@required

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section;

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

@optional

// Default is 1 if not implemented

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView;

- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section; //每个section的title

- (NSString *)tableView:(UITableView *)tableView titleForFooterInSection:(NSInteger)section; //每个section的footer  

// Editing/Moving or Reordering  

// 不同的row可以有同的-editing属性。当row的editing属性为NO，则它不可编辑(tableview setEditing改变的时候它没影响)；为YES时，可编辑，可以有不同的editingStyle，详见"editingStyleForRowAtIndexPath方法"。Default is YES；

- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath;

// 不同的row是否可以移动。当tableview处于editing状态时：如果某个row返回值为NO，则它的reorder accessory view不会显示，不可移动；如果某个row的返回值为YES的时候，且datasource有实现-tableView:moveRowAtIndexPath:toIndexPath:方法，则显示该row的reorder accessory view 可以移动，否则还是不显示reorder accessory view,不可移动；

- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath;  

// Index   

//返回list of section titles to display in section index view (e.g. "ABCD...Z#")

- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView;

// which section corresponds to sectionIndexTitle，当点击某个sectionIndexTitle时候，返回某个section的值，tableview就移动到该section；

- (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index;    

// Data manipulation - insert and delete / reorder or moving  support  

// 当tableview处于editing状态时，如果row可编辑，则会has the minus or plus button invoked(based on the UITableViewCellEditingStyle for the cell)。当点击minus or plus button的时候，就会调用该方法(如果是minus button，需要点击到随后的delete才会触发方法)；

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath;

// 当tableview处于editing状态，并且row可以canMove，如果拖动某row换行，则调用改方法；

- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath;

@end

@optional

// Display customization

- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath;

- (void)tableView:(UITableView *)tableView willDisplayHeaderView:(UIView *)view forSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);

- (void)tableView:(UITableView *)tableView willDisplayFooterView:(UIView *)view forSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);

- (void)tableView:(UITableView *)tableView didEndDisplayingCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath*)indexPath NS_AVAILABLE_IOS(6_0);

- (void)tableView:(UITableView *)tableView didEndDisplayingHeaderView:(UIView *)view forSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);

- (void)tableView:(UITableView *)tableView didEndDisplayingFooterView:(UIView *)view forSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);  

// Variable height support

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

- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section;

- (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section;  

// tableview在每次reload data时都会要所有cell的高度，这非常影响程序性能，使用estimatedHeight methods to quickly calcuate guessed values 去快速加载tableview

// 原理：If these methods are implemented, the above -tableView:heightForXXX calls will be deferred until views are ready to be displayed, so more expensive logic can be placed there.

- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(7_0);

- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForHeaderInSection:(NSInteger)section NS_AVAILABLE_IOS(7_0);

- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForFooterInSection:(NSInteger)section NS_AVAILABLE_IOS(7_0);  

// Section header & footer information.

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section; //custom view for header. will be adjusted to default or specified header height

- (UIView *)tableView:(UITableView *)tableView viewForFooterInSection:(NSInteger)section; //custom view for footer. will be adjusted to default or specified footer height  

// Accessories (disclosures).

// 当cell的accessaryType为UITableViewCellAccessoryDetailDisclosureButton时，点击accessaryView将会调用delegate的tableView:accessoryButtonTappedForRowWithIndexPath方法。否则只是didSelectRowAtIndexPath；

- (UITableViewCellAccessoryType)tableView:(UITableView *)tableView accessoryTypeForRowWithIndexPath:(NSIndexPath *)indexPath NS_DEPRECATED_IOS(2_0, 3_0);

- (void)tableView:(UITableView *)tableView accessoryButtonTappedForRowWithIndexPath:(NSIndexPath *)indexPath;  

// Selection  

// -tableView:shouldHighlightRowAtIndexPath: is called when a touch comes down on a row.

// Returning NO or YES 当前选中的row是否高亮

- (BOOL)tableView:(UITableView *)tableView shouldHighlightRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(6_0);

- (void)tableView:(UITableView *)tableView didHighlightRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(6_0);

- (void)tableView:(UITableView *)tableView didUnhighlightRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(6_0);

// Called before the user changes the selection. Return a new indexPath, or nil, to change the proposed selection.

