代码备忘：

1、点击空白处，收起键盘

UITapGestureRecognizer *tapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(hideKeyBoard)];
tapGestureRecognizer.cancelsTouchesInView = NO;
[self.tableView addGestureRecognizer:tapGestureRecognizer];

- (void)hideKeyBoard {

    [self.textField endEditing:YES];
}

2、拨打电话

NSString *phoneStr = @"telprompt:400-8888888";
NSURL *url  =[NSURL URLWithString:phoneStr];
[[UIApplication sharedApplication] openURL:url];

3、web加载网址

NSURLRequest *request = [[NSURLRequest alloc] initWithURL:[NSURL URLWithString:urlString]];
[self.webView loadRequest:request];

4、定时器定义

- (NSTimer *)timer {

    if (_timer == nil) {
    
        _timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerFireMethod) userInfo:nil repeats:YES];
    }

    return _timer;
}

5、UICollectionView的代理和数据源

#pragma mark - UICollectionViewDataSource

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {

    return 1;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {

    return 10;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"UICollectionViewCell" forIndexPath:indexPath];

    return cell;
}

#pragma mark - UICollectionViewDelegate

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {


}

6、UITableView的代理和数据源

#pragma mark - UITableViewDataSource

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

    return 1;
}

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

    return 10;
}

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

    NSInteger row = indexPath.row;
    NSInteger section = indexPath.section;
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"UITableViewCell" forIndexPath:indexPath];

    cell.selectionStyle = UITableViewCellSelectionStyleNone;

    return cell;
}

#pragma mark - UITableViewDelegates

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

    [tableView deselectRowAtIndexPath:indexPath animated:YES];

}

7、隐藏导航栏

- (void)viewWillAppear:(BOOL)animated {

    [super viewWillAppear:animated];

    [self.navigationController setNavigationBarHidden:YES animated:animated];
}

- (void)viewWillDisappear:(BOOL)animated {

    [super viewWillDisappear:animated];

    [self.navigationController setNavigationBarHidden:NO animated:animated];
}

8、提示框

self.loginTipAlertController = [UIAlertController alertControllerWithTitle:@"提示" message:@"" preferredStyle:UIAlertControllerStyleAlert];

    @weakify(self);

    UIAlertAction *loginAction = [UIAlertAction actionWithTitle:@"" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
    
    @strongify(self);
    
    [self testBack];
}];

UIAlertAction *returnPwdAction = [UIAlertAction actionWithTitle:@"" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
    
    @strongify(self);
    
    [self testReturnPwdControllerView];
}];

[self.loginTipAlertController addAction:loginAction];
[self.loginTipAlertController addAction:returnPwdAction];
[self presentViewController:self.loginTipAlertController animated:YES completion:nil];

9、约束动画

[UIView animateWithDuration:0.3 animations:^{
    
    [self.view layoutIfNeeded];
}];

10、代码执行时间

CFAbsoluteTime startTime1 = CFAbsoluteTimeGetCurrent();
///……
CFAbsoluteTime startTime2 = CFAbsoluteTimeGetCurrent();
CFAbsoluteTime linkTime1 = (startTime2 - startTime1);
NSLog(@"添加数据花费的时间为 in %f ms", linkTime1 * 1000.0);

11、iOS 11及以上系统可用

if (@available(iOS 11.0, *)) {
        
}

12、iOS系统判断

#define iOS7Later ([UIDevice currentDevice].systemVersion.floatValue >= 7.0f)
#define iOS8Later ([UIDevice currentDevice].systemVersion.floatValue >= 8.0f)
#define iOS9Later ([UIDevice currentDevice].systemVersion.floatValue >= 9.0f)

if ([[UIDevice currentDevice].systemVersion floatValue] >= 10.0) {

}

if ([[UIDevice currentDevice].systemVersion floatValue] >= 11.0) {

}

13、跳转到指定的控制器

for (UIViewController *viewController in self.navigationController.childViewControllers) {
    
    if ([NSStringFromClass([viewController class]) isEqualToString:@"UIViewController"]) {
        
