Merge pull request #10 from Yelp/YLTableViewCellEstimatedRowHeight

YLTableView 2.0 - YLTableViewCell as protocol

Author: benasher44

Classes/YLTableView.m

@@ -12,7 +12,6 @@
 #import "YLRefreshHeaderView.h"
 #import "YLRefreshHeaderViewPrivate.h"
 #import "YLTableViewCell.h"
-#import "YLTableViewCellPrivate.h"
 #import "YLTableViewDataSource.h"
 #import "YLTableViewSectionHeaderFooterView.h"
 
@@ -49,7 +48,7 @@ - (instancetype)initWithFrame:(CGRect)frame style:(UITableViewStyle)style {
 
 - (void)registerClass:(Class)cellClass forCellReuseIdentifier:(NSString *)identifier {
   NSAssert(identifier, @"Must have a reuse identifier.");
-  NSAssert([cellClass isSubclassOfClass:[YLTableViewCell class]], @"You can only use subclasses of YLTableViewCell.");
+  NSAssert([cellClass conformsToProtocol:@protocol(YLTableViewCell)], @"You can only use cells conforming to YLTableViewCell.");
 
   [super registerClass:cellClass forCellReuseIdentifier:identifier];
 
@@ -73,20 +72,6 @@ - (void)registerClass:(Class)headerFooterViewClass forHeaderFooterViewReuseIdent
   }
 }
 
-- (YLTableViewCell *)sizingCellForReuseIdentifier:(NSString *)reuseIdentifier {
-  NSAssert(reuseIdentifier, @"Must have a reuse identifier.");
-  NSAssert(self.cellClassForReuseIdentifier[reuseIdentifier], @"You must register a class for this reuse identifier.");
-
-  if (!self.sizingCellForReuseIdentifier[reuseIdentifier]) {
-    Class cellClass = NSClassFromString(self.cellClassForReuseIdentifier[reuseIdentifier]);
-    YLTableViewCell *const sizingCell = [(YLTableViewCell *)[cellClass alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:reuseIdentifier];
-    sizingCell.sizingCell = YES;
-    self.sizingCellForReuseIdentifier[reuseIdentifier] = sizingCell;
-  }
-
-  return self.sizingCellForReuseIdentifier[reuseIdentifier];
-}
-
 - (YLTableViewSectionHeaderFooterView *)sizingHeaderFooterViewForReuseIdentifier:(NSString *)reuseIdentifier {
   NSAssert(reuseIdentifier, @"Must have a reuse identifier.");
   NSAssert(self.headerFooterViewClassForReuseIdentifier[reuseIdentifier], @"You must register a class for this reuse identifier.");

Classes/YLTableViewCell.h

@@ -8,17 +8,12 @@
 
 #import <UIKit/UIKit.h>
 
-extern const CGFloat kUITableViewCellDefaultHeight;
-
-@interface YLTableViewCell : UITableViewCell
+@protocol YLTableViewCell <NSObject>
 
 //! Apply a cell model to a cell.  Subclasses should implement this to decide how they display a model's content.
 - (void)setModel:(nullable id)model;
 
-/*! Set by YLTableView to indicate that this cell will be used solely for sizing and will never be displayed on screen.
- *
- *  For example, subclasses can use this information to optimize away unnecessary configuration.
- */
-@property (readonly, assign, nonatomic, getter=isSizingCell) BOOL sizingCell;
+//! Estimated height for a cell, called within tableView:estimatedHeightForRowAtIndexPath
++ (CGFloat)estimatedRowHeight;
 
 @end

Classes/YLTableViewCell.m

@@ -19,5 +19,15 @@ NS_ASSUME_NONNULL_BEGIN
 //! Set as the parent view controller of any cells implementing YLTableViewChildViewControllerCell.
 @property (weak, nonatomic, nullable) UIViewController *parentViewController;
 
+/*!
+ Defaults to NO. If you would like to cache the estimated heights for rows, set this to YES.
+
+ @note This is only really necessary for iOS 8. If you are using estimated row height + UITableViewAutomaticDimension in iOS 8, there's a bug
+ when reloadData is called: if the estimated height is different from the real height for the cells, the table view will jump when you scroll
+ after calling reloadData. To fix this, we can record the actual height as it comes on screen (willDisplayCell), and return this for the
+ estimated row height. This bug is fixed in iOS 9.
+ */
+@property (assign, nonatomic) BOOL shouldCacheEstimatedRowHeights;
+
 @end
 NS_ASSUME_NONNULL_END

