Developers are constantly refining their workflow in order to master their craft. There is a plethora of tools available that can help bootstrap a project, increase efficiency, or simply make developers happy. Let’s explore the newly introduced Xcode Source Editor Extensions; an Application Extension that gives developers the power to create custom actions in Xcode’s Editor menu.

1. Enhancing Your Workflow with Xcode Source Editor Extensions
By: Jesse Black
Software Engineer
stable|kernel
jesse.black@stablekernel.com

2. @stablekernel
Hi, I’m Jesse Black.
• Programming for over eight years
• Created a Mac App for my family business
• Worked for 3 years with Gramercy Consultants developing iOS and Android apps
• Working for stable|kernel for the past 3 years developing iOS apps, Android apps
and their supporting APIs

3. We’re stable|kernel.
stable|kernel is an Atlanta-based mobile development company
to craft smartly-designed mobile applications that connect brands
directly with their users.

4. Enhancing Your Workflow with Xcode Source Editor Extensions
@stablekernel
Overview
Mac App Extensions
Xcode Source Editor Extensions
Demo: Create Source Editor Extension and debugging it
XC Classes
Example: JSON formatter
Demo: JSON formatter in action

5. Mac App Extensions
@stablekernel
• Mac App Extensions
• Affect the user experience of other apps
• Need to be lightweight and run fast
• Require user interaction in order to be run
• Distribute via host app

6. Why use Xcode Source Editor Extensions
@stablekernel
• Less context switching
• It is too fun to customize your workflow

7. Xcode Source Editor Extensions
@stablekernel
• Differences with general Mac App Extensions
• Extensions are installed by just putting the host application in your
applications folder
• Only works with one type of target application, which is Xcode
• Doesn’t have UI

8. Xcode Source Editor Extensions
@stablekernel
• Allows you to add custom commands under Xcode’s Editor menu
• Commands can manipulate text and text selections
• Users can put bind keyboard shortcuts to invoke your commands

9. Limitations to Xcode Source Editor Extensions
@stablekernel
• Can only start with user interaction
• Lack of ability to integrate into the build process and archive process. It
is for modifying source code while it is being edited.

10. Expectations of Xcode Source Editor Extensions
@stablekernel
• Fast start up
• Fast execution
• Security and Stability

11. Demo
@stablekernel
Overview
Create Source Editor Extension
How to install
How to debug
How to uninstall

12. Defining Commands
@stablekernel
• Command Identifier
• Class Name
• Command Name
Commands can be defined in the Extension’s plist or by supplying a
dictionary at runtime. Commands provided at runtime override commands
defined in the plist.

13. XC Source Editor Extension
@stablekernel
func extensionDidFinishLaunching() {}
var commandDefinitions: [[XCSourceEditorCommandDefinitionKey: Any]] {}

14. XC Source Editor Command
@stablekernel
func perform(with invocation: XCSourceEditorCommandInvocation,
completionHandler: @escaping (Error?) -> Void ) -> Void {

15. XC Source Editor Command
@stablekernel
• Modify text, text selection
• Exit early with an error message that is displayed in Xcode

16. XC Source Editor Command Invocation
@stablekernel
• Encapsulates all details needed to fulfill the user’s request
• contentUTI
• usesTabsForIndentation
• indentationWidth
• tabWidth
• buffer

17. XC Source Text Buffer
@stablekernel
• completeBuffer
• lines
• selections
• defined in terms of lines and columns

18. Example: JSON formatter
@stablekernel
• Define minify and prettify commands
• Implement XCSourceEditorCommand’s perform method
• Validate requirements for command
• Get first text selection
• Return error if selected text isn’t valid JSON
• Use JSONSerialization class to format text
• Replace selected text

19. XCSourceEditorExtension
@stablekernel
var commandDefinitions: [[XCSourceEditorCommandDefinitionKey: Any]] {
return [
[
.classNameKey: "JeSON.SourceEditorCommand",
.identifierKey: JeSONInvocation.Minify.rawValue,
.nameKey: "Minify"
],
[
.classNameKey: "JeSON.SourceEditorCommand",
.identifierKey: JeSONInvocation.Prettify.rawValue,
.nameKey: "Prettify"
],
]
}

