ios - Is it ok not to invoke [super init] in a custom init method? -

ios - Is it ok not to invoke [super init] in a custom init method? -

i have mkpolyline subblass want implement nscoding, i.e.

@interface rsroutepolyline : mkpolyline <nscoding>

i asked question on best way encode c-array , got first-class answer. however, there no init method defined on mkpolyline, i.e. there no other way give info other class method polylinewithpoints:points.

is code comment ok?

- (void)encodewithcoder:(nscoder *)acoder { mkmappoint *points = self.points; nsuinteger pointcount = self.pointcount; nsdata *pointdata = [nsdata datawithbytes:points length:pointcount * sizeof(mkmappoint)]; [acoder encodeobject:pointdata forkey:@"points"]; [acoder encodeinteger:pointcount forkey:@"pointcount"]; } - (id)initwithcoder:(nscoder *)adecoder { nsdata* pointdata = [adecoder decodeobjectforkey:@"points"]; nsuinteger pointcount = [adecoder decodeintegerforkey:@"pointcount"]; // edit here @ughoavgfhw's comment mkmappoint* points = (mkmappoint*)[pointdata bytes]; // line ok? self = (rsroutepolyline*)[mkpolyline polylinewithpoints:points count:pointcount]; homecoming self; }

you should phone call init method on subclass of nsobject. since mkpolyline nsobject, should init it.

but mkpolyline has no methods , no init. objective c's of telling you can't subclass it.

instead, wduk suggested, define own class. keeps track of list point points, , manages nscoding save , restore them needed.

@interface rspolyline: nsobject<nscoding> - (id) initwithpoints: (nsarray*) points; - (id) initwithcoder:(nscoder *)adecoder; - (void) encodewithcoder:(nscoder *)acoder; - (mkpolyline*) polyline; @end

your class can generate polyline on request, perhaps caching result if performance issue.

as rule, don't reach inheritance first. when want extend , improve class, think first of composition.

ios objective-c cocoa-touch nscoding