Swfit5 Kingfisher 5.4.0 