place where people can play

import Foundation

// Example struct
struct Customer: CustomStringConvertible {
    let name: String
    let age: Int
    
    var description: String {
        return "Beneficiary: \(name) is \(age) years old."
    }
}

// Protocol for the customer portal
protocol CustomerPortal {

    func getCustomers() throws -> [Customer]
    
}

// Protocol that contains the customer portal
protocol UsesCustomerPortal {
    
    var customerPortal: CustomerPortal! { get }
    
}

// Private implementation of the customer portal
struct CustomerPortalImplementation: CustomerPortal {
    
    // contains implemented methods
    func getCustomers() throws -> [Customer] {
        let customer1 = Customer(name: "Justin", age: 22)
        let customer2 = Customer(name: "Leo", age: 100000)
        return [customer1, customer2]
    }
    
}

// Default extension for the UsesCustomerPortal (This would be contained in the same file as the CustomerPortalImplementation)
extension UsesCustomerPortal {
    
    // Default implementation for customer portal property
    var customerPortal: CustomerPortal! {
        
        return CustomerPortalImplementation()
        
    }
    
}

// Somewhere in the distant file system we create a view model that uses the UsesCustomerPortal protocol and
// automatically gets the default extension for the customer portal
struct ViewModel: UsesCustomerPortal {
    
    // Some method that uses the repository
    func doSomething() {
        let customers = try? self.customerPortal.getCustomers()
        if let customers = customers {
            customers.forEach { print($0.description) }
        }
    }
    
}

// Using the view model
let viewModel = ViewModel()

// Do something
viewModel.doSomething()