added shorthand vars for inspecting MigrationType values. updated readme

CoreStore.xcodeproj/project.pbxproj

@@ -19,6 +19,7 @@
 		B56964D41B22FFAD0075EE4A /* DataStack+Migration.swift in Sources */ = {isa = PBXBuildFile; fileRef = B56964D31B22FFAD0075EE4A /* DataStack+Migration.swift */; };
 		B56965241B356B820075EE4A /* MigrationResult.swift in Sources */ = {isa = PBXBuildFile; fileRef = B56965231B356B820075EE4A /* MigrationResult.swift */; };
 		B59D5C221B5BA34B00453479 /* NSFileManager+Setup.swift in Sources */ = {isa = PBXBuildFile; fileRef = B59D5C211B5BA34B00453479 /* NSFileManager+Setup.swift */; };
+		B5A261211B64BFDB006EB6D3 /* MigrationType.swift in Sources */ = {isa = PBXBuildFile; fileRef = B5A261201B64BFDB006EB6D3 /* MigrationType.swift */; };
 		B5D1E22C19FA9FBC003B2874 /* NSError+CoreStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = B5D1E22B19FA9FBC003B2874 /* NSError+CoreStore.swift */; };
 		B5D372841A39CD6900F583D9 /* Model.xcdatamodeld in Sources */ = {isa = PBXBuildFile; fileRef = B5D372821A39CD6900F583D9 /* Model.xcdatamodeld */; };
 		B5D372861A39CDDB00F583D9 /* TestEntity1.swift in Sources */ = {isa = PBXBuildFile; fileRef = B5D372851A39CDDB00F583D9 /* TestEntity1.swift */; };
@@ -116,6 +117,7 @@
 		B56964D31B22FFAD0075EE4A /* DataStack+Migration.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "DataStack+Migration.swift"; sourceTree = "<group>"; };
 		B56965231B356B820075EE4A /* MigrationResult.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MigrationResult.swift; sourceTree = "<group>"; };
 		B59D5C211B5BA34B00453479 /* NSFileManager+Setup.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "NSFileManager+Setup.swift"; sourceTree = "<group>"; };
+		B5A261201B64BFDB006EB6D3 /* MigrationType.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MigrationType.swift; sourceTree = "<group>"; };
 		B5D1E22B19FA9FBC003B2874 /* NSError+CoreStore.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "NSError+CoreStore.swift"; sourceTree = "<group>"; };
 		B5D372831A39CD6900F583D9 /* Model.xcdatamodel */ = {isa = PBXFileReference; lastKnownFileType = wrapper.xcdatamodel; path = Model.xcdatamodel; sourceTree = "<group>"; };
 		B5D372851A39CDDB00F583D9 /* TestEntity1.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TestEntity1.swift; sourceTree = "<group>"; };
@@ -276,6 +278,7 @@
 				B56964D31B22FFAD0075EE4A /* DataStack+Migration.swift */,
 				B5FAD6AD1B518DCB00714891 /* CoreStore+Migration.swift */,
 				B56007151B4018AB00A9A8F9 /* MigrationChain.swift */,
+				B5A261201B64BFDB006EB6D3 /* MigrationType.swift */,
 				B56965231B356B820075EE4A /* MigrationResult.swift */,
 			);
 			path = Migrating;
@@ -552,6 +555,7 @@
 				B504D0D61B02362500B2BBB1 /* CoreStore+Setup.swift in Sources */,
 				B5D1E22C19FA9FBC003B2874 /* NSError+CoreStore.swift in Sources */,
 				B5E84F131AFF847B0064E85B /* Where.swift in Sources */,
+				B5A261211B64BFDB006EB6D3 /* MigrationType.swift in Sources */,
 				B5E84F141AFF847B0064E85B /* DataStack+Querying.swift in Sources */,
 				B56007141B3F6C2800A9A8F9 /* SectionBy.swift in Sources */,
 				B5E84F371AFF85470064E85B /* NSManagedObjectContext+Transaction.swift in Sources */,

CoreStore/Migrating/MigrationResult.swift

@@ -2,7 +2,7 @@
 //  MigrationResult.swift
 //  CoreStore
 //
-//  Copyright (c) 2014 John Rommel Estropia
+//  Copyright (c) 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
@@ -26,81 +26,6 @@
 import Foundation
 
