Recreate JSON data in Objective-C - objective-c

Question

I'm trying to build an app on the Feedly API. In order to be able to mark categories as read, I need to post some data to the API. I'm having no success, though.
This is what the API needs as input:
{
"lastReadEntryId": "TSxGHgRh4oAiHxRU9TgPrpYvYVBPjipkmUVSHGYCTY0=_1449255d60a:22c3491:9c6d71ab",
"action": "markAsRead",
"categoryIds": [
"user/c805fcbf-3acf-4302-a97e-d82f9d7c897f/category/design",
"user/c805fcbf-3acf-4302-a97e-d82f9d7c897f/category/photography"
],
"type": "categories"
}
And this is my method:
- (void)markCategoryAsRead: (NSString*)feedID{
NSLog(#"Feed ID is: %#", feedID);
NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];
NSString *accessToken = [standardUserDefaults objectForKey:#"AccessToken"];
NSString *feedUrl = [NSURL URLWithString:#"https://sandbox.feedly.com/v3/markers"];
NSError *error = nil;
NSDictionary *tmp = [[NSDictionary alloc] initWithObjectsAndKeys:
#"markAsRead", #"action",
#"categories", #"type",
#[feedID], #"categoryIds",
#"1367539068016", #"asOf",
nil];
NSData *postdata = [NSJSONSerialization dataWithJSONObject:tmp options:0 error:&error];
NSLog(#"Postdata is: %#", postdata);
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:feedUrl];
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-type"];
[request addValue:accessToken forHTTPHeaderField:#"Authorization"];
//[NSURLRequest setAllowsAnyHTTPSCertificate:YES forHost:[url host]];
NSError *errror = [[NSError alloc] init];
NSHTTPURLResponse *response = nil;
NSData *urlData=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&errror];
NSLog(#"Response code: %ld", (long)[response statusCode]);
if ([response statusCode] >= 200 && [response statusCode] < 300)
{
NSLog(#"It's marked as read.");
} else {
if (error) NSLog(#"Error: %#", errror);
NSLog(#"No success marking this as read. %#", response);
}
}
It keeps throwing a 400 error though, saying bad input. What am I doing wrong?

Answer 1

You're not doing anything with postdata after creating it. Attach it to the request.
[request setHTTPBody:postData];

Answer 2

There are a few problems in your code. Here are some I noticed:
You're not using postData.
The dictionary you make in tmp doesn't look like the dictionary you said you wanted to send. Where's lastReadEntryId, for example?
NSString *feedUrl should be NSURL *feedUrl
Stylistically, you should be using the dictionary literal syntax to create your dictionary. This will make it easier to debug.