How to add JSON data to a NSMutableArray? - ios

Question

Im trying to read rows from my SQLite DB and then convert the data to JSON and put it into an NSMutableArray. I then want to loop over the array and print the data into my table view.
This is what i do to load the data from SQLite:
entries = [[NSMutableArray alloc] init];
NSString *sql = [NSString stringWithFormat:#"SELECT * FROM chatHistory GROUP BY channelID ORDER BY time DESC"];
sqlite3_stmt *statement;
if(sqlite3_prepare_v2([box db], [sql UTF8String], -1, &statement, nil) == SQLITE_OK) {
while(sqlite3_step(statement) == SQLITE_ROW) {
char *field1 = (char *) sqlite3_column_text(statement, 0);
NSString *channelID = [[NSString alloc] initWithUTF8String:field1];
char *field2 = (char *) sqlite3_column_text(statement, 0);
NSString *sender = [[NSString alloc] initWithUTF8String:field2];
char *field3 = (char *) sqlite3_column_text(statement, 0);
NSString *message = [[NSString alloc] initWithUTF8String:field3];
char *field4 = (char *) sqlite3_column_text(statement, 0);
NSString *recipient = [[NSString alloc] initWithUTF8String:field4];
char *field5 = (char *) sqlite3_column_text(statement, 0);
NSString *time = [[NSString alloc] initWithUTF8String:field5];
NSString *messageArray = [[NSString alloc] initWithFormat:#"[{ \"channelID\":\"%#\", \"sender\":\"%#\", \"message\":\"%#\", \"recipient\":\"%#\", \"time\":\"%#\"}]", channelID, sender, message, recipient, time];
// Convert to JSON object:
NSArray *jsonObject = [NSJSONSerialization JSONObjectWithData:[messageArray dataUsingEncoding:NSUTF8StringEncoding]
options:0 error:NULL];
[entries addObject:jsonObject];
Now here is how i try to add it to my table view:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"ConvCell";
ConvCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[ConvCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
NSArray *tableData = [self.entries valueForKey:#"message"];
NSLog(#"Message=%#", tableData);
cell.visitorName.text = (NSString *) [self.entries objectAtIndex:indexPath.row]; // This trows an error
cell.visitorAvatar.image = [UIImage imageNamed:#"hello.png"];
cell.messageTime.text = #"19.10";
return cell;
}
The error im getting is:
exception 'NSInvalidArgumentException', reason: '-[__NSCFArray length]: unrecognized selector sent to instance 0xa0cfc40'
Any ideas what I'm doing wrong?

Answer 1

Your use of JSON is interesting, it's just a short code way of creating dictionaries and nesting them in arrays. There are more containers than you really need and you could just create the dictionaries without all of the JSON wrangling.
That said, your actual error is because this line:
cell.visitorName.text = (NSString *) [self.entries objectAtIndex:indexPath.row];
should be
cell.visitorName.text = (NSString *) [tableData objectAtIndex:indexPath.row];
because you have those nested arrays are you aren't digging right to the bottom of them...

Answer 2

Your setup is not ideal. That being said...
You are casting your array of messages to a string.
[self.entries objectAtIndex:indexPath.row]
should return an array, not a string. What you want is something like this:
NSArray* jsonArray = [self.entries objectAtIndex:indexPath.row];
NSDictionary *dictionary = [jsonArray lastObject];
cell.visitorName.text = dictionary[#"sender"];
You can see that wrapping your one dictionary into an array does not really make any sense. Instead you could leave out the [...] in your JSON template. Then you would have
NSDictionary *dictionary = [self.entries objectAtIndex:indexPath.row];
BTW, the proper way to do this is to have a custom object Message with appropriate properties that you set right in your database fetch.