Merge: iOS: implement data_store and missing life cycle callbacks

Implement the main missing features of _app.nit_ on iOS: `data_store` and life-cycle hooks (like `on_save_state`). These changes can be seen on the calculator app, as it preserves its context using the `data_store`.

`data_store` is implemented with `NSUserDefaults` to store objects sertialized to Json. It is very similar to Android's implementation using shared preferences. This may be a bit limited as it is not meant to hold large strings, and some data objects (like game saves) should instead be saved to a file.

This PR also implements all life-cycle callbacks in iOS, until now only `on_create` was implemented. We may have to update _app.nit_ life-cycle to fit better with the life-cycle of iOS, the states between a running app and a fully stopped app are different between iOS and Android. I'm thinking of removing the two callbacks on_start/on_stop and keep only the more general callbacks on_create/on_destroy and on_resume/on_pause, and the services on_restore_state/on_save_state.

Pull-Request: #1947
Reviewed-by: Jean Privat <jean@pryen.org>

lib/app/data_store.nit

@@ -26,6 +26,7 @@ import serialization
 # TODO: move on the platform once qualified names are understand in the condition
 import linux::data_store is conditional(linux)
 import android::data_store is conditional(android)
+import ios::data_store is conditional(ios)
 
 redef class App
 	# Services to store and load data

lib/binary/serialization.nit

@@ -336,6 +336,12 @@ redef class Text
 
 		return true
 	end
+
+	redef fun serialize_to_binary(v)
+	do
+		v.stream.write_byte kind_string
+		v.stream.write_block to_s
+	end
 end
 
 # ---
@@ -397,14 +403,6 @@ redef class Char
 	end
 end
 
-redef class String
-	redef fun serialize_to_binary(v)
-	do
-		v.stream.write_byte kind_string
-		v.stream.write_block self
-	end
-end
-
 redef class NativeString
 	redef fun serialize_to_binary(v)
 	do

lib/cocoa/foundation.nit

@@ -149,3 +149,24 @@ extern class NSIndexPath in "ObjC" `{ NSIndexPath * `}
 		return [self indexAtPosition: position];
 	`}
 end
+
+# Interface to the defaults system for an app to customize its behavior to match a user's preferences
+extern class NSUserDefaults in "ObjC" `{ NSUserDefaults * `}
+	super NSObject
+
+	# Wraps: `[NSUserDefaults standardUserDefaults]`
+	new standard_user_defaults in "ObjC" `{
+		return [NSUserDefaults standardUserDefaults];
+	`}
+
+	# Wraps: `[NSIndexPath stringForKey:]`
+	fun string_for_key(key: NSString): NSString in "ObjC" `{
+		return [self stringForKey: key];
+	`}
+
+	# Wraps: `[NSIndexPath setObject: forKey:]`
+	fun set_object(value: NSObject, default_name: NSString)
+	in "ObjC" `{
+		[self setObject:value forKey:default_name];
+	`}
+end

lib/ios/app.nit

@@ -139,7 +139,12 @@ redef class App
 	# The application just launched but is not yet displayed to the user
 	#
 	# Redef this method to customize the behavior.
-	fun did_finish_launching_with_options: Bool do return true
+	fun did_finish_launching_with_options: Bool
+	do
+		on_create
+		on_restore_state
+		return true
+	end
 
 	# The application is about to move from active to inactive state
 	#
@@ -151,7 +156,7 @@ redef class App
 	# Redef this method to pause ongoing tasks, disable timers, and
 	# throttle down OpenGL ES frame rates. Games should use this
 	# method to pause.
-	fun will_resign_active do end
+	fun will_resign_active do on_pause
 
 	# The application just left foreground it can be suspended at any time
 	#
@@ -161,27 +166,38 @@ redef class App
 	#
 	# If your application supports background execution, this method
 	# is called instead of `will_terminate` when the user quits.
-	fun did_enter_background do end
+	fun did_enter_background
+	do
+		on_save_state
+		on_stop
+	end
 
 	# The application will enter the foreground
 	#
 	# Called as part of the transition from the background to the
 	# inactive state.
 	#
-	# Redef to und changes made on entering the background.
-	fun will_enter_foreground do end
+	# Redef to undo changes made on entering the background.
+	fun will_enter_foreground do on_start
 
 	# The application just became active
 	#
 	# Redef to restart any tasks that were paused (or not yet started) while
 	# the application was inactive. If the application was previously
 	# in the background, optionally refresh the user interface.
-	fun did_become_active do end
+	fun did_become_active do on_resume
 
-	# The application is about to terminate (not suspended)
+	# The application is about to terminate (from a state other than suspended)
 	#
 	# Redef to save data if appropriate.
-	fun will_terminate do end
+	fun will_terminate
+	do
+		# Usually a forced termination by the system
+		on_save_state
+		on_pause
+		on_stop
+		on_destroy
+	end
 end
 
 app.register_args(program_name.to_cstring, args.length, args)

lib/ios/data_store.nit

@@ -0,0 +1,60 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Implements `app::data_store` using `NSUserDefaults`
+module data_store
+
+import app::data_store
+import cocoa::foundation
+private import json::serialization
+
+redef class App
+	redef var data_store = new UserDefaultView
+end
+
+private class UserDefaultView
+	super DataStore
+
+	# The `NSUserDefaults` used to implement `DataStore`
+	var user_defaults = new NSUserDefaults.standard_user_defaults is lazy
+
+	redef fun [](key)
+	do
+		var nsstr = user_defaults.string_for_key(key.to_nsstring)
+
+		if nsstr.address_is_null then return null
+
+		# TODO report errors
+		var deserializer = new JsonDeserializer(nsstr.to_s)
+		return deserializer.deserialize
+	end
+
+	redef fun []=(key, value)
+	do
+		var nsobject: NSString
+
+		if value == null then
+			nsobject = new NSString.nil
+		else
+			var serialized_string = new StringWriter
+			var serializer = new JsonSerializer(serialized_string)
+			serializer.serialize(value)
+
+			# TODO report errors
+			nsobject = serialized_string.to_s.to_nsstring
+		end
+
+		user_defaults.set_object(nsobject, key.to_nsstring)
+	end
+end

lib/ios/ui/ui.nit

@@ -78,7 +78,7 @@ in "ObjC" `{
 redef class App
 	redef fun did_finish_launching_with_options
 	do
-		on_create
+		super
 		window.native.make_key_and_visible
 		return true
 	end

lib/json/serialization.nit

@@ -466,6 +466,8 @@ redef class Text
 		end
 		return res
 	end
+
+	redef fun serialize_to_json(v) do v.stream.write(to_json)
 end
 
 redef class Serializable
@@ -534,10 +536,6 @@ redef class Char
 	end
 end
 
-redef class String
-	redef fun serialize_to_json(v) do v.stream.write(to_json)
-end
-
 redef class NativeString
 	redef fun serialize_to_json(v) do to_s.serialize_to_json(v)
 end

lib/serialization/serialization.nit

@@ -221,7 +221,7 @@ redef class Char super DirectSerializable end
 redef class Int super DirectSerializable end
 redef class Float super DirectSerializable end
 redef class NativeString super DirectSerializable end
-redef class String super DirectSerializable end
+redef class Text super DirectSerializable end
 redef class SimpleCollection[E] super Serializable end
 redef class Map[K, V] super Serializable end