/* 先点击row1，再点击row2，俩着执行顺序：在下一行将要选中后才取消上一行的选中

willSelectRowAtIndexPath 当前row为:0

didSelectRowAtIndexPath 当前row为:0

willSelectRowAtIndexPath 当前row为:1

willDeselectRowAtIndexPath 当前row为:0

didDeselectRowAtIndexPath 当前row为:0

didSelectRowAtIndexPath 当前row为:1

*/

- (NSIndexPath *)tableView:(UITableView *)tableView willSelectRowAtIndexPath:(NSIndexPath *)indexPath;

- (NSIndexPath *)tableView:(UITableView *)tableView willDeselectRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(3_0);

// Called after the user changes the selection.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath;

- (void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(3_0);  

// Editing  

// 允许cell自定义editingStyle.Default is UITableViewCellEditingStyleDelete（when the table has editing property set to YES)

- (UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath;

// 当tableview editing为YES，点击minus时出来deleteButton的title.Default is 'Delete'；

- (NSString *)tableView:(UITableView *)tableView titleForDeleteConfirmationButtonForRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(3_0);  

// 当tableview处于编辑时，控制row的background是否is indented就是row所在的那个框，例如缩不缩进可能会导致左边的edit按钮是在row框里面or外面）。Default is YES.（方法仅仅适用于grouped style 且跟之后的indentation level 方法没有关系）

- (BOOL)tableView:(UITableView *)tableView shouldIndentWhileEditingRowAtIndexPath:(NSIndexPath *)indexPath;  

// 方法被调whenever the 'editing' property is automatically changed by the table (allowing insert/delete/move). 注意，如果是tableview的'editing'改变，方法不会调用。只有This is done by a swipe activating a single row。

- (void)tableView:(UITableView*)tableView willBeginEditingRowAtIndexPath:(NSIndexPath *)indexPath;

- (void)tableView:(UITableView*)tableView didEndEditingRowAtIndexPath:(NSIndexPath *)indexPath;  

// Moving/reordering  

// Allows customization of the target row for a particular row as it is being moved/reordered

// 注意区别之前的tableView:moveRowAtIndexPath:toIndexPath方法。当手指按住reorder accessory view移动时，只要有row moved/reordered都会调用该方法，而前者方法只有当手指放开reorder accessory view时，结束move/order操作才会调用它。返回值代表进行移动操作后回到的行，如果设置为当前行，则不论怎么移动都会回到当前行。

- (NSIndexPath *)tableView:(UITableView *)tableView targetIndexPathForMoveFromRowAtIndexPath:(NSIndexPath *)sourceIndexPath toProposedIndexPath:(NSIndexPath *)proposedDestinationIndexPath;                 

// Indentation

- (NSInteger)tableView:(UITableView *)tableView indentationLevelForRowAtIndexPath:(NSIndexPath *)indexPath; //不同row的缩进  

// 长按出来的Copy/Paste操作

- (BOOL)tableView:(UITableView *)tableView shouldShowMenuForRowAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(5_0);

- (BOOL)tableView:(UITableView *)tableView canPerformAction:(SEL)action forRowAtIndexPath:(NSIndexPath *)indexPath withSender:(id)sender NS_AVAILABLE_IOS(5_0);

- (void)tableView:(UITableView *)tableView performAction:(SEL)action forRowAtIndexPath:(NSIndexPath *)indexPath withSender:(id)sender NS_AVAILABLE_IOS(5_0);

@end

@属性 CGFloat rowHeight；sectionHeaderHeight;sectionFooterHeight; //类似相应方法，只不过是个统一值

@属性 CGFloat estimatedRowHeight; estimatedSectionHeaderHeight;estimatedSectionFooterHeight NS_AVAILABLE_IOS(7_0); //类似相应方法，只不过是个统一值

@属性 UIView *backgroundView ; //the background view will be automatically resized to track the size of the table view.

@属性 UIEdgeInsets  separatorInset NS_AVAILABLE_IOS(7_0) ; //allows customization of the frame of cell separators  测试发现仅UIEdgeInsets中的right、left起作用

// Data  

- (void)reloadData; // reloads everything from scratch. redisplays visible rows. because we only keep info about visible rows, this is cheap. will adjust offset if table shrinks

- (void)reloadSectionIndexTitles NS_AVAILABLE_IOS(3_0); // reloads the index bar.  

