This is a super v0.1 of what I think a new UI API may look like.

SwiftUI_API.swift

// Benefits:
//   - UI is nested, making it easy to tell what contains what UI elements
//   - All UI is *one file* - no need to hunt down other files/locations (UITableViewCells, for example). 
//       This is a huge boon to productivity. Going back to edit this means I only have to look in one place.
//   - All event handling info is inline with the UI, making it easy to tell what is interacting how. 
//       (Not very different from current target:action: methods, tbh)
//   - Styling and layout is separated out, and styling allows for inheritence to keep it DRY
//   - All UI and styling is declarative (as much as possible), so there's no "order" of doing things, reducing complexity.

// Cons:
//   - Kind of lose out on the type system by using these strings to refer to everything. 
//       There must be some way to make the compiler smarter about this stuff (obviously outside the scope of a library),
//       or some better solution that still allows you to typecheck everything.

let alert = UIView.addView(UIView, name: "alertView", events: nil) { alertView in
  alertView.addView(UIView, name: "titleBar", events: nil) { titleBar in
    // Events are inline with view declarations somehow
    titleBar.addButtonWithName("doneButton", text: "Done", events: [
      UIControlEventTouchUpInside: { button in // Not sure if you can add blocks to dictionaries in swift
        alertView.hidden = true
      }])
    titleBar.addLabelWithName("titleLabel", text: "Welcome")
  }
  
  alertView.addTableViewWithName("tableView", numberOfRows:{ section in section == 0 ? 5 : 2 }) { tableView, indexPath in
    if indexPath.row == 0 {
      // The tableView looks for cells named "personCell" that may have already been initialized and can be reused.
      // If so, reuses them, skips the initialize block, and only runs the configure.
      // Note: this means we don't need a separate class at all, and avoid having to write + maintain a lot of boilerplate
      tableView.addCellWithName("personCell", initialize: { 
        return UITableViewCell().addView(UIView, name: "cellView", events: nil) { cellView in
          cellView.addLabelWithName("nameLabel", text: nil)
          cellView.addLabelWithName("profileLabel", text: nil)
        }
      }, configure: { cell in
        cell.get("nameLabel").text = self.users[indexPath.row].name
        cell.get("profileLabel").text = self.users[indexPath.row].profileText
      }
    }
  }
}

// Styling and UI look and feel code is compartmentalized and allows you to inherit
alertView.styleButton("button") { button in
  button.backgroundColor = UIColor.blackColor
  button.textColor = UIColor.whiteColor
  button.layer.cornerRadius = 5.0
}

alertView.styleButton("doneButton", inheritsFrom: "button") { button in
  button.backgroundColor = UIColor.blueColor
}

// Since we already named all views, getting a dictionary of named subviews is easy
alertView.addConstraintsForName("titleBar", visualConstraints: [
  "H:|-[titleLabel]-[doneButton]-|"
  "V:|-[titleLabel]-|",
  "V:|-[doneButton]-|",
], metrics:0 views: alertView.subviewsDictionary())