为什么Autolayout不更改视图框架

我在其superview的func中创建了一个视图

let black = NSView(frame: NSRect(x: 0, y: 0, width: 10, height: 10))

black.translatesAutoresizingMaskIntoConstraints = false
black.wantsLayer = true
black.layer?.backgroundColor = NSColor.black.cgColor
self.addSubview(black)

black.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -15).isActive = true
black.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 15).isActive = true
black.heightAnchor.constraint(equalToConstant: 115).isActive = true
black.widthAnchor.constraint(equalToConstant: 115).isActive = true

print ("origin (\(black.frame.origin.x),\(black.frame.origin.y)) size (\(black.frame.size.width),\(black.frame.size.height)) ")

输出为 origin(0,0) , size(10,10) ,这些是创建视图时使用的值。 屏幕上的黑色视图按预期定位 origin:(15,15) size:(115,115) .

为什么框架没有更新?