swift使用Aspects修改内容及修改约束

关键点：
1、在podfile

 pod 'Aspects'

2、引入

import Aspects

3、调试查看对象的属性：

// 这种方式才可以在开发调试时通过查看obj来了解包含的属性，如果只有是通过
let obj = aspectInfo.instance()
guard let vc = obj as? UIViewController else { return }

// 通过这种方式不能查看属性
guard let vc2 = aspectInfo.instance() as? UIViewController else { return }

4、在hook要知道某个类的名字，由于swift有命名空间，一般的类名为yyy，使用一些三方库时类名为xxx.yyy这样的格式，可以使用Xcode来查看或者LookServer这种好用的工具来获取

5、获取view的约束及修改约束

// top、left、right、bottom的constraints保存在父容器里
if let constraints = contextView.superview?.constraints {
    for constraint in constraints {
          if constraint.secondItem === contextView, constraint.secondAttribute == .bottom {
                constraint.constant = 10
           }
     }
  }

 // 宽高约束在自己的constraints
  let constraints = contextView.constraints
  for constraint in constraints {
         if constraint.firstItem === contextView, constraint.firstAttribute == .height {
             constraint.constant = 56
         }
  }

完整使用示例

 private func hookTestUI() {
        do {
            let wrappedBlock: @convention(block) (AspectInfo) -> Void = { aspectInfo in
                // 这里要先用一个值来接收，方便调试查看obj里各个属性
                let obj = aspectInfo.instance()
                guard let vc = obj as? UIViewController else { return }
                if let contextView = vc.value(forKeyPath: "contextView") as? UIView {
                    // 操作一般属性
                    contextView.backgroundColor = UIColor.red
                    // 修改约束
                    // top、left、right、bottom的constraints保存在父容器里
                    if let constraints = contextView.superview?.constraints {
                        for constraint in constraints {
                            if constraint.secondItem === contextView, constraint.secondAttribute == .bottom {
                                constraint.constant = 10
                            }
                        }
                    }
                    // 宽高约束在自己的constraints
                    let constraints = contextView.constraints
                    for constraint in constraints {
                        if constraint.firstItem === contextView, constraint.firstAttribute == .height {
                            constraint.constant = 56
                        }
                    }
                }
            }
            let wrappedObject: AnyObject = unsafeBitCast(wrappedBlock, to: AnyObject.self)
            let aspectToken = try (NSClassFromString("XX.YYY"))?.aspect_hook(#selector(UIViewController.viewDidAppear(_:)), with: AspectOptions.positionBefore, usingBlock: wrappedObject)
            // 在特殊的时期类移除hook
            print(aspectToken)
            // aspectToken?.remove()
        } catch {
            print(error)
        }
    }