@interface ViewController (){          UIView *firstView;    UIView *secondView;    UIView *thirdView;    }@end@implementation ViewController- (void)viewDidLoad{    [super viewDidLoad];        /**      第一个view     */    firstView = [[UIView alloc]init];    firstView.translatesAutoresizingMaskIntoConstraints = NO;    firstView.backgroundColor = [UIColor blueColor];    [self.view addSubview:firstView];        /**     第二个view     */    secondView = [[UIView alloc]init];    secondView.translatesAutoresizingMaskIntoConstraints = NO;    secondView.backgroundColor = [UIColor brownColor];    [self.view addSubview:secondView];        /**     第三个view     */    thirdView = [[UIView alloc]init];    thirdView.translatesAutoresizingMaskIntoConstraints = NO;    thirdView.backgroundColor = [UIColor yellowColor];    [self.view addSubview:thirdView];        /**绑定三个view*/    NSDictionary *dic_bind = NSDictionaryOfVariableBindings(firstView,secondView,thirdView);    /**设置view之间的间距和高度*/    NSDictionary *dic_Constraint = @{ @"padding":@(10.f),                                      @"height":@(150.f)                                     };        /**     *  第一个view添加约束     */    /**垂直方向居中对齐*/    NSLayoutConstraint *first_CenterY = [NSLayoutConstraint constraintWithItem:firstView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1 constant:0];        /**垂直方向添加高度约束*/    NSArray *first_V = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[firstView(height)]" options:0 metrics:dic_Constraint views:dic_bind];    [self.view addConstraints:@[first_CenterY]];    [self.view addConstraints:first_V];            /**     *  第二个view添加约束     */    /**垂直方向居中对齐*/     NSLayoutConstraint *second_CenterY = [NSLayoutConstraint constraintWithItem:secondView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1 constant:0];         /**垂直方向添加高度约束*/    NSArray *second_V = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[secondView(height)]" options:0 metrics:dic_Constraint views:dic_bind];    [self.view addConstraint:second_CenterY];    [self.view addConstraints:second_V];        /**     *  第三个view添加约束     */    /**垂直方向居中对齐*/    NSLayoutConstraint *third_CenterY = [NSLayoutConstraint constraintWithItem:thirdView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1 constant:0];         /**垂直方向添加高度约束*/    NSArray *third_V = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[thirdView(height)]" options:0 metrics:dic_Constraint views:dic_bind];    [self.view addConstraints:@[third_CenterY]];    [self.view addConstraints:third_V];        /**给三个view添加水平约束等宽等间距*/    NSArray * allConstraint_H = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-padding-[firstView]-10-[secondView(firstView)]-padding-[thirdView(secondView)]-padding-|" options:0 metrics:dic_Constraint views:dic_bind];    [self.view addConstraints:allConstraint_H];        }