AdjustsFontSizeToFitWidth的异常行为

Question

我想知道当numberOfLines设置为1时，为什么UILabel不能正确调整字体大小。我在游乐场设置了以下代码：

import UIKit
import PlaygroundSupport

let labelFrame = CGRect(x: 0, y: 0, width: 100, height: 100)
let label = UILabel(frame: labelFrame)
label.backgroundColor = .lightGray
label.text = "Something that's pretty long"

label.baselineAdjustment = .alignCenters
label.adjustsFontSizeToFitWidth = true

label.numberOfLines = 1
label.minimumScaleFactor = 0.1

let frame = CGRect(x: 0, y: 0, width: 300, height: 300)
let view = UIView(frame: frame)
view.backgroundColor = .white

view.addSubview(label)

PlaygroundPage.current.liveView = view

这就是结果

但是，当我将numberOfLines更改为2时，字体会缩小，就像我期望的那样：

import UIKit
import PlaygroundSupport

let labelFrame = CGRect(x: 0, y: 0, width: 100, height: 100)
let label = UILabel(frame: labelFrame)
label.backgroundColor = .lightGray
label.text = "Something that's pretty long"

label.baselineAdjustment = .alignCenters
label.adjustsFontSizeToFitWidth = true

label.numberOfLines = 2   // <<<<<< this is the only change
label.minimumScaleFactor = 0.1

let frame = CGRect(x: 0, y: 0, width: 300, height: 300)
let view = UIView(frame: frame)
view.backgroundColor = .white

view.addSubview(label)

PlaygroundPage.current.liveView = view

结果如下：

这是怎么回事？这是错误还是我做错了什么？

Answer 1

嗯，看来这只是Playgrounds中的错误。如果我添加这一行

label.lineBreakMode = .byTruncatingMiddle

一切正常。实际上，任何这些工作：

label.lineBreakMode = .byCharWrapping
label.lineBreakMode = .byClipping
label.lineBreakMode = .byTruncatingHead
label.lineBreakMode = .byTruncatingMiddle
label.lineBreakMode = .byWordWrapping

不起作用（也是默认值）的是

label.lineBreakMode = .byTruncatingTail

当我在真实的模拟器中尝试此操作时，一切看起来都不错，所以我认为我刚遇到了Playgrounds错误。