为什么ASTextNode不显示？

Question

我不明白为什么不显示文本

导入UIKit 导入AsyncDisplayKit

ViewController类：ASViewController {

python MyProgram.py 

}

init() {
    super.init(node: ASDisplayNode())
    let text = ASTextNode()
    let attrs = [NSAttributedStringKey.font: UIFont(name: "HelveticaNeue", size: 12.0)!]
    let string = NSAttributedString(string: "Hello World!", attributes: attrs)
    text.attributedText = string
    self.node.addSubnode(text)
}
required init?(coder aDecoder: NSCoder) {
    super.init(node: ASDisplayNode.init())
}

Answer 1

import UIKit
import AsyncDisplayKit

class ViewController: ASViewController<ASDisplayNode>  {
    init() {
    super.init(node: LayoutExampleNode())
}
required init?(coder aDecoder: NSCoder) {
    super.init(node: ASDisplayNode.init())
}
}

class LayoutExampleNode: ASDisplayNode {
override required init() {
    super.init()
    automaticallyManagesSubnodes = true
    backgroundColor = .white
}

}

extension LayoutExampleNode {

override func layoutSpecThatFits(_ constrainedSize: ASSizeRange) -> ASLayoutSpec {
    let someVerticalStack = ASStackLayoutSpec.vertical()
    someVerticalStack.style.flexShrink = 1.0
    someVerticalStack.style.flexGrow = 1.0

    let text = ASTextNode()
    let attrs = [NSAttributedStringKey.font: UIFont(name: "HelveticaNeue", size: 12.0)!]
    let string = NSAttributedString(string: "Hello World!", attributes: attrs)
    text.attributedText = string

    someVerticalStack.children = [text]

    let someVerticalStackSpec = ASStackLayoutSpec(direction: .horizontal,
                                            spacing: 40,
                                            justifyContent: .start,
                                            alignItems: .center,
                                            children: [someVerticalStack])

    return ASInsetLayoutSpec(insets: UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 10), child: someVerticalStackSpec)
}
}