Saturday, August 29, 2015

Interlude 15 - Site Update (Last update 6/04/16)

Over the years, Codea has continued to grow and evolve. As of this post, the current version is 2.3.1(47). With each new build, features are added and some old ways of doing things are dropped (deprecated if you want to get fancy).

This means that tutorials also need to be updated otherwise they become more of a problem than a solution. For the past year or so, I have been focussed on other activities but the time has come to do a major upgrade to the Codea Tutorials site. I will start by upgrading and retesting all of the tutorials against the latest version of Codea.

As each tutorial is updated, I will note this at the top and indicate the latest version of Codea it has been tested against.

In addition to updating all of the screenshots and adding figure numbers, I have added a lot of additional material and tried to make the tutorials clearer. All the code examples are also now correctly formatted using the online markup tool.

Finally, there are some new tutorials coming which will show how to build the classic lunar lander game in Codea.

As always, your comments and suggestions are welcome. Leave a comment here or contact me via the Reefwing Software site.

Status:

- Tutorial 1 updated                   - Interlude 7 updated
- Tutorial 2 updated                   - Interlude 8 updated
- Interlude 1 updated                 - Interlude 9 updated
- Tutorial 3 updated
- Interlude 2 updated
- Interlude 3 updated
- Interlude 4 updated
- Tutorial 4 updated
- Interlude 5 updated
- Tutorial 5 updated
- Interlude 6 updated
- Tutorial 6 updated

Friday, July 5, 2013

Tutorial 31 - Codea Collision Detection



31.1 Overview


Collision detection is a common requirement in game or simulator programming. It involves determining whether two or more objects have intersected. We will only be examining this problem in 2D (two dimensions) for this tutorial.

There are two main approaches to detecting collisions, discrete and continuous. In the discrete case, we advance the physical model by a small time step, and then check if any of our objects are intersecting, or are so close to each other that for all intents and purposes we consider them intersecting. For the continuous case, we write a collision detection algorithm which will be able to predict the trajectories of the physical bodies. The instants of collision are calculated, and the physical bodies never actually have to collide for us to detect the collision. 

The continuous approach is more accurate but is also more difficult. So for this tutorial, we will develop a few different discrete detection algorithms. Discrete detection will get the job done in many situations and is well suited to the Codea draw loop architecture. As long as your time steps are small enough, there aren't too many objects and the objects are large enough, you shouldn't miss any collisions.

Note that collision detection can chew up a lot of CPU time. If n is the number of objects on the screen that we need to test, then the:

Number of collision detection tests = (n² - n) / 2

Thus the number of tests increases exponentially with the number of objects being modeled. Consequently, if you have more than a few objects, you will want to look at optimising your tests.

31.2 Bounding Box Detection


If we have two rectangular objects with origins at (x1, y1) and (x2, y2) and dimensions (i.e. width and heights) of (w1, h1) and (w2, h2), then we can use the following function to determine whether the two rectangles are overlapping at a particular point in time.

function CollisionDetected(x1,  y1,  w1,  h1,  x2,  y2,  w2,  h2) 

  Collision = false

 
  if (y2 >= y1 and y1 + h1 >= y2) or (y2 + h2 >= y1 and y1 + h1 >= y2 + h2) 
    or (y1 >= y2 and y2 + h2 >= y1) 
        or (y1 + h1 >= y2 and y2 + h2 >= y1 + h1) then
     if x2 >= x1 and x1 + w1 >= x2 then          -- corner 1
        Collision = true
     end
     if x2 + w2 >= x1 and x1 + w1 >= x2 + w2 then  -- corner 2
        Collision = true 
     end
     if x1 >= x2 and x2 + w2 >= x1 then           -- corner 3
       Collision = true 
     end
     if x1 + w1 >= x2 and x2 + w2 >= x1 + w1 then  -- corner 4
       Collision = true
     end
  end

  return Collision -- return whether or not a collision is detected 


end
 


A faster version (about 10%) of the same function (albeit a bit more difficult to follow) is:

function CollisionDetected(x1,  y1,  w1,  h1,  x2,  y2,  w2,  h2) 
return not ((y1+h1 < y2) or (y1 > y2+h2) or (x1 > x2+w2) or (x1+w1 < x2))
end

