Why we are checking if (cell == nil) in UITableViewController? - objective-c

Question

I am trying to implement UITableView based Application.For that I select UITableViewStyle is Group.In my TableView their is 15 section each section having 1 row.
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 15;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return 1;
}
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.section==12)
{
return 120;
}
else
{
return 60;
}
}
I want add a UITextView on Section 12
For that i did following code
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
if ([indexPath section] == 12)
{
if([indexPath row]==0)
{
descriptionTextField=[[UITextView alloc] initWithFrame:CGRectMake(5, 8, 290, 106)];
descriptionTextField.font = [UIFont systemFontOfSize:15.0];
descriptionTextField.backgroundColor=[UIColor scrollViewTexturedBackgroundColor];
[descriptionTextField setDelegate:self];
[descriptionTextField setTag:2];
[descriptionTextField setText:#"Enter Location Description."];
descriptionTextField.keyboardType=UIKeyboardTypeDefault;
descriptionTextField.returnKeyType=UIReturnKeyNext;
descriptionTextField.textColor=[UIColor blackColor];
descriptionTextField.editable=YES;
descriptionTextField.autocapitalizationType=UITextAutocapitalizationTypeWords;
descriptionTextField.autocorrectionType=UITextAutocorrectionTypeDefault;
descriptionTextField.textAlignment=UITextAlignmentLeft;
UIToolbar* keboardToolBar=[[UIToolbar alloc]initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, 32)];
UIBarButtonItem *extra=[[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];
UIBarButtonItem *Done=[[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:#selector(keyboardDoneButtonActin:)];
[Done setWidth:65.0f];
[keboardToolBar setItems:[[[NSArray alloc]initWithObjects:extra,Done, nil]autorelease] ];
[extra release];
[Done release];
[keboardToolBar setTintColor:[UIColor blackColor]];
[keboardToolBar setAlpha:.70];
[descriptionTextField setInputAccessoryView:keboardToolBar];
[descriptionTextField setTag:101];
[cell.contentView addSubview:descriptionTextField];
[descriptionTextField release];
}
}
return cell;
}
In the initil stage the table view like this
if i am scrolling tableview up and down , then the uitextView section changed and it will display multiple location.
I can't understand my fault, why this happend?
if am implementing the above code in side the if(cell==nil)
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
if ([indexPath section] == 12)
{
if([indexPath row]==0)
{
**/* implemention all code here*/**
[cell.contentView addSubview:descriptionTextField];
[descriptionTextField release];
}
}
return cell;
}
UITextView not disply, i think it is not allocating.
so what is the difference between code implementing in
if (cell == nil)
{
inside
}
if (cell == nil)
{
}
out side

Answer 1

The test if (cell == nil) handles the case where there are no reusable cells to dequeue, in which case you must create a new cell. When you create the new cell, you are responsible for constructing its view hierarchy.

Answer 2

NSString *CellIdentifier = [NSString stringWithFormat:#"%i",indexPath.row];
// Dequeue or create a cell of the appropriate type.
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
This can be used instead of
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
this is the simple example to write inside the cell ==nill
- (UITableViewCell *)tableView:(UITableView *)tableView1 cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"CellIdentifier";
// Dequeue or create a cell of the appropriate type.
UITableViewCell *cell = [tableView1 dequeueReusableCellWithIdentifier:CellIdentifier];
cell= nil;
if (cell == nil)
{
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
[[cell.contentView viewWithTag:100+indexPath.row] removeFromSuperview];
UIView *selectview = [[UIView alloc]initWithFrame:CGRectMake(0, 0, cell.frame.size.width, 30)];
[selectview setBackgroundColor:[UIColor colorWithPatternImage:[UIImage imageNamed:#"strip_s12A-1_h.png"]]];
cell.selectedBackgroundView = selectview;
[selectview release];
UILabel *cellTitle=[[UILabel alloc]initWithFrame:CGRectMake(40, 0, 300, 30)];
//cellTitle.adjustsFontSizeToFitWidth=YES;
[cellTitle setBackgroundColor:[UIColor clearColor]];
[cellTitle setFont:[UIFont fontWithName:#"Arial Rounded MT Bold" size:17]];
[cellTitle setTextColor:[UIColor blackColor]];
cellTitle.tag = 100+indexPath.row;
cellTitle.text= [[[cellArray objectAtIndex:indexPath.section]objectAtIndex:indexPath.row] valueForKey:#"Des2"];
[cell.contentView addSubview:cellTitle];
[cellTitle release];
}
return cell;
}
i think will be enough right