Classes/YLTableViewCellPrivate.h

@@ -13,27 +13,51 @@
 #import "YLTableView.h"
 #import "YLTableViewPrivate.h"
 #import "YLTableViewCell.h"
-#import "YLTableViewCellPrivate.h"
 #import "YLTableViewChildViewControllerCell.h"
 #import "YLTableViewSectionHeaderFooterView.h"
 #import "YLTableViewSectionHeaderFooterViewPrivate.h"
 
+@interface YLTableViewDataSource ()
+
+//! This is used to cache the estimated row heights.
+@property (strong, nonatomic) NSMutableDictionary<NSString *, NSNumber *> * indexPathToEstimatedRowHeight;
+
+@end
+
 @implementation YLTableViewDataSource
 
+
+#pragma mark indexPathToEstimatedRowHeight property methods
+
+- (NSMutableDictionary<NSString *,NSNumber *> *)indexPathToEstimatedRowHeight {
+  if (!_indexPathToEstimatedRowHeight) {
+    _indexPathToEstimatedRowHeight = [[NSMutableDictionary alloc] init];
+  }
+
+  return _indexPathToEstimatedRowHeight;
+}
+
 #pragma mark Public Helpers
 
 - (void)reloadVisibleCellForModel:(id)model inTableView:(UITableView *)tableView {
   for (NSIndexPath *indexPath in [tableView indexPathsForVisibleRows]) {
     if ([self tableView:tableView modelForCellAtIndexPath:indexPath] == model) {
-      [(YLTableViewCell *)[tableView cellForRowAtIndexPath:indexPath] setModel:model];
+      [(UITableViewCell<YLTableViewCell> *)[tableView cellForRowAtIndexPath:indexPath] setModel:model];
       return;
     }
   }
 }
 
+#pragma mark Private Helpers
+
+//! Constructs a cache key for the given index path. UITableView sometimes returns a different subclass, NSMutableIndexPath, so we can't use the index path as the key by itself.
++ (NSString *)_keyForIndexPath:(NSIndexPath *)indexPath {
+  return [NSString stringWithFormat:@"%ld,%ld", (long)indexPath.section, (long)indexPath.row];
+}
+
 #pragma mark Configuration
 
-- (void)tableView:(UITableView *)tableView configureCell:(YLTableViewCell *)cell forIndexPath:(NSIndexPath *)indexPath {
+- (void)tableView:(UITableView *)tableView configureCell:(UITableViewCell<YLTableViewCell> *)cell forIndexPath:(NSIndexPath *)indexPath {
   [cell setModel:[self tableView:tableView modelForCellAtIndexPath:indexPath]];
 }
 
@@ -77,7 +101,7 @@ - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger
 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
   NSString *const reuseID = [self tableView:tableView reuseIdentifierForCellAtIndexPath:indexPath];
   NSAssert(reuseID != nil, @"Must have a reuse identifier.");
-  YLTableViewCell *cell = (YLTableViewCell *)[tableView dequeueReusableCellWithIdentifier:reuseID forIndexPath:indexPath];
+  UITableViewCell<YLTableViewCell> *cell = (UITableViewCell<YLTableViewCell> *)[tableView dequeueReusableCellWithIdentifier:reuseID forIndexPath:indexPath];
   [self tableView:tableView configureCell:cell forIndexPath:indexPath];
   return cell;
 }
@@ -112,16 +136,7 @@ - (UIView *)tableView:(UITableView *)tableView viewForFooterInSection:(NSInteger
 
 - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
   NSAssert([tableView isKindOfClass:[YLTableView class]], @"This can only be the delegate of a YLTableView.");
-  
-  if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) {
-    return UITableViewAutomaticDimension;
-  }
-  
-  NSString *const reuseID = [self tableView:tableView reuseIdentifierForCellAtIndexPath:indexPath];
-  YLTableViewCell *cell = [(YLTableView *)tableView sizingCellForReuseIdentifier:reuseID];
-  [self tableView:tableView configureCell:cell forIndexPath:indexPath];
-  
-  return [cell heightForWidth:CGRectGetWidth(tableView.bounds) separatorStyle:tableView.separatorStyle];
+  return UITableViewAutomaticDimension;
 }
 
 - (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section {
@@ -152,9 +167,26 @@ - (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSIntege
   }
 }
 
+- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath {
+  NSAssert([tableView isKindOfClass:[YLTableView class]], @"This can only be the delegate of a YLTableView.");
+
+  if (self.shouldCacheEstimatedRowHeights && self.indexPathToEstimatedRowHeight[[[self class] _keyForIndexPath:indexPath]]) {
+      return [self.indexPathToEstimatedRowHeight[[[self class] _keyForIndexPath:indexPath]] floatValue];
+  }
+
+  Class cellClass = NSClassFromString([self tableView:tableView reuseIdentifierForCellAtIndexPath:indexPath]);
+  NSAssert([cellClass conformsToProtocol:@protocol(YLTableViewCell)], @"You can only use cells conforming to YLTableViewCell.");
+  return [(id<YLTableViewCell>)cellClass estimatedRowHeight];
+}
+
 #pragma mark ChildViewController support
 
