XIB 修改约束multiplier属性

#pragma mark - 修改约束multiplier属性
- (void)changeMultiplierOfConstraint:(NSLayoutConstraint *)constraint multiplier:(CGFloat)multiplier {
    [NSLayoutConstraint deactivateConstraints:@[constraint]];
    NSLayoutConstraint *newConstraint = [NSLayoutConstraint constraintWithItem:constraint.firstItem attribute:constraint.firstAttribute relatedBy:constraint.relation toItem:constraint.secondItem attribute:constraint.secondAttribute multiplier:multiplier constant:constraint.constant];
    newConstraint.priority = constraint.priority;
    newConstraint.shouldBeArchived = constraint.shouldBeArchived;
    newConstraint.identifier = constraint.identifier;
    [NSLayoutConstraint activateConstraints:@[newConstraint]];
}