Swift 3 UILabel获取实际高度（intrinsicContentSize）

Question

I'm trying to simulate a kind of "Please wait..." UILabel. The label's text must be regularly updated. So far everything works as expected. However, I need to get the intrinsic content height of the label to be able to position its container view (UIView).

The label is the one with the red background, whereas the one with the white background is its container.

I've tried a few different approaches, unfortunately, all in vain. Any help would be greatly appreciated.

private func createBusyLabel(labelText: String) -> CGFloat {

    self.busyViewContainer.addSubview(self.busyLabel)

    self.busyLabel.backgroundColor = UIColor.red

    self.busyLabel.numberOfLines = 0
    self.busyLabel.lineBreakMode = NSLineBreakMode.byWordWrapping
    self.busyLabel.sizeToFit()

    //set the constraints, but skip height constraints
    self.busyLabel.translatesAutoresizingMaskIntoConstraints = false
    self.busyLabel.horizontalLeft(toItem: self.busyViewContainer, constant: 60)
    self.busyLabel.horizontalRight(toItem: self.busyViewContainer, constant: -10)
    self.busyLabel.topConstraints(toItem: self.busyViewContainer, constant: 10)


    self.busyLabel.text = labelText
    //calculate height with margin
    let height: CGFloat = self.busyLabel.intrinsicContentSize.height + 20
    return height

}

Also, the line counting function, from a previously asked and already answered question , delivers only 1

Here is what it look like after I set the bottom constraint:

Answer 1

The simple fix is adding the bottom constraint between 'self.busyViewContainer' and its superview.

Following your code and syntax it can be something like this:

self.busyLabel.bottomConstraints(toItem: self.busyViewContainer, constant: 10)

It is a common problem with 'Unsatisfiable Constraints'. The autolayout should ensure it satisfies horizontal axis layout so it needs to have both top and bottom constraints in this case.

Apple doc - Unsatisfiable Constraints

Apple doc - Logical Errors

UPD: In this case, the layout of the superview can define a height with intrinsicContentSize :

var intrinsicContentSize: CGSize { return ... }

Where the height of the parent view will be calculated based on the label one.

Answer 2

A million Thanks to ozgur, who changed my approach. Ozgur, your code works perfect, but unfortunately not for me, as I faced problems with bottomLayoutGuide part. The reason for this is that the label and its container are created in an external class.

Previously I tried to set bottom constraint to the label, which did not return the expected result. However, inspired by ozgur's answer, this time I simply set the bottom constraint to its container and not the label, giving in expected result, like following:

    self.busyViewContainer.bottomConstraints(toItem: self.busyLabel, constant: 10)

Thanks to all who put in their precious efforts.

private func createBusyLabel(labelText: String) -> Void {

    self.busyLabel.text = labelText
    self.busyLabel.font = UIFont.getGlobalFont(size: _textSizeSmall, type: "bold")

    self.busyLabel.backgroundColor = UIColor.red

    // handle multiline problem
    self.busyLabel.numberOfLines = 0
    self.busyLabel.lineBreakMode = NSLineBreakMode.byWordWrapping
    self.busyLabel.sizeToFit()

    self.busyViewContainer.addSubview(self.busyLabel)
    self.busyLabel.translatesAutoresizingMaskIntoConstraints = false
    self.busyLabel.horizontalLeft(toItem: self.busyViewContainer, constant: 60)
    self.busyLabel.horizontalRight(toItem: self.busyViewContainer, constant: -10)
    self.busyLabel.topConstraints(toItem: self.busyViewContainer, constant: 10)

    // the following line made the difference
    self.busyViewContainer.bottomConstraints(toItem: self.busyLabel, constant: 10)

}