 - (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
+
+  if (self.shouldCacheEstimatedRowHeights) {
+    self.indexPathToEstimatedRowHeight[[[self class] _keyForIndexPath:indexPath]] = @(cell.frame.size.height);
+  }
+
   UIViewController *parentViewController = self.parentViewController;
   if ([cell conformsToProtocol:@protocol(YLTableViewChildViewControllerCell)]) {
     NSAssert(parentViewController != nil, @"Must have a parent view controller to support cell %@", cell);

Classes/YLTableViewDataSource.h

@@ -8,7 +8,7 @@
 
 #import "YLTableViewDataSource.h"
 
-@class YLTableViewCell;
+@protocol YLTableViewCell;
 @class YLTableViewSectionHeaderFooterView;
 
 NS_ASSUME_NONNULL_BEGIN
@@ -44,7 +44,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * Override this method if you need to do cell-specific configuration (for example, alternating background colors) but call super implementation first.
  */
-- (void)tableView:(UITableView *)tableView configureCell:(YLTableViewCell *)cell forIndexPath:(NSIndexPath *)indexPath NS_REQUIRES_SUPER;
+- (void)tableView:(UITableView *)tableView configureCell:(UITableViewCell<YLTableViewCell> *)cell forIndexPath:(NSIndexPath *)indexPath NS_REQUIRES_SUPER;
 
 //! Override this method to configure headerView to display content in section but call super implementation first.
 - (void)tableView:(UITableView *)tableView configureHeader:(YLTableViewSectionHeaderFooterView *)headerView forSection:(NSUInteger)section NS_REQUIRES_SUPER;

Classes/YLTableViewDataSource.m

@@ -8,15 +8,11 @@
 
 #import "YLTableView.h"
 
-@class YLTableViewCell;
 @class YLTableViewSectionHeaderFooterView;
 
 NS_ASSUME_NONNULL_BEGIN
 @interface YLTableView ()
 
-//! Returns a cached cell for this reuse identifier. The cell should only be used for sizing purposes, not for display.
-- (YLTableViewCell *)sizingCellForReuseIdentifier:(NSString *)reuseIdentifier;
-
 //! Returns a cached section header/footer view for this reuse identifier. The view should only be used for sizing purposes, not for display.
 - (YLTableViewSectionHeaderFooterView *)sizingHeaderFooterViewForReuseIdentifier:(NSString *)reuseIdentifier;
 

Classes/YLTableViewDataSourceSubclass.h

@@ -33,16 +33,6 @@ - (void)_installLabelConstraints {
   [self.contentLayoutGuideView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[_label]|" options:0 metrics:nil views:views]];
 }
 
-- (void)layoutSubviews {
-  [super layoutSubviews];
-
-  if ([[[UIDevice currentDevice] systemVersion] floatValue] < 8.0) {
-    self.label.preferredMaxLayoutWidth = CGRectGetWidth(self.label.bounds);
-    [super layoutSubviews];
-  }
-}
-
-
 #pragma mark Text property
 
 - (void)setText:(NSString *)text {

Classes/YLTableViewPrivate.h

@@ -53,10 +53,6 @@ - (void)layoutSubviews {
   // The layout guide doesn't like being told to have a negative width, so we have to make sure it's at least 0.
   self.contentLayoutGuideWidthConstraint.constant = MAX(CGRectGetWidth(self.bounds) - edgeInsets.left - edgeInsets.right, 0);
 
-  if ([[[UIDevice currentDevice] systemVersion] floatValue] < 8.0) {
-    [self.contentView layoutIfNeeded];
-  }
-
   [super layoutSubviews];
 }
 

Classes/YLTableViewSectionHeaderFooterView/YLTableViewSectionHeaderFooterLabelView.m

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = 'YLTableView'
-  s.version      = '1.0.3'
+  s.version      = '2.0.0'
   s.license      = 'Apache V2'
   s.summary      = 'Yelp iOS table view framework'
   s.homepage     = 'https://github.com/Yelp/YLTableView'
@@ -9,7 +9,7 @@ Pod::Spec.new do |s|
   s.requires_arc = true
 
   s.platform     = :ios
-  s.ios.deployment_target = '7.0'
+  s.ios.deployment_target = '8.0'
 
   s.public_header_files = 'Classes/**/*.h'
   s.source_files = 'Classes/**/*.{h,m}'