UITextView is not scrolled to top when loaded

UITextView is a subclass of UIScrollView, so you can use its methods. If all you want to do is ensure that it's scrolled to the top, then wherever the text is added try:

[self.mainTextView setContentOffset:CGPointZero animated:NO];

EDIT: AutoLayout with any kind of scrollview gets wonky fast. That setting a fixed width solves it isn't surprising. If it doesn't work in -viewDidLayoutSubviews then that is odd. Setting a layout constraint manually may work. First create the constraints in IB:

@property (weak, nonatomic) IBOutlet NSLayoutConstraint *textViewWidthConstraint;
@property (weak, nonatomic) IBOutlet NSLayoutConstraint *textViewHeightConstraint;

then in the ViewController

    -(void)updateViewConstraints {
            self.textViewWidthConstraint.constant = self.view.frame.size.width - 40.0f;
            self.textViewHeightConstraint.constant = self.view.frame.size.height - 40.0f;
            [super updateViewConstraints];
        }

May still be necessary to setContentOffset in -viewDidLayoutSubviews.

(Another method would be to create a layout constraint for "'equal' widths" and "'equal' heights" between the textView and its superView, with a constant of "-40". It's only 'equal' if the constant is zero, otherwise it adjusts by the constant. But because you can only add this constraint to a view that constraints both views, you can't do this in IB.)

You may ask yourself, if I have to do this, what's the point of AutoLayout? I've studied AutoLayout in depth, and that is an excellent question.

add the following function to your view controller class...

Swift 3

override func viewDidLayoutSubviews() {
    self.mainTextView.setContentOffset(.zero, animated: false)
}

Swift 2.1

override func viewDidLayoutSubviews() {
    self.mainTextView.setContentOffset(CGPointZero, animated: false)
}

Objective C

- (void)viewDidLayoutSubviews {
    [self.mainTextView setContentOffset:CGPointZero animated:NO];
}

Swift

self.textView.scrollRangeToVisible(NSMakeRange(0, 0))

Objective-C

[self.textView scrollRangeToVisible:(NSMakeRange(0, 0))];

i had same issue! Reset to suggested constrains and just put (y offset)

@IBOutlet weak var textContent: UITextView!

    override func viewDidLoad() {
        textContent.scrollsToTop = true
        var contentHeight = textContent.contentSize.height
        var offSet = textContent.contentOffset.x
        var contentOffset = contentHeight - offSet
        textContent.contentOffset = CGPointMake(0, -contentOffset)
    }