`tableView:heightForHeaderInSection:`在没有实现它的委托上调用

Question

因未捕获的异常'NSInvalidArgumentException'而终止应用程序,原因:' - [SomeClassNameController tableView:heightForHeaderInSection:]:无法识别的选择器发送到实例0x1805f1f0'

除非我误解了文档,否则这是不可能的.如果tableView:heightForHeaderInSection:未在委托中实现,则应使用存储的任何值sectionHeaderHeight.在任何情况下都不应该呼吁tableView:heightForHeaderInSection:没有实现它的代表.

这是正确的还是我实际上误解了文档？

编辑:按要求堆栈跟踪.

Last Exception Backtrace:
0   CoreFoundation                      0x30443e83 __exceptionPreprocess + 131
1   libobjc.A.dylib                     0x3aadf6c7 _objc_exception_throw + 39
2   CoreFoundation                      0x304477b7 -[NSObject(NSObject) doesNotRecognizeSelector:] + 203
3   CoreFoundation                      0x30445f4d ___forwarding___ + 353
4   CoreFoundation                      0x30394dc8 __CF_forwarding_prep_0 + 24
5   UIKit                               0x32cabfff -[UISectionRowData heightForHeaderInSection:canGuess:] + 123
6   UIKit                               0x32cabf2b -[UITableViewRowData rectForHeaderInSection:heightCanBeGuessed:] + 391
7   UIKit                               0x32dc83b3 -[_UITableViewUpdateSupport(Private) _setupAnimationsForExistingHeadersAndFooters] + 1603
8   UIKit                               0x32dc37db -[_UITableViewUpdateSupport _setupAnimations] + 187
9   UIKit                               0x32dc328b -[UITableView _updateWithItems:updateSupport:] + 1363
10  UIKit                               0x32d9b397 -[UITableView _endCellAnimationsWithContext:] + 8019
11  appname                             0x000704a9 -[SomeClassNameView layoutSubviews] (SomeClassNameView.m:47)
12  UIKit                               0x32bc8353 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 347
13  QuartzCore                          0x3284e943 -[CALayer layoutSublayers] + 143
14  QuartzCore                          0x3284a167 CA::Layer::layout_if_needed(CA::Transaction*) + 351
15  QuartzCore                          0x32849ff9 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 17
16  QuartzCore                          0x32849a0d CA::Context::commit_transaction(CA::Transaction*) + 229
17  QuartzCore                          0x3284981f CA::Transaction::commit() + 315
18  QuartzCore                          0x3284354d CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 57
19  CoreFoundation                      0x3040ef69 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 21
20  CoreFoundation                      0x3040c8f7 __CFRunLoopDoObservers + 287
21  CoreFoundation                      0x3040cc43 __CFRunLoopRun + 739
22  CoreFoundation                      0x30377471 _CFRunLoopRunSpecific + 525
23  CoreFoundation                      0x30377253 _CFRunLoopRunInMode + 107
24  GraphicsServices                    0x350782eb _GSEventRunModal + 139
25  UIKit                               0x32c2c845 _UIApplicationMain + 1137
26  appname                             0x00386767 main (main.m:32)
27  appname                             0x00020e48 start + 40

Answer 1

来自文档

tableView:viewForHeaderInSection:
...
Discussion
The returned object can be a UILabel or UIImageView object, as well as a custom view.
This method only works correctly when tableView:heightForHeaderInSection: is also implemented.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

显然苹果将“无法正常工作”解释为“可能会崩溃”。