And here is another version:

function CollisionDetected(x1,  y1,  w1,  h1,  x2,  y2,  w2,  h2) 
    local ax2, bx2, ay2, by2 = x1 + w1, x2 + w2, y1 + h1, y2 + h2
    return ax2 > x2 and bx2 > x1 and ay2 > y2 and by2 > y2
end

We will leave it as an exercise for the reader to demonstrate that these functions are all logically equivalent.


31.3 Bounding Circle Detection


The simplest method to detect circles colliding is to check whether the circles are overlapping. This can be done by calculating the distance between the centers of the two circles and seeing if it is less than or equal to the sum of the radii of the circles. If it is then a collision has occurred. 

function CollisionDetected(x1, y1, r1, x2, y2, r2)

    local dx = x2 - x1

    local dy = y2 - y1

    return math.sqrt(dx^2 + dy^2) <= r1 + r2


end


The square root in the distance formula is unnecessary because the inequality will still hold if we square both sides. Removing the square root will increase your collision detection speed, especially if you are checking for many collisions, because this is a relatively expensive calculation. 

function CollisionDetected(x1, y1, r1, x2, y2, r2)

    local dx = x2 - x1

    local dy = y2 - y1

    return (dx^2 + dy^2) <= (r1 + r2)^2


end





31.3 Box2D Collision Detection


If you don't want to roll your own collision detection, then you can utilise the built in collision detection functionality of Codea, which is provided courtesy of its Box2D implementation. To use this, the bodies which are colliding need to be created using the physics.body() function.  The downside of using this approach is that physics bodies can only have the following shapes (the property is called shapeType):
  • Circle; 
  • Polygon; 
  • Chain; or 
  • Edge (usually used for the ground or walls).

So for pixel perfect collisions you will need to use another approach if your sprites can't be outlined using one of the shapes above. In many cases however, you can approximate the sprite shape using these.

In addition to the shape type, we need to define the body type for our physics object. There are three options:
  1. Dynamic - these objects move under the influence of collisions, forces, joints and gravity (we will use this type for our asteroids);
  2. Static - these objects are not supposed to move and are unaffected by collisions and forces (e.g. the ground or walls); and 
  3. Kinematic - these objects can move by setting their linear velocity but like static bodies are unaffected by collisions and forces (we will use this type for our ship, if the ship collides with an asteroid we want it to explode not bounce away). 
To demonstrate how easy this is to implement we will create a simple Asteroids game with a ship in the center of the screen and randomly generated asteroids, which will destroy our ship if we detect a collision.

While Box2D will model the movement of our physics bodies for us, it is our responsibility to render (i.e. draw) representations of these bodies on the screen. To do this we will use a simplified version of the PhysicsDebugDraw class (called PhysicsDraw) which is included with the Physics Lab example. A copy of this simplified class is included at the end of the tutorial.

function setup()

    physics.gravity(0.0, 0.0)
    physicsDraw = PhysicsDraw()
    ship = createShip(WIDTH/2, HEIGHT/2)
    physicsDraw:addBody(ship)
    asteroidTimer = 0

end


The physics.gravity function allows us to set the gravity for our game for the x and y axis respectively. The units are pixels per second squared. We have set our program gravity to zero since we are in space. The createShip function will create a new physics body which we add to the table of bodies in PhysicsDraw. Every draw cycle, PhysicsDraw will render all the physics bodies at their current location.

function createShip(x, y, w, h)

   -- (x, y) are the centre co-ordinates of the ship.
   -- (w, h) define the width and height of the box containing the ship,
   -- if not specified they are 50 and 35 respectively.

