ViewSpitter: Programmatic UIView Boilerplate generator

ViewSpitter.swift

extension String {
    mutating func appendLine(line: String = "") {
        self += "\n\(line)"
    }

    mutating func appendMark(mark: String) {
        self.appendLine()
        self.appendLine("//MARK - \(mark)")
        self.appendLine()
    }
}

struct ViewModel: ArrayLiteralConvertible {
    typealias Element = String

    let name: String
    let type: String
    let style: String
    let color: String

    init(arrayLiteral elements: ViewModel.Element...) {
        name = elements[0]
        type = elements[1]
        style = elements[2]
        color = elements [3]
    }
}

struct ClassModel {
    let className: String
    let superClass: String
    let views: [ViewModel]
    let viewRelations: [(String, String)]
}

extension ClassModel {
    func generateBoilerplate() -> String {
        // Header
        var result = ""
        result.appendLine("import UIKit")
        result.appendLine("import Cartography")
        result.appendLine()
        result.appendLine("final class \(className): \(superClass) {")

        //View declaration
        for viewModel in views {
            result.appendLine("private var \(viewModel.name): \(viewModel.type)? {")
            result.appendLine("didSet {")
            result.appendLine("guard let \(viewModel.name) = \(viewModel.name) where \(viewModel.name) != oldValue else { return }")
            result.appendLine()
            result.appendLine("\(viewModel.name).setStyle(.\(viewModel.style))")
            result.appendLine("\(viewModel.name).textColor = .\(viewModel.color)Color()")
            result.appendLine("addSubview(\(viewModel.name))")
            result.appendLine("}")
            result.appendLine("}")
            result.appendLine()
        }

        //Designated initializer
        result.appendMark("Designated initializer")
        result.appendLine("required init?(coder aDecoder: NSCoder) {")
        result.appendLine("super.init(coder: aDecoder)")
        result.appendLine("setupViews()")
        result.appendLine("}")
        result.appendLine("}")

        //Configuration
        result.appendMark("Configuration")
        result.appendLine("extension \(className) {")
        result.appendLine("func configureWith(viewModel viewModel: Any) {")
        result.appendLine("//FIXME: Replace me with ViewModel and implement me")
        result.appendLine("}")
        result.appendLine("}")

        //Layout
        result.appendMark("Layout")

        result.appendLine("private extension \(className) {")
        result.appendLine("private func setupViews() {")

        for viewModel in views {
            result.appendLine("\(viewModel.name) = \(viewModel.type)()")
        }
        result.appendLine("setupConstraints()")
        result.appendLine("}")

        result.appendLine()
        result.appendLine("private func setupConstraints() {")
        if let first = views.first {
            var line = "guard let \(first.name) = \(first.name)"
            let otherViews = Array(views.dropFirst())

            if otherViews.count == 0 {
                line += " else {"
                result.appendLine(line)
            } else {
                line += ","
                result.appendLine(line)
                for (index, view) in otherViews.enumerate() {
                    var shadowing = "\(view.name) = \(view.name)"
                    shadowing += index == otherViews.count - 1 ? " else {" : ","

                    result.appendLine(shadowing)
                }
            }

            result.appendLine("print(\"[WARNING]: Setting subviews failed\")")
            result.appendLine("return")
            result.appendLine("}")
        }

        result.appendLine()
        if viewRelations.count > 0 {
            result.appendLine("//TODO: Layout constraints")
            result.appendLine()
            for (first, second) in viewRelations {
                let translatedFirst = first == "self" ? "view" : first
                let translatedSecond = second == "self" ? "view" : second
                result.appendLine("constrain(\(first), \(second)) { \(translatedFirst), \(translatedSecond) in")
                result.appendLine("//FIXME: Add constraints")
                result.appendLine("}")
                result.appendLine()
            }
        } else if let first = views.first {
            result.appendLine("/*")
            result.appendLine("constrain(\(first.name), self) { \(first.name), view in")
            result.appendLine("\(first.name).leading          == view.leading + 20")
            result.appendLine("\(first.name).top              == view.top + 20")
            result.appendLine("}")
            result.appendLine("*/")
        }
        result.appendLine("}")
        result.appendLine("}")

        return result
    }
}