CODEWITHSUNDEEP
iosobjective-cuitableview
Bir
Bir

Reputation: 812

How to create object in Objective-C?

I am new in iOS development. Currently I am reading this tutorial http://www.appcoda.com/how-to-handle-row-selection-in-uitableview/ . I am facing problem when I am reading this line

UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
cell.accessoryType = UITableViewCellAccessoryCheckmark;

I know object in objective-c is created by following way

 classname *objecname = [[classname alloc]init];

My confusion point is here UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

How cell object is created here? Please tell details.

Upvotes: 1

Views: 8721

Answers (3)

Alexander
Alexander

Reputation: 4257

Based on the tutorial you linked to, I'm assuming you are dealing with selecting a row. When you select a row, you have access to the NSIndexPath of that row, which contains two parts:

  1. The section of the cell
  2. The row of the cell

With that information, let's break down the confusing code: UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

UITableViewCell *cell

This part declares your variable. You've chosen to name it cell. You could just as easily have named it theCell, like so:

UITableViewCell *theCell

The * means that you're declaring a pointer, which is just a reference to an actual object, or the table view cell.

[tableView cellForRowAtIndexPath:indexPath]

The tableView refers to the UITableView that was just selected. UITableView has a method called cellForRowAtIndexPath, and what that method does is retrieve the cell at the specified section and row of the UITableView. In your case, it retrieves the row that you've just selected and stores the reference to it in your cell variable.

When declaring a new object, yes, it would take on the following syntax:

classname *objecname = [[classname alloc] init];

The key word here is new. When dealing with selecting rows in a UITableView, you don't want to create a new cell because you can't select a cell that doesn't exist. You want to get the cell that the user has just selected.

Upvotes: 5

rdelmar
rdelmar

Reputation: 104082

The cell is not created with that line. That line gets a reference to a cell that is already in the table view at that indexPath.

Upvotes: 2

TotoroTotoro
TotoroTotoro

Reputation: 17622

I assume you have this code in your didSelectRowAtIndexPath: method, is that right?

If so, you're tapping on a cell that is on the screen, so the cell object already exists. Where and how was it created? Inside cellForRowAtIndexPath:, which you have already written.

So when you make this call

UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];

it just gives you the cell object to work with, but it doesn't create a new one.

Upvotes: 3

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