Declarative and Imperative Syntax

Declarative vs Imperative programming
     Decalrative and Imperative programming are not mutually exclusive. Declarative code enables you to focus on the expected result, instead of steps to get there.
     Imperative code is great when making a change to state, or when there might not be an existing declarative component.
     SwiftUI embraces both. Example of this is button. Buttons are added to the view declaratively, and part of this declaration is the action perform when tapped.
     This action uses imperative code to make a change.

     SwiftUI views are descriptions of what the current state of 
     the UI should be they are not long lived object instances that receive imperative commands over time.
     This is why SwiftUI views are value types, defined using structs instead of classes.

     SwiftUI takes these descriptions and creates an efficient data structure to represent them. 
     It maintains this data structure behind the scenes. 
     And it's used to produce different outputs, 
     for example, what is shown on the screen, the gestures and interactive aspects of the view and its accessibility representation.

      In imperative programming you need to provide specific order of execution. 
      This method of creating code by specifying orders is called imperative syntax.

      The method of writing code for the user interface elements by specifying what you need instead of how you need it, is called declarative syntax. 
      Worry about what you want - do not worry about how its done. 

      Benefits of declarative syntax
      1. Easy to learn 
      2. Simple to read and understand 
      3. A clean and modern syntax
      4. Easy to create complex interfaces
      5. Xcode provides live previews. 
      6. No working with view constraints 
      7. Localizations and UI variations. 
      8. Simplifies development of an app for multi-platform. 

      Limitations of declarative syntax 
      1. Full functionality only available in UIKit 
      2. Xcode preview bugs 
      3. Market is still adopting to SwiftUI.