Dynamically change cell height programmatically

Question

I've tried plenty of answers on SO but nothing really worked. I'm probably doing something wrong so I need someone to point out what I'm doing wrong..

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{

    NSLog(@"text : %@", self.cell.comment.text);

    NSString *text = self.cell.comment.text;
    CGFloat width = self.cell.frame.size.width;
    UIFont *font = [UIFont fontWithName:@"HelveticaNeue" size:15];
    NSAttributedString *attributedText =
    [[NSAttributedString alloc] initWithString:text
                                    attributes:@{NSFontAttributeName: font}];
    CGRect rect = [attributedText boundingRectWithSize:(CGSize){width, CGFLOAT_MAX}
                                               options:NSStringDrawingUsesLineFragmentOrigin
                                               context:nil];
    CGSize size = rect.size;
    CGFloat height = ceilf(size.height);

    return height;
}

I get "NSInvalidArgumentException" with reason "NSConcreteAttributedString initWithString:: nil value" because self.cell.comment.text isn't getting anything by the time I set cell height but it does come through just not when heightForRowAtIndexPath gets called.

Many people have commented on that answer that this method works just fine so I guess I'm missing something?

Edit

I'm setting self.cell.comment.text here -

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath object:(PFObject *)object{
static NSString *simpleTableIdentifier = @"cell";

self.cell = [tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
if (self.cell == nil) {
    self.cell = [[CommentCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];
}

// Configure the cell

self.cell.comment.text = [object objectForKey:@"comment"];
[self.cell.comment sizeToFit];

return self.cell;}

Answer 1

Your problem as you already comment is that function heightForRowAtIndexPath is called before cells are populated.

For every cell that become visible it first call

• get height of this cell
• populate cell

So you know that

a) your text is not yet populated on the cell

b) some other text might be inside, because apple use reusable cells, so UITableView can grab some cell (with different text) and try to resize it and then populate it.

In your case it will grab some other text, resize cell to its size and then populate it with some other text that is (probably) different size then previous text.

But inside cell populations you set text from some business logic (maybe array?), and you can get same text in this method.

if cell population you call

cell.comment.text = [self.someArray getObjectAtIndex:index.row];

you call this in your heightForRowAtIndexPath method.

NSString *text = [self.someArray getObjectAtIndex:index.row];

---

I see your edit just call :

 - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{

NSLog(@"text : %@", self.cell.comment.text);

NSString *text = [object objectForKey:@"comment"];;
CGFloat width = self.cell.frame.size.width;
UIFont *font = [UIFont fontWithName:@"HelveticaNeue" size:15];
NSAttributedString *attributedText =
[[NSAttributedString alloc] initWithString:text
                                attributes:@{NSFontAttributeName: font}];
CGRect rect = [attributedText boundingRectWithSize:(CGSize){width, CGFLOAT_MAX}
                                           options:NSStringDrawingUsesLineFragmentOrigin
                                           context:nil];
CGSize size = rect.size;
CGFloat height = ceilf(size.height);

return height;
}

---

ADDITION :

Tel say you would like to have cells like this :

-------------------------
|  bla bla bla         |
------------------------
| second longer text   |
| over more line       |
------------------------

You need to have texts bla bla and "second longer text over more line" somewhere saved.

Let say you have array with size 2.

NSArray * myTextArray = @[@"bla bla", @"second longer text over more line"];

and when populating cells

 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath object:(PFObject *)object{
   static NSString *simpleTableIdentifier = @"cell";

   self.cell = [tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
   if (self.cell == nil) {
        self.cell = [[CommentCell alloc] initWithStyle:UITableViewCellStyleDefault         reuseIdentifier:simpleTableIdentifier];
    }

    // Configure the cell

    self.cell.comment.text = [myTextArray objectAtIndex:indexPath.row];
    [self.cell.comment sizeToFit];

    return self.cell;
 }

because heightForRowAtIndexPath is called before cellForRowAtIndexPath we need to check text from business (array) side and not visual.

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{

   NSLog(@"text : %@", self.cell.comment.text); // -> this is null because cell is not populated yet.

