How to change constraints programmatically that is added from storyboard?

问题

I have one screen. It will display like below

Now When User clicked I have an Account and Password(button) it will display like below

I want to move both views accordingly I added constraints using storyboard.Now need to change constraints from programming..

回答1:

You need to create an IBOutlet of your constraint.

Then you set the constant value of your constraint in code:

labelWidthConstraint.constant = newValue

If you want it animated you can do something like this:

Swift

labelWidthConstraint.constant = newValue
UIView.animate(withDuration: 0.3, animations: { 
    self.view.layoutIfNeeded()
})

Objective-C

self.labelWidthConstraint.constant = newValue;
[UIView animateWithDuration:0.3 animations:^{        
    [self.view layoutIfNeeded];
}];

来源：https://stackoverflow.com/questions/40583602/how-to-change-constraints-programmatically-that-is-added-from-storyboard