UIApplicationWillChangeStatusBarOrientationNotification v.s. UIApplicationDidChangeStatusBarOrientationNotification

結論：
UIApplicationWillChangeStatusBarOrientationNotification
會先被呼叫，而且userInfo 是傳送將要轉換的 orientation。

UIApplicationDidChangeStatusBarOrientationNotification
後被呼叫，但userInfo是傳送轉換前的 orientation。

code:

    [NSNotificationCenter.defaultCenter addObserver:self selector:@selector(statusOrientationWillChange:)
                                               name:UIApplicationWillChangeStatusBarOrientationNotification object:nil];
   
    [NSNotificationCenter.defaultCenter addObserver:self selector:@selector(statusOrientationDidChange:)
                                               name:UIApplicationDidChangeStatusBarOrientationNotification object:nil];

- (void)statusOrientationWillChange:(NSNotification *)notification {
    if (notification.userInfo != nil && notification.userInfo[UIApplicationStatusBarOrientationUserInfoKey] != nil) {
        UIInterfaceOrientation orientation = (UIInterfaceOrientation)[(NSNumber *)notification.userInfo[UIApplicationStatusBarOrientationUserInfoKey] integerValue];
        if (UIInterfaceOrientationIsLandscape(orientation)) {
            self.isLandscape = YES;
        } else {
            self.isLandscape = NO;
        }
    }
   
    [self.tableView reloadData];
}

- (void)statusOrientationDidChange:(NSNotification *)notification {
    if (notification.userInfo != nil && notification.userInfo[UIApplicationStatusBarOrientationUserInfoKey] != nil) {
        UIInterfaceOrientation orientation = (UIInterfaceOrientation)[(NSNumber *)notification.userInfo[UIApplicationStatusBarOrientationUserInfoKey] integerValue];
        if (UIInterfaceOrientationIsLandscape(orientation)) {
            self.isLandscape = YES;
        } else {
            self.isLandscape = NO;
        }
    }
   
}

Strange thing: A - 2 > 0 is not equvalent to A > 2

(lldb) po self.customFields.count - 2 > 0
true

(lldb) po self.customFields.count > 2
false

(lldb) po self.customFields
<__NSArrayM 0x108e54540>(

)

(lldb) po self.customFields.count
<nil>

reuse custom tableview cell

當你用dynamic style cell的時候
所有關於cell的改變都要基於cell source
所以最好的方式就是直接create a Class for table view source
讓整個改動都變得有彈性
不要直接去改當下那個cell，那是不合邏輯的，而且你會修bug修不完
例如，你從coredate的一個表中拿到資料，不要直接拿來用
創一個class去包它，這個class可以自由加入你要的其他設定給你的custom table cell