objective c - NSDate's initWithString: is returning nil -

i'm using stig brautaset's json framework serialize objects, including nsdates (which not directly supported).

i decided use nsdate's description jsonfragment representation of date (i don't care minor loss of precision incurred in doing so).

to extend stig brautaset's json framework include nsdates, defined category:

@interface nsdate  (nsdate_json) <jsoninitializer>  -(nsstring *) jsonfragment;  @end 

to recreate nsdate (and other classes) json, defined protocol following initializer:

@protocol jsoninitializer <nsobject>  -(id) initwithjsonrepresentation: (nsstring *) ajsonrepresentation;  @end 

i'm having issues initializer. in nsdate's case, calls initwithstring:, , that's trouble: returns nil. implementation:

#import "nsdate+json.h"   @implementation nsdate (nsdate_json)  -(nsstring *) jsonfragment{     nsstring *strrepr = [self description];     return [strrepr jsonfragment]; }  -(id) initwithjsonrepresentation:(nsstring *)ajsonrepresentation{       return [self initwithstring: ajsonrepresentation]; //returns nil! } @end 

i'm not sure what's going on. besides, compiler warns me initwithstring: method in initwithjsonrepresentation: not found.

anybody knows might going on?

the full source code test case available here.

your test program is:

nsdate *d1 = [[[nsdate alloc] init] autorelease]; nsstring *repr = [d1 jsonfragment];  nsdate *dd = [[[nsdate alloc] initwithstring:[d1 description]] autorelease ]; nsdate *d2 = [[[nsdate alloc] initwithjsonrepresentation:repr] autorelease]; 

your -jsonfragment category method is:

-(nsstring *) jsonfragment{     nsstring *strrepr = [self description];     return [strrepr jsonfragment]; } 

what’s happening in method obtain string representation of date using -description, , json representation of string using -jsonfragment.

in sbjson, -jsonfragment returns representation of given object json data. json specification requires strings quoted. in program:

nsstring *repr = [d1 jsonfragment]; 

repr contains string @"\"2011-04-29 10:20:30 -0600\"". because of quotes, string not valid string used -[nsdate initwithstring:].

if change:

nsstring *repr = [d1 jsonfragment]; 

to:

nsstring *repr = [[d1 jsonfragment] jsonfragmentvalue]; 

so sbjson parses fragment , returns string without quotes, should work.