Swift Language Design Patterns - Creational Factory Method
Example
In class-based programming, the factory method pattern is a creational pattern that uses factory methods to deal with the problem of creating objects without having to specify the exact class of the object that will be created. Wikipedia reference
protocol SenderProtocol
{
func send(package: AnyObject)
}
class Fedex: SenderProtocol
{
func send(package: AnyObject)
{
print("Fedex deliver")
}
}
class RegularPriorityMail: SenderProtocol
{
func send(package: AnyObject)
{
print("Regular Priority Mail deliver")
}
}
// This is our Factory
class DeliverFactory
{
// It will be responsable for returning the proper instance that will handle the task
static func makeSender(isLate isLate: Bool) -> SenderProtocol
{
return isLate ? Fedex() : RegularPriorityMail()
}
}
// Usage:
let package = ["Item 1", "Item 2"]
// Fedex class will handle the delivery
DeliverFactory.makeSender(isLate:true).send(package)
// Regular Priority Mail class will handle the delivery
DeliverFactory.makeSender(isLate:false).send(package)
By doing that we don't depend on the real implementation of the class, making the sender() completely transparent to who is consuming it.
In this case all we need to know is that a sender will handle the deliver and exposes a method called send(). There are several other advantages: reduce classes coupling, easier to test, easier to add new behaviours without having to change who is consuming it.
Within object-oriented design, interfaces provide layers of abstraction that facilitate conceptual explanation of the code and create a barrier preventing dependencies.Wikipedia reference
