attaching binary data to Salesforce attachment obj

attachment.m

    ZKSObject *attachment = [ZKSObject withType:@"Attachment"];
    [attachment setFieldValue:[NSString stringWithFormat:@"Nameofyourattachment%@.png", [NSDate date]] field:@"Name"];
    [attachment setFieldValue:@"a07M0000000FV5VIAW" field:@"ParentId"];
    
    NSData *cSign = UIImagePNGRepresentation([UIImage imageNamed:@"signature.png"]);
    
    [attachment setFieldValue:[cSign base64EncodedString] field:@"Body"];
    
    [[FDCServerSwitchboard switchboard] create:[NSArray arrayWithObject:attachment] target:self selector:@selector(saveAttachmentToSFResult:error:context:) context:attachment];


/*Call back from SF when done*/


- (void)saveSignatureToSFResult:(NSArray *)results error:(NSError *)error context:(id)attachment
{

    if (results && !error){
        NSString* attachmentId = [[results objectAtIndex:0] id]; 
        NSLog(@"Attachment ObjId: %@ saved to Salesforce", attachmentId);
    }
    else if (error){
         NSLog(@"Attachment %@", [error description]);
    }
}