将布局锚点与 UIStackView 一起使用时出错

尝试向其添加 stackView 和一些子项，但出现布局错误。我究竟做错了什么？

当 trailinAchors 常数低于leadingAchors 常数时，问题似乎会发生。

    self.stackview.axis = .vertical
    self.stackview.alignment = .fill
    self.stackview.distribution = .fill
    self.stackview.spacing = 5
    self.addSubview(self.stackview)
    self.stackview.translatesAutoresizingMaskIntoConstraints = false
    self.stackview.topAnchor.constraint(equalTo: self.topAnchor, constant: 0).isActive = true
    self.stackview.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: 0).isActive = true
    self.stackview.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 0).isActive = true
    self.stackview.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: 0).isActive = true

    // Holder
    let holderView = UIView()
    holderView.backgroundColor = UIColor.red
    self.stackview.addArrangedSubview(holderView)

    // Subview
    let view3 = UIView()
    view3.backgroundColor = UIColor.orange
    holderView.addSubview(view3)

    view3.translatesAutoresizingMaskIntoConstraints = false
    view3.topAnchor.constraint(equalTo: holderView.topAnchor, constant: 0).isActive = true
    view3.bottomAnchor.constraint(equalTo: holderView.bottomAnchor, constant: 0).isActive = true
    view3.leadingAnchor.constraint(equalTo: holderView.leadingAnchor, constant: 30).isActive = true
    view3.trailingAnchor.constraint(equalTo: holderView.trailingAnchor, constant: -30).isActive = true

错误：

    2017-06-30 17:38:37.124333+0200 XXXXX[83954:2132661] [LayoutConstraints] Unable to simultaneously satisfy constraints.
    Probably at least one of the constraints in the following list is one you don't want. 
    Try this: 
        (1) look at each constraint and try to figure out which you don't expect; 
        (2) find the code that added the unwanted constraint or constraints and fix it. 
(
    "<NSLayoutConstraint:0x61000028b680 H:|-(30)-[UIView:0x7f8dab565720]   (active, names: '|':UIView:0x7f8dab566620 )>",
    "<NSLayoutConstraint:0x61000028b6d0 UIView:0x7f8dab565720.trailing == UIView:0x7f8dab566620.trailing - 30   (active)>",
    "<NSLayoutConstraint:0x61000028b4a0 H:|-(0)-[UIStackView:0x7f8dab569320]   (active, names: '|': XXXXX.MultipleBarGraphsView:0x7f8dab561190'What are you doing' )>",
    "<NSLayoutConstraint:0x61000028b3b0 UIStackView:0x7f8dab569320.trailing == XXXXX.MultipleBarGraphsView:0x7f8dab561190'Hur ofta svarar du r\U00e4tt?'.trailing   (active)>",
    "<NSLayoutConstraint:0x61000028b900 '_UITemporaryLayoutWidth' XXXXX.MultipleBarGraphsView:0x7f8dab561190'Hur ofta svarar du r\U00e4tt?'.width == 0   (active)>",
    "<NSLayoutConstraint:0x61000028af00 'UISV-canvas-connection' UIStackView:0x7f8dab569320.leading == UIView:0x7f8dab566620.leading   (active)>",
    "<NSLayoutConstraint:0x61000028bbd0 'UISV-canvas-connection' H:[UIView:0x7f8dab566620]-(0)-|   (active, names: '|':UIStackView:0x7f8dab569320 )>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x61000028b6d0 UIView:0x7f8dab565720.trailing == UIView:0x7f8dab566620.trailing - 30   (active)>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.