// Info

- (NSInteger)numberOfSections;

- (NSInteger)numberOfRowsInSection:(NSInteger)section;  

- (CGRect)rectForSection:(NSInteger)section; // includes header, footer and all rows

- (CGRect)rectForHeaderInSection:(NSInteger)section;

- (CGRect)rectForFooterInSection:(NSInteger)section;

- (CGRect)rectForRowAtIndexPath:(NSIndexPath *)indexPath;  

- (NSIndexPath *)indexPathForRowAtPoint:(CGPoint)point; // returns nil if point is outside of any row in the table

- (NSIndexPath *)indexPathForCell:(UITableViewCell *)cell; // returns nil if cell is not visible

- (NSArray *)indexPathsForRowsInRect:(CGRect)rect; // returns nil if rect not valid   

- (UITableViewCell *)cellForRowAtIndexPath:(NSIndexPath *)indexPath; // returns nil if cell is not visible or index path is out of range

- (NSArray *)visibleCells;

- (NSArray *)indexPathsForVisibleRows;

- (UITableViewHeaderFooterView *)headerViewForSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);

- (UITableViewHeaderFooterView *)footerViewForSection:(NSInteger)section NS_AVAILABLE_IOS(6_0);  

// 滚动row identified by index path到特殊位置

- (void)scrollToRowAtIndexPath:(NSIndexPath *)indexPath atScrollPosition:(UITableViewScrollPosition)scrollPosition animated:(BOOL)animated;

// 滚动table使得selected row nearest to a specified position

- (void)scrollToNearestSelectedRowAtScrollPosition:(UITableViewScrollPosition)scrollPosition animated:(BOOL)animated;  

// Row insertion/deletion/reloading.

// 这两个方法，是配合起来使用的，标记了一个tableView的动画块。分别代表动画的开始开始和结束。两者成对出现，可以嵌套使用。一般，在添加，删除，选择tableView中使用，并实现动画效果。在动画块内，不建议使用reloadData方法，如果使用，会影响动画。

- (void)beginUpdates; // allow multiple insert/delete of rows and sections to be animated simultaneously.

- (void)endUpdates; // only call insert/delete/reload calls or change the editing state inside an update block.  otherwise things like row count, etc. may be invalid.  

- (void)insertSections:(NSIndexSet *)sections withRowAnimation:(UITableViewRowAnimation)animation;

- (void)deleteSections:(NSIndexSet *)sections withRowAnimation:(UITableViewRowAnimation)animation;

- (void)reloadSections:(NSIndexSet *)sections withRowAnimation:(UITableViewRowAnimation)animation NS_AVAILABLE_IOS(3_0);

- (void)moveSection:(NSInteger)section toSection:(NSInteger)newSection NS_AVAILABLE_IOS(5_0);  

- (void)insertRowsAtIndexPaths:(NSArray *)indexPaths withRowAnimation:(UITableViewRowAnimation)animation;

- (void)deleteRowsAtIndexPaths:(NSArray *)indexPaths withRowAnimation:(UITableViewRowAnimation)animation;

- (void)reloadRowsAtIndexPaths:(NSArray *)indexPaths withRowAnimation:(UITableViewRowAnimation)animation NS_AVAILABLE_IOS(3_0);

- (void)moveRowAtIndexPath:(NSIndexPath *)indexPath toIndexPath:(NSIndexPath *)newIndexPath NS_AVAILABLE_IOS(5_0);  

// Editing. When set, rows show insert/delete/reorder controls based on data source queries  

@property(nonatomic,getter=isEditing) BOOL editing;                             // default is NO. setting is not animated.

- (void)setEditing:(BOOL)editing animated:(BOOL)animated;  

@属性 BOOL allowsSelection;allowsSelectionDuringEditing; allowsMultipleSelection;allowsMultipleSelectionDuringEditing;

// Selection  

- (NSIndexPath *)indexPathForSelectedRow; // returns nil or index path representing section and row of selection.

- (NSArray *)indexPathsForSelectedRows NS_AVAILABLE_IOS(5_0); // returns nil or a set of index paths representing the sections and rows of the selection.  

// Selects and deselects rows. These methods will not call the delegate methods (-tableView:willSelectRowAtIndexPath: or tableView:didSelectRowAtIndexPath:), nor will it send out a notification.

