UITableViewCell reuse good practice

Question

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {


    static NSString *CellIdentifier = @"NotificationViewCell";
    CardViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if(cell==nil){

        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"CardViewCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];


        cell.contentView.backgroundColor=[UIColor clearColor];
        [ModelClass addSublayer:cell.contentView];


        cell.cellbg.layer.cornerRadius = 8;
        cell.cellbg.layer.masksToBounds = YES;

         cell.cellbg.layer.borderWidth = 1;
         cell.cellbg.layer.borderColor = [[UIColor grayColor] CGColor];


        cell.logoImage.layer.cornerRadius = 8;
        cell.logoImage.layer.masksToBounds = YES;

        cell.logoImage.layer.borderWidth = 1;
        cell.logoImage.layer.borderColor = [[UIColor grayColor] CGColor];



        Merchant *merchantList= [self.cardListArr objectAtIndex:indexPath.row];

        cell.nameLab.text=merchantList.name;

        NSLog(@"merchantList.myloyalty.points=%@",merchantList.myloyalty.points);
    //    NSLog(@"memberNO=%@",merchantList.myloyalty.memberNO);
        cell.integralLab.text=[NSString stringWithFormat:NSLocalizedString(@"points_dot", @"") ,[merchantList.myloyalty.points intValue]];


        cell.cardNumberLab.text=[NSString stringWithFormat:@"%@%@",NSLocalizedString(@"ID", nil), merchantList.myloyalty.memberNO];



        if(![ModelClass isBlankString:merchantList.introPic])
        {
              NSLog(@"merchantList.introPic=%@",merchantList.introPic);

            [cell.logoImage setImageUrl:merchantList.introPic];


        }
    }

    return cell;

}

1. i want to use the above code to reuse UITableViewCell,i donot know if it is correct,i want to get some advice.

2. you can see my code i use if(cell==nil),i want to know i should write what code if(cell!=nil)(if(cell==nil) else{ i should do what can improve the cell reuse})

3. if every cell have have same views，but have different height,for example imageview sometimes is 20 or is 40 and so on ,how to deal with the situation.

Solution 1

1.It is not correct , because your cell is reused , and when it is created , it will not to go into the if-statement , so , in the if-statement you only need to do is to init the cell , the setText and setImage you should code outside the if-statement .

such as :

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {


    static NSString *CellIdentifier = @"NotificationViewCell";
    CardViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if(cell==nil){

        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"CardViewCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];


        cell.contentView.backgroundColor=[UIColor clearColor];
        [ModelClass addSublayer:cell.contentView];


        cell.cellbg.layer.cornerRadius = 8;
        cell.cellbg.layer.masksToBounds = YES;

         cell.cellbg.layer.borderWidth = 1;
         cell.cellbg.layer.borderColor = [[UIColor grayColor] CGColor];


        cell.logoImage.layer.cornerRadius = 8;
        cell.logoImage.layer.masksToBounds = YES;

        cell.logoImage.layer.borderWidth = 1;
        cell.logoImage.layer.borderColor = [[UIColor grayColor] CGColor];

        }

        Merchant *merchantList= [self.cardListArr objectAtIndex:indexPath.row];

        cell.nameLab.text=merchantList.name;

        NSLog(@"merchantList.myloyalty.points=%@",merchantList.myloyalty.points);
    //    NSLog(@"memberNO=%@",merchantList.myloyalty.memberNO);
        cell.integralLab.text=[NSString stringWithFormat:NSLocalizedString(@"points_dot", @"") ,[merchantList.myloyalty.points intValue]];


        cell.cardNumberLab.text=[NSString stringWithFormat:@"%@%@",NSLocalizedString(@"ID", nil), merchantList.myloyalty.memberNO];



        if(![ModelClass isBlankString:merchantList.introPic])
        {
              NSLog(@"merchantList.introPic=%@",merchantList.introPic);

            [cell.logoImage setImageUrl:merchantList.introPic];


        }


        return cell;

    }

2 Most people code like this :

if(cell==nil)
{
    //init code
}

// setting code

3.If you want set the cell height , you can not code in the - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

you should code in the method of dataSource : - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath

code like this :

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (index.row % 2)
        return 20.0f;
    return 40.0f;
}

Solution 2

I usually separate the creation and configuration of the cell into two logical parts:

1. Create the cell and set up all its properties that are the same for every single cell (i.e. layout, layer)
2. Write a separate -(void)configureCell:(UITableViewCell*)cell; function where I set up everything specific for a particular cell from the datasource (i.e. values of labels and imageView).

Then in cellForRowAtIndexPath:

-(UITableViewCell *)tableView:(UITableView *)tableView 
        cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{
    static NSString *CellIdentifier = @"NotificationViewCell";
    CardViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if(cell==nil){
       [self createCell:&cell];
    }

    Mercant* mercantList = [self.cardListArr objectAtIndex:indexPath.row];

    [self configureCell:cell withMercant:mercantList];

    return cell;
}

-(void)createCell:(CardViewCell**)cellPtr
{
    NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"CardViewCell" 
                                                 owner:self 
                                               options:nil];
    *cellPtr = [nib objectAtIndex:0];

    CardViewCell* cell = *cellPtr;

    cell.contentView.backgroundColor=[UIColor clearColor];
    [ModelClass addSublayer:cell.contentView];

    cell.cellbg.layer.cornerRadius = 8;
    cell.cellbg.layer.masksToBounds = YES;

    cell.cellbg.layer.borderWidth = 1;
    cell.cellbg.layer.borderColor = [[UIColor grayColor] CGColor];


    cell.logoImage.layer.cornerRadius = 8;
    cell.logoImage.layer.masksToBounds = YES;

    cell.logoImage.layer.borderWidth = 1;
    cell.logoImage.layer.borderColor = [[UIColor grayColor] CGColor];
}

-(void)configureCell:(CardViewCell*)cell withMercant:(Mercant*)mercantList
{
    cell.nameLab.text=merchantList.name;

    NSLog(@"merchantList.myloyalty.points=%@",merchantList.myloyalty.points);
//    NSLog(@"memberNO=%@",merchantList.myloyalty.memberNO);
    cell.integralLab.text=[NSString stringWithFormat:NSLocalizedString(@"points_dot", @"") ,[merchantList.myloyalty.points intValue]];


    cell.cardNumberLab.text=[NSString stringWithFormat:@"%@%@",NSLocalizedString(@"ID", nil), merchantList.myloyalty.memberNO];



    if(![ModelClass isBlankString:merchantList.introPic])
    {
          NSLog(@"merchantList.introPic=%@",merchantList.introPic);

        [cell.logoImage setImageUrl:merchantList.introPic];


    }
}

Comments

[pengwang]

i think you are right,i vote your post,if no other good answer i will receive it.

[pengwang]

developer.apple.com/library/ios/#documentation/userexperienc‌​e/…

[pengwang]

can you give more code,and some -(void)configureCell:(UITableViewCell*)cell

[pengwang]

if every cell have have same view，but have different height,for example imageview sometimes is 20 or is 40 and so on ,how to deal with the situation.

[MrTJ]

in configureCell you can use cell.frame = CGRectMake(0, 0, 320, currentHeight);. You should also return the height of each cell in tableView:heightForRowAtIndexPath: