有什么方法可以移除影响UIView的约束?在这个例子中是一个按钮(UIButton)。topConstraint=NSLayoutConstraint(item:button,attribute:.Top,relatedBy:.LessThanOrEqual,toItem:rowView,attribute:.Top,multiplier:1.0,constant:12.0)bottomConstraint=NSLayoutConstraint(item:button,attribute:.Bottom,relatedBy:.Equal,toItem:rowView,attribute