如何"find"自己约束？
How to "find" your own constraint?
假设我有一个 UIView，
class CleverView: UIView
在自定义class中，我想这样做：
func changeWidth() {
let c = ... find my own layout constraint, for "width"
c.constant = 70 * Gameinfo.ImportanceOfEnemyFactor
}
同样，我希望能够像那样"find"，将约束（或者我猜，所有约束，可能不止一个）附加到四个边之一。
因此，查看所有附加到我的约束，并找到任何 width/height 个，或者确实与给定的（例如，"left"）边缘相关的任何约束。
有什么想法吗？
也许值得注意
请注意，（显然）我在问如何做到这一点 dynamically/programmatically。
（是的，您可以说 "link to the constraint" 或 "use an ID" - QA 的重点是如何即时找到它们并动态工作。）
如果您不熟悉约束，请注意 .constraints 只为您提供了存储的末端 "there"。
我猜你可以使用 constraints 属性 of UIView。 constraints 基本上 returns 直接分配给 UIView 的约束数组。它无法让您获得 superview 持有的约束，例如前导、尾随、顶部或底部，但宽度和高度约束由 View 本身持有。对于superview的约束，可以循环遍历superview的约束。假设聪明的观点有这些限制：
class CleverView: UIView {
func printSuperViewConstriantsCount() {
var c = 0
self.superview?.constraints.forEach({ (constraint) in
guard constraint.secondItem is CleverView || constraint.firstItem is CleverView else {
return
}
c += 1
print(constraint.firstAttribute.toString())
})
print("superview constraints:\(c)")
}
func printSelfConstriantsCount() {
self.constraints.forEach { (constraint) in
return print(constraint.firstAttribute.toString())
}
print("self constraints:\(self.constraints.count)")
}
}
输出:
顶部
领先
尾随
超级视图 constraints:3
身高
自我 constraints:1
基本上，您可以查看 NSLayoutConstraint class 以获取有关特定约束的信息。
要打印约束的名称，我们可以使用这个扩展
extension NSLayoutAttribute {
func toString() -> String {
switch self {
case .left:
return "left"
case .right:
return "right"
case .top:
return "top"
case .bottom:
return "bottom"
case .leading:
return "leading"
case .trailing:
return "trailing"
case .width:
return "width"
case .height:
return "height"
case .centerX:
return "centerX"
case .centerY:
return "centerY"
case .lastBaseline:
return "lastBaseline"
case .firstBaseline:
return "firstBaseline"
case .leftMargin:
return "leftMargin"
case .rightMargin:
return "rightMargin"
case .topMargin:
return "topMargin"
case .bottomMargin:
return "bottomMargin"
case .leadingMargin:
return "leadingMargin"
case .trailingMargin:
return "trailingMargin"
case .centerXWithinMargins:
return "centerXWithinMargins"
case .centerYWithinMargins:
return "centerYWithinMargins"
case .notAnAttribute:
return "notAnAttribute"
}
}
}
真的有两种情况：
- 有关视图大小或与后代视图关系的约束在自身中保存
- 两个视图之间的约束保存在视图的最低共同祖先中
重复。对于两个视图之间的约束。 iOS 事实上，总是将它们存储在最低的共同祖先中。 因此，始终可以通过搜索视图的所有祖先来找到视图的约束。
因此，我们需要检查视图本身及其所有父视图的约束。一种方法可能是：
extension UIView {
// retrieves all constraints that mention the view
func getAllConstraints() -> [NSLayoutConstraint] {
// array will contain self and all superviews
var views = [self]
// get all superviews
var view = self
while let superview = view.superview {
views.append(superview)
view = superview
}
// transform views to constraints and filter only those
// constraints that include the view itself
return views.flatMap({ [=10=].constraints }).filter { constraint in
return constraint.firstItem as? UIView == self ||
constraint.secondItem as? UIView == self
}
}
}
您可以在获得有关视图的所有约束后应用各种过滤器，我想这是最困难的部分。一些例子：
extension UIView {
// Example 1: Get all width constraints involving this view
// We could have multiple constraints involving width, e.g.:
// - two different width constraints with the exact same value
// - this view's width equal to another view's width
// - another view's height equal to this view's width (this view mentioned 2nd)
