cocos2d iphone - What role does contentSize play in positioning and anchor points? -

i've read countless posts , articles on anchor points , affect on positioning, , yet still find myself in situations things make absolutely no sense.

example:

@interface displaytest : ccsprite;  @property (nonatomic, strong) ccsprite *body; @end  @implementation displaytest  -(instancetype)init {     if (self = [super initwithfile:@"test.png" rect:cgrectzero]) {         self.position = ccp(384, 512);         [self addchild:self.body];         self.body.scalex = 384;         self.anchorpoint = ccp(0.5f, 0.5f);     }     return self; }  -(ccsprite *)body {     if (!_body) {         cgrect rect = cgrectmake(1, 1, 1, 16);         _body             = [[ccsprite alloc] initwithtexture:self.texture rect:rect];         _body.anchorpoint = ccp(0.5f, 0.5f);     }     return _body; } 

i 384px wide, 16px high rectangle centered in screen.

excellent..

now, let's want touch detection on object.. let's going have many other ccsprite children, , want perform touch detection on top level object instead of performing on children...

i can't because:

(lldb) expr self.contentsize (cgsize) $17 = (width = 0, height = 0) 

ok, so... no big deal right?

(lldb) expr self.contentsize = self.body.boundingbox.size (cgsize) $19 = (width = 384, height = 16) 

now rectangle half way off screen. what??? wtf?? why?!?!?!?!?!

so put should be, have either 1 of following:

self.anchorpoint = ccp(0.0, 0.0); 

or

self.position = ccp(384 + (self.contentsize.width/2), 512 + (self.contentsize.height / 2)); 

although setting anchor point (0.0, 0.0) "fixes" putting in center of screen, makes touch detection impossible because, when call converttonodespace:, if have touched sprite on left side of it, value negative , negative value cannot found in rectangle. see post wrote years ago this: touch detection of ccnode anchored 0,0 center?

so, in order make work, have had go positioning things offset of 1/2 it's content size, , don't understand why have that. anchor point of 0.5, 0.5 supposed mean child sprites placed relative position (centered), assuming child sprites have anchor point of 0.5, 0.5-- in case does.

can please explain me?