Move fetchObjectsWithIDs from AttachmentsTable to default protocol implementation since AuthorsTable needs the exact same thing.

Frameworks/Database/AttachmentsTable.swift

@@ -14,7 +14,7 @@ final class AttachmentsTable: DatabaseRelatedObjectsTable {
 
 	let name: String
 	let databaseIDKey = DatabaseKey.attachmentID
-	var cache = [String: Attachment]()
+	var cache = DatabaseObjectCache()
 
 	init(name: String) {
 
@@ -23,39 +23,6 @@ final class AttachmentsTable: DatabaseRelatedObjectsTable {
 	
 	// MARK: DatabaseRelatedObjectsTable
 
-	func fetchObjectsWithIDs(_ databaseIDs: Set<String>, in database: FMDatabase) -> [DatabaseObject]? {
-
-		if databaseIDs.isEmpty {
-			return nil
-		}
-
-		var cachedAttachments = Set<Attachment>()
-		var databaseIDsToFetch = Set<String>()
-
-		for attachmentID in databaseIDs {
-			if let cachedAttachment = cache[attachmentID] {
-				cachedAttachments.insert(cachedAttachment)
-			}
-			else {
-				databaseIDsToFetch.insert(attachmentID)
-			}
-		}
-
-		if databaseIDsToFetch.isEmpty {
-			return cachedAttachments.databaseObjects()
-		}
-
-		guard let resultSet = selectRowsWhere(key: databaseIDKey, inValues: Array(databaseIDsToFetch), in: database) else {
-			return cachedAttachments.databaseObjects()
-		}
-		let fetchedDatabaseObjects = objectsWithResultSet(resultSet)
-		let fetchedAttachments = Set(fetchedDatabaseObjects.map { $0 as Attachment })
-		cacheAttachments(fetchedAttachments)
-
-		let allAttachments = cachedAttachments.union(fetchedAttachments)
-		return allAttachments.databaseObjects()
-	}
-
 	func objectWithRow(_ row: FMResultSet) -> DatabaseObject? {
 		
 		if let attachment = attachmentWithRow(row) {
@@ -76,7 +43,7 @@ final class AttachmentsTable: DatabaseRelatedObjectsTable {
 			return true
 		})
 
-		cacheAttachments(attachmentsToSave)
+		cache.add(attachmentsToSave.databaseObjects())
 		
 		insertRows(attachmentsToSave.databaseDictionaries(), insertType: .orIgnore, in: database)
 	}
@@ -84,13 +51,6 @@ final class AttachmentsTable: DatabaseRelatedObjectsTable {
 
 private extension AttachmentsTable {
 
-	func cacheAttachments(_ attachments: Set<Attachment>) {
-
-		for attachment in attachments {
-			cache[attachment.attachmentID] = attachment
-		}
-	}
-
 	func attachmentWithRow(_ row: FMResultSet) -> Attachment? {
 
 		// attachmentID is non-null in database schema.

Frameworks/Database/AuthorsTable.swift

@@ -21,14 +21,15 @@ final class AuthorsTable: DatabaseRelatedObjectsTable {
 	
 	let name: String
 	let databaseIDKey = DatabaseKey.authorID
+	var cache = [String: Author]()
 
 	init(name: String) {
 
 		self.name = name
 	}
 	
-	// MARK: DatabaseTable Methods
+	// MARK: DatabaseRelatedObjectsTable
-	
+
 	func objectWithRow(_ row: FMResultSet) -> DatabaseObject? {
 	
 		if let author = Author.authorWithRow(row) {
@@ -38,7 +39,20 @@ final class AuthorsTable: DatabaseRelatedObjectsTable {
 	}
 	
 	func save(_ objects: [DatabaseObject], in database: FMDatabase) {
-		// TODO
+
-	}
+		let attachments = objects.map { $0 as! Author }
+
+		// Authors in cache must already exist in database. Filter them out.
+		let authorsToSave = Set(attachments.filter { (attachment) -> Bool in
+			if let _ = cache[attachment.attachmentID] {
+				return false
+			}
+			return true
+		})
+
+		cacheAttachments(attachmentsToSave)
+
+		insertRows(attachmentsToSave.databaseDictionaries(), insertType: .orIgnore, in: database)
+}
 }
 