func getWidthConstraints() -> [NSLayoutConstraint] {
return getAllConstraints().filter( {
([=11=].firstAttribute == .width && [=11=].firstItem as? UIView == self) ||
([=11=].secondAttribute == .width && [=11=].secondItem as? UIView == self)
} )
}
// Example 2: Change width constraint(s) of this view to a specific value
// Make sure that we are looking at an equality constraint (not inequality)
// and that the constraint is not against another view
func changeWidth(to value: CGFloat) {
getAllConstraints().filter( {
[=11=].firstAttribute == .width &&
[=11=].relation == .equal &&
[=11=].secondAttribute == .notAnAttribute
} ).forEach( {[=11=].constant = value })
}
// Example 3: Change leading constraints only where this view is
// mentioned first. We could also filter leadingMargin, left, or leftMargin
func changeLeading(to value: CGFloat) {
getAllConstraints().filter( {
[=11=].firstAttribute == .leading &&
[=11=].firstItem as? UIView == self
}).forEach({[=11=].constant = value})
}
}
// 编辑：增强示例并在评论中阐明它们的解释
可能会节省一些打字时间......
根据 stakri 的赏金答案，以下是获得赏金的确切方法
“另一个视图的部分宽度”类型的所有约束
“定点宽度”类型的所有约束
“您的 x 位置”类型的所有约束
所以..
fileprivate extension UIView {
func widthAsPointsConstraints()->[NSLayoutConstraint] {}
func widthAsFractionOfAnotherViewConstraints()->[NSLayoutConstraint] {}
func xPositionConstraints()->[NSLayoutConstraint]
}
完整代码如下。当然，你也可以用同样的方法来做“高度”。
所以，像这样使用它们...
let cc = someView.widthAsFractionOfAnotherViewConstraints()
for c in cc {
c.changeToNewConstraintWith(multiplier: 0.25)
}
或
let cc = someView.widthAsPointsConstraints()
for c in cc {
c.constant = 150.0
}
此外，我在底部粘贴了一个简单的演示代码，示例输出...
这是代码。 V2 ...
fileprivate extension UIView { // experimental
func allConstraints()->[NSLayoutConstraint] {
var views = [self]
var view = self
while let superview = view.superview {
views.append(superview)
view = superview
}
return views.flatMap({ [=13=].constraints }).filter { constraint in
return constraint.firstItem as? UIView == self ||
constraint.secondItem as? UIView == self
}
}
func widthAsPointsConstraints()->[NSLayoutConstraint] {
return self.allConstraints()
.filter({
( [=13=].firstItem as? UIView == self && [=13=].secondItem == nil )
})
.filter({
[=13=].firstAttribute == .width && [=13=].secondAttribute == .notAnAttribute
})
}
func widthAsFractionOfAnotherViewConstraints()->[NSLayoutConstraint] {
func _bothviews(_ c: NSLayoutConstraint)->Bool {
if c.firstItem == nil { return false }
if c.secondItem == nil { return false }
if !c.firstItem!.isKind(of: UIView.self) { return false }
if !c.secondItem!.isKind(of: UIView.self) { return false }
return true
}
func _ab(_ c: NSLayoutConstraint)->Bool {
return _bothviews(c)
&& c.firstItem as? UIView == self
&& c.secondItem as? UIView != self
&& c.firstAttribute == .width
}
func _ba(_ c: NSLayoutConstraint)->Bool {
return _bothviews(c)
&& c.firstItem as? UIView != self
&& c.secondItem as? UIView == self
&& c.secondAttribute == .width
}
// note that .relation could be anything: and we don't mind that
return self.allConstraints()
.filter({ _ab([=13=]) || _ba([=13=]) })
}
func xPositionConstraints()->[NSLayoutConstraint] {
return self.allConstraints()
.filter({
return [=13=].firstAttribute == .centerX || [=13=].secondAttribute == .centerX
})
}
}
extension NSLayoutConstraint {
// typical routine to "change" multiplier fraction...