   local width = w or 50
   local height = h or 35
   local shipBody = physics.body(POLYGON, 
                                  vec2(0, height), vec2(width, height/2), 
                                  vec2(0, 0), vec2(height/2, height/2), 
                                  vec2(0, height))

   shipBody.x = x
   shipBody.y = y
   shipBody.type = KINEMATIC
   shipBody.sleepingAllowed = false
   shipBody.info = "ship"
   shipBody.interpolate = true

   return shipBody


end

Next up we need functions to create our asteroids. We will use the same function (createRandPoly) to generate the debris field for when our ship collides with an asteroid and explodes.

function createRandPoly(x, y, s1, s2)

   -- s1 and s2 define the range of length for the poly sides
   -- count defines the number of sides of the poly

   local minLength = s1 or 1
   local maxLength = s2 or 5
   local count = math.random(5,10)
   local r = math.random(minLength, maxLength)
   local a = 0
   local d = 2 * math.pi / count
   local points = {}

   for i = 1,count do
       local v = vec2(r,0):rotate(a) 
                     + vec2(math.random(-10,10), math.random(-10,10))
       a = a + d
       table.insert(points, v)
   end

   local poly = physics.body(POLYGON, unpack(points))

   poly.x = x
   poly.y = y
   poly.type = DYNAMIC
   poly.sleepingAllowed = false
   poly.restitution = 0.5
   poly.info = "poly"
   physicsDraw:addBody(poly)

   return poly

end

function createAsteroid(x, y)

   return createRandPoly(x, y, 25, 65)


end

The asteroids are placed off the screen in random locations and accelerated towards the screen where eventually one of them will collide with our ship. Inside the draw() function we create a new asteroid every second.

function placeRandomAsteroid()

   -- Generate (x, y) co-ordinates which are
   -- initially off the screen.

   local x = math.random(WIDTH)

   if x < WIDTH/2 then
       x = x - WIDTH
   else
       x = x + WIDTH
   end

   local y = math.random(HEIGHT)

   if y < HEIGHT/2 then
       y = y - HEIGHT
   else
       y = y + HEIGHT
   end

   -- Create an asteroid at the new co-ordinates

   local asteroid = createAsteroid(x, y)

   -- Give the asteroid a linear velocity
   -- towards the screen (and our ship)

   local dX, dY = math.random(50, 100), math.random(50, 100)

   if x > WIDTH then
       dX = -dX
   end

   if y > HEIGHT then
       dY = -dY
   end

   asteroid.linearVelocity = vec2(dX, dY)

end

function createExplosionAt(x, y)

   -- Creates 6 small polygon moving out from (x, y)
   -- to simulate our ship exploding.
   --
   -- the body.info field is set to debris so that we
   -- can render it the same colour as our ship (i.e. to
   -- distinguish them from the asteroid polygons.

   randPoly1 = createRandPoly(x, y)
   randPoly1:applyForce(vec2(50,50))
   randPoly1.info = "debris"
   randPoly2 = createRandPoly(x, y)
   randPoly2:applyForce(vec2(50,50))
   randPoly2.info = "debris"
   randPoly3 = createRandPoly(x, y)
   randPoly3:applyForce(vec2(50,50))
   randPoly3.info = "debris"
   randPoly4 = createRandPoly(x, y)
   randPoly4:applyForce(vec2(-50,50))
   randPoly4.info = "debris"
   randPoly5 = createRandPoly(x, y)
   randPoly5:applyForce(vec2(-50,50))
   randPoly5.info = "debris"
   randPoly6 = createRandPoly(x, y)
   randPoly6:applyForce(vec2(-50,50))     
   randPoly6.info = "debris"   

end

-- This function gets called once every frame

function draw()

   -- This sets a dark background color 

   background(40, 40, 50)

   -- Generate a random asteroid every second

   asteroidTimer = asteroidTimer + DeltaTime

   if asteroidTimer > 1.0 then
       placeRandomAsteroid()
       asteroidTimer = 0
   end

   -- Do your drawing here

   physicsDraw:draw()

end

-- Collision Detection
--
-- This is simply a matter of checking whether one of the two
-- colliding bodies are our ship.

function collide(contact)

   if contact.bodyA == ship or contact.bodyB == ship then
       createExplosionAt(ship.x, ship.y)
       ship.info = "destroyed"
       ship = nil
   end


end

Collision detection is then just a matter of calling the built in collide() function and checking whether one of the two colliding bodies is our ship. Included below is the simplified PhysicsDebugDraw class which is responsible for rendering our physics bodies each frame.

