SOLID. Dependency conversion. Abstractions should not depend on details. Details should depend on abstractions. What do you mean by "details"?

Question

Objective-C

if possible, an example in Objective C / Swift

Answer 1

Robert Martin once said about this that there should be no dependencies on concrete classes, and relationships should lead to an abstract class or interface. Consider that "details" are a concrete implementation, and "abstraction" is a certain selected basis, necessary and sufficient for defining a connection.