complete few todos;

Author: Roman Kyrylenko

Source/Core/DBClient.swift

@@ -46,18 +46,14 @@ public protocol DBClient {
   */
   func observable<T: Stored>(for request: FetchRequest<T>) -> RequestObservable<T>
 
-  // TODO: remove
-  func fetch<T: Stored>(id: String) -> Task<[T]>
-  func fetch<T: Stored>(with predicate: NSPredicate?) -> Task<[T]>
-
   /**
     Saves objects to database.
 
     - Parameter objects: list of objects to be saved
 
     - Returns: `Task` with saved objects or appropriate error in case of failure.
   */
-  func save<T: Stored>(_ objects: [T]) -> Task<[T]>
+  @discardableResult func save<T: Stored>(_ objects: [T]) -> Task<[T]>
 
   /**
     Updates changed performed with objects to database.
@@ -66,7 +62,7 @@ public protocol DBClient {
 
     - Returns: `Task` with updated objects or appropriate error in case of failure.
   */
-  func update<T: Stored>(_ objects: [T]) -> Task<[T]>
+  @discardableResult func update<T: Stored>(_ objects: [T]) -> Task<[T]>
 
   /**
     Deletes objects from database.
@@ -75,7 +71,7 @@ public protocol DBClient {
 
     - Returns: `Task` with deleted objects or appropriate error in case of failure.
   */
-  func delete<T: Stored>(_ objects: [T]) -> Task<[T]>
+  @discardableResult func delete<T: Stored>(_ objects: [T]) -> Task<[T]>
 
 }
 
@@ -91,13 +87,19 @@ public extension DBClient {
 
     - Returns: `Task` with found object or nil.
   */
-  func findFirst<T: Stored>(_ type: T.Type, primaryValue: String) -> Task<T?> {
+  func findFirst<T: Stored>(_ type: T.Type, primaryValue: String, predicate: NSPredicate? = nil) -> Task<T?> {
     guard let primaryKey = type.primaryKey else {
       return Task(nil)
     }
 
-    let predicate = NSPredicate(format: "\(primaryKey) == %@", primaryValue)
-    let request = FetchRequest<T>(predicate: predicate, fetchLimit: 1)
+    let primaryKeyPredicate = NSPredicate(format: "\(primaryKey) == %@", primaryValue)
+    var fetchPredicate: NSPredicate
+    if let predicate = predicate {
+      fetchPredicate = NSCompoundPredicate(andPredicateWithSubpredicates: [primaryKeyPredicate, predicate])
+    } else {
+      fetchPredicate = primaryKeyPredicate
+    }
+    let request = FetchRequest<T>(predicate: fetchPredicate, fetchLimit: 1)
 
     return execute(request).continueWithTask { task -> Task<T?> in
       if let first = task.result?.first {
@@ -114,7 +116,7 @@ public extension DBClient {
 
    - Returns: `Task` with deleted object or appropriate error in case of failure.
    */
-  func delete<T: Stored>(_ object: T) -> Task<T> {
+  @discardableResult func delete<T: Stored>(_ object: T) -> Task<T> {
     return convertArrayTaskToSingleObject(delete([object]))
   }
 
@@ -125,7 +127,7 @@ public extension DBClient {
 
    - Returns: `Task` with updated object or appropriate error in case of failure.
    */
-  func update<T: Stored>(_ object: T) -> Task<T> {
+  @discardableResult func update<T: Stored>(_ object: T) -> Task<T> {
     return convertArrayTaskToSingleObject(update([object]))
   }
 
@@ -136,7 +138,7 @@ public extension DBClient {
 
    - Returns: `Task` with saved object or appropriate error in case of failure.
    */
-  func save<T: Stored>(_ object: T) -> Task<T> {
+  @discardableResult func save<T: Stored>(_ object: T) -> Task<T> {
     return convertArrayTaskToSingleObject(save([object]))
   }
 

