分享一些iOS开发实用的小技巧

 UIColor *whiteColor = [UIColor whiteColor];
NSDictionary *dic = [NSDictionary dictionaryWithObject:whiteColor forKey:NSForegroundColorAttributeName];
[self.navigationController.navigationBar setTitleTextAttributes:dic];

 UIColor *color = [UIColor colorWithRed:0.0 green:0.0 blue:1.0 alpha:1.0];
const CGFloat *components = CGColorGetComponents(color.CGColor);
NSLog(@"Red: %f", components[0]);
NSLog(@"Green: %f", components[1]);
NSLog(@"Blue: %f", components[2]);
NSLog(@"Alpha: %f", components[3]);

 [self.textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];
[self.textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];

 - (UIImage *)createImageWithColor:(UIColor *)color {
 CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
 UIGraphicsBeginImageContext(rect.size);
 CGContextRef context = UIGraphicsGetCurrentContext();
 CGContextSetFillColorWithColor(context, [color CGColor]);
 CGContextFillRect(context, rect);
 UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();
 return theImage;
}

/**
 * 获取按钮title的size
 */
- (CGFloat)getBtnTitleWidth:(UIButton*)btn {
 CGSize titleSize = [btn.titleLabel.text sizeWithAttributes:@{NSFontAttributeName:btn.titleLabel.font}];
 return titleSize;
}

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, -20, ScreenWidth, 20)];[view setBackgroundColor:COLOR_APP_MAIN];
[viewController.navigationController.navigationBar addSubview:view];

+ (NSString*)dictionaryToJson:(NSDictionary *)dic {

 NSError *parseError = nil;

 NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dic options:NSJSONWritingPrettyPrinted error:&parseError];

 return [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];

}

+(NSDictionary *)jsonToDic:(NSString*)jsonStr {
  NSData *jsonData = [jsonStr dataUsingEncoding:NSUTF8StringEncoding];
  NSError *err;
  NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:jsonData
               options:NSJSONReadingMutableContainers
                error:&err];
  return dic;
}

+(BOOL)isAllowedNotification{

 if ([[UIDevice currentDevice].systemVersion floatValue] >= 8.0) {

  UIUserNotificationSettings *setting = [[UIApplication sharedApplication] currentUserNotificationSettings];

  if(UIUserNotificationTypeNone != setting.types) {

   return YES;
  }
 }
 NSLog(@"不允许推送");
 return NO;
}

+ (NSString *)memoryFormatter:(long long)diskSpace {
 NSString *formatted;
 double bytes = 1.0 * diskSpace;
 double megabytes = bytes / MB;
 double gigabytes = bytes / GB;
 if (gigabytes >= 1.0)
  formatted = [NSString stringWithFormat:@"%.2f GB", gigabytes];
 else if (megabytes >= 1.0)
  formatted = [NSString stringWithFormat:@"%.2f MB", megabytes];
 else
  formatted = [NSString stringWithFormat:@"%.2f bytes", bytes];
 NSLog(@"fotmatted=%@",formatted);

 return formatted;
}

+ (NSString *)totalDiskSpace {

 long long space = [[[[NSFileManager defaultManager] attributesOfFileSystemForPath:NSHomeDirectory() error:nil] objectForKey:NSFileSystemSize] longLongValue];
 return [self memoryFormatter:space];
}

+ (NSString *)freeDiskSpace {

 long long freeSpace = [[[[NSFileManager defaultManager] attributesOfFileSystemForPath:NSHomeDirectory() error:nil] objectForKey:NSFileSystemFreeSize] longLongValue];
 return [self memoryFormatter:freeSpace];
}

 //设置代理
self.interactivePopGestureRecognizer.delegate = self;
#pragma mark - <UIGestureRecognizerDelegate>
//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;
}

/** 设置圆形图片(放到分类中使用) */
- (UIImage *)cutCircleImage {
 UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0);
 // 获取上下文
 CGContextRef ctr = UIGraphicsGetCurrentContext();
 // 设置圆形
 CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
 CGContextAddEllipseInRect(ctr, rect);
 // 裁剪
 CGContextClip(ctr);
 // 将图片画上去
 [self drawInRect:rect];
 UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();
 return image;
}

//xib的awakeFromNib方法中设置UIViewAutoresizingNone进行清空

 - (void)awakeFromNib {
 self.autoresizingMask = UIViewAutoresizingNone;
}

- (NSString *)contentTypeForImageData:(NSData *)data {
 uint8_t c;
 [data getBytes:&c length:1];
 switch (c) {
  case 0xFF:
   return @"jpeg";
  case 0x89:
   return @"png";  
  case 0x47:
   return @"gif";  
  case 0x49: 
  case 0x4D:
   return @"tiff";  
  case 0x52: 
   if ([data length] < 12) {
    return nil;
   }
   NSString *testString = [[NSString alloc] initWithData:[data subdataWithRange:NSMakeRange(0, 12)] encoding:NSASCIIStringEncoding];
   if ([testString hasPrefix:@"RIFF"] && [testString hasSuffix:@"WEBP"]) {
    return @"webp";
   }
   return nil;
 }
 return nil;
}

NSInteger count = 5;
//02代表:如果count不足2位 用0在最前面补全(2代表总输出的个数)
NSString *string = [NSString stringWithFormat:@"%02zd",count];
//输出结果是: 05
NSLog(@"%@", string);