iOS-Swift-setContentCompressionResistancePriority与setContentHuggingPri

两个UILabel放在同一行，需要设置它们的抗压缩和抗拉伸属性。

class MyView: UIView {
 
    lazy var leftLabel = UILabel()
    lazy var rightLabel = UILabel()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        backgroundColor = .lightGray
        
        leftLabel.text = "左边的文案"
        leftLabel.textColor = .red
        leftLabel.backgroundColor = .red.withAlphaComponent(0.2)
        rightLabel.text = "右边的文案"
        rightLabel.textColor = .blue
        rightLabel.backgroundColor = .blue.withAlphaComponent(0.2)
        
        leftLabel.addTo(self).snp.makeConstraints { make in
            make.left.equalToSuperview()
            make.centerY.equalToSuperview()
        }
        rightLabel.addTo(self).snp.makeConstraints { make in
            make.left.equalTo(leftLabel.snp.right)
            make.right.equalToSuperview()
            make.centerY.equalToSuperview()
        }
        
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
}

短文字情况：默认拉伸左边

短文字、左边抗拉伸属性设置为高：拉伸右边

        leftLabel.setContentHuggingPriority(.defaultHigh, for: .horizontal)

文字超长：默认压缩右边

文字超长、左边抗压缩属性设置为低：压缩左边

        leftLabel.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)

总结

1. setContentHuggingPriority是抗拉伸属性，属性低更容易被拉伸，被拉伸是指控件的宽度超过文字宽度，用空白填充
2. setContentCompressionResistancePriority是抗压缩属性，属性低更容易被压缩，被压缩是指控件的宽度不足以放下文字，用省略号...代替
3. 同一个控件的拉伸和压缩是两个独立的属性，可以同时设置setContentHuggingPriority与setContentCompressionResistancePriority，互不冲突
4. 基于布局先放左边文字的情况，默认拉伸左边、压缩右边。也就是默认左边的抗拉伸属性更低，右边的拉压缩属性更低