--# PhysicsDraw

PhysicsDraw = class()

-- Simplified Physics Debug Draw class from the Physics Lab
-- example in Codea.

function PhysicsDraw:init()
   self.bodies = {}
   self.contacts = {}
end

function PhysicsDraw:addBody(body)
   table.insert(self.bodies,body)
end

function PhysicsDraw:draw()

   pushStyle()
   smooth()
   noFill()

   for i,body in ipairs(self.bodies) do

       pushMatrix()
       translate(body.x, body.y)
       rotate(body.angle)

       if body.type == STATIC then
           stroke(255,255,255,255)
       elseif body.type == DYNAMIC and body.info ~= "debris" then
           stroke(150,255,150,255)
       else
           stroke(150,150,255,255)
       end

       if body.shapeType == POLYGON and body.info ~= "destroyed" then
           strokeWidth(3.0)
           local points = body.points
           for j = 1,#points do
               a = points[j]
               b = points[(j % #points)+1]
               line(a.x, a.y, b.x, b.y)
           end
       elseif body.shapeType == CHAIN or body.shapeType == EDGE then
           strokeWidth(3.0)
           local points = body.points
           for j = 1,#points-1 do
               a = points[j]
               b = points[j+1]
               line(a.x, a.y, b.x, b.y)
           end      
       elseif body.shapeType == CIRCLE then
           strokeWidth(3.0)
           line(0,0,body.radius-3,0)            
           ellipse(0,0,body.radius*2)
       end

       popMatrix()
   end 

   stroke(255, 0, 0, 255)
   fill(255, 0, 0, 255)

   for k,v in pairs(self.contacts) do
       for m,n in ipairs(v.points) do
           ellipse(n.x, n.y, 10, 10)
       end
   end

   popStyle()
end

function PhysicsDraw:collide(contact)
   if contact.state == BEGAN then
       self.contacts[contact.id] = contact
       sound(SOUND_HIT, 2643)
   elseif contact.state == MOVING then
       self.contacts[contact.id] = contact
   elseif contact.state == ENDED then
       self.contacts[contact.id] = nil
   end

end

A complete download of the code presented in this tutorial is available from our Gist repository.

Thursday, April 25, 2013

Tutorial 30 - Codea v1.5.2: Objective C Add On, Game Center

Figure 0. iOS Dev Center


30.1 Overview


CodeaAddon is an experimental protocol for adding native extensions to exported Codea projects. You must deal with Lua directly to register your functions and globals. This protocol should be considered alpha and is subject to change in future Codea releases.As with the previous tutorial on iAds, we have provided a lot of background on Game Center in these tutorials:
Have a look at the above to refresh your knowledge on what is required from an iTunes Connect perspective as we will only cover that area briefly in this tutorial.


Figure 1. Find out the Bundle Identifier for your App.


30.2 Registering your Application in iTunes Connect


In order to test your app's Game Center functionality you need to register an app ID associated with this app which enables Game Center. The association is done via the bundle identifier of your app (Figure 1). Click on the app title in the top left of the project navigator screen in Xcode to bring up this screen. Make sure that you have selected the "Summary" tab. Write down the bundle identifier shown, we will need this shortly.

Figure 2. Set up a new App ID for your app.

