NSInvalidArgumentException, reason: 'Invalid type in JSON write (__NSDate)'

Question

I\'m getting this exception when I try to JSON encode NSDate object.I believe NSDate is not compatible for JSON encoding. but I must encode the date.Any solutions?

Answer 1

As noted, you must first convert your NSDate to an NSString. It's not immediately clear, however, which format the date should be represented in. The answer can be found here: "JSON itself does not specify how dates should be represented, but Javascript does" -- ISO8601.

Here is an ISO8601 conversion method from a helper category for NSDate, courtesy Erica Sadun:

- (NSString *)ISO8601 {
    struct tm time;
    time_t interval = [self timeIntervalSince1970];
    gmtime_r(&interval, &time);
    char *x = calloc(1, 21);
    strftime_l(x, 20, "%FT%TZ", &time, gmtlocale);
    NSString *string = [NSString stringWithUTF8String:x];
    free(x);
    return string;
}

If you get an ISO8601 string back in a JSON payload and want to convert it to an NSDate, use this class method for NSDate:

+ (NSDate *)dateFromISO8601:(NSString *)string {
    if(!string) return nil;
    if (![string isKindOfClass:[NSString class]]) return nil;
    struct tm time;
    strptime_l([string UTF8String], "%FT%TZ", &time, gmtlocale);
    return [NSDate dateWithTimeIntervalSince1970:timegm(&time)];
}