How does cellForRowAtIndexPath work

Question

I HAVE READ apple documentation and it s not understandable for such a beginner in Objective-C as me  I m trying to implement multicolumn UITableView following this  link example and it just doesn t work so i need to comprehend how cellForRowAtIndexPath work  cause for me personally this method seems pretty complicated   1  What does it return  UITableViewCell  But why does it look so odd    - UITableViewCell   tableView  UITableView   tableView     What is that  Could you please explain    2  How does it get called and what is more important how am i to connect it to a certain UITableView    What if i have two UITableView s named firstTableView and secondTableView and i want them to be different  to perform cellForRowAtIndexPath differently   How am i supposed to link my UITableViews to this   - UITableViewCell   tableView  UITableView   tableView cellForRowAtIndexPath  NSIndexPath   indexPath   the method accepts NSIndexPath  not UITableView  What am i gonna do

User · Answer

I ll try and break it down  example from documention            The cellForRowAtIndexPath takes for argument the tableView  so if the same object      is delegate for several tableViews it can identify which one is asking for a cell        and an indexPath which determines which row and section the cell is returned for        -  UITableViewCell   tableView  UITableView   tableView cellForRowAtIndexPath  NSIndexPath   indexPath                    This is an important bit  it asks the table view if it has any available cells          already created which it is not using  if they are offScreen   so that it can          reuse them  saving the time of alloc init load from xib a new cell             The identifier is there to differentiate between different types of cells           you can display different types of cells in the same table view               UITableViewCell  cell    tableView dequeueReusableCellWithIdentifier   MyIdentifier                     If the cell is nil it means no cell was available for reuse and that we should          create a new one              if  cell    nil                              Actually create a new cell  with an identifier so that it can be dequeued                         cell      UITableViewCell alloc  initWithStyle UITableViewCellStyleSubtitle reuseIdentifier   MyIdentifier   autorelease            cell selectionStyle   UITableViewCellSelectionStyleNone                          Now that we have a cell we can configure it to display the data corresponding to          this row section              NSDictionary  item    NSDictionary    self content objectAtIndex indexPath row       cell textLabel text    item objectForKey   mainTitleKey        cell detailTextLabel text    item objectForKey   secondaryTitleKey        NSString  path     NSBundle mainBundle  pathForResource  item objectForKey   imageKey   ofType   png        UIImage  theImage    UIImage imageWithContentsOfFile path       cell imageView image   theImage          Now that the cell is configured we return it to the table view so that it can display it         return cell       This is a DataSource method so it will be called on whichever object has declared itself as the DataSource of the UITableView  It is called when the table view actually needs to display the cell onscreen  based on the number of rows and sections  which you specify in other DataSource methods

User · Answer

Basically it s designing your cell  The cellforrowatindexpath is called for each cell and the cell number is found by indexpath row and section number by indexpath section   Here you can use a label  button or textfied image  anything that you want which are updated for all rows in the table  Answer for second question In cell for row at index path use an if statement  In Objective C  - UITableViewCell   tableView  UITableView   tableView  cellForRowAtIndexPath  NSIndexPath   indexPath     NSString  CellIdentifier     CellIdentifier   UITableViewCell  cell    tableView dequeueReusableCellWithIdentifier CellIdentifier      if tableView    firstTableView              code for first table view         cell contentView addSubview  someView          if tableview    secondTableView              code for secondTableView         cell contentView addSubview  someView         return cell      In Swift 3 0  func tableView   tableView  UITableView  cellForRowAt indexPath  IndexPath  - gt  UITableViewCell      let cell UITableViewCell   self tableView dequeueReusableCell withIdentifier  cellReuseIdentifier  as UITableViewCell     if tableView    firstTableView             code for first table view         if tableview    secondTableView                code for secondTableView         return cell

User · Answer

1  The function returns a cell for a table view yes  So  the returned object is of type UITableViewCell  These are the objects that you see in the table s rows  This function basically returns a cell  for a table view  But you might ask  how the function would know what cell to return for what row  which is answered in the 2nd question  2 NSIndexPath is essentially two things-   Your Section Your row   Because your table might be divided to many sections and each with its own rows  this NSIndexPath will help you identify precisely which section and which row  They are both integers  If you re a beginner  I would say try with just one section   It is called if you implement the UITableViewDataSource protocol in your view controller  A simpler way would be to add a UITableViewController class  I strongly recommend this because it Apple has some code written for you to easily implement the functions that can describe a table  Anyway  if you choose to implement this protocol yourself  you need to create a UITableViewCell object and return it for whatever row  Have a look at its class reference to understand re-usablity because the cells that are displayed in the table view are reused again and again this is a very efficient design btw    As for when you have two table views  look at the method  The table view is passed to it  so you should not have a problem with respect to that

[ios] How does cellForRowAtIndexPath work?

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