Added Identifier for item & section

Author: ivanvorobei

Sources/SPDiffable/CellProvider/Models/SPDiffableItem.swift

@@ -34,13 +34,15 @@ open class SPDiffableItem: NSObject, NSCopying {
      Always shoud be uniq. But if it changed, diffable system remove old and insert new (not reload).
      Identifier uses in `Hashable` and `Equatable` protocols.
      */
-    public var identifier: String
+    public var identifier: Identifier
 
-    public init(identifier: String) {
+    // MARK: - Init
+    
+    public init(identifier: Identifier) {
         self.identifier = identifier
     }
 
-    // MARK: Hashable and Equatable
+    // MARK: - Hashable and Equatable
 
     public override var hash: Int {
         var hasher = Hasher()
@@ -53,11 +55,15 @@ open class SPDiffableItem: NSObject, NSCopying {
         return identifier == object.identifier
     }
 
-    // MARK: NSCopying
+    // MARK: - NSCopying
 
     // Implemented becouse when using with collection,
     // sometimes catch error about unregognized selector.
     public func copy(with zone: NSZone? = nil) -> Any {
         return SPDiffableItem(identifier: self.identifier)
     }
+    
+    // MARK: - Identifier
+    
+    public typealias Identifier = String
 }

Sources/SPDiffable/CellProvider/Models/SPDiffableSection.swift

@@ -35,20 +35,22 @@ open class SPDiffableSection: NSObject, NSCopying {
      Always shoud be uniq. But if it changed, diffable system remove old and insert new (not reload).
      Identifier uses in `Hashable` and `Equatable` protocols.
      */
-    public var identifier: String
+    public var identifier: SectionIdentifier
     public var header: SPDiffableItem?
     public var footer: SPDiffableItem?
 
     public var items: [SPDiffableItem]
 
-    public init(identifier: String, header: SPDiffableItem? = nil, footer: SPDiffableItem? = nil, items: [SPDiffableItem] = []) {
+    // MARK: - Init
+    
+    public init(identifier: SectionIdentifier, header: SPDiffableItem? = nil, footer: SPDiffableItem? = nil, items: [SPDiffableItem] = []) {
         self.identifier = identifier
         self.header = header
         self.footer = footer
         self.items = items
     }
 
-    // MARK: Hashable and Equatable
+    // MARK: - Hashable and Equatable
 
     public override var hash: Int {
         var hasher = Hasher()
@@ -61,7 +63,7 @@ open class SPDiffableSection: NSObject, NSCopying {
         return identifier == object.identifier
     }
 
-    // MARK: NSCopying
+    // MARK: - NSCopying
 
     // Implemented becouse when using with collection,
     // sometimes catch error about unregognized selector.
@@ -73,4 +75,8 @@ open class SPDiffableSection: NSObject, NSCopying {
             items: self.items
         )
     }
+    
+    // MARK: - Item Identifier
+    
+    public typealias SectionIdentifier = String
 }

Sources/SPDiffable/Collection/Models/SPDiffableSideBarButton.swift

@@ -34,7 +34,7 @@ open class SPDiffableSideBarButton: SPDiffableItem {
     public var accessories: [UICellAccessory]
     public var action: Action
 
-    public init(identifier: String? = nil, title: String, image: UIImage?, accessories: [UICellAccessory] = [], action: @escaping Action) {
+    public init(identifier: SPDiffableItem.Identifier? = nil, title: String, image: UIImage?, accessories: [UICellAccessory] = [], action: @escaping Action) {
         self.title = title
         self.image = image
         self.accessories = accessories

Sources/SPDiffable/Collection/Models/SPDiffableSideBarHeader.swift

@@ -30,7 +30,7 @@ open class SPDiffableSideBarHeader: SPDiffableItem {
     public var text: String
     public var accessories: [UICellAccessory]
 
-    public init(identifier: String? = nil, text: String, accessories: [UICellAccessory] = []) {
+    public init(identifier: SPDiffableItem.Identifier? = nil, text: String, accessories: [UICellAccessory] = []) {
         self.text = text
         self.accessories = accessories
         super.init(identifier: identifier ?? text)

Sources/SPDiffable/Collection/Models/SPDiffableSideBarItem.swift

@@ -34,7 +34,7 @@ open class SPDiffableSideBarItem: SPDiffableItem {
     public var accessories: [UICellAccessory]
     public var action: Action
 
-    public init(identifier: String? = nil, title: String, image: UIImage?, accessories: [UICellAccessory] = [], action: @escaping Action) {
+    public init(identifier: SPDiffableItem.Identifier? = nil, title: String, image: UIImage?, accessories: [UICellAccessory] = [], action: @escaping Action) {
         self.title = title
         self.image = image
         self.accessories = accessories

Sources/SPDiffable/DataSource/SPDiffableTableDataSource.swift

@@ -94,14 +94,14 @@ open class SPDiffableTableDataSource: UITableViewDiffableDataSource<SPDiffableSe
     /**
      SPDiffable: Get index path for item by identifier.
      */
-    public func indexPath(for itemIdentifier: String) -> IndexPath? {
+    public func indexPath(for itemIdentifier: SPDiffableItem.Identifier) -> IndexPath? {
         return indexPath(for: SPDiffableItem(identifier: itemIdentifier))
     }
 
     /**
      SPDiffable: Get cell specific type `T` by indetifier.
      */
-    public func cell<T: UITableViewCell>(_ type: T.Type, for itemIdentifier: String) -> T? {
+    public func cell<T: UITableViewCell>(_ type: T.Type, for itemIdentifier: SPDiffableItem.Identifier) -> T? {
         guard let indexPath = indexPath(for: itemIdentifier) else { return nil }
         guard let cell = self.tableView?.cellForRow(at: indexPath) as? T else { return nil }
         return cell