#import "ViewController.h"
@interface ViewController ()
@property (weak, nonatomic) IBOutlet NSLayoutConstraint *widthConstrant;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
}
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
self.widthConstrant.constant = 50.f;
//设置刷新动画
[UIView animateWithDuration:2.f animations:^{
//父控件刷新布局
[self.view layoutIfNeeded];
}];
}
@end重点: 约束也是对象[万物皆对象],只要是对象，那么在storyboard中的约束就可以通过连线来修改其对应属性值。