What basis UITableViewCell object become nil - ios

Question

I am asking very basic doubt belongs to Tableview, I created tableview programmatically without Storyboard/Xib.
The tableView numberOfRowsInSection it will return 14, the cell view fully dynamic and each cell height will different from one another.
My questaion is in tableview delegate method
static NSString *cellIdentifier = #"Cell";
UITableViewCell *cell=(UITableViewCell *)[tableview dequeueReusableCellWithIdentifier:cellIdentifer];
if (cell == nil )
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifer];
// how many time entering this loop
}
// ( adding subview to cell view).
cell==nil means need to enter loop right. Depending on what parameter cell object become nil? how many times it will enter, is it once? not at all.
When I checked, it entered 6 times.
if I use cellIdentifier, it will enter 14 times because Identifier different and every time it will create space for cell, its right because each time name will different and while scrolling it will reused.
NSString *cellIdentifer= [NSString stringWithFormat:#"%ld,%ld",(long)indexPath.section,(long)indexPath.row];
which basis it will enter 6 times. why not one's or 14 times. Please suggest what I did wrong. Because if used #"Cell" identifier, while scrolling repeatedly view will overlap. If I used second one cell view object will not overlaps & looks like perfect, but device memory size will increase
ref by https://developer.apple.com/library/ios/documentation/UIKit/Reference/UITableViewCell_Class/index.html

Answer 1

If I right got your question you need register your class in viewDidLoad method or loadView where you created a tableview like that [tableView registerClass:[UITableViewCell class] forCellReuseIdentifier:CellIdentifier]; for right reuse in tableview

Answer 2

Code : 1
static NSString *cellIdentifier = #"Cell";
UITableViewCell *cell=(UITableViewCell *)[tableview dequeueReusableCellWithIdentifier:cellIdentifer];
if (cell == nil ){
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifer];
// how many time entering this loop
}
In above code the loop will execute as number of visible rows in your tableview at first time. After that it will reuse cell as the cellIdentifier is same Cell and you need to update cell data as per indexpath.
it means if your table display 6 rows then it will execute for 6 times. Change rowheight and you can check.
Code : 2
NSString *cellIdentifer= [NSString stringWithFormat:#"%ld,%ld",(long)indexPath.section,(long)indexPath.row];
for above code the loop will execute total number of rows you have declared, Because it will create new cell for each indexpath.

Answer 3

If we give same Identifier to all cells, Disappearing cell uses the memory of Appearing cell. But, If we give different Identifier then every cell will have its own memory location and shows data perfectly.
Now suppose we have 1000 or more records to load in Table-view. If we will give different Identifiers, there will be lots of allocations in memory. This is the benefit of re-using cells.
Why 6 times ?
Because, if you give same identifiers, table will re-use cells. Maximum number of cells visible at the moment, are allocated at first. Then on scroll, appearing cell uses a memory location of a disappearing cell (cell dequeuing). So, every time you scroll, new cells are not allocated. Instead, already allocated cells are re-used
Why 14 times ?
Because, every cell has different identifier in this case. Every cell will have its own memory location.
Remember
Add subviews inside cell nil condition. Cell specific content should be assigned outside nil condition. Have a look at following code snippet:
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *cellIdentifier = #"MY_CELL";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellIdentifier];
/* Everything that is similar in all cells should be defined here
like background colors, label colors, indentation etc. */
}
/* Everything that is row specific should go here
like label text, progress view progress etc. */
return cell;
}

Answer 4

With same identifier:
When table cell is going to disappeared then this cell will be added in stack and these are reusable.
Now when we are going to show a cell then:
If we are using same identifier then controller will check that cell is available in stack with same identifier.
If yes, then we will get a table cell which is already used and UI was already set for this cell. So we need to reset UI before using it.
If not, then it will create new cell and trying to use it.
In your case I think 4-5 table cell is visible at a time so it is creating 6 table cell and reusing those cell.
With different identifier:
Table cell cell will not available in stack at creating cell for different indexpath. So it will create new one. so cell method will be called 14 times.