Box2d Objective C Basic Sample

Javascript Version is here
http://jslogic.blogspot.in/2013/03/box2d-javascript-basic-sample.html

Which I have made in Box2D with Javascript. Now its time to convert this in Objective C. So here it is 

First Install Cocos2d as per RayWenderlich Blog
http://www.raywenderlich.com/28602/intro-to-box2d-with-cocos2d-2-x-tutorial-bouncing-balls

Now create a new Box2D project
and update HelloWorldLayer.h as below, If not

#import <GameKit/GameKit.h>

// When you import this file, you import all the cocos2d classes

#import "cocos2d.h"

#import "Box2D.h"

#import "GLES-Render.h"

//Pixel to metres ratio. Box2D uses metres as the unit for measurement.

//This ratio defines how many pixels correspond to 1 Box2D "metre"

//Box2D is optimized for objects of 1x1 metre therefore it makes sense

//to define the ratio so that your most common object type is 1x1 metre.

#define PTM_RATIO 32

// HelloWorldLayer

@interface HelloWorldLayer : CCLayer <GKAchievementViewControllerDelegate, GKLeaderboardViewControllerDelegate>

{

    CCTexture2D *spriteTexture_; // weak ref

    b2World* world;     // strong ref

    GLESDebugDraw *m_debugDraw;  // strong ref

}

// returns a CCScene that contains the HelloWorldLayer as the only child

+(CCScene *) scene;

@end

Now Delete the Code in init function of HelloWorld.mm and put the following code in init function

-(id) init

{

    if( (self=[super init])) {

        // init physics

        [self initPhysics];

        //This method allows to update the screen used for animation

        [self scheduleUpdate];

    }

    return self;

}

Now the main logic is written in initPhysics function

-(void) initPhysics

{

    

    CGSize s = [[CCDirector sharedDirector] winSize];

    

    b2Vec2 gravity;

    gravity.Set(0.0f, -10.0f);

    world = new b2World(gravity);

    

    

    // Do we want to let bodies sleep?

    world->SetAllowSleeping(true);

    

    world->SetContinuousPhysics(true);

    

    m_debugDraw = new GLESDebugDraw( PTM_RATIO );

    world->SetDebugDraw(m_debugDraw);

    

    uint32 flags = 0;

    flags += b2Draw::e_shapeBit;

    //  flags += b2Draw::e_jointBit;

    //  flags += b2Draw::e_aabbBit;

    //  flags += b2Draw::e_pairBit;

    //  flags += b2Draw::e_centerOfMassBit;

    m_debugDraw->SetFlags(flags);

    

    

    // Define the ground body.

    b2BodyDef groundBodyDef;

    groundBodyDef.position.Set(0, 0); // bottom-left corner

    

    // Call the body factory which allocates memory for the ground body

    // from a pool and creates the ground box shape (also from a pool).

    // The body is also added to the world.

    b2Body* groundBody = world->CreateBody(&groundBodyDef);

    

    // Define the ground box shape.

    b2EdgeShape groundBox;

    

    // bottom

    

    groundBox.Set(b2Vec2(0,0), b2Vec2(s.width/PTM_RATIO,0));

    groundBody->CreateFixture(&groundBox,0);

    

    // top

    groundBox.Set(b2Vec2(0,s.height/PTM_RATIO), b2Vec2(s.width/PTM_RATIO,s.height/PTM_RATIO));

    groundBody->CreateFixture(&groundBox,0);

    

    // left

    groundBox.Set(b2Vec2(0,s.height/PTM_RATIO), b2Vec2(0,0));

    groundBody->CreateFixture(&groundBox,0);

    

    // right

    groundBox.Set(b2Vec2(s.width/PTM_RATIO,s.height/PTM_RATIO), b2Vec2(s.width/PTM_RATIO,0));

    groundBody->CreateFixture(&groundBox,0);

    

    b2BodyDef bodyDef;

    bodyDef.type = b2_dynamicBody;

    

    b2PolygonShape carShape;

    b2Vec2 vertics[] = {

        b2Vec2 (0.0f, 0.0f),

        b2Vec2 (0.5f, -2.0f),

        b2Vec2 (1.0f, 3.0f),

        b2Vec2 (0.3f, 3.0f),

        b2Vec2 (0.0f, 1.0f)

    };

    carShape.Set(vertics, 5);

    

    b2FixtureDef fixtureDef;

    fixtureDef.shape = &carShape;

    fixtureDef.density = 1.0f;

    fixtureDef.friction = 0.5f;

    fixtureDef.restitution = 0.2f;

    

    bodyDef.position.Set(5, 400/PTM_RATIO/2);

    world->CreateBody(&bodyDef)->CreateFixture(&fixtureDef);

}

get Orientation of iPhone/iPad at runtime

Define previousOrientation first, as below in your class.h file

UIDeviceOrientation previousOrientation;

then write code in class.m as below to check the orientation of device. Remember Its not for accelerometer. 

- (id)init {

    

    if ((self=[super init])) {

        [[NSNotificationCenter defaultCenter] addObserver:self

                                                 selector:@selector(orientationChanged: )

                                                    name:@"UIDeviceOrientationDidChangeNotification" object:nil];

    }

}

- (void) orientationChanged:(NSNotification *)notification{

    UIDeviceOrientation orientation = [[UIDevice currentDevice] orientation];

    

    previousOrientation = orientation;

    if (previousOrientation == UIDeviceOrientationPortrait)

    {
        NSLog(@"PORTRAIT");
    }

    else if (previousOrientation == UIDeviceOrientationLandscapeLeft)

    {
        NSLog(@"LANDSCAPE LEFT");
    }

    else if (previousOrientation == UIDeviceOrientationLandscapeRight)

    {
        NSLog(@"LANDSCAPE RIGHT");
    }
    else
    {
        NSLog(@"PORTRAIT DOWN");
    }
}

Random Number between some number in xCode

Here is the code to find the Random Values between some numbers in Objective C

int minValue = 100;
int maxValue = 4500;
int rangeValue = maxValue - minValue;
int actualValue = (arc4random() % rangeValue) + minValue;

Get Screen Size of iPhone/iPad

Here is a simple line to get the screen size in xCode.

UIScreen *screen = [UIScreen mainScreen];

CGRect fullScreenRect = screen.bounds;

//This will be used to get the width and height

fullScreenRect.size.width, fullScreenRect.size.height

And For Games, where Cocoas is using

CGSize winSize = [CCDirector sharedDirector].winSize;

NSLog(@" %f, %f", winSize.width, winSize.height);


Swift:

var screen: UIScreen = UIScreen.mainScreen()

var fullScreenRect: CGRect = screen.bounds

//This will be used to get the width and height

fullScreenRect.size.width, fullScreenRect.size.height