@discardableResult
func changeToNewConstraintWith(multiplier:CGFloat) -> NSLayoutConstraint {
//NSLayoutConstraint.deactivate([self])
self.isActive = false
let nc = NSLayoutConstraint(
item: firstItem as Any,
attribute: firstAttribute,
relatedBy: relation,
toItem: secondItem,
attribute: secondAttribute,
multiplier: multiplier,
constant: constant)
nc.priority = priority
nc.shouldBeArchived = self.shouldBeArchived
nc.identifier = self.identifier
//NSLayoutConstraint.activate([nc])
nc.isActive = true
return nc
}
}
只是一个示例演示...
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
_teste()
delay(5) {
print("changing any 'fraction fo another view' style widths ...\n\n")
let cc = self.animeHolder.widthAsFractionOfAnotherViewConstraints()
for c in cc {
c.changeToNewConstraintWith(multiplier: 0.25)
}
self._teste()
}
delay(10) {
print("changing any 'points' style widths ...\n\n")
let cc = self.animeHolder.widthAsPointsConstraints()
for c in cc {
c.constant = 150.0
}
self._teste()
}
}
func _teste() {
print("\n---- allConstraints")
for c in animeHolder.allConstraints() {
print("\n \(c)")
}
print("\n---- widthAsPointsConstraints")
for c in animeHolder.widthAsPointsConstraints() {
print("\n \(c)\n \(c.multiplier) \(c.constant)")
}
print("\n---- widthAsFractionOfAnotherViewConstraints")
for c in animeHolder.widthAsFractionOfAnotherViewConstraints() {
print("\n \(c)\n \(c.multiplier) \(c.constant)")
}
print("\n----\n")
}
假设我有一个 UIView，
class CleverView: UIView
在自定义class中，我想这样做：
func changeWidth() {
let c = ... find my own layout constraint, for "width"
c.constant = 70 * Gameinfo.ImportanceOfEnemyFactor
}
同样，我希望能够像那样"find"，将约束（或者我猜，所有约束，可能不止一个）附加到四个边之一。
因此，查看所有附加到我的约束，并找到任何 width/height 个，或者确实与给定的（例如，"left"）边缘相关的任何约束。
有什么想法吗？
也许值得注意
请注意，（显然）我在问如何做到这一点 dynamically/programmatically。
（是的，您可以说 "link to the constraint" 或 "use an ID" - QA 的重点是如何即时找到它们并动态工作。）
如果您不熟悉约束，请注意 .constraints 只为您提供了存储的末端 "there"。
我猜你可以使用 constraints 属性 of UIView。 constraints 基本上 returns 直接分配给 UIView 的约束数组。它无法让您获得 superview 持有的约束，例如前导、尾随、顶部或底部，但宽度和高度约束由 View 本身持有。对于superview的约束，可以循环遍历superview的约束。假设聪明的观点有这些限制：
class CleverView: UIView {
func printSuperViewConstriantsCount() {
var c = 0
self.superview?.constraints.forEach({ (constraint) in
guard constraint.secondItem is CleverView || constraint.firstItem is CleverView else {
return
}
c += 1
print(constraint.firstAttribute.toString())
})
print("superview constraints:\(c)")
}
func printSelfConstriantsCount() {
self.constraints.forEach { (constraint) in
return print(constraint.firstAttribute.toString())
}
print("self constraints:\(self.constraints.count)")
}
}
输出:
顶部
领先
尾随
超级视图 constraints:3
身高
自我 constraints:1
基本上，您可以查看 NSLayoutConstraint class 以获取有关特定约束的信息。
要打印约束的名称，我们可以使用这个扩展
extension NSLayoutAttribute {
func toString() -> String {
switch self {
case .left:
return "left"
case .right:
return "right"
case .top:
return "top"
case .bottom:
return "bottom"
case .leading:
return "leading"
case .trailing:
return "trailing"
case .width:
return "width"
case .height:
return "height"
case .centerX:
return "centerX"
case .centerY:
return "centerY"
case .lastBaseline:
return "lastBaseline"
case .firstBaseline:
