獲取app版本號
[[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleShortVersionString"]; //app版本號
[[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleVersion"]; //build
獲取系統版本號
[UIDevice currentDevice].systemVersion;
判斷字符串是否為空
我習慣把它定義成宏，數組字典類似。
if (str == nil || (NSNull *)str == [NSNull null] || str.length == 0)
{}
打印沙盒路徑
NSLog(@"app = %@",NSHomeDirectory());
不想讓tableView顯示無用的cell分割線
self.tableView.tableFooterView = [[UIView alloc] init];
用NSLog輸出NSRange，CGRect等結構體
NSString中的方法：
NSStringFromCGPoint(CGPoint point);
NSStringFromCGVector(CGVector vector);
NSStringFromCGSize(CGSize size);
NSStringFromCGRect(CGRect rect);
NSStringFromCGAffineTransform(CGAffineTransform transform);
NSStringFromUIEdgeInsets(UIEdgeInsets insets);
NSStringFromUIOffset(UIOffset offset);
NSLog(@"%@",NSStringFromCGPoint(CGPointZero));
隱藏navigationBar
有時候我們使用navigationController，需要首頁隱藏導航欄其他頁面顯示導航欄。
- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self.navigationController setNavigationBarHidden:YES animated:YES];
}
- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [self.navigationController setNavigationBarHidden:NO animated:YES];
}