随机数

    arc4random()
    0-10之间的随机数
    arc4random()%10
    0-100之间的随机数
    arc4random()%100
    ......

随机颜色

    [UIColor colorWithRed: (arc4random()%256/256.0) green: (arc4random()%256/256.0) blue:(arc4random()% 256/256.0)  alpha:1]

字符串排序

    NSArray * strArray = @[@"as",@"fd",@"bd",@"wd",@"ca"];
    NSStringCompareOptions comparisonOptions = NSCaseInsensitiveSearch|NSNumericSearch|NSWidthInsensitiveSearch|NSForcedOrderingSearch;
    NSComparator sort = ^(NSString *obj1,NSString *obj2){
           NSRange range = NSMakeRange(0,obj1.length);
           return [obj1 compare:obj2 options:comparisonOptions range:range];
    };
    NSArray *resultArray = [strArray sortedArrayUsingComparator:sort];
    NSLog(@"%@",resultArray);

改变状态栏颜色

iOS手机状态栏默认是黑色，在某些情况下需要改变状态栏的颜色

在info.plist文件中添加：View controller-based status bar appearance：NO

info.png

隐藏状态栏

    //隐藏状态栏
    if([self respondsToSelector:@selector(setNeedsStatusBarAppearanceUpdate)]){
       [self prefersStatusBarHidden];
       [self performSelector:@selector(setNeedsStatusBarAppearanceUpdate)];
       }
    -(BOOL)prefersStatusBarHidden{
      return  YES;
    }