return "firstBaseline"
case .leftMargin:
return "leftMargin"
case .rightMargin:
return "rightMargin"
case .topMargin:
return "topMargin"
case .bottomMargin:
return "bottomMargin"
case .leadingMargin:
return "leadingMargin"
case .trailingMargin:
return "trailingMargin"
case .centerXWithinMargins:
return "centerXWithinMargins"
case .centerYWithinMargins:
return "centerYWithinMargins"
case .notAnAttribute:
return "notAnAttribute"
}
}
}
真的有两种情况：
- 有关视图大小或与后代视图关系的约束在自身中保存
- 两个视图之间的约束保存在视图的最低共同祖先中
重复。对于两个视图之间的约束。 iOS 事实上，总是将它们存储在最低的共同祖先中。 因此，始终可以通过搜索视图的所有祖先来找到视图的约束。
因此，我们需要检查视图本身及其所有父视图的约束。一种方法可能是：
extension UIView {
// retrieves all constraints that mention the view
func getAllConstraints() -> [NSLayoutConstraint] {
// array will contain self and all superviews
var views = [self]
// get all superviews
var view = self
while let superview = view.superview {
views.append(superview)
view = superview
}
// transform views to constraints and filter only those
// constraints that include the view itself
return views.flatMap({ [=10=].constraints }).filter { constraint in
return constraint.firstItem as? UIView == self ||
constraint.secondItem as? UIView == self
}
}
}
您可以在获得有关视图的所有约束后应用各种过滤器，我想这是最困难的部分。一些例子：
extension UIView {
// Example 1: Get all width constraints involving this view
// We could have multiple constraints involving width, e.g.:
// - two different width constraints with the exact same value
// - this view's width equal to another view's width
// - another view's height equal to this view's width (this view mentioned 2nd)
func getWidthConstraints() -> [NSLayoutConstraint] {
return getAllConstraints().filter( {
([=11=].firstAttribute == .width && [=11=].firstItem as? UIView == self) ||
([=11=].secondAttribute == .width && [=11=].secondItem as? UIView == self)
} )
}
// Example 2: Change width constraint(s) of this view to a specific value
// Make sure that we are looking at an equality constraint (not inequality)
// and that the constraint is not against another view
func changeWidth(to value: CGFloat) {
getAllConstraints().filter( {
[=11=].firstAttribute == .width &&
[=11=].relation == .equal &&
[=11=].secondAttribute == .notAnAttribute
} ).forEach( {[=11=].constant = value })
}
// Example 3: Change leading constraints only where this view is
// mentioned first. We could also filter leadingMargin, left, or leftMargin
func changeLeading(to value: CGFloat) {
getAllConstraints().filter( {
[=11=].firstAttribute == .leading &&
[=11=].firstItem as? UIView == self
}).forEach({[=11=].constant = value})
}
}
// 编辑：增强示例并在评论中阐明它们的解释
可能会节省一些打字时间......
根据 stakri 的赏金答案，以下是获得赏金的确切方法
“另一个视图的部分宽度”类型的所有约束
“定点宽度”类型的所有约束
“您的 x 位置”类型的所有约束
所以..
fileprivate extension UIView {
func widthAsPointsConstraints()->[NSLayoutConstraint] {}
func widthAsFractionOfAnotherViewConstraints()->[NSLayoutConstraint] {}
func xPositionConstraints()->[NSLayoutConstraint]
}
完整代码如下。当然，你也可以用同样的方法来做“高度”。
所以，像这样使用它们...
let cc = someView.widthAsFractionOfAnotherViewConstraints()
for c in cc {
c.changeToNewConstraintWith(multiplier: 0.25)
}
或
let cc = someView.widthAsPointsConstraints()
for c in cc {
c.constant = 150.0
}
此外，我在底部粘贴了一个简单的演示代码，示例输出...
