swift outline view with two sub children - swift

Question

i working with swift 4 for macOS and i have a NSOutlineView:
i get the data from core data.
structure:
entity Person (relationship to entity Book)
entity Book
My Code for this result:
#IBOutlet weak var myOutlineView: NSOutlineView!
let context = (NSApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
var people = [Person]()
override func viewWillAppear() {
requestPeople()
}
func outlineView(_ outlineView: NSOutlineView, viewFor tableColumn: NSTableColumn?, item: Any) -> NSView? {
let view = outlineView.makeView(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "Cell"), owner: self) as? CustomCell
if let person = item as? Person {
// Show Person
} else if let book = item as? Book {
// Show Books
}
return view
}
func outlineView(_ outlineView: NSOutlineView, numberOfChildrenOfItem item: Any?) -> Int {
if let person = item as? Person {
return person.books.count
}
return people.count
}
func outlineView(_ outlineView: NSOutlineView, child index: Int, ofItem item: Any?) -> Any {
if let person = item as? Person {
return person.books[index]
}
return people[index]
}
func outlineView(_ outlineView: NSOutlineView, isItemExpandable item: Any) -> Bool {
if let person = item as? Person {
return person.books.count > 0
}
return false
}
func requestPeople() {
let request = NSFetchRequest<Person>(entityName: "Person")
do {
people = try context.fetch(request)
myOutlineView.reloadData()
} catch { print(error) }
}
now my problem:
i would like create another outline view.
My Book entity looks like this (attributes):
name
creationDate
My new outlineview should get this structure:
+ Year
++ Month
+++ Bookname
but i dont know how can I realize this structure.
It is different as my first outline view.
can somebody help me?
=======
i guess that i have create arrays for year and month without duplicates.
for this i try a this function to get the data:
var year = [String]()
var month = [String]()
var books = [Book]()
func requestBooks() {
let request = NSFetchRequest<Book>(entityName: "Book")
do {
books = try context.fetch(request)
for x in 0 ...< books.count {
if !year.contains("\(Calendar.current.component(.year, from: books[x].creationDate))") {
year.append("\(Calendar.current.component(.year, from: books[x].creationDate))")
}
if !month.contains("\(Calendar.current.component(.month, from: books[x].creationDate))") {
month.append("\(Calendar.current.component(.month, from: books[x].creationDate))")
}
}
myOutlineView.reloadData()
} catch { print(error) }
}

Answer 1

A multi-level outline is easier to manage when your underlying data structure is hierarchical (i.e. a tree structure).
Here's an example of how you can create a "Tree" node class for your Books:
class BookNode
{
// levels and relationships, from parent to children
enum Level { case Top, Year, Month, Book }
let subLevels:[Level:Level] = [ .Top:.Year, .Year:.Month, .Month:.Book ]
var label = "" // description and unique "key"
var level = Level.Top
var children : [BookNode] = []
var book : Book! = nil // .Book level will store the actual Book
// add book to hierarchy, auto-create intermediate levels
func add(_ book:Book)
{
var subLabel = ""
switch level
{
case .Top : subLabel = String(Calendar.current.component(.year, from:book.creationDate))
case .Year : subLabel = String(Calendar.current.component(.month, from:book.creationDate))
case .Month : subLabel = book.name
case .Book : self.book = book // last level stores the book
return // and has no children
}
// Add branch (.Year, .Month) or leaf (.Book) node as needed
var subNode:BookNode! = children.first{$0.label == subLabel}
if subNode == nil
{
subNode = BookNode()
subNode.level = subLevels[level]!
subNode.label = subLabel
children.append(subNode)
}
// keep adding recursively down to .Book level
subNode.add(book)
}
}
Your data will be stored in a hierarchy of BookNodes which you can load from your fetch request
(you can pre-sort it, as I did, or leave that up to the BookNode class)
var topNode = BookNode()
func requestBooks()
{
let request = NSFetchRequest<Book>(entityName: "Book")
do {
let books = try context.fetch(request)
topNode = BookNode()
for book in books.sorted(by:{$0.creationDate < $1.creationDate})
{
topNode.add(book)
}
}
}
With this, it will be easy to respond to your outline protocols using the BookNodes as the outline items:
func outlineView(_ outlineView: NSOutlineView, viewFor tableColumn: NSTableColumn?, item: Any) -> NSView?
{
let view = outlineView.makeView(withIdentifier: NSUserInterfaceItemIdentifier(rawValue: "Cell"), owner: self) as? CustomCell
let node = (item as? BookNode) ?? topNode
switch node.level
{
case .Year : // show year : node.label
case .Month : // show month : node.label
case .Book : // show book name : node.label and/or node.book
default : break
}
return view
}
func outlineView(_ outlineView: NSOutlineView, numberOfChildrenOfItem item: Any?) -> Int
{
let node = (item as? BookNode) ?? topNode
return node.children.count
}
func outlineView(_ outlineView: NSOutlineView, child index: Int, ofItem item: Any?) -> Any
{
let node = (item as? BookNode) ?? topNode
return node.children[index]
}
func outlineView(_ outlineView: NSOutlineView, isItemExpandable item: Any) -> Bool
{
let node = (item as? BookNode) ?? topNode
return node.children.count > 0
}
If you program needs to allow adding/changing/removing individual books, the BookNode class can be used to reflect the individual changed (e.g. remove a book child or add a new one). You will then only need to call reloadData() on the outline without having to get everything back from the database.