ios7 - SKSpriteNode collision detection error -

i creating game ball suppose bounce off platforms. have set physics properties ball , platform(platform attains physics property when it's below ball). problem is: ball not bouncing (i have applied impulse in didbegincontact method) when ball makes contact platform, detects contact.

here didbegincontact code:

- (void) didbegincontact:(skphysicscontact *)contact {      skspritenode *firstnode, *secondnode;      firstnode = (skspritenode*) contact.bodya.node;     secondnode = (skspritenode*) contact.bodyb.node;      if ((contact.bodya.categorybitmask == ballcategory) && (contact.bodyb.categorybitmask == solidplatformcategory)) {          nslog(@"platform hit");          cgpoint contactpoint = contact.contactpoint;          [_ball.physicsbody applyimpulse:cgvectormake(0, 4) atpoint:contactpoint];      }  }    ///// here code skspritenode ball  - (void) addball {      _myball = [skspritenode spritenodewithimagenamed:@"ball.png"];      if (ui_user_interface_idiom() == uiuserinterfaceidiompad) {         _myball.scale = 0.4;     } else {         _myball.scale = 0.3;     }     _ball.position = cgpointmake(self.frame.size.width/2, _solidplatform.position.y + 2.5*_ball.size.height);     _ball.zposition = 2;     _ball.name = @"doodle";     _ball.physicsbody = [skphysicsbody bodywithrectangleofsize:_mydoodle.frame.size];     _ball.physicsbody.mass = 1.0;     _ball.physicsbody.restitution = 0.8;     _ball.physicsbody.dynamic = yes;     _ball.physicsbody.allowsrotation = no;     _ball.physicsbody.usesprecisecollisiondetection = yes;     _ball.physicsbody.categorybitmask = ballcategory;     _ball.physicsbody.collisionbitmask = solidplatformcategory;     _ball.physicsbody.contacttestbitmask = solidplatformcategory;      //skaction *moveupaction = [skaction movebyx:0.0 y:8*numberofplatforms duration:0.5];       [self addchild:_ball]; }  ////platform has been defined (not complete code):  _solidplatform7.physicsbody = [skphysicsbody bodywithrectangleofsize:_solidplatform7.frame.size];         _solidplatform7.physicsbody.dynamic = no;         _solidplatform7.physicsbody.affectedbygravity = no;         _solidplatform7.physicsbody.usesprecisecollisiondetection = yes;         _solidplatform7.physicsbody.categorybitmask = solidplatformcategory; 

ps: not getting collusion detection if define platform bodywithedgefromrect

difficult answer without seeing code, i'll try:

if ball not bounce @ all, check restitution property. higher values provide higher "bounciness":

ball.physicsbody.restitution=0.8; 

if want ball bounce endless between bottom , ceiling can invert gravity after each collision:

self.physicsworld.gravity = cgvectormake(0, self.physicsworld.gravity.dy * (-1)); 

hope helps. if not, please share code.

i've tried code. smaller changes works:

- (void) addball {      // bottom platforms     (int i=0; i<10; i++) {         skspritenode *mysprite = [skspritenode  spritenodewithcolor:[uicolor redcolor] size:cgsizemake(40, 20)];         cgpoint location = cgpointmake(i*40+60, 10);         //mysprite.size =cgsizemake(20, 40);         mysprite.position=location;         mysprite.physicsbody=[skphysicsbody bodywithrectangleofsize:mysprite.size];         mysprite.physicsbody.dynamic=false;         mysprite.physicsbody.categorybitmask=solidplatformcategory;         [self addchild:mysprite];     }       _ball = [skspritenode spritenodewithimagenamed:@"ball.png"];      if (ui_user_interface_idiom() == uiuserinterfaceidiompad) {         _ball.scale = 0.4;     } else {         _ball.scale = 0.3;     }      _ball.position = cgpointmake(self.frame.size.width/2, self.frame.size.width/2);     _ball.zposition = 2;     _ball.name = @"doodle";     //_ball.physicsbody = [skphysicsbody bodywithrectangleofsize:_mydoodle.frame.size];     _ball.physicsbody=[skphysicsbody bodywithcircleofradius:_ball.size.width/2];     _ball.physicsbody.mass = 1.0;     _ball.physicsbody.restitution = 1;     _ball.physicsbody.dynamic = yes;     _ball.physicsbody.allowsrotation = no;     _ball.physicsbody.usesprecisecollisiondetection = yes;     _ball.physicsbody.categorybitmask = ballcategory;     _ball.physicsbody.collisionbitmask = solidplatformcategory;     _ball.physicsbody.contacttestbitmask = solidplatformcategory;         //skaction *moveupaction = [skaction movebyx:0.0 y:8*numberofplatforms duration:0.5];       [self addchild:_ball]; }