本文主要记录一些常用知识点：

一：UILabel处理

• 设置UILabel行间距

NSMutableAttributedString* attrString = [[NSMutableAttributedString  alloc] initWithString:label.text];
    NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];
    [style setLineSpacing:20];
    [attrString addAttribute:NSParagraphStyleAttributeName value:style range:NSMakeRange(0, label.text.length)];
    label.attributedText = attrString;

• UILabel显示不同颜色字体

NSMutableAttributedString * string = [[NSMutableAttributedString alloc] initWithString:label.text];
[string addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0,5)];
[string addAttribute:NSForegroundColorAttributeName value:[UIColor greenColor] range:NSMakeRange(5,6)];
[string addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:NSMakeRange(11,5)];
label.attributedText = string;

二：比较两个CGRect/CGSize/CGPoint是否相等

if (CGRectEqualToRect(rect1, rect2)) { // 两个区域相等
        // do some
    }
    if (CGPointEqualToPoint(point1, point2)) { // 两个点相等
        // do some
    }
    if (CGSizeEqualToSize(size1, size2)) { // 两个size相等
        // do some
    }

三：比较两个NSDate相差多少小时

 NSDate* date1 = someDate;
 NSDate* date2 = someOtherDate;
 NSTimeInterval distanceBetweenDates = [date1 timeIntervalSinceDate:date2];
 double secondsInAnHour = 3600;
// 除以3600是把秒化成小时，除以60得到结果为相差的分钟数
 NSInteger hoursBetweenDates = distanceBetweenDates / secondsInAnHour;

四：每个cell之间增加间距

• 方法一，每个分区只显示一行cell，分区头当作你想要的间距(注意，从数据源数组中取值的时候需要用indexPath.section而不是indexPath.row)
• 方法二，自定义cell，重写setFrame：

- (void)setFrame:(CGRect)frame
{
    frame.size.height -= 20;
    [super setFrame:frame];
}

五：播放一张张连续的图片

加入现在有三张图片分别为animate_1、animate_2、animate_3

• 方法一

imageView.animationImages = @[[UIImage imageNamed:@"animate_1"], [UIImage imageNamed:@"animate_2"], [UIImage imageNamed:@"animate_3"]];
imageView.animationDuration = 1.0;

• 方法二

 imageView.image = [UIImage animatedImageNamed:@"animate_" duration:1.0];
// 方法二解释下，这个方法会加载animate_为前缀的，后边0-1024，也就是animate_0、animate_1一直到animate_1024

六：防止离屏渲染为image添加圆角

// image分类
- (UIImage *)circleImage
{
// NO代表透明
UIGraphicsBeginImageContextWithOptions(self.size, NO, 1);
// 获得上下文
CGContextRef ctx = UIGraphicsGetCurrentContext();
// 添加一个圆
CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
// 方形变圆形
CGContextAddEllipseInRect(ctx, rect);
// 裁剪
CGContextClip(ctx);
// 将图片画上去
[self drawInRect:rect];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}

七：键盘上方增加工具栏

UIToolbar *keyboardDoneButtonView = [[UIToolbar alloc] init];
[keyboardDoneButtonView sizeToFit];
UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] initWithTitle:@"Done"
                                                               style:UIBarButtonItemStyleBordered target:self
                                                              action:@selector(doneClicked:)];
[keyboardDoneButtonView setItems:[NSArray arrayWithObjects:doneButton, nil]];
txtField.inputAccessoryView = keyboardDoneButtonView;

八：判断某一行的cell是否已经显示

CGRect cellRect = [tableView rectForRowAtIndexPath:indexPath];
BOOL completelyVisible = CGRectContainsRect(tableView.bounds, cellRect);

九：让导航控制器pop回指定的控制器

NSMutableArray *allViewControllers = [NSMutableArray arrayWithArray:[self.navigationController viewControllers]];
for (UIViewController *aViewController in allViewControllers) {
    if ([aViewController isKindOfClass:[RequiredViewController class]]) {
        [self.navigationController popToViewController:aViewController animated:NO];
    }
}

十：获取屏幕方向

UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;

if(orientation == 0) //Default orientation 
    //默认
else if(orientation == UIInterfaceOrientationPortrait)
    //竖屏
else if(orientation == UIInterfaceOrientationLandscapeLeft)
    // 左横屏
else if(orientation == UIInterfaceOrientationLandscapeRight)
    //右横屏

十一：UIWebView添加单击手势不响应

UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(webViewClick)];
        tap.delegate = self;
        [_webView addGestureRecognizer:tap];

// 因为webView本身有一个单击手势，所以再添加会造成手势冲突，从而不响应。需要绑定手势代理，并实现下边的代理方法
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
    return YES;
}

十二：获取手机RAM容量

// 需要导入#import
mach_port_t host_port;
    mach_msg_type_number_t host_size;
    vm_size_t pagesize;

    host_port = mach_host_self();
    host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
    host_page_size(host_port, &pagesize);

    vm_statistics_data_t vm_stat;

    if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS) {
        NSLog(@"Failed to fetch vm statistics");
    }

    /* Stats in bytes */
    natural_t mem_used = (vm_stat.active_count +
                          vm_stat.inactive_count +
                          vm_stat.wire_count) * pagesize;
    natural_t mem_free = vm_stat.free_count * pagesize;
    natural_t mem_total = mem_used + mem_free;
    NSLog(@"已用: %u 可用: %u 总共: %u", mem_used, mem_free, mem_total);