        [self.navigationController popToViewController:viewController animated:YES];
        
        break ;
    }
}

14、Debug环境下

#ifdef DEBUG

#endif

15、将视图添加到UIWindow

UIWindow *rootWindow = [UIApplication sharedApplication].keyWindow;
[rootWindow addSubview:view];

其他一些：

1、通知的#define定义

#define NOTIF_ADD(n, f)         [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(f) name:n object:nil]
#define NOTIF_POST(n, o)        [[NSNotificationCenter defaultCenter] postNotificationName:n object:o]
#define NOTIF_POSTU(n, o, u)    [[NSNotificationCenter defaultCenter] postNotificationName:n object:o userInfo:u];
#define NOTIF_REMVN(n)          [[NSNotificationCenter defaultCenter] removeObserver:self name:n object:nil];
#define NOTIF_REMV()            [[NSNotificationCenter defaultCenter] removeObserver:self]

2、只能输入数字

NSCharacterSet *characterSet = [[NSCharacterSet characterSetWithCharactersInString:@"0123456789"] invertedSet];
NSString *filtered = [[self.phoneTextField.text componentsSeparatedByCharactersInSet:characterSet] componentsJoinedByString:@""];
self.phoneTextField.text = filtered;

3、获取根导航控制器

- (UINavigationController *)rootNavigationController {

    UITabBarController *tabBarController = nil;
    UINavigationController *navigation = nil;
    id rootViewController = [UIApplication sharedApplication].keyWindow.rootViewController;
    if ([rootViewController isKindOfClass:[UITabBarController class]]) {
    
        tabBarController = (UITabBarController *)[UIApplication sharedApplication].keyWindow.rootViewController;
        navigation = tabBarController.selectedViewController;
    
    } else if ([rootViewController isKindOfClass:[UINavigationController class]]) {
    
        navigation = rootViewController;
    }

    return navigation;
}

4、跳转到升级页面，并杀掉进程

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"https://itunes.apple.com/cn/app/id1288408888?mt=8"]];
abort();

5、获取资源目录和document目录

/*说明：资源文件目录     */
NSBundle *bundle = [NSBundle mainBundle];
NSLog(@"%@",bundle);

/*说明：documents文件目录      */
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSLog(@"%@",paths);

6、播放声音代码

    NSURL *fileURL = [[NSBundle mainBundle] URLForResource:fileName withExtension:nil];
    NSData *encryptedData = [NSData dataWithContentsOfURL:fileURL];
    
    NSError *otherError;
    self.player = [[AVAudioPlayer alloc] initWithData:encryptedData error:&otherError];
    [self.player prepareToPlay];
    self.player.delegate = self;
    
    //静音情况下播放
    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setCategory:AVAudioSessionCategoryPlayback error:nil];
    [audioSession setActive:YES error:nil];
    
    [self.player play];

7、图片压缩

/**
 图片压缩

 @param image 图片
 @param kb 压缩到多少K
 @return 图片数据
 */
+ (NSData *)scaleImage:(UIImage *)image toKb:(NSInteger)kb {

    if (!image) {
    
        return nil;
    }

    if (kb < 1) {
    
        return nil;
    }

    kb *= 1024;

    CGFloat compression = 0.9f;
    CGFloat maxCompression = 0.1f;
    NSData *imageData = UIImageJPEGRepresentation(image, compression);

    while ([imageData length] > kb && compression > maxCompression) {
    
        compression -= 0.1;
        imageData = UIImageJPEGRepresentation(image, compression);
    }

#ifdef DEBUG
    NSLog(@"Current picture file size: %f kb",(float)[imageData length]/1024.0f);
#endif

    return imageData;
}

8、几个常用的xcode快捷键

1、control + command + 上/下       切换.m和.h
2、control + command + 左/右       上一个文件和下一个文件
3、shift + command + j            快速定位
4、shift + command + o            查找文件