Swift Academy · Lesson

Protocol-Based Abstractions

Depend on protocols, not concrete types.

Injecting a protocol instead of a concrete type lets you swap implementations freely. The consumer depends only on the behavior, not the class.

Define a Protocol

Describe the capability as a protocol. Any type that conforms can be supplied as the dependency.

protocol Logging {
    func log(_ message: String)
}
print("Protocol describes behavior, not a concrete class.")