ios - view as property of model object alternative -

i'm building arithmetic app & in there subclasses of nsobject numbers , digits.both of these have corresponding view objects take datasource (either number or digit) , delegate, view controller.

i have found useful in getting views & model work set digit views property of corresponding digits.

for example, number class has nsmutablearray property holds digits.

if want find size corresponding numberview, write can write code in controller:

-(void) updatenumberviewframesize:(acnumberview*) sender {     nsuinteger i;     float width = 0, height = 0;     (acdigit* digit in [sender.datasource returnnumberviewdatasource].digitarray)     {         width += digit.digitview.size.width;         height += digit.digitview.size.width;     }     sender.frame = cgrectmake(sender.frame.origin.x, sender.frame.origin.y, width, height); } 

the code works fine, feel not practice hold pointer view model, if model isn't using itself.

if bad practice, potential pitfalls, , there better way achieve type end ?

first: right. no design.

second: calculate size of number view inside model. number view should know size itself. knows number through data source , can digits. has information calculating size.

to show problem, imagine (even situation on ios not common), display same number @ 2 places (= different number views). break model. why?

solution: put code related graphic state (drawing, size, …) number view , digit view. on half of way additional work. @ end, when every code migrated view layer, easy computing inside model.