Frameworks/Database/TagsTable.swift

@@ -21,6 +21,8 @@ final class TagsTable: DatabaseRelatedObjectsTable {
 	
 	let name: String
 	let databaseIDKey = DatabaseKey.tagName
+	let cache = DatabaseObjectCache() // Unused, but protocol requires it
+	
 	init(name: String) {
 
 		self.name = name

Frameworks/RSDatabase/RSDatabase.xcodeproj/project.pbxproj

@@ -25,6 +25,7 @@
 		8400AC101E0CFD6B00AA7C57 /* RSDatabase.h in Headers */ = {isa = PBXBuildFile; fileRef = 84F22C581B52E0D9000060CE /* RSDatabase.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		840405DB1F1C158C00DF0296 /* DatabaseTable.swift in Sources */ = {isa = PBXBuildFile; fileRef = 840405DA1F1C158C00DF0296 /* DatabaseTable.swift */; };
 		840405DC1F1C15EA00DF0296 /* DatabaseTable.swift in Sources */ = {isa = PBXBuildFile; fileRef = 840405DA1F1C158C00DF0296 /* DatabaseTable.swift */; };
+		84314F4A1F68ECC600F710B2 /* DatabaseObjectCache.swift in Sources */ = {isa = PBXBuildFile; fileRef = 84314F491F68ECC600F710B2 /* DatabaseObjectCache.swift */; };
 		84419AD61B5ABD6D00C26BB2 /* FMDatabase+RSExtras.h in Headers */ = {isa = PBXBuildFile; fileRef = 84419AD41B5ABD6D00C26BB2 /* FMDatabase+RSExtras.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		84419AD71B5ABD6D00C26BB2 /* FMDatabase+RSExtras.m in Sources */ = {isa = PBXBuildFile; fileRef = 84419AD51B5ABD6D00C26BB2 /* FMDatabase+RSExtras.m */; };
 		84419ADA1B5ABD7400C26BB2 /* NSString+RSDatabase.h in Headers */ = {isa = PBXBuildFile; fileRef = 84419AD81B5ABD7400C26BB2 /* NSString+RSDatabase.h */; settings = {ATTRIBUTES = (Public, ); }; };
@@ -67,6 +68,7 @@
 		8400ABFA1E0CFBD800AA7C57 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		8400AC0E1E0CFC5600AA7C57 /* libsqlite3.tbd */ = {isa = PBXFileReference; lastKnownFileType = "sourcecode.text-based-dylib-definition"; name = libsqlite3.tbd; path = Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS10.2.sdk/usr/lib/libsqlite3.tbd; sourceTree = DEVELOPER_DIR; };
 		840405DA1F1C158C00DF0296 /* DatabaseTable.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DatabaseTable.swift; sourceTree = "<group>"; };
+		84314F491F68ECC600F710B2 /* DatabaseObjectCache.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = DatabaseObjectCache.swift; path = RSDatabase/DatabaseObjectCache.swift; sourceTree = "<group>"; };
 		84419AD41B5ABD6D00C26BB2 /* FMDatabase+RSExtras.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = "FMDatabase+RSExtras.h"; path = "RSDatabase/FMDatabase+RSExtras.h"; sourceTree = "<group>"; };
 		84419AD51B5ABD6D00C26BB2 /* FMDatabase+RSExtras.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = "FMDatabase+RSExtras.m"; path = "RSDatabase/FMDatabase+RSExtras.m"; sourceTree = "<group>"; };
 		84419AD81B5ABD7400C26BB2 /* NSString+RSDatabase.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = "NSString+RSDatabase.h"; path = "RSDatabase/NSString+RSDatabase.h"; sourceTree = "<group>"; };
@@ -178,6 +180,7 @@
 				84419AD91B5ABD7400C26BB2 /* NSString+RSDatabase.m */,
 				84C6DD001F395C13009AFB47 /* DatabaseObject.swift */,
 				840405DA1F1C158C00DF0296 /* DatabaseTable.swift */,
+				84314F491F68ECC600F710B2 /* DatabaseObjectCache.swift */,
 				848E22531F66528C0031D7C5 /* Related Objects */,
 				84DDF18A1C94FC45005E6CF5 /* FMDB */,
 				84F22C5A1B52E0D9000060CE /* Info.plist */,
@@ -389,6 +392,7 @@
 			files = (
 				84419AE71B5ABD7F00C26BB2 /* RSDatabaseQueue.m in Sources */,
 				84419AD71B5ABD6D00C26BB2 /* FMDatabase+RSExtras.m in Sources */,
+				84314F4A1F68ECC600F710B2 /* DatabaseObjectCache.swift in Sources */,
 				84C6DD011F395C13009AFB47 /* DatabaseObject.swift in Sources */,
 				84419ADB1B5ABD7400C26BB2 /* NSString+RSDatabase.m in Sources */,
 				840405DB1F1C158C00DF0296 /* DatabaseTable.swift in Sources */,

