In iOS application development, we need to handle states. We use the Delta, ReactiveCocoa, and ReactiveSwift libraries to manage our Todo app's State.

Delta takes an App that has custom State management spread throughout all the ViewControllers and simplifies it by providing a simple interface to change State and subscribe to its changes.

ReactiveSwift offers composable, declarative, and flexible primitives that are built around the concept of streams of values over time. These primitives can be used to uniformly represent observation patterns. ReactiveCocoa wraps various aspects of Cocoa frameworks with the declarative ReactiveSwift primitives.

We will implement a State struct to observable properties.