Swift Functional Programming - Second Edition

Copy constructors

The first solution is to provide a new init method that copies the current instance. This approach is called a copy constructor. Let's add our new init method and leverage it:

init(products: [FunctionalProduct], lastModified: Date) {     self.products = products     self.lastModified = lastModified } init(productTracker: FunctionalProductTracker,     products: [FunctionalProduct]? = nil,      lastModified: Date? = nil) {     self.products = products ?? productTracker.products     self.lastModified = lastModified ?? productTracker.lastModified } 

We added the default init as well because by adding a new init method to our struct, we lost the benefit of automatic init generation. We also need to change our addNewProduct to accommodate these ...