SnapKit/Source/Constraint.swift

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//
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// SnapKit
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//
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// Copyright (c) 2011-Present SnapKit Team - https://github.com/SnapKit
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
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#if os(iOS) || os(tvOS)
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import UIKit
#else
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import AppKit
#endif
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public class Constraint {
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internal let sourceLocation: (String, UInt)
internal let label: String?
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private let from: ConstraintItem
private let to: ConstraintItem
private let relation: ConstraintRelation
private let multiplier: ConstraintMultiplierTarget
private var constant: ConstraintConstantTarget {
didSet {
self.updateConstantAndPriorityIfNeeded()
}
}
private var priority: ConstraintPriorityTarget {
didSet {
self.updateConstantAndPriorityIfNeeded()
}
}
private let layoutConstraints: NSHashTable<LayoutConstraint>
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// MARK: Initialization
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internal init(from: ConstraintItem,
to: ConstraintItem,
relation: ConstraintRelation,
sourceLocation: (String, UInt),
label: String?,
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multiplier: ConstraintMultiplierTarget,
constant: ConstraintConstantTarget,
priority: ConstraintPriorityTarget) {
self.from = from
self.to = to
self.relation = relation
self.sourceLocation = sourceLocation
self.label = label
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self.multiplier = multiplier
self.constant = constant
self.priority = priority
self.layoutConstraints = NSHashTable<LayoutConstraint>.weakObjects()
// get attributes
let layoutFromAttributes = self.from.attributes.layoutAttributes
let layoutToAttributes = self.to.attributes.layoutAttributes
// get layout from
let layoutFrom: ConstraintView = self.from.view!
// get relation
let layoutRelation = self.relation.layoutRelation
for layoutFromAttribute in layoutFromAttributes {
// get layout to attribute
let layoutToAttribute = (layoutToAttributes.count > 0) ? layoutToAttributes[0] : layoutFromAttribute
// get layout constant
let layoutConstant: CGFloat = self.constant.constraintConstantTargetValueFor(layoutAttribute: layoutToAttribute)
// get layout to
var layoutTo: AnyObject? = self.to.target
// use superview if possible
if layoutTo == nil && layoutToAttribute != .width && layoutToAttribute != .height {
layoutTo = layoutFrom.superview
}
// create layout constraint
let layoutConstraint = LayoutConstraint(
item: layoutFrom,
attribute: layoutFromAttribute,
relatedBy: layoutRelation,
toItem: layoutTo,
attribute: layoutToAttribute,
multiplier: self.multiplier.constraintMultiplierTargetValue,
constant: layoutConstant
)
// set label
layoutConstraint.label = self.label
// set priority
layoutConstraint.priority = self.priority.constraintPriorityTargetValue
// set constraint
layoutConstraint.constraint = self
// append
self.layoutConstraints.add(layoutConstraint)
}
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}
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// MARK: Public
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public func activate() {
self.activateIfNeeded()
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}
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public func deactivate() {
self.deactivateIfNeeded()
}
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@discardableResult
public func update(offset: ConstraintOffsetTarget) -> Constraint {
self.constant = offset.constraintOffsetTargetValue
return self
}
@discardableResult
public func update(inset: ConstraintInsetTarget) -> Constraint {
self.constant = inset.constraintInsetTargetValue
return self
}
@discardableResult
public func update(priority: ConstraintPriorityTarget) -> Constraint {
self.priority = priority.constraintPriorityTargetValue
return self
}
@available(*, deprecated:0.40.0, message:"Use update(offset: ConstraintOffsetTarget) instead.")
public func updateOffset(amount: ConstraintOffsetTarget) -> Void { self.update(offset: amount) }
@available(*, deprecated:0.40.0, message:"Use update(inset: ConstraintInsetTarget) instead.")
public func updateInsets(amount: ConstraintInsetTarget) -> Void { self.update(inset: amount) }
@available(*, deprecated:0.40.0, message:"Use update(priority: ConstraintPriorityTarget) instead.")
public func updatePriority(amount: ConstraintPriorityTarget) -> Void { self.update(priority: amount) }
@available(*, obsoleted:0.40.0, message:"Use update(priority: ConstraintPriorityTarget) instead.")
public func updatePriorityRequired() -> Void {}
@available(*, obsoleted:0.40.0, message:"Use update(priority: ConstraintPriorityTarget) instead.")
public func updatePriorityHigh() -> Void { fatalError("Must be implemented by Concrete subclass.") }
@available(*, obsoleted:0.40.0, message:"Use update(priority: ConstraintPriorityTarget) instead.")
public func updatePriorityMedium() -> Void { fatalError("Must be implemented by Concrete subclass.") }
@available(*, obsoleted:0.40.0, message:"Use update(priority: ConstraintPriorityTarget) instead.")
public func updatePriorityLow() -> Void { fatalError("Must be implemented by Concrete subclass.") }
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// MARK: Internal
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internal func updateConstantAndPriorityIfNeeded() {
for layoutConstraint in self.layoutConstraints.allObjects {
let attribute = (layoutConstraint.secondAttribute == .notAnAttribute) ? layoutConstraint.firstAttribute : layoutConstraint.secondAttribute
layoutConstraint.constant = self.constant.constraintConstantTargetValueFor(layoutAttribute: attribute)
layoutConstraint.priority = self.priority.constraintPriorityTargetValue
}
}
internal func activateIfNeeded(updatingExisting: Bool = false) {
let view = self.from.view!
let layoutConstraints = self.layoutConstraints.allObjects
let existingLayoutConstraints = view.snp.layoutConstraints
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if updatingExisting && existingLayoutConstraints.count > 0 {
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for layoutConstraint in layoutConstraints {
let existingLayoutConstraint = existingLayoutConstraints.first { $0 == layoutConstraint }
guard let updateLayoutConstraint = existingLayoutConstraint else {
fatalError("Updated constraint could not find existing matching constraint to update: \(layoutConstraint)")
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}
let updateLayoutAttribute = (updateLayoutConstraint.secondAttribute == .notAnAttribute) ? updateLayoutConstraint.firstAttribute : updateLayoutConstraint.secondAttribute
updateLayoutConstraint.constant = self.constant.constraintConstantTargetValueFor(layoutAttribute: updateLayoutAttribute)
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}
} else {
NSLayoutConstraint.activate(layoutConstraints)
view.snp.add(layoutConstraints: layoutConstraints)
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}
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}
internal func deactivateIfNeeded() {
let view = self.from.view!
let layoutConstraints = self.layoutConstraints.allObjects
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NSLayoutConstraint.deactivate(layoutConstraints)
view.snp.remove(layoutConstraints: layoutConstraints)
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}
}