 
-// MARK: - MigrationType
-
-/**
-The `MigrationType` specifies the type of migration required for a store.
-*/
-public enum MigrationType: BooleanType {
-    
-    // MARK: Public
-    
-    /**
-    Indicates that the persistent store matches the latest model version and no migration is needed
-    */
-    case None(version: String)
-    
-    /**
-    Indicates that the persistent store does not match the latest model version but Core Data can infer the mapping model, so a lightweight migration is needed
-    */
-    case Lightweight(sourceVersion: String, destinationVersion: String)
-    
-    /**
-    Indicates that the persistent store does not match the latest model version and Core Data could not infer a mapping model, so a custom migration is needed
-    */
-    case Heavyweight(sourceVersion: String, destinationVersion: String)
-    
-    /**
-    Returns the source model version for the migration type. If no migration is required, `sourceVersion` will be equal to the `destinationVersion`.
-    */
-    public var sourceVersion: String {
-        
-        switch self {
-            
-        case .None(let version):
-            return version
-            
-        case .Lightweight(let sourceVersion, _):
-            return sourceVersion
-            
-        case .Heavyweight(let sourceVersion, _):
-            return sourceVersion
-        }
-    }
-    
-    /**
-    Returns the destination model version for the migration type. If no migration is required, `destinationVersion` will be equal to the `sourceVersion`.
-    */
-    public var destinationVersion: String {
-        
-        switch self {
-            
-        case .None(let version):
-            return version
-            
-        case .Lightweight(_, let destinationVersion):
-            return destinationVersion
-            
-        case .Heavyweight(_, let destinationVersion):
-            return destinationVersion
-        }
-    }
-    
-    
-    // MARK: BooleanType
-    
-    public var boolValue: Bool {
-        
-        switch self {
-            
-        case .None:         return false
-        case .Lightweight:  return true
-        case .Heavyweight:  return true
-        }
-    }
-}
-
-
 // MARK: - MigrationResult
 
 /**

CoreStore/Migrating/MigrationType.swift

@@ -0,0 +1,125 @@
+//
+//  MigrationType.swift
+//  CoreStore
+//
+//  Copyright (c) 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
+
+
+// MARK: - MigrationType
+
+/**
+The `MigrationType` specifies the type of migration required for a store.
+*/
+public enum MigrationType: BooleanType {
+    
+    // MARK: Public
+    
+    /**
+    Indicates that the persistent store matches the latest model version and no migration is needed
+    */
+    case None(version: String)
+    
+    /**
+    Indicates that the persistent store does not match the latest model version but Core Data can infer the mapping model, so a lightweight migration is needed
+    */
+    case Lightweight(sourceVersion: String, destinationVersion: String)
+    
+    /**
+    Indicates that the persistent store does not match the latest model version and Core Data could not infer a mapping model, so a custom migration is needed
+    */
+    case Heavyweight(sourceVersion: String, destinationVersion: String)
+    
+    /**
+    Returns the source model version for the migration type. If no migration is required, `sourceVersion` will be equal to the `destinationVersion`.
+    */
+    public var sourceVersion: String {
+        
+        switch self {
+            
+        case .None(let version):
+            return version
+            
+        case .Lightweight(let sourceVersion, _):
+            return sourceVersion
+            
+        case .Heavyweight(let sourceVersion, _):
+            return sourceVersion
+        }
+    }
+    
+    /**
+    Returns the destination model version for the migration type. If no migration is required, `destinationVersion` will be equal to the `sourceVersion`.
+    */
+    public var destinationVersion: String {
+        
+        switch self {
+            
+        case .None(let version):
+            return version
+            
+        case .Lightweight(_, let destinationVersion):
+            return destinationVersion
+            
+        case .Heavyweight(_, let destinationVersion):
+            return destinationVersion
+        }
+    }
+    
+    /**
+    Returns `true` if the `MigrationType` is a lightweight migration. Used as syntactic sugar.
+    */
+    public var isLightweightMigration: Bool {
+        
+        if case .Lightweight = self {
+            
+            return true
+        }
+        return false
+    }
+    
+    /**
+    Returns `true` if the `MigrationType` is a heavyweight migration. Used as syntactic sugar.
+    */
+    public var isHeavyweightMigration: Bool {
+        
+        if case .Heavyweight = self {
+            
+            return true
+        }
+        return false
+    }
+    
+    
+    // MARK: BooleanType
+    
+    public var boolValue: Bool {
+        
+        switch self {
+            
+        case .None:         return false
+        case .Lightweight:  return true
+        case .Heavyweight:  return true
+        }
+    }
+}

CoreStoreDemo/CoreStoreDemo/MIgrations Demo/MyAppModel.xcdatamodeld/.xccurrentversion

