iOS 开发中你是否遇到这些经验问题(二)

#define LRWeakSelf(type)  __weak typeof(type) weak##type = type;
#define LRStrongSelf(type)  __strong typeof(type) type = weak##type;

LRShop *shop = [[LRShop alloc]init];
    shop.string = @"welcome to our company";
    //弱引用
    LRWeakSelf(shop);
    shop.myBlock = ^{
        NSLog(@"%@",weakshop.string);
    };
    shop.myBlock();

LRShop *shop = [[LRShop alloc]init];
    shop.string = @"welcome to our company";
    //弱引用
    LRWeakSelf(shop);
    shop.myBlock = ^{
        //强引用
        LRStrongSelf(shop)
        NSLog(@"%@",shop.string);
    };
    shop.myBlock();

//弱引用
 LRWeakSelf(shop);
    shop.myBlock = ^{
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            NSLog(@"%@",weakshop.string);
        });
    };
    shop.myBlock();

//弱引用
 LRWeakSelf(shop);
    shop.myBlock = ^{
        //强引用
        LRStrongSelf(shop)
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            NSLog(@"%@",shop.string);
        });
    };
    shop.myBlock();

// 刷新
[self.navigationController.navigationBar layoutIfNeeded];

//先设置占位文字
textField.placeholder = @"设置了占位文字内容以后, 才能设置占位文字的颜色";
//占位文字颜色
[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];

#pragma mark - 
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
//这里监听文字改变
    return YES;
}

[textField addTarget:self action:@selector(textEditingChanged) forControlEvents:UIControlEventEditingChanged];

/** 占位文字 */
@property (nonatomic, copy)NSString *placeholder;
/** 占位文字颜色 */
@property (nonatomic, strong)UIColor *placeholderColor;

// 设置默认字体
self.font = [UIFont systemFontOfSize:17];
// 设置默认的占位文字颜色
self.placeholderColor = [UIColor grayColor];

/** 占位文字label */
@property (nonatomic, weak) UILabel *placeholderLabel;

//懒加载
- (UILabel *)placeholderLabel
{
    if (_placeholderLabel == nil) {
        UILabel *placeholderLabel = [[UILabel alloc] init];
        placeholderLabel.numberOfLines = 0;
        [self addSubview:placeholderLabel];
        _placeholderLabel = placeholderLabel;
    }
    return _placeholderLabel;
}

// 监听文字
 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChangeNotification) name:UITextViewTextDidChangeNotification object:nil];

//监听的方法
- (void)textDidChangeNotification {
    // 有文字就隐藏占位文字
    self.placeholderLabel.hidden = self.hasText;
}

UIViewController *viewC = [[UIViewController alloc]init];
 // 取出当前的导航控制器
 UITabBarController *tabBarVc = (UITabBarController *)[UIApplication sharedApplication].keyWindow.rootViewController;
 //The view controller associated with the currently selected tab item
 //当前选择的导航控制器
 UINavigationController *navC = (UINavigationController *)tabBarVc.selectedViewController;
 [navC pushViewController:viewC animated:YES];

UIViewController *viewC = [[UIViewController alloc]init];
 //获取最终的根控制器
 UIViewController *rootC = [UIApplication sharedApplication].keyWindow.rootViewController;
 //如果是modal出来的控制器,它就会通过presentedViewController拿到上一个控制器
 UINavigationController *navC = (UINavigationController *)rootC.presentedViewController;
 [navC pushViewController:viewC animated:YES];

//设置代理
self.interactivePopGestureRecognizer.delegate = self;
#pragma mark - 
//实现代理方法:return YES :手势有效, NO :手势无效
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    //当导航控制器的子控制器个数 大于1 手势才有效
    return self.childViewControllers.count > 1;
}

//随便添加一个UITextField
    UITextField *field = [UITextField new];
    //可以通过 | 组合使用UIControlEventEditingDidBegin, UIControlEventValueChanged,UIControlEventEditingDidEnd
    [field addTarget:self action:@selector(textFieldDidChanged) forControlEvents:UIControlEventEditingDidBegin | UIControlEventValueChanged | UIControlEventEditingDidEnd];
    [self.view addSubview:field];

//1 < < 16 代表:2的16次方
 UIControlEventEditingDidBegin = 1 < < 16,
//1 < < 17 代表:2的17次方     
 UIControlEventEditingChanged  = 1 < < 17,
//1 < < 18 代表:2的18次方
 UIControlEventEditingDidEnd  = 1 < < 18,
//1 < < 19 代表:2的19次方
 UIControlEventEditingDidEndOnExit  = 1 < < 19,

NSUInteger controlEvents = UIControlEventEditingDidBegin | UIControlEventValueChanged | UIControlEventEditingDidEnd;
    /**
    //通过 & 符号来判断是否包含:
    UIControlEventEditingDidBegin,
    UIControlEventValueChanged,
    UIControlEventEditingDidEnd
     */
    if (controlEvents & UIControlEventEditingDidBegin) {

        NSLog(@"UIControlEventEditingDidBegin");

    }else if (controlEvents & UIControlEventValueChanged) {

        NSLog(@"UIControlEventValueChanged");

    }else if (controlEvents & UIControlEventEditingDidEnd) {

        NSLog(@"UIControlEventEditingDidEnd");
    }

//在这里拿出的宽度是不正确的
- (void)awakeFromNib {}
//对尺寸计算我们一般拿到这个方法中计算(拿到自己宽度计算子控件的尺寸)
- (void)layoutSubviews {
    [super layoutSubviews];
    //在这里拿到自己的宽度是正确的
}

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
    //在这里计算尺寸
}