Design patterns aren’t concrete implementations, but rather, serve as starting points for writing code. They describe generic solutions to problems that many experienced developers have encountered many times before. What does this mean exactly...? Learn this and more in this chapter…

…strategy pattern defines a family of interchangeable objects that can be set or switched at runtime: the object using a strategy, the strategy protocol, and the set of strategies. You continue to build out RabbleWabble and learn how these three components work together in the strategy pattern…

…coordinator pattern is a structural design pattern for organizing flow logic between view controllers. This pattern can be adopted for only part of an app, or it can be used as an “architectural pattern” to define the structure of an entire app. You’ll see both of these at work…

…builder pattern allows the creation of complex objects step-by-step, instead of all at once, via an initializer. For example, you can use this pattern to implement a “hamburger builder”. The product could be a “hamburger” model, which has inputs such as meat selection, toppings and sauces. The director…

…model-view-controller (MVC) pattern separates objects into three distinct types: models, views and controllers! MVC is very common in iOS programming, because it's the design pattern that Apple chose to adopt heavily in UIKit. In this chapter you’ll implement the MVC pattern as you start to build…

Design Patterns: Elements of Reusable, Object-Oriented Software, the first book to ever describe design patterns, inspired the revolutionary idea of reusable, template solutions to common software development problems. Design patterns aren’t specific to a particular situation, but rather, they are solutions you can adapt and use in countless…

…multicast delegate pattern is a behavioral pattern that’s a variation on the delegate pattern. It allows you to create one-to-many delegate relationships, instead of one-to-one relationships in a simple delegate…

…state pattern is a behavioral pattern that allows an object to change its behavior at runtime. It does so by changing its current state. "State" here means the set of data that describes how a given object should behave at a given time…

This is a structural pattern that groups a set of objects into a tree so that they may be manipulated as though they were one object. If your app's class hierarchy forms a branching pattern, trying to create two types of classes for branches and nodes can make…

This is a behavioral design pattern that encapsulates how objects, called colleagues for this pattern, communicate with one another. This pattern is useful to separate interactions between colleagues into an object, the mediator. Learn how to use it when you need one or more colleagues to act upon events initiated…

This is a behavioral pattern that encapsulates information to perform an action into a command object. Learn how you can model the concept of executing an action and to use this pattern whenever you want to create actions that can be executed on different receivers…

…observer pattern lets one object observe changes on another object. You’ll learn two different ways to implement the observer pattern in this chapter: using key value observation (KVO), and using an `Observable` wrapper…

…factory pattern provides a way to create objects without exposing creation logic. Technically, there are multiple "flavors" of this pattern, including a simple factory, abstract factory and others. However, each of these share a common goal: to isolate object creation logic within its own construct…

…singleton pattern restricts a class to only one instance. Every reference to the class refers to the same underlying instance. It is extremely common in iOS app development, because Apple makes extensive…

…adapter pattern is a behavioral pattern that allows incompatible types to work together. It involves four components: An object using an adapter is the object that depends on the new protocol. The new protocol is the desired protocol for use. A legacy object existed before the protocol was made…

This creational design pattern minimizes memory usage and processing. It also provides objects that all share the same underlying data, thus saving memory. Learn about flyweight objects and static methods to return them…

This is a behavioral design pattern that allows an event to be processed by one of many handlers. See how to use this pattern whenever you have a group of related objects that handle similar events but vary based on event type, attributes or something else related to the event…

…this pattern when you need to transform models into another representation for a view. This pattern compliments MVC especially well. You’ll embark on a new project — CoffeeQuest — to help you find the best coffee shops around…

…facade pattern is a structural pattern that provides a simple interface to a complex system. Use this pattern whenever you have a system made up of multiple components and want to provide a simple way for users to perform complex tasks…