20. XCSourceEditorExtension
@stablekernel
enum JeSONInvocation: String {
case Prettify = "com.jesseblack.HelloWorldProject.JeSON.Prettify"
case Minify = "com.jesseblack.HelloWorldProject.JeSON.Minify"
}

21. @stablekernel
func textAtSelectionIndex(_ at: Int, buffer: XCSourceTextBuffer) -> String {
let textRange = buffer.selections[at] as! XCSourceTextRange
let selectionLines = buffer.lines.enumerated().filter { (offset, element) -> Bool in
return offset >= textRange.start.line && offset <= textRange.end.line
}.map { return $1 }
return selectionLines.enumerated().reduce("") { (result, enumeration) -> String in
let line = enumeration.element as! String
if enumeration.offset == 0 && enumeration.offset == selectionLines.count - 1 {
let startIndex = line.index(line.startIndex, offsetBy: textRange.start.column)
let endIndex = line.index(line.startIndex, offsetBy: textRange.end.column + 1)
return result + line.substring(with: startIndex..<endIndex)
} else if enumeration.offset == 0 {
let startIndex = line.index(line.startIndex, offsetBy: textRange.start.column)
return result + line.substring(from: startIndex)
} else if enumeration.offset == selectionLines.count - 1 {
let endIndex = line.index(line.startIndex, offsetBy: textRange.end.column + 1)
return result + line.substring(to: endIndex)
}
return result + line
}
}

22. @stablekernel
func replaceTextAtSelectionIndex(_ at: Int, replacementText: String, buffer: XCSourceTextBuffer)
{
let textRange = buffer.selections[at] as! XCSourceTextRange
let lastLine = buffer.lines[textRange.end.line] as! String
let endIndex = lastLine.index(lastLine.startIndex, offsetBy: textRange.end.column+1)
let suffix = lastLine.substring(from: endIndex)
let firstLine = buffer.lines[textRange.start.line] as! String
let startIndex = firstLine.index(firstLine.startIndex, offsetBy: textRange.start.column)
let prefix = firstLine.substring(to: startIndex)
let range = NSMakeRange(textRange.start.line, textRange.end.line - textRange.start.line + 1)
buffer.lines.removeObjects(in: range)
buffer.lines.insert(prefix+replacementText+suffix, at: textRange.start.line)
let newRange = XCSourceTextRange(start: textRange.start, end: textRange.start)
buffer.selections.setArray([newRange])
}

23. Performing the command
@stablekernel
func perform(with invocation: XCSourceEditorCommandInvocation, completionHandler: @escaping
(Error?) -> Void ) -> Void {
guard let jeSONInvocation = JeSONInvocation(rawValue: invocation.commandIdentifier) else {
let errorInfo = [NSLocalizedDescriptionKey: "Command not recognized"]
completionHandler(NSError(domain: "", code: 0, userInfo: errorInfo))
return
}
let buffer = invocation.buffer
guard buffer.selections.count == 1 else {
let errorInfo = [NSLocalizedDescriptionKey: "Command only handles 1 selection at a time"]
completionHandler(NSError(domain: "", code: 0, userInfo: errorInfo))
return
}

24. Performing the command
@stablekernel
// perform continued
let selectedText = textAtSelectionIndex(0, buffer: buffer)
let data = selectedText.data(using: .utf8)
do {
let jsonObject = try JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions())
switch jeSONInvocation {
case .Minify:
let miniData = try! JSONSerialization.data(withJSONObject: jsonObject, options: JSONSerialization.WritingOptions())
let string = String.init(data: miniData, encoding: .utf8)!
replaceTextAtSelectionIndex(0, replacementText: string, buffer: buffer)
case .Prettify:
let miniData = try! JSONSerialization.data(withJSONObject: jsonObject, options: .prettyPrinted)
let string = String.init(data: miniData, encoding: .utf8)!
replaceTextAtSelectionIndex(0, replacementText: string, buffer: buffer)
}
}
catch {
completionHandler(error)
}
completionHandler(nil)
}

25. JSON Formatter Demo
@stablekernel
Overview
See all the hard work pay off

26. Questions?
Business Inquiries:
Sarah Woodward
Director of Business Development
sarah.woodward@stablekernel.com
Jesse Black
Software Engineer
jesse.black@stablekernel.com
blog.stablekernel.com
@JesseBlack82
http://www.slideshare.net/stablekernel
https://github.com/JesseBlack82/HelloExtensions