   NSString *text = [myTextArray objectAtIndex:indexPath.row]; -> this is same text as we will take when populating cell and is not random.
   CGFloat width = self.cell.frame.size.width;
   UIFont *font = [UIFont fontWithName:@"HelveticaNeue" size:15];
   NSAttributedString *attributedText =
   [[NSAttributedString alloc] initWithString:text
                                attributes:@{NSFontAttributeName: font}];
   CGRect rect = [attributedText boundingRectWithSize:(CGSize){width, CGFLOAT_MAX}
                                           options:NSStringDrawingUsesLineFragmentOrigin
                                           context:nil];
   CGSize size = rect.size;
   CGFloat height = ceilf(size.height);

   return height;
}

---

EXAMPLE :

#import "ViewController.h"

@interface ViewController ()

@property NSArray * myArray;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.myArray = @[@"Some short text",@"Some longer text that take some more space throw more lines",@"bfusdbfjdsfjs fj yfsdy fgsydu fyudsfy fyudsyu fdsy fuysdyuf ydsug fyu sdgyfgsuyff ius fhs fiusdhi ufdshu uifsd ufsdh hfiuds uifdsh fsduih ufdshu hfsd ifshui"];

}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return 3;
}


- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{

    NSString *text = self.myArray[indexPath.row];
    CGFloat width = 300;
    UIFont *font = [UIFont fontWithName:@"HelveticaNeue" size:15];
    NSAttributedString *attributedText =
    [[NSAttributedString alloc] initWithString:text
                                attributes:@{NSFontAttributeName: font}];
    CGRect rect = [attributedText boundingRectWithSize:(CGSize){width, CGFLOAT_MAX}
                                           options:NSStringDrawingUsesLineFragmentOrigin
                                           context:nil];
    CGSize size = rect.size;
    CGFloat height = ceilf(size.height);

    return height;
}

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

    static NSString *simpleTableIdentifier = @"cell";

    UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];
    }

    // Configure the cell

    cell.textLabel.text = self.myArray[indexPath.row];
    cell.textLabel.numberOfLines = 0;
    return cell;
}

this example works.

Answer 2

Spent all day trying to figure this out and finally found out that the solution was super simple, I just needed to know how to use Parse better.

Thanks to Marko, I've learned how UITableView really works and that's great but the solution to my problem was a bit different.

As everyone suggested my problem was assuming that heightForRowAtIndexPath would get called after all cells are populated but I did not need an array to save objects or make any change. Parse apparently saves all retrieved objects before heightForRowAtIndexPath gets called and they're all in self.objects.

self.cell.comment.text = [self.objects objectAtIndex:indexPath.row];

And as Andy passionately suggested, I'm now using Auto-size UITableViewCell.

In your PFQueryTableViewController

 - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{

PFObject *object = [self.objects objectAtIndex:indexPath.row];

if (object) {
    NSString *commentString = [self.objects[indexPath.row] objectForKey:@"comment"];

    NSLog(@"commentString : %@",commentString);

    CommentCell *cell = [[CommentCell alloc] init];
    cell.textLabel.text = commentString;


    [cell setNeedsLayout];
    [cell layoutIfNeeded];

    self.height = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;

    self.height += 1;

}

return self.height;}

In your CustomCell

- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier{
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {

    self.textLabel.lineBreakMode = NSLineBreakByWordWrapping;
    self.textLabel.numberOfLines = 0;
    self.textLabel.translatesAutoresizingMaskIntoConstraints = NO;


    [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-6-[bodyLabel]-6-|" options:0 metrics:nil views:@{ @"bodyLabel": self.textLabel }]];
    [self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-6-[bodyLabel]-6-|" options:0 metrics:nil views:@{ @"bodyLabel": self.textLabel }]];

}

return self;}


 - (void)layoutSubviews{
[super layoutSubviews];

[self.contentView setNeedsLayout];
[self.contentView layoutIfNeeded];

self.textLabel.preferredMaxLayoutWidth = CGRectGetWidth(self.textLabel.frame);}

This definitely works.

Answer 3

In heightForRowAtIndexPath:

For width, I think you can fix it, and don't need this line:

 CGFloat width = self.cell.frame.size.width;

For the comment text

NSString *text = self.cell.comment.text;

Try this

NSString *text = [object objectForKey:@"comment"];