Log into your apple developer account, go to the iOS Dev Center (Figure 0) and select the Certificates, Identifiers & Profiles link on the right hand side of the page. Select a name for your app ID (pick something you can remember e.g. we used AudioDemoAppID) and fill in the App ID Suffix bundle identifier. This is the critical step which will link your app to the configuration in iTunes Connect. Use the bundle identifier that you wrote down earlier. Click "confirm" and then "submit".

Figure 3. Associate your bundle identifier with the App ID.

Head back to the iOS Dev Center (Figure 0) and this time click on iTunes Connect link in the top right of the page. You will be asked to sign in again, do so and then click on the Manage your Apps link (Figure 4).

Figure 4. iTunes Connect

On the Manage your Apps page (Figure 5), click on the "Add New App" button at the top left of the screen. Click on iOS App on the next screen.

Figure 5. Manage your Apps

Fill in the app name, SKU number (this can be any unique identifier, we normally use the date), and then select the App ID that you just created for the bundle identifier (Figure 6). Click "Continue" when you are done.

Figure 6. iTunes Connect App Information.

Fill in all the meta data (have a look at the earlier tutorials if you get stuck) and save the configuration. When you are done (Figure 7), we can enable Game Center for your app. Click on the "Manage Game Center" button on the right hand side of the page (Figure 7).

Figure 7. Metadata addition complete.

Click on the button that says "Enable for Single Game" and then either configure some achievements and leader boards or just click "Done". We can now test our exported app once we have included the Game Center add on.

Figure 8. Adding the GameKit Framework.


30.3 Add the GameKit Framework to Your App


Fire up Xcode and load the exported version of your Codea application (See Tutorial 27). Click on the imported project file at the top of the project navigator then in the Build Phases tab, scroll down to the link binary with libraries area and select the drop down arrow. Click on the "+" button below your existing frameworks to add a new framework. Find GameKit and click on "Add"


30.4 Changes to your Exported AppDelegate Files


All of the source code files are provided at the end of this tutorial. You need to update AppDelegate.h as follows:

//
// AppDelegate.h
// AudioDemo
//
// Used to demonstrate the audio, game center and iAds add on libraries
//
// Created by Reefwing Software on Sunday, 14 April 2013
// Copyright (c) Reefwing Software. All rights reserved.
//

    #import <UIKit/UIKit.h>
    #import "AudioAddOn.h"
    #import "IAdsAddOn.h"
    #import "GameCenterAddOn.h"

    @class CodeaViewController;

    @interface AppDelegate : UIResponder <UIApplicationDelegate>

    @property (strong, nonatomic) IAdsAddOn *iAdsAddOn;
    @property (strong, nonatomic) AudioAddOn *audioAddOn;
    @property (strong, nonatomic) GameCenterAddOn *gameCenterAddOn;
    @property (strong, nonatomic) UIWindow *window;
    @property (strong, nonatomic) CodeaViewController *viewController;

@end


And AppDelegate.mm, should now look like:

//
// AppDelegate.mm
// AudioDemo
//
// Created by Reefwing Software on Sunday, 14 April 2013
// Copyright (c) Reefwing Software. All rights reserved.
//

#import "AppDelegate.h"
#import "CodeaViewController.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{

    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.viewController = [[CodeaViewController alloc] init];

    // Create and add our AudioAddOn to Codea

    self.audioAddOn = [[AudioAddOn alloc] init];
    [self.viewController registerAddon: self.audioAddOn];

    // Create and add our iAdsAddOn to Codea

    self.iAdsAddOn = [[IAdsAddOn alloc] init];
    [self.viewController registerAddon: self.iAdsAddOn];

    // Create and add our GameCenterAddOn to Codea

    self.gameCenterAddOn = [[GameCenterAddOn alloc] init];
    [self.viewController registerAddon: self.gameCenterAddOn];

    NSString* projectPath = [[[NSBundle mainBundle] bundlePath]    stringByAppendingPathComponent:@"AudioDemo.codea"];

    [self.viewController loadProjectAtPath:projectPath];

    self.window.rootViewController = self.viewController;
    [self.window makeKeyAndVisible];

    return YES;

}

- (void)applicationWillResignActive:(UIApplication *)application
{

}

- (void)applicationDidEnterBackground:(UIApplication *)application
{

}

- (void)applicationWillEnterForeground:(UIApplication *)application
{

}

- (void)applicationDidBecomeActive:(UIApplication *)application

}

- (void)applicationWillTerminate:(UIApplication *)application
{

}

@end


Obviously there is no need to register the iAds and Audio add ons if you are just using Game Center. We have just left these in to demonstrate how you can stack add ons.



