RPAutoLayout

RPAutoLayout是一个轻量级自动布局Swift框架，对系统NSLayoutAnchor做了封装，采用链式语法, 支持iOS 9，Swift 5.0之后的版本

如果你使用的是Objective-C，点击这里Objective-C 版本

iOS 6系统推出了AutoLayout，但由于其VFL格式语法比较晦涩，为开发和维护带来许多问题:

let redView = UIView()
view.addSubview(redView)
redView.translatesAutoresizingMaskIntoConstraints = false
let top = NSLayoutConstraint(item: redView, attribute: .top, relatedBy: .equal, toItem: view, attribute: .top, multiplier: 1, constant: 50)
let left = NSLayoutConstraint(item: redView, attribute: .left, relatedBy: .equal, toItem: view, attribute: .left, multiplier: 1, constant: 80)
let width = NSLayoutConstraint(item: redView, attribute: .width, relatedBy: .equal, toItem:nil, attribute: .notAnAttribute, multiplier:1, constant:80)
let height = NSLayoutConstraint(item: redView, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1, constant: 80)
view.addConstraints([top, left, width, height]) // iOS 6的写法
NSLayoutConstraint.activate([top, left, width, height]) // iOS 8的写法
redView.backgroundColor = .red

iOS 9之后，系统提供了NSLayoutAnchor,

let redView = UIView()
view.addSubview(redView)
redView.translatesAutoresizingMaskIntoConstraints = false
let top = redView.topAnchor.constraint(equalTo: view.topAnchor, constant: 50)
let left = redView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 80)
let width = redView.widthAnchor.constraint(equalToConstant: 80)
let height = redView.heightAnchor.constraint(equalToConstant: 80)
NSLayoutConstraint.activate([top, left, width, height])
redView.backgroundColor = .red

RPAutoLayout对系统NSLayoutAnchor做了封装采用链式语法，使代码更简洁。

redView.rp_layout(view)
    .rp_top(to: view.top, constant: 50)
    .rp_left(to: view.left, constant: 80)
    .rp_width(constant: 80)
    .rp_height(constant: 80)
    .rp_activate()
redView.backgroundColor = .red

1、如何导入工程

目前只支持Carthage：

• 1、open terminfo

cd ./yourProbject
touch Cartfile
vim Cartfile
github "dengfeng520/RPAutoLayout"
carthage update --platform iOS

完成后会提示 Building scheme "RPAutoLayout" in yourProbject.xcodeproj

更新完成后，打开工程，选择TARGETS -->Build Phases--> Link Binary With Libries 点击加号，选择 Add File --> Carthage --> Build --> iOS 添加RPAutoLayout.framework

打开工程，TARGETS --> New Run Script Phase

/usr/local/bin/carthage copy-frameworks

在Input Files中添加

$(SRCROOT)/Carthage/Build/iOS/RPAutoLayout.framework

2、如何使用

• 添加约束

import RPAutoLayout

centerView.rp_layout(view)
    .rp_centerX(to: view.centerX)
    .rp_centerY(to: view.centerY)
    .rp_width(to: view.width, multiplier: 0.4)
    .rp_height(to: centerView.width)
    .rp_activate()
centerView.backgroundColor = .blue

• 更新约束

centerView.rp_remakeHeight(to: centerView.widthAnchor, multiplier: 1.5)