iOS 用代码添加约束

iOS 用代码添加约束

 contentView.translatesAutoresizingMaskIntoConstraints = false
        let attributes: [NSLayoutConstraint.Attribute] = [.leading, .trailing, .top, .bottom]
        let constraints = attributes.map({
            NSLayoutConstraint(
                item: contentView,
                attribute: $0,
                relatedBy: .equal,
                toItem: view,
                attribute: $0,
                multiplier: 1,
                constant: 0)
        })
 view.addConstraints(constraints)