Source/CoreData/CoreDataDBClient.swift

@@ -135,9 +135,7 @@ extension CoreDataDBClient: DBClient {
         let result = try context.fetch(fetchRequest) as! [NSManagedObject]
         let resultModels = result.map { coreDataModelType.from($0) as! T }
         taskCompletionSource.set(result: resultModels)
-      } catch {
-        // TODO - generate proper error
-        let error = NSError()
+      } catch let error {
         taskCompletionSource.set(error: error)
       }
     }
@@ -149,11 +147,6 @@ extension CoreDataDBClient: DBClient {
     return CoreDataObservable(request: request, context: managedObjectContext)
   }
 
-  public func fetch<T: Stored>(id: String) -> Task<[T]> {
-    let predicate = NSPredicate(format: "id = %@", id)
-    return fetch(with: predicate)
-  }
-  
   public func save<T: Stored>(_ objects: [T]) -> Task<[T]> {
     // For each element in collection:
     // 1. Cast T object to CoreDataModelConvertible if it is possible
@@ -170,9 +163,7 @@ extension CoreDataDBClient: DBClient {
       do {
         try context.save()
         taskCompletionSource.set(result: objects)
-      } catch {
-        // TODO - generate proper error
-        let error = NSError()
+      } catch let error {
         taskCompletionSource.set(error: error)
       }
     }
@@ -207,40 +198,7 @@ extension CoreDataDBClient: DBClient {
       do {
         try context.save()
         taskCompletionSource.set(result: objects)
-      } catch {
-        // TODO - generate proper error
-        let error = NSError()
-        taskCompletionSource.set(error: error)
-      }
-    }
-    return taskCompletionSource.task
-  }
-
-  public func fetch<T: Stored>(with predicate: NSPredicate? = nil) -> Task<[T]> {
-    // 1. Make sure passed T type conforms to CoreDataModelConvertible protocol to fetch from CoreData DB
-    // 2. Convert type to CoreDataModelConvertible type
-    // 3. Create required NSFetchRequest with passed predicate
-    // 4. Fetch items of CoreDataModelConvertible type
-    // 5. Convert fetched items back to T type
-    
-    // warning: Use preconditions
-    
-    guard let coreDataModelType = T.self as? CoreDataModelConvertible.Type else {
-      fatalError("CoreDataDBClient can manage only types which conform to CoreDataModelConvertible")
-    }
-    
-    let taskCompletionSource = TaskCompletionSource<[T]>()
-    
-    performBackgroundTask { context in
-      let fetchRequest = self.fetchRequest(for: coreDataModelType)
-      fetchRequest.predicate = predicate
-      do {
-        let result = try context.fetch(fetchRequest) as! [NSManagedObject]
-        let resultModels = result.map { coreDataModelType.from($0) as! T }
-        taskCompletionSource.set(result: resultModels)
-      } catch {
-        // TODO - generate proper error
-        let error = NSError()
+      } catch let error {
         taskCompletionSource.set(error: error)
       }
     }

Source/Realm/RealmDBClient.swift

@@ -52,30 +52,6 @@ public class RealmDBClient {
 
 extension RealmDBClient: DBClient {
 
-  public func fetch<T: Stored>(id: String) -> Task<[T]> {
-    guard let realmModelType = T.self as? RealmModelConvertible.Type else {
-      fatalError("CoreDataDBClient can manage only types which conform to CoreDataModelConvertible")
-    }
-    let result = realm.objects(realmModelType.realmClass())
-    let objects = Array(result.map { realmModelType.from($0) as! T})
-        
-    return Task(objects)
-  }
-  
-  public func fetch<T: Stored>(with predicate: NSPredicate?) -> Task<[T]> {
-    guard let realmModelType = T.self as? RealmModelConvertible.Type else {
-      fatalError("CoreDataDBClient can manage only types which conform to CoreDataModelConvertible")
-    }
-    
-    var result = realm.objects(realmModelType.realmClass())
-    if let predicate = predicate {
-      result = result.filter(predicate)
-    }
-    let objects = Array(result.map { realmModelType.from($0) as! T})
-    
-    return  Task(objects)
-  }
-  
   public func save<T: Stored>(_ objects: [T]) -> Task<[T]> {
     let taskCompletionSource = TaskCompletionSource<[T]>()