GitHub - Raizlabs/Anchorage: A collection of operators and utilities that simpli...
source link: https://github.com/Raizlabs/Anchorage
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README.md
Anchorage
A lightweight collection of intuitive operators and utilities that simplify Auto Layout code. Anchorage is built directly on top of the NSLayoutAnchor
API.
Each expression acts on one or more NSLayoutAnchor
s, and returns active NSLayoutConstraint
s. If you want inactive constraints, here's how to do that.
Usage
Alignment
// Pin the button to 12 pt from the leading edge of its container button.leadingAnchor == container.leadingAnchor + 12 // Pin the button to at least 12 pt from the trailing edge of its container button.trailingAnchor <= container.trailingAnchor - 12 // Center one or both axes of a view button.centerXAnchor == container.centerXAnchor button.centerAnchors == container.centerAnchors
Relative Alignment
// Position a view to be centered at 2/3 of its container's width view.centerXAnchor == 2 * container.trailingAnchor / 3 // Pin the top of a view at 25% of container's height view.topAnchor == container.bottomAnchor / 4
Sizing
// Constrain a view's width to be at most 100 pt view.widthAnchor <= 100 // Constraint a view to a fixed size imageView.sizeAnchors == CGSize(width: 100, height: 200) // Constrain two views to be the same size imageView.sizeAnchors == view.sizeAnchors // Constrain view to 4:3 aspect ratio view.widthAnchor == 4 * view.heightAnchor / 3
Composite Anchors
Constrain multiple edges at a time with this syntax:
// Constrain the leading, trailing, top and bottom edges to be equal imageView.edgeAnchors == container.edgeAnchors // Inset the edges of a view from another view let insets = UIEdgeInsets(top: 5, left: 10, bottom: 15, right: 20) imageView.edgeAnchors == container.edgeAnchors + insets // Inset the leading and trailing anchors by 10 imageView.horizontalAnchors >= container.horizontalAnchors + 10 // Inset the top and bottom anchors by 10 imageView.verticalAnchors >= container.verticalAnchors + 10
Use leading and trailing
Using leftAnchor
and rightAnchor
is rarely the right choice. To encourage this, horizontalAnchors
and edgeAnchors
use the leadingAnchor
and trailingAnchor
layout anchors.
Inset instead of Shift
When constraining leading/trailing or top/bottom, it is far more common to work in terms of an inset from the edges instead of shifting both edges in the same direction. When building the expression, Anchorage will flip the relationship and invert the constant in the constraint on the far side of the axis. This makes the expressions much more natural to work with.
Priority
The ~
is used to specify priority of the constraint resulting from any Anchorage expression:
// Align view 20 points from the center of its superview, with system-defined low priority view.centerXAnchor == view.superview.centerXAnchor + 20 ~ .low // Align view 20 points from the center of its superview, with (required - 1) priority view.centerXAnchor == view.superview.centerXAnchor + 20 ~ .required - 1 // Align view 20 points from the center of its superview, with custom priority view.centerXAnchor == view.superview.centerXAnchor + 20 ~ 752
The layout priority is an enum with the following values:
.required
-UILayoutPriorityRequired
(default).high
-UILayoutPriorityDefaultHigh
.low
-UILayoutPriorityDefaultLow
.fittingSize
-UILayoutPriorityFittingSizeLevel
Storing Constraints
To store constraints created by Anchorage, simply assign the expression to a variable:
// A single (active) NSLayoutConstraint let topConstraint = (imageView.topAnchor == container.topAnchor) // EdgeConstraints represents a collection of constraints // You can retrieve the NSLayoutConstraints individually, // or get an [NSLayoutConstraint] via .all, .horizontal, or .vertical let edgeConstraints = (button.edgeAnchors == container.edgeAnchors).all
Batching Constraints
By default, Anchorage returns active layout constraints. If you'd rather return inactive constraints for use with the NSLayoutConstraint.activate(_:)
method for performance reasons, you can do it like this:
let constraints = Anchorage.batch(active: false) { view1.widthAnchor == view2.widthAnchor view1.heightAnchor == view2.heightAnchor / 2 ~ .low // ... as many constraints as you want } // Later: NSLayoutConstraint.activate(constraints)
You can also pass active: true
if you want the constraints in the array to be automatically activated in a batch.
Autoresizing Mask
Anchorage sets the translatesAutoresizingMaskIntoConstraints
property to false
on the left hand side of the expression, so you should never need to set this property manually. This is important to be aware of in case the container view relies on translatesAutoresizingMaskIntoConstraints
being set to true
. We tend to keep child views on the left hand side of the expression to avoid this problem, especially when constraining to a system-supplied view.
Installation
CocoaPods
To integrate Anchorage into your Xcode project using CocoaPods, specify it in your Podfile:
pod 'Anchorage'
Carthage
To integrate Anchorage into your Xcode project using Carthage, specify it in your Cartfile:
github "Raizlabs/Anchorage"
Run carthage update
to build the framework and drag the built
Anchorage.framework
into your Xcode project.
License
This code and tool is under the MIT License. See LICENSE
file in this repository.
Any ideas and contributions welcome!
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