iOS - 通过 Swift 更改约束的乘数
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iOS - Change the multiplier of constraint by Swift
提问by ryo
How to change the multiplier of a constraint by using Swift.
如何使用 Swift 更改约束的乘数。
someConstraint.multiplier = 0.6 // error: 'multiplier' is get-only property
I would like to know how to change the multiplier in code (Swift).
我想知道如何更改代码（Swift）中的乘数。
回答by KlimczakM
Since multiplieris a read-only property and you can't change it, you need to replace the constraint with its modified clone.
由于multiplier是只读属性并且您无法更改它，因此您需要将约束替换为其修改后的克隆。
You can use an extension to do it, like this:
您可以使用扩展来执行此操作，如下所示：
Swift 4/5:
斯威夫特 4/5：
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)
}
}
Usage:
用法：
let newConstraint = constraintToChange.constraintWithMultiplier(0.75)
view.removeConstraint(constraintToChange)
view.addConstraint(newConstraint)
view.layoutIfNeeded()
constraintToChange = newConstraint
