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// main.m
// Sample6
// Created by Andreas Grosam on 5/22/12.
// Copyright (c) 2012 __MyCompanyName__. All rights reserved.
#if !__has_feature(objc_arc)
#error This Objective-C file shall be compiled with ARC enabled.
#import <Foundation/Foundation.h>
#import "JPJson/JPJsonWriter.h"
#import "JPJson/JPJsonWriterExtensions.h"
#include <time.h>
// Objectives:
// 1) Create a custom class which can be serialized by JPJsonWriter
// Helper category for creating a RFC3339DateFormatter
@implementation NSDateFormatter (RFC3339DateFormatter)
+(NSDateFormatter*) rfc3339DateFormatter {
NSDateFormatter* rfc3339DateFormatter = [[NSDateFormatter alloc] init];
NSLocale* enUSPOSIXLocale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];
[rfc3339DateFormatter setLocale:enUSPOSIXLocale];
[rfc3339DateFormatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"];
[rfc3339DateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
return rfc3339DateFormatter;
// Serializing a NSDate
// An NSDate object cannot be serialized directly with a JPJsonWriter. Thus, the
// occurence of an NSDate object within a hierarchy of objects which should
// be serialzed to JSON will not work by default.
// A NSDate object may be serialized as a formatted date string. So, in order to
// make this work - we just ned to define a Category for NSDate and implement the
// JPJsonSerializableProtocol.
// Serializing a NSDate involves to convert the date into a string with an
// appropriate format. The format purposfully meets RFC 3339. Then we just serialize
// the string using the JPJsonSerializableProtocol. The JPJsonSerializableProtocol
// is already implemented for a NSString by the JPJson library.
@interface NSDate (JPJsonWriterExtension) <JPJsonSerializableProtocol>
@implementation NSDate (JPJsonWriterExtension)
- (int) JPJson_serializeTo:(id<JPJsonStreambufferProtocol>) buffer
#if 0 /* Using a NSDateFormatter */
NSDateFormatter* rfc3339DateFormatter = [NSDateFormatter rfc3339DateFormatter];
id<JPJsonSerializableProtocol> dateString = (id<JPJsonSerializableProtocol>)[rfc3339DateFormatter stringFromDate:self];
return [dateString JPJson_serializeTo:buffer encoding:encoding options:options level:level];
/* Use time utilities from ISO C (or POSIX, C99 UNIX Spec)*/
struct tm* timeinfo;
char buf[64];
time_t rawtime = [self timeIntervalSince1970];
timeinfo = gmtime(&rawtime);
size_t len = strftime(buf, sizeof(buf), "%FT%TZ", timeinfo);
CFStringRef cfDateString = CFStringCreateWithBytesNoCopy(NULL, (const UInt8 *)buf, len, kCFStringEncodingASCII, false, kCFAllocatorNull);
int result = [(__bridge id)cfDateString JPJson_serializeTo:buffer encoding:encoding options:options level:level];
return result;
// A custom class `Person` having four properties, one of them is an array.
@interface Person : NSObject
- (id) initWithFirstName:(NSString*)firstName lastName:(NSString*)lastName dayOfBirth:(NSDate*)dob;
@property (nonatomic, retain) NSString* firstName;
@property (nonatomic, retain) NSString* lastName;
@property (nonatomic, retain) NSDate* dayOfBirth;
@property (nonatomic, readonly, retain) NSArray* comments;
- (void) addComment:(NSString*)comment;
@implementation Person {
NSString* _firstName;
NSString* _lastName;
NSDate* _dayOfBirth;
NSMutableArray* _comments;
- (id) initWithFirstName:(NSString*)firstName lastName:(NSString*)lastName dayOfBirth:(NSDate*)dob
self = [super init];
if (self) {
_firstName = firstName;
_lastName = lastName;
_dayOfBirth = dob;
return self;
@synthesize firstName = _firstName;
@synthesize lastName = _lastName;
@synthesize dayOfBirth = _dayOfBirth;
@synthesize comments = _comments;
- (void) addComment:(NSString*) comment
if (comment == nil)
if (_comments == nil) {
_comments = [[NSMutableArray alloc] initWithCapacity:12];
[_comments addObject:comment];
// Serializing a Custom Class
// The following class `Person` shall be serialized directly using the `JPJsonWriter`.
// The class `Person` shall be mapped to a JSON Object - that is a list of key-value
// pairs, where the key are comprised by the properties.
// For this purpose the implementation utilizes the JPJsonWriter class method
// `serializeObjectAsJSONObject:buffer:encoding:options:level:`, which in turn
// requires that the class Person implements the `NSFastEnumeration` protocol,
// the JPJsonSerializableProtocol, and as well responds to message `count` and
// message `objectForKey:`
@interface Person (JPJsonWriterExtension) <JPJsonSerializableProtocol, NSFastEnumeration>
@implementation Person (JPJsonWriterExtension)
- (id) objectForKey:(id)aKey {
return [self valueForKey:aKey];
- (NSUInteger) count {
return 4; // return the number of properies
- (NSUInteger) countByEnumeratingWithState:(NSFastEnumerationState *)state
objects:(id __unsafe_unretained [])buffer
static id __unsafe_unretained properties[] = {@"firstName", @"lastName", @"dayOfBirth", @"comments"};
if (state->state >= 4) {
return 0;
state->itemsPtr = properties;
state->state = 4;
state->mutationsPtr = &state->extra[0];
return 4;
- (int) JPJson_serializeTo:(id<JPJsonStreambufferProtocol>) buffer
return [JPJsonWriter serializeObjectAsJSONObject:self buffer:buffer encoding:encoding options:options level:level];
int main (int argc, const char * argv[])
@autoreleasepool {
// Date in local time zone
NSDateFormatter* dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]];
[dateFormatter setDateFormat:@"yyyy'-'MM'-'dd' 'HH:mm:ss"];
//[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
// Create an array of Persons:
NSArray* json = [[NSArray alloc] initWithObjects:
[[Person alloc] initWithFirstName:@"John"
dayOfBirth:[dateFormatter dateFromString:@"1962-04-21 20:00:00"]],
[[Person alloc] initWithFirstName:@"Pete"
dayOfBirth:[dateFormatter dateFromString:@"1912-10-12 08:00:00"]],
[[Person alloc] initWithFirstName:@"Tab"
dayOfBirth:[dateFormatter dateFromString:@"1970-03-09 09:00:00"]],
Person* p0 = [json objectAtIndex:0];
[p0 addComment:@"This is a comment"];
[p0 addComment:@"This is another comment"];
NSError* error;
NSData* jsonData = [JPJsonWriter dataWithObject:json
if (!jsonData) {
NSLog(@"Extracting JSON into string failed with error: %@", error);
return -1;
else {
NSError* error;
NSString* filePath = @"persons-json-pretty.json";
BOOL result = [jsonData writeToFile:filePath options:0 error:&error];
if (!result) {
NSLog(@"Writing JSON document to file '%@' failed with error: %@", filePath, error);
else {
NSLog(@"Wrote JSON document to file '%@'" , filePath);
#if defined (DEBUG)
NSString* s = [NSString stringWithContentsOfFile:filePath
NSLog(@"%@:\n%@", filePath, s);
return 0;
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