iOS - 通过Swift更改约束的乘数

Question

如何使用Swift更改约束的乘数.

someConstraint.multiplier = 0.6 // error: 'multiplier' is get-only property

我想知道如何更改代码中的乘数(Swift).

Answer 1

由于multiplier是只读属性而您无法更改它,因此需要将约束替换为其已修改的克隆.

您可以编写扩展来执行此操作,例如:

extension NSLayoutConstraint {
    func constraintWithMultiplier(_ multiplier: CGFloat) -> NSLayoutConstraint {
        return NSLayoutConstraint(item: self.firstItem!, attribute: self.firstAttribute, relatedBy: self.relation, toItem: self.secondItem, attribute: self.secondAttribute, multiplier: multiplier, constant: self.constant)
    }
}

Swift 3+版本:

let newConstraint = constraintToChange.constraintWithMultiplier(0.75)
view.removeConstraint(constraintToChange)
view.addConstraint(newConstraint)
view.layoutIfNeeded()
constraintToChange = newConstraint

用法:

extension NSLayoutConstraint {
    func constraintWithMultiplier(_ multiplier: CGFloat) -> NSLayoutConstraint {
        return NSLayoutConstraint(item: self.firstItem!, attribute: self.firstAttribute, relatedBy: self.relation, toItem: self.secondItem, attribute: self.secondAttribute, multiplier: multiplier, constant: self.constant)
    }
}