十三：当UITextView/UITextField中没有文字时，禁用回车键

textField.enablesReturnKeyAutomatically = YES;

十四：UISearchBar

• 修改UISearBar内部背景颜色

UITextField *textField = [_searchBar valueForKey:@"_searchField"];
textField.backgroundColor = [UIColor redColor];

• 修改UISearchBar的占位文字颜色

UITextField *searchField = [searchBar valueForKey:@"_searchField"];
    [searchField setValue:[UIColor blueColor] forKeyPath:@"_placeholderLabel.textColor"];

• 用户停止输入的时候自动搜索

// 输入框文字改变的时候调用
-(void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText{
    // 先取消调用搜索方法
    [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(searchNewResult) object:nil];
    // 0.5秒后调用搜索方法
    [self performSelector:@selector(searchNewResult) withObject:nil afterDelay:0.5];
}

• 删除UISearchBar系统默认边框

    // 方法一
    searchBar.searchBarStyle = UISearchBarStyleMinimal;

    // 方法二
    [searchBar setBackgroundImage:[[UIImage alloc]init]];

    // 方法三
    searchBar.barTintColor = [UIColor whiteColor];

十五：触摸事件类型

UIControlEventTouchCancel 取消控件当前触发的事件
UIControlEventTouchDown 点按下去的事件
UIControlEventTouchDownRepeat 重复的触动事件
UIControlEventTouchDragEnter 手指被拖动到控件的边界的事件
UIControlEventTouchDragExit 一个手指从控件内拖到外界的事件
UIControlEventTouchDragInside 手指在控件的边界内拖动的事件
UIControlEventTouchDragOutside 手指在控件边界之外被拖动的事件
UIControlEventTouchUpInside 手指处于控制范围内的触摸事件
UIControlEventTouchUpOutside 手指超出控制范围的控制中的触摸事件

十六：多个网络请求的情况，需要监听所有网络请求结束后刷新UI

dispatch_group_t group = dispatch_group_create();
    dispatch_queue_t serialQueue = dispatch_queue_create("com.wzb.test.www", DISPATCH_QUEUE_SERIAL);
    dispatch_group_enter(group);
    dispatch_group_async(group, serialQueue, ^{
        // 网络请求一
        [WebClick getDataSuccess:^(ResponseModel *model) {
            dispatch_group_leave(group);
        } failure:^(NSString *err) {
            dispatch_group_leave(group);
        }];
    });
    dispatch_group_enter(group);
    dispatch_group_async(group, serialQueue, ^{
        // 网络请求二
        [WebClick getDataSuccess:getBigTypeRM onSuccess:^(ResponseModel *model) {
            dispatch_group_leave(group);
        }                                  failure:^(NSString *errorString) {
            dispatch_group_leave(group);
        }];
    });
    dispatch_group_enter(group);
    dispatch_group_async(group, serialQueue, ^{
        // 网络请求三
        [WebClick getDataSuccess:^{
            dispatch_group_leave(group);
        } failure:^(NSString *errorString) {
            dispatch_group_leave(group);
        }];
    });

    // 所有网络请求结束后会来到这个方法
    dispatch_group_notify(group, serialQueue, ^{
        dispatch_async(dispatch_get_global_queue(0, 0), ^{
            dispatch_async(dispatch_get_main_queue(), ^{
                // 刷新UI
            });
        });
    });

dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group, queue, ^{ /*任务a */ });
dispatch_group_async(group, queue, ^{ /*任务b */ });
dispatch_group_async(group, queue, ^{ /*任务c */ }); 
dispatch_group_async(group, queue, ^{ /*任务d */ }); 
dispatch_group_notify(group,dispatch_get_main_queue(), ^{
 // 在a、b、c、d异步执行完成后，会回调这里
});

十七：单例模式宏

大神们把单例模式的各种套路封装成了宏。这样使用的时候，就不需要每个类都手动写一遍里面的重复代码了。省去了敲代码的时间。

#define DJ_SINGLETON_DEF(_type_) + (_type_ *)sharedInstance;\
+(instancetype) alloc __attribute__((unavailable("call sharedInstance instead")));\
+(instancetype) new __attribute__((unavailable("call sharedInstance instead")));\
-(instancetype) copy __attribute__((unavailable("call sharedInstance instead")));\
-(instancetype) mutableCopy __attribute__((unavailable("call sharedInstance instead")));\
#define DJ_SINGLETON_IMP(_type_) + (_type_ *)sharedInstance{\
static _type_ *theSharedInstance = nil;\
static dispatch_once_t onceToken;\
dispatch_once(&onceToken, ^{\
theSharedInstance = [[super alloc] init];\
});\
return theSharedInstance;\
}

那么，在定义和实现的时候就很简单了：

@interface DJSingleton : NSObject
    DJ_SINGLETON_DEF(DJSingleton);
@end
@implementation DJSingleton
    DJ_SINGLETON_IMP(DJSingleton);
@end

十八：给UIImage添加生成圆角图片的扩展API

- (UIImage *)imageWithCornerRadius:(CGFloat)radius {
   CGRect rect = (CGRect){0.f, 0.f, self.size};
   UIGraphicsBeginImageContextWithOptions(self.size, NO, UIScreen.mainScreen.scale);
   CGContextAddPath(UIGraphicsGetCurrentContext(),
   [UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:radius].CGPath);
   CGContextClip(UIGraphicsGetCurrentContext());

   [self drawInRect:rect];
   UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();
   return image;
}

这车怎么样？

待续。。。