iOS UITableView unable to compute proper cell height for each cell - ios

Question

The basic setup is like this: I have a UITableView with two proto cells that I am working with (think of a messaging app, where one cell type shows messages you send and the other, messages you recieve). Now obviously the message length can vary from one line to even 100+ lines thus I need variable cell heights.
First attempt:
tableView.estimatedRowHeight = 75
tableView.rowHeight = UITableViewAutomaticDimension
I used estimatedRowHeight in my viewDidLoad(). This works perfectly and computes cell heights very nicely. But because this is a messaging app I need to scroll the tableView all the way to bottom on viewDidLoad() and whenever a new message is recieved / sent. But the estimatedRowHeight messes with the tableView scrolling all the way to bottom. Some say it's a bug, some say it's to be expected. Nonetheless, this way won't work for me at all.
Second Attempt:
func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat
I thought to compute heights manually as so:
let measuerWidth = UIScreen.mainScreen().bounds
var w = measuerWidth.size.width // this is so that we can limit label width to screen width so the text is forced to go to multiple lines
// I probably should use my custom cell width here, but if I try to `dequeue` that cell it's frame contents are always `zero`. Is that a problem?
let lbl = UILabel(frame: CGRect.zeroRect)
lbl.text = chatMessages[indexPath.row][ChatRoomKeys.MESSAGE_TEXT] as? String
lbl.font = UIFont.systemFontOfSize(20)
lbl.numberOfLines = 0
lbl.lineBreakMode = NSLineBreakMode.ByWordWrapping
lbl.frame = CGRectMake(0, 0, w, 0)
lbl.sizeToFit()
return lbl.frame.height + 20
This way works almost perfectly however at times cell height isn't what it should be. Meaning sometimes if the text is one line plus one word, that one word won't show because the cell height was only for one line.
Is there some better way to calculate the cell height?
UPDATE:
Here's a screenshot of kinda what happens
as you can see the label ends at x but the original text goes upto y.
UPDATE 2:
These are the proto cells I am using, the bottom cell is simply a mirror of the top one.

Answer 1

I use this one:
- (CGFloat) tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
if (indexPath.row == 2)
{
NSString *cellText = #"init some text";
CGSize labelSize = [self calculateTextSize:cellText];
return labelSize.height + 20.0f;
}
return 45;
}
- (CGSize) calculateTextSize: (NSString*) text
{
UIFont *cellFont = [UIFont fontWithName:#"HelveticaNeue" size:12.0];
CGFloat width = CGRectGetWidth(self.tableView.frame) - 40.0f;
CGSize constraintSize = CGSizeMake(width, MAXFLOAT);
CGRect labelRect = [cellText boundingRectWithSize:constraintSize options:NSStringDrawingUsesLineFragmentOrigin attributes:#{NSFontAttributeName:cellFont} context:NSLineBreakByWordWrapping];
CGSize labelSize = labelRect.size;
return labelSize;
}
Edit:
CGFloat width = CGRectGetWidth(self.tableView.frame) - 40.0f;
Calculation of the maximum available width of the text, you can use self.view.frame or etc. -40.0f - because i have indentation from the edge = 20.0f

Answer 2

You can do this with the automatic height as you were doing. See the code below, when your view is about to appear, ask the UITableView for the number of rows in the section (0) in this case. Then you can create an NSIndexPath for the last row in that section then ask the UITableView to scroll that index path into view. Using the code below you can still have the UITableView calculate the heights for you.
import UIKit
final class ViewController: UIViewController {
// MARK: - Constants
let kFromCellIdentifier = "FromCell"
let kToCellIdentifier = "ToCell"
// MARK: - IBOutlets
#IBOutlet private weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
tableView.estimatedRowHeight = 75.0
tableView.rowHeight = UITableViewAutomaticDimension
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
let numRows = tableView.numberOfRowsInSection(0) - 1 // -1 because numbering in the array starts from 0 not 1
let indexPath = NSIndexPath(forRow: numRows, inSection: 0)
tableView.scrollToRowAtIndexPath(indexPath, atScrollPosition: .Bottom, animated: false)
}
}
extension ViewController: UITableViewDataSource {
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 50
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
if indexPath.row % 2 == 0 {
let cell = tableView.dequeueReusableCellWithIdentifier(kFromCellIdentifier, forIndexPath: indexPath) as! CustomTableViewCell
cell.configureCell(UIImage(named: "Talk")!, text: "From Some text \(indexPath.row)")
return cell
} else {
let cell = tableView.dequeueReusableCellWithIdentifier(kToCellIdentifier, forIndexPath: indexPath) as! CustomTableViewCell
cell.configureCell(UIImage(named: "Email")!, text: "To Some text \(indexPath.row)")
return cell
}
}
}