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Sources/Fetching and Querying/Concrete Clauses/OrderBy.swift

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+//
+//  OrderBy.swift
+//  CoreStore
+//
+//  Copyright © 2015 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+import Foundation
+import CoreData
+
+
+public func +(left: OrderBy, right: OrderBy) -> OrderBy {
+    
+    return OrderBy(left.sortDescriptors + right.sortDescriptors)
+}
+
+public func +=(inout left: OrderBy, right: OrderBy) {
+    
+    left = left + right
+}
+
+
+// MARK: - KeyPath
+    
+public typealias KeyPath = String
+
+
+// MARK: - SortKey
+
+/**
+ The `SortKey` is passed to the `OrderBy` clause to indicate the sort keys and their sort direction.
+ */
+public enum SortKey {
+    
+    /**
+     Indicates that the `KeyPath` should be sorted in ascending order
+     */
+    case Ascending(KeyPath)
+    
+    /**
+     Indicates that the `KeyPath` should be sorted in descending order
+     */
+    case Descending(KeyPath)
+}
+
+
+// MARK: - OrderBy
+
+/**
+ The `OrderBy` clause specifies the sort order for results for a fetch or a query.
+ */
+public struct OrderBy: FetchClause, QueryClause, DeleteClause {
+    
+    /**
+     Initializes a `OrderBy` clause with a list of sort descriptors
+     
+     - parameter sortDescriptors: a series of `NSSortDescriptor`s
+     */
+    public init(_ sortDescriptors: [NSSortDescriptor]) {
+        
+        self.sortDescriptors = sortDescriptors
+    }
+    
+    /**
+     Initializes a `OrderBy` clause with an empty list of sort descriptors
+     */
+    public init() {
+        
+        self.init([NSSortDescriptor]())
+    }
+    
+    /**
+     Initializes a `OrderBy` clause with a single sort descriptor
+     
+     - parameter sortDescriptor: a `NSSortDescriptor`
+     */
+    public init(_ sortDescriptor: NSSortDescriptor) {
+        
+        self.init([sortDescriptor])
+    }
+    
+    /**
+     Initializes a `OrderBy` clause with a series of `SortKey`s
+     
+     - parameter sortKey: a series of `SortKey`s
+     */
+    public init(_ sortKey: [SortKey]) {
+        
+        self.init(
+            sortKey.map { sortKey -> NSSortDescriptor in
+                
+                switch sortKey {
+                    
+                case .Ascending(let keyPath):
+                    return NSSortDescriptor(key: keyPath, ascending: true)
+                    
+                case .Descending(let keyPath):
+                    return NSSortDescriptor(key: keyPath, ascending: false)
+                }
+            }
+        )
+    }
+    
+    /**
+     Initializes a `OrderBy` clause with a series of `SortKey`s
+     
+     - parameter sortKey: a single `SortKey`
+     - parameter sortKeys: a series of `SortKey`s
+     */
+    public init(_ sortKey: SortKey, _ sortKeys: SortKey...) {
+        
+        self.init([sortKey] + sortKeys)
+    }
+    
+    public let sortDescriptors: [NSSortDescriptor]
+    
+    
+    // MARK: FetchClause, QueryClause, DeleteClause
+    
+    public func applyToFetchRequest(fetchRequest: NSFetchRequest) {
+        
+        if let sortDescriptors = fetchRequest.sortDescriptors where sortDescriptors != self.sortDescriptors {
+            
+            CoreStore.log(
+                .Warning,
+                message: "Existing sortDescriptors for the \(typeName(NSFetchRequest)) was overwritten by \(typeName(self)) query clause."
+            )
+        }
+        
+        fetchRequest.sortDescriptors = self.sortDescriptors
+    }
+}