Set preferredMaxLayoutWidth based on an initial layout pass instead of hardcoding it

This method is somewhat less efficient as it requires a second layout
pass once the preferredMaxLayoutWidth is set on multi-line labels,
however it is much more flexible and generic and can scale to
arbitrarily complex layouts that would be very difficult to determine
the correct preferredMaxLayoutWidth value manually.

Author: smileyborg

TableViewCellWithAutoLayout/TableViewController/RJTableViewCell.h

@@ -26,8 +26,6 @@
 
 #import <UIKit/UIKit.h>
 
-#define kLabelHorizontalInsets 20.0f
-
 @interface RJTableViewCell : UITableViewCell
 
 @property (strong, nonatomic) IBOutlet UILabel *titleLabel;

TableViewCellWithAutoLayout/TableViewController/RJTableViewCell.m

@@ -26,6 +26,8 @@
 
 #import "RJTableViewCell.h"
 
+#define kLabelHorizontalInsets 20.0f
+
 @interface RJTableViewCell ()
 
 @property (nonatomic, assign) BOOL didSetupConstraints;
@@ -34,11 +36,10 @@ @interface RJTableViewCell ()
 
 @implementation RJTableViewCell
 
-- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier {
+- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
+{
     self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
     if (self) {
-        // Initialization code
-        
         self.titleLabel = [[UILabel alloc] initWithFrame:CGRectZero];
         [self.titleLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
         [self.titleLabel setLineBreakMode:NSLineBreakByTruncatingTail];
@@ -65,7 +66,8 @@ - (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reus
     return self;
 }
 
-- (void)updateConstraints {
+- (void)updateConstraints
+{
     [super updateConstraints];
 
     if (self.didSetupConstraints) return;

TableViewCellWithAutoLayout/TableViewController/RJTableViewController.m

@@ -89,19 +89,16 @@ - (void)contentSizeCategoryChanged:(NSNotification *)notification
 
 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
 {
-    // Return the number of sections.
     return 1;
 }
 
 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
 {
-    // Return the number of rows in the section.
     return [self.model.dataSource count];
 }
 
 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
 {
-    
     RJTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
 
     [cell updateFonts];
@@ -119,7 +116,6 @@ - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(N
 
 - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
 {
-   
     RJTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
 
     [cell updateFonts];
@@ -128,13 +124,18 @@ - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPa
     cell.titleLabel.text =  [dataSourceItem valueForKey:@"title"];
     cell.bodyLabel.text = [dataSourceItem valueForKey:@"body"];
 
-    cell.bodyLabel.preferredMaxLayoutWidth = tableView.bounds.size.width - (kLabelHorizontalInsets * 2.0f);
-    
     [cell setNeedsUpdateConstraints];
     [cell updateConstraintsIfNeeded];
+    
+    // Do the initial layout pass of the cell's contentView & subviews
     [cell.contentView setNeedsLayout];
     [cell.contentView layoutIfNeeded];
 
+    // Since we have multi-line labels, set the preferredMaxLayoutWidth now that their width has been determined,
+    // and then do a second layout pass so they can take on the correct height
+    cell.bodyLabel.preferredMaxLayoutWidth = CGRectGetWidth(cell.bodyLabel.frame);
+    [cell.contentView layoutIfNeeded];
+    
     CGFloat height = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
 
     return height;
@@ -145,55 +146,4 @@ - (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(
     return 500.0f;
 }
 
-/*
-// Override to support conditional editing of the table view.
-- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
-{
-    // Return NO if you do not want the specified item to be editable.
-    return YES;
-}
-*/
-
-/*
-// Override to support editing the table view.
-- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
-{
-    if (editingStyle == UITableViewCellEditingStyleDelete) {
-        // Delete the row from the data source
-        [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
-    }   
-    else if (editingStyle == UITableViewCellEditingStyleInsert) {
-        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
-    }   
-}
-*/
-
-/*
-// Override to support rearranging the table view.
-- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
-{
-}
-*/
-
-/*
-// Override to support conditional rearranging of the table view.
-- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
-{
-    // Return NO if you do not want the item to be re-orderable.
-    return YES;
-}
-*/
-
-/*
-#pragma mark - Navigation
-
-// In a story board-based application, you will often want to do a little preparation before navigation
-- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
-{
-    // Get the new view controller using [segue destinationViewController].
-    // Pass the selected object to the new view controller.
-}
-
- */
-
 @end