这是代码。 V2 ...
fileprivate extension UIView { // experimental
func allConstraints()->[NSLayoutConstraint] {
var views = [self]
var view = self
while let superview = view.superview {
views.append(superview)
view = superview
}
return views.flatMap({ [=13=].constraints }).filter { constraint in
return constraint.firstItem as? UIView == self ||
constraint.secondItem as? UIView == self
}
}
func widthAsPointsConstraints()->[NSLayoutConstraint] {
return self.allConstraints()
.filter({
( [=13=].firstItem as? UIView == self && [=13=].secondItem == nil )
})
.filter({
[=13=].firstAttribute == .width && [=13=].secondAttribute == .notAnAttribute
})
}
func widthAsFractionOfAnotherViewConstraints()->[NSLayoutConstraint] {
func _bothviews(_ c: NSLayoutConstraint)->Bool {
if c.firstItem == nil { return false }
if c.secondItem == nil { return false }
if !c.firstItem!.isKind(of: UIView.self) { return false }
if !c.secondItem!.isKind(of: UIView.self) { return false }
return true
}
func _ab(_ c: NSLayoutConstraint)->Bool {
return _bothviews(c)
&& c.firstItem as? UIView == self
&& c.secondItem as? UIView != self
&& c.firstAttribute == .width
}
func _ba(_ c: NSLayoutConstraint)->Bool {
return _bothviews(c)
&& c.firstItem as? UIView != self
&& c.secondItem as? UIView == self
&& c.secondAttribute == .width
}
// note that .relation could be anything: and we don't mind that
return self.allConstraints()
.filter({ _ab([=13=]) || _ba([=13=]) })
}
func xPositionConstraints()->[NSLayoutConstraint] {
return self.allConstraints()
.filter({
return [=13=].firstAttribute == .centerX || [=13=].secondAttribute == .centerX
})
}
}
extension NSLayoutConstraint {
// typical routine to "change" multiplier fraction...
@discardableResult
func changeToNewConstraintWith(multiplier:CGFloat) -> NSLayoutConstraint {
//NSLayoutConstraint.deactivate([self])
self.isActive = false
let nc = NSLayoutConstraint(
item: firstItem as Any,
attribute: firstAttribute,
relatedBy: relation,
toItem: secondItem,
attribute: secondAttribute,
multiplier: multiplier,
constant: constant)
nc.priority = priority
nc.shouldBeArchived = self.shouldBeArchived
nc.identifier = self.identifier
//NSLayoutConstraint.activate([nc])
nc.isActive = true
return nc
}
}
只是一个示例演示...
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
_teste()
delay(5) {
print("changing any 'fraction fo another view' style widths ...\n\n")
let cc = self.animeHolder.widthAsFractionOfAnotherViewConstraints()
for c in cc {
c.changeToNewConstraintWith(multiplier: 0.25)
}
self._teste()
}
delay(10) {
print("changing any 'points' style widths ...\n\n")
let cc = self.animeHolder.widthAsPointsConstraints()
for c in cc {
c.constant = 150.0
}
self._teste()
}
}
func _teste() {
print("\n---- allConstraints")
for c in animeHolder.allConstraints() {
print("\n \(c)")
}
print("\n---- widthAsPointsConstraints")
for c in animeHolder.widthAsPointsConstraints() {
print("\n \(c)\n \(c.multiplier) \(c.constant)")
}
print("\n---- widthAsFractionOfAnotherViewConstraints")
for c in animeHolder.widthAsFractionOfAnotherViewConstraints() {
print("\n \(c)\n \(c.multiplier) \(c.constant)")
}
print("\n----\n")
}