Figure 9. If you try to show Achievements or Leaderboards with none set up in iTunes Connect, you will see this screen.

30.5 The Game Center Add On


You need to add the GameCenterAddOn.h and GameCenterAddOn.m files to your project (plus the other iAds and Audio add on classes if you are using them). These are available below.

To do this, right click on the Addons folder in the project navigator and select Add files to "YourProjectName"... Navigate to where ever you saved these files and select them.

This Game Center Add On will make four new functions available in your Lua code:

  • gameCenterStart(); 
  • showLeaderBoardWithIdentifier(int ident); 
  • showAchievementsView(); and
  • playerIsAuthenticated;

You need to call gameCenterStart() first as your game must authenticate a local player before you can use any Game Center classes. 


Figure 10. You may need to sign in the first time you try to authenticate a player.

If you want to add more Game Center functionality the just follow the pattern in the add on. For example, if you want to add a save score function then, in GameCenterAddOn.h add:

static int saveScore(struct lua_State *state);

Then in GameCenterAddOn.m add/modify:

// Add to method

- (void)codea:(CodeaViewController*)controller didCreateLuaState:(struct lua_State*)L
{
    ...
    lua_register(L, "saveScore", saveScore);
    ...
}

// New Objective C method

- (void) saveNewScore: (int) score
{
    // INSERT YOUR LEADERBOARD IDENTIFIER IN THE LINE BELOW
    // Replace "Easy Difficulty" with your identifier from iTunes Connect

    GKScore *scoreReporter = [[GKScore alloc] initWithCategory: @"Easy Difficulty"];

    if (scoreReporter)
    {
        scoreReporter.value = score;

        [scoreReporter reportScoreWithCompletionHandler: ^(NSError *error)
        {
            if (error != nil)
            {
                // handle the reporting error

                NSLog(@"Game Center: Error Saving Score - %@", [error localizedDescription]);
            }
        }];   
    }
}

// New C function

static int saveScore(struct lua_State *state)
{
    [gameCenterAddOnInstance saveNewScore: lua_tonumber(state, 1)];

    return 0;
}

Then in your Lua code you can use saveScore(yourNewScore).

Figure 11. Player Authenticated.


30.6 Download the Code



Saturday, April 20, 2013

Tutorial 29 - Codea v1.5.2: Objective C Add On, iAds


Figure 0. Codea implementing iAds - showAdFromTop()

29.1 Overview


CodeaAddon is an experimental protocol for adding native extensions to exported Codea projects. You must deal with Lua directly to register your functions and globals. This protocol should be considered alpha and is subject to change in future Codea releases.

With that disclaimer out of the way, let's have a look at what we can do with this new functionality. We have previously done tutorials to add Game Center and iAd functionality using the old runtime but with the great new export to Xcode functionality, this is no longer the best way to skin that particular cat.

You may want to re-read our previous tutorial on implementing iAds in Codea as we won't cover the same background in this tutorial.

We will build on the previous tutorial which uses the audio add on. This has the added benefit of showing how you can stack a number of add ons to the same project.

Note that before you start adding advertising support to your applications available on iTunes, you must first agree to the iAd Network agreement. Further, you must explicitly enable iAd for each application in iTunes Connect. As a part of the iAd Network, you control the kinds of ads that are delivered to your application. We don't need to do this to test it in the simulator though.