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict/>
+</plist>

CoreStoreDemo/CoreStoreDemo/MIgrations Demo/MyAppModel.xcdatamodeld/MyAppModel.xcdatamodel/contents

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<model userDefinedModelVersionIdentifier="" type="com.apple.IDECoreDataModeler.DataModel" documentVersion="1.0" lastSavedToolsVersion="8166.2" systemVersion="14E46" minimumToolsVersion="Xcode 7.0">
+    <elements/>
+</model>

README.md

@@ -35,6 +35,7 @@ Unleashing the real power of Core Data with the elegance and safety of Swift
     - [Setting up](#setting-up)
     - [Migrations](#migrations)
         - [Incremental migrations](#incremental-migrations)
+        - [Forecasting migrations](#forecasting-migrations)
     - [Saving and processing transactions](#saving-and-processing-transactions)
         - [Transaction types](#transaction-types)
             - [Asynchronous transactions](#asynchronous-transactions)
@@ -287,7 +288,70 @@ This closure is executed on the main thread so UIKit calls can be done safely.
 
 
 ### Incremental migrations
-(README pending)
+By default, CoreStore uses Core Data's default automatic migration mechanism. In other words, CoreStore will try to migrate the existing persistent store to the *.xcdatamodeld* file's current model version. If no mapping model is found from the store's version to the data model's version, CoreStore gives up and reports an error.
+
+The `DataStack` lets you specify hints on how to break a migration into several sub-migrations using a `MigrationChain`. This is typically passed to the `DataStack` initializer and will be applied to all stores added to the `DataStack` with `addSQLiteStore(...)` and its variants:
+```swift
+let dataStack = DataStack(migrationChain: 
+    ["MyAppModel", "MyAppModelV2", "MyAppModelV3", "MyAppModelV4"])
+```
+The most common usage is to pass in the *.xcdatamodeld* version names in increasing order as above.
+
+For more complex migration paths, you can also pass in a version tree that maps the key-values to the source-destination versions:
+```swift
+let dataStack = DataStack(migrationChain: [
+    "MyAppModel": "MyAppModelV3",
+    "MyAppModelV2": "MyAppModelV4",
+    "MyAppModelV3": "MyAppModelV4"
+])
+```
+This allows for different migration paths depending on the starting version. The example above resolves to the following paths:
+- MyAppModel-MyAppModelV3-MyAppModelV4
+- MyAppModelV2-MyAppModelV4
+- MyAppModelV3-MyAppModelV4
+
+Initializing with empty values (either `nil`, `[]`, or `[:]`) instructs the `DataStack` to disable incremental migrations and revert to the default migration behavior (i.e. use the .xcdatamodel's current version as the final version):
+```swift
+let dataStack = DataStack(migrationChain: nil)
+```
+
+The `MigrationChain` is validated when passed to the `DataStack` and unless it is empty, will raise an assertion if any of the following conditions are met:
+- a version appears twice in an array
+- a version appears twice as a key in a dictionary literal
+- a loop is found in any of the paths
+
+One important thing to remember is that **if a `MigrationChain` is specified, the *.xcdatamodeld*'s "Current Version" will be bypassed** and the `MigrationChain`'s leafmost version will be the `DataStack`'s base model version.
+
+
+### Forecasting migrations
+
+Sometimes migrations are huge and you may want prior information so your app could display a loading screen, or to display a confirmation dialog to the user. For this, CoreStore provides a `requiredMigrationsForSQLiteStore(...)` method you can use to inspect a persistent store before you actually call `addSQLiteStore(...)`:
+```swift
+do {
+    let migrationTypes: [MigrationType] = CoreStore.requiredMigrationsForSQLiteStore(fileName: "MyStore.sqlite")
+    if migrationTypes.count > 1
+        || (migrationTypes.filter { $0.isHeavyweightMigration }.count) > 0 {
+        // ... Show special waiting screen
+    }
+    else if migrationTypes.count > 0 {
+        // ... Show simple activity indicator
+    }
+    else {
+        // ... Do nothing
+    }
+
+    CoreStore.addSQLiteStore(/* ... */)
+}
+catch {
+    // ...
+}
+```
+`requiredMigrationsForSQLiteStore(...)` returns an array of `MigrationType`s, where each item in the array may be either of the following values:
+```swift
+case Lightweight(sourceVersion: String, destinationVersion: String)
+case Heavyweight(sourceVersion: String, destinationVersion: String)
+```
+Each `MigrationType` indicates the migration type for each step in the `MigrationChain`. Use these information as fit for your app.