有没有一种方法可以通过代码创建大于或等于关系的约束 [英] Is there is a way to create constraint greater than or equal relation through code

问题描述

我正在处理可扩展表格单元格，我的算法如下:

I'm working on expandable table cell, and my algorithm is follow:

1. 我创建两个视图.
2. 创建第二个视图的高度约束，将其作为IBOutlet拖动到我的单元格中.
3. 选中单元格后，更改所选单元格的状态.

---

class ExpandableCell: UITableViewCell {

    @IBOutlet weak var expandableCellHeightConstraint: NSLayoutConstraint!

    @IBOutlet weak var expandableView: UIView!

    var isExpanded:Bool = false
    {
        didSet
        {
            if !isExpanded {
                self.expandableCellHeightConstraint.constant = 0.0

            } else {
                self.expandableCellHeightConstraint.constant = 120
            }
        }
    }
}

一切都很好，但是我希望我的第二个视图调整与内部内容相关的大小.

Everything is fine, but I want my second view resize related to inner content.

这是我的限制条件:

所以，我的问题是:

将非严格值写入self.expandableCellHeightConstraint.constant的最佳方法是什么?实际上，我曾想过编写self.expandableCellHeightConstraint.constant >= 120之类的东西，但据我所知，这是不可能的.

What is the best way to write non-strict value to self.expandableCellHeightConstraint.constant? Actually I thought of writing something like self.expandableCellHeightConstraint.constant >= 120, but as far as I get it is impossible.

推荐答案

作为

As Martin R suggests, you can create the height constraint in code like this:

let heightConstraint = NSLayoutConstraint(
        item: yourExpandableView,
        attribute: .height,
        relatedBy: .greaterThanOrEqual,
        toItem: nil,
        attribute: .notAnAttribute,
        multiplier: 1.0,
        constant: 120
)

或者，您也可以这样:

let heightConstraint = yourExpandableView.heightAnchor.constraint(greaterThanOrEqualToConstant: 120)

然后，当需要启用/禁用此约束时，可以将其isActive属性设置为true或false.您可能还希望将此约束保留为类的属性，因为一旦将约束的属性isActive设置为false，约束就会变为nil.

Then you can set its isActive property to true or false whenever you need to enable/disable this constraint. You probably also want to hold this constraint as a property of the class, because constraints become nil, once their property isActive is set to false.

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