Frameworks/RSDatabase/RSDatabase/DatabaseObjectCache.swift

@@ -0,0 +1,33 @@
+//
+//  DatabaseObjectCache.swift
+//  RSDatabase
+//
+//  Created by Brent Simmons on 9/12/17.
+//  Copyright © 2017 Ranchero Software, LLC. All rights reserved.
+//
+
+import Foundation
+
+public final class DatabaseObjectCache {
+
+	private var d = [String: DatabaseObject]()
+
+	public init() {
+		//
+	}
+	public func add(_ databaseObjects: [DatabaseObject]) {
+
+		for databaseObject in databaseObjects {
+			self[databaseObject.databaseID] = databaseObject
+		}
+	}
+
+	public subscript(_ databaseID: String) -> DatabaseObject? {
+		get {
+			return d[databaseID]
+		}
+		set {
+			d[databaseID] = newValue
+		}
+	}
+}

Frameworks/RSDatabase/Related Objects/DatabaseRelatedObjectsTable.swift

@@ -13,7 +13,8 @@ import Foundation
 public protocol DatabaseRelatedObjectsTable: DatabaseTable {
 
 	var databaseIDKey: String { get}
-
+	var cache: DatabaseObjectCache { get }
+	
 	func fetchObjectsWithIDs(_ databaseIDs: Set<String>, in database: FMDatabase) -> [DatabaseObject]?
 	func objectsWithResultSet(_ resultSet: FMResultSet) -> [DatabaseObject]
 	func objectWithRow(_ row: FMResultSet) -> DatabaseObject?
@@ -27,10 +28,34 @@ public extension DatabaseRelatedObjectsTable {
 
 	func fetchObjectsWithIDs(_ databaseIDs: Set<String>, in database: FMDatabase) -> [DatabaseObject]? {
 
-		guard let resultSet = selectRowsWhere(key: databaseIDKey, inValues: Array(databaseIDs), in: database) else {
+		if databaseIDs.isEmpty {
 			return nil
 		}
-		return objectsWithResultSet(resultSet)
+
+		var cachedObjects = [DatabaseObject]()
+		var databaseIDsToFetch = Set<String>()
+
+		for databaseID in databaseIDs {
+			if let cachedObject = cache[databaseID] {
+				cachedObjects += [cachedObject]
+			}
+			else {
+				databaseIDsToFetch.insert(databaseID)
+			}
+		}
+
+		if databaseIDsToFetch.isEmpty {
+			return cachedObjects
+		}
+
+		guard let resultSet = selectRowsWhere(key: databaseIDKey, inValues: Array(databaseIDsToFetch), in: database) else {
+			return cachedObjects
+		}
+
+		let fetchedDatabaseObjects = objectsWithResultSet(resultSet)
+		cache.add(fetchedDatabaseObjects)
+
+		return cachedObjects + fetchedDatabaseObjects
 	}
 
 	func objectsWithResultSet(_ resultSet: FMResultSet) -> [DatabaseObject] {