Figure 1. Add the iAd Framework to your App



29.2 Add the iAd Framework to your App


Fire up Xcode and load the exported version of your Codea application (See Tutorial 27). Click on the imported project file at the top of the project navigator then in the Build Phases tab, scroll down to the link binary with libraries area and select the drop down arrow. Click on the "+" button below your existing frameworks to add a new framework. Find iAds and click on "Add" (Figure 1).


29.3 Update the AppDelegate Files


In the AppDelegate we need to register our new add on classes. The new AppDelegate.h file now looks like:


//
//  AppDelegate.h
//  AudioDemo
//
//  Used to demonstrate the audio add on and iAds add on libraries
//
//  Created by Reefwing Software on Sunday, 14 April 2013
//  Copyright (c) Reefwing Software. All rights reserved.
//

#import <UIKit/UIKit.h>
#import "AudioAddOn.h"
#import "IAdsAddOn.h"

@class CodeaViewController;

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) IAdsAddOn *iAdsAddOn;
@property (strong, nonatomic) AudioAddOn *audioAddOn;
@property (strong, nonatomic) UIWindow *window;
@property (strong, nonatomic) CodeaViewController *viewController;

@end


And similarly to what we had in the previous tutorial AppDelegate.mm now looks like:


//
//  AppDelegate.mm
//  AudioDemo
//
//  Created by Reefwing Software on Sunday, 14 April 2013
//  Copyright (c) Reefwing Software. All rights reserved.
//

#import "AppDelegate.h"
#import "CodeaViewController.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.viewController = [[CodeaViewController alloc] init];
    
    //  Create and add our AudioAddOn to Codea
    
    self.audioAddOn = [[AudioAddOn alloc] init];
    [self.viewController registerAddon: self.audioAddOn];
    
    //  Create and add our iAdsAddOn to Codea
    
    self.iAdsAddOn = [[IAdsAddOn alloc] init];
    [self.viewController registerAddon: self.iAdsAddOn];
    
    NSString* projectPath = [[[NSBundle mainBundle] bundlePath] stringByAppendingPathComponent:@"AudioDemo.codea"];
    
    [self.viewController loadProjectAtPath:projectPath];
    
    self.window.rootViewController = self.viewController;
    [self.window makeKeyAndVisible];
    
    return YES;
}

- (void)applicationWillResignActive:(UIApplication *)application
{
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
}

- (void)applicationDidBecomeActive:(UIApplication *)application
{
}

- (void)applicationWillTerminate:(UIApplication *)application
{
}

@end



29.4 The iAds Add On


Our iAds add on implements two internal booleans, isBannerVisible and showBannerFromTop. Hopefully the use of these should be fairly obvious. We also register three new functions for use within Codea:


  1. showAdFromTop();
  2. showAdFromBottom(); and
  3. hideAd()
Our example project demonstrates the use of all 3 of these functions. We start by displaying Ads from the top of the page (once the ad has been loaded from the ad server). We hide ads when the play button is tapped and then show them from the bottom when the stop button is tapped.

In the simulator apple will send you ad errors regularly (e.g. Ad inventory unavailable) to make sure that your code can handle this. Your app will get rejected if it displays an empty ad banner so the add on takes care of this situation. When displaying the ad banner, it will slide down from the top or up from the bottom depending on which function that you have used. Similarly hideAd() will animate the ad sliding above or below the screen depending on the state of the boolean showBannerFromTop.

Figure 2. Codea implementing iAds - showAdFromBottom()


This example add on only handles ads for an iPad in portrait orientation. We have included device detection macros in IAdsAddOn.h, just remove the comment slashes if you want to use these to position your Ads. To handle different orientations and devices update the banner view frame variables in the two methods:
  1. - (void)showBannerViewAnimated:(BOOL)animated; and
  2. - (void)hideBannerViewAnimated:(BOOL)animated.

If you don't want the banner views to slide to the new position then set animated = NO for the above two methods.

29.5 Download the Code


The complete code listing is available below.