- (void)selectRowAtIndexPath:(NSIndexPath *)indexPath animated:(BOOL)animated scrollPosition:(UITableViewScrollPosition)scrollPosition;

- (void)deselectRowAtIndexPath:(NSIndexPath *)indexPath animated:(BOOL)animated;  

// Appearance  

@属性 NSInteger sectionIndexMinimumDisplayRowCount;//当tableView中多少行的时候开始显示IndexList，默认的设置是NSIntegerMax，即默认是不显示indexList的

@属性 UIColor *sectionIndexColor; sectionIndexBackgroundColor; sectionIndexTrackingBackgroundColor;

@property(nonatomic) UITableViewCellSeparatorStyle separatorStyle; // default is UITableViewCellSeparatorStyleSingleLine

@property(nonatomic,retain) UIColor               *separatorColor; // default is the standard separator gray

@property(nonatomic,retain) UIView *tableHeaderView; tableFooterView;  

//Reusable 重用

/*

A:UITableView头文件，会找到NSMutableArray*  visiableCells，和NSMutableDictnery* reusableTableCells两个结构。visiableCells内保存当前显示的cells，reusableTableCells保存可重用的cells；

B:TableView显示之初，reusableTableCells为空，那么tableView dequeueReusableCellWithIdentifier:CellIdentifier返回nil。开始的cell都是通过[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]来创建，而且cellForRowAtIndexPath只是调用最大显示cell数的次数；

例如：有100条数据，iPhone一屏最多显示10个cell。程序最开始显示TableView的情况是：

1. 用[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]创建10次cell，并给cell指定同样的重用标识(当然，可以为不同显示类型的cell指定不同的标识)。并且10个cell全部都加入到visiableCells数组，reusableTableCells为空。

2. 向下拖动tableView，当cell1完全移出屏幕，并且cell11(它也是alloc出来的，原因同上)完全显示出来的时候。cell11加入到visiableCells，cell1移出visiableCells，cell1加入到reusableTableCells。

3. 接着向下拖动tableView，因为reusableTableCells中已经有值，所以，当需要显示新的cell，cellForRowAtIndexPath再次被调用的时候，tableView dequeueReusableCellWithIdentifier:CellIdentifier，返回cell1。cell1加入到visiableCells，cell1移出reusableTableCells(测试发现cell1会被移出，而不是还留在reusableTableCells中复用)；cell2移出visiableCells，cell2加入到reusableTableCells。之后再需要显示的Cell就可以正常重用了。

*/

- (id)dequeueReusableCellWithIdentifier:(NSString *)identifier;  // Used by the delegate to acquire an already allocated cell, in lieu of allocating a new one.

- (id)dequeueReusableCellWithIdentifier:(NSString *)identifier forIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(6_0); // newer dequeue method guarantees a cell is returned and resized properly, assuming identifier is registered

- (id)dequeueReusableHeaderFooterViewWithIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(6_0);  // like dequeueReusableCellWithIdentifier:, but for headers/footers  

// Beginning in iOS 6, clients can register a nib or class for each cell.

// If all reuse identifiers are registered, use the newer -dequeueReusableCellWithIdentifier:forIndexPath: to guarantee that a cell instance is returned.

// Instances returned from the new dequeue method will also be properly sized when they are returned.

- (void)registerNib:(UINib *)nib forCellReuseIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(5_0);

- (void)registerClass:(Class)cellClass forCellReuseIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(6_0);  

- (void)registerNib:(UINib *)nib forHeaderFooterViewReuseIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(6_0);

- (void)registerClass:(Class)aClass forHeaderFooterViewReuseIdentifier:(NSString *)identifier NS_AVAILABLE_IOS(6_0);  

// 关于：俩种dequeueReusableCellWithIdentifier 方法的区别：

1.一个6.0才能使用的方法；

2.使用6.0新方法的前提是，必须使用配套的register 相关方法，例如：

[_tableView registerClass:[MXCustomCell class] forCellReuseIdentifier:CellIdentifier];

 _tableView.dataSource = self;

  _tableView.delegate = self;

  [self.view addSubview:self.notNib_tableView];   

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

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier

                                                            forIndexPath:indexPath];

    cell.textLabel.text = [NSString stringWithFormat:@"6.0方法 %d", indexPath.row];

    return cell;

}

3.用处：to dequeue your cell, it will be the right size and you'll be able to do layout inside your cell's contentView