Swift 4

1. Codable Protocol: Simplifies encoding and decoding of data types to and from JSON, Property List, or other formats.

2. Improved String Handling: Enhancements for Unicode support, multi-line string literals, and performance improvements.

3. Key-Value Observing (KVO) Compliance: Support for observing changes to properties of Swift objects using Objective-C-like syntax.

4. Enhanced Dictionary and Set Functionality: New features for dictionaries and sets, such as default values for missing keys and improved set operations.

Before learning Swift 4, it's beneficial to have a basic understanding of programming fundamentals such as variables, data types, control flow (loops and conditionals), functions, and object-oriented programming concepts. Familiarity with programming languages like C, Objective-C, or Java can also be helpful due to Swift's similarities with these languages.

Learning Swift 4 equips you with several valuable skills, including:

1. Mobile app development: Swift is primarily used for developing iOS, macOS, watchOS, and tvOS applications, so you'll gain proficiency in building mobile apps for Apple platforms.
2. Modern programming language concepts: Swift incorporates modern programming language features such as optionals, closures, generics, and type inference, enhancing your understanding of modern programming paradigms.
3. Swift ecosystem: You'll become familiar with the Swift ecosystem, including frameworks, libraries, and tools like Xcode, Interface Builder, and SwiftUI for building user interfaces.
4. Code readability and maintainability: Swift emphasizes clean, concise, and expressive syntax, improving code readability and making maintenance easier.