Remove all objects in cocos2d game world with box2d

You can remove all objects in cocos2d game world with box2d

for(b2Body *b = _world->GetBodyList(); b; b=b->GetNext()) {

        if (b->GetUserData() != NULL) {

            CCSprite *sprite = (CCSprite *)b->GetUserData();

            [self removeChild:sprite cleanup:YES];

            _world->DestroyBody(b);

           

        }

    }

Box2D Joints

1. Mouse Joint

-(BOOL) ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event {
    CGPoint touchLocation = [touch locationInView:[touch view]];
    touchLocation = [[CCDirector sharedDirector]

        convertToGL:touchLocation];
    touchLocation = [self convertToNodeSpace:touchLocation];
    b2Vec2 locationWorld =

        b2Vec2(touchLocation.x/PTM_RATIO, touchLocation.y/PTM_RATIO);

    b2AABB aabb;
    b2Vec2 delta = b2Vec2(1.0/PTM_RATIO, 1.0/PTM_RATIO);
    aabb.lowerBound = locationWorld - delta;
    aabb.upperBound = locationWorld + delta;
    SimpleQueryCallback callback(locationWorld);
    world->QueryAABB(&callback, aabb);

if (callback.fixtureFound) {
        b2Body *body = callback.fixtureFound->GetBody();
        b2MouseJointDef mouseJointDef;
        mouseJointDef.bodyA = groundBody;
        mouseJointDef.bodyB = body;
        mouseJointDef.target = locationWorld;
        mouseJointDef.maxForce = 50 * body->GetMass();
        mouseJointDef.collideConnected = true;

        mouseJoint = (b2MouseJoint *)
            world->CreateJoint(&mouseJointDef);

        body->SetAwake(true);

return YES; }

    return TRUE;
}

-(void) ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event {
    CGPoint touchLocation = [touch locationInView:[touch view]];
    touchLocation = [[CCDirector sharedDirector]

        convertToGL:touchLocation];
    touchLocation = [self convertToNodeSpace:touchLocation];
    b2Vec2 locationWorld = b2Vec2(touchLocation.x/PTM_RATIO,

        touchLocation.y/PTM_RATIO);

    if (mouseJoint) {
        mouseJoint->SetTarget(locationWorld);

} }

-(void) ccTouchEnded:(UITouch *)touch withEvent:(UIEvent *)event {
     if (mouseJoint) {

        world->DestroyJoint(mouseJoint);

        mouseJoint = NULL;
     }

}

        2. Revolute Joint  

    wheelL = [Box2DSprite spriteWithSpriteFrameName:@"Wheel.png"];

    wheelL.gameObjectType = kCartType;

    wheelLBody = [self createWheelWithSprite:wheelL

                                      offset:b2Vec2(-63.0/100.0, -48.0/100.0)];

   

    b2RevoluteJointDef revJointDef;

    revJointDef.Initialize(body, wheelLBody,

                           wheelLBody->GetWorldCenter());

   

    revJointDef.enableMotor = true;

    revJointDef.maxMotorTorque = 1000;

    revJointDef.motorSpeed = 0;

//restrict revolute joints to a certain angle range with Box2D

revJointDef.lowerAngle = CC_DEGREES_TO_RADIANS(-30);

revJointDef.upperAngle = CC_DEGREES_TO_RADIANS(60);

revJointDef.enableLimit = true;

 ///////////////////////

    wheelLJoint = (b2RevoluteJoint *) world->CreateJoint(&revJointDef);


        3. Prismatic Joint

A prismatic joint is a type of joint that restricts two bodies so they can move relative to each other only along a specified axis. 

   b2PrismaticJointDef prisJointDef;

    prisJointDef.Initialize(body, legsBody,

                            legsBody->GetWorldCenter(), axis);

    prisJointDef.enableLimit = true;

    prisJointDef.lowerTranslation = 0.0;

    prisJointDef.upperTranslation = 43.0/100.0;

    world->CreateJoint(&prisJointDef);

Add Pop Up Message to the Game

#import "cocos2d.h"

@interface Scene4UILayer : CCLayer {

    CCLabelTTF *label;

}

- (BOOL)displayText:(NSString *)text

andOnCompleteCallTarget:(id)target selector:(SEL)selector;

@end

//////////////

#import "Scene4UILayer.h"

@implementation Scene4UILayer

- (id)init {   

    if ((self = [super init])) {       

        CGSize winSize = [CCDirector sharedDirector].winSize;

        label = [CCLabelTTF labelWithString:@"" fontName:@"Helvetica"

                                   fontSize:48.0];

        label.position = ccp(winSize.width/2, winSize.height/2);

        label.visible = NO;

        [self addChild:label];       

    }

    return self;   

}

- (BOOL)displayText:(NSString *)text

andOnCompleteCallTarget:(id)target selector:(SEL)selector {

    [label stopAllActions];

    [label setString:text];

    label.visible = YES;

    label.scale = 0.0;

    label.opacity = 255;

   

    CCScaleTo *scaleUp = [CCScaleTo actionWithDuration:0.5 scale:1.2];

    CCScaleTo *scaleBack =

    [CCScaleTo actionWithDuration:0.1 scale:1.0];

    CCDelayTime *delay = [CCDelayTime actionWithDuration:2.0];

    CCFadeOut *fade = [CCFadeOut actionWithDuration:0.5];

    CCHide *hide = [CCHide action];

    CCCallFuncN *onComplete =

    [CCCallFuncN actionWithTarget:target selector:selector];

    CCSequence *sequence = [CCSequence actions:scaleUp, scaleBack,

                            delay, fade, hide, onComplete, nil];

    [label runAction:sequence];   

    return TRUE;   

}

@end

Adding Box2D Files to your Cocos2D Project

1. First, download 'cocos2d-iphone-x.0.tar.gz' , and Open a Finder window and navigate to where you downloaded the Cocos2D source.
2. Open the folder and navigate to external\Box2d\Box2D. 
3. Open a second Finder window, navigate to your project, and navi-
   gate to libs. 
4. Copy the Box2D folder to the libs folder. 

• Adding the Box2D directory to your Xcode project   

• You have to set "User Header Search Paths" as 'Project_Name/libs'

• And also you have to add two more files :
  the ones responsible for drawing Box2D objects to the screen for debug purposes.

  navigate to your Cocos2D directory, and navigate to templates\cocos2d_box2d_app\Classes. Inside you’ll find the files GLES- Render.h and GLES-Render.mm. Select those two files and drag them to your new Box2D group in Xcode. Make sure Copy items into destination group’s folder (if needed) is checked, and click Finish.

• After that  #import "Box2D.h", what ever file you want and mack sure rename the file with a '.mm' extension. Because you are importing the Box2D header file (which uses C++) in files that are set up to use only Objective-C. To instruct the compiler to allow both C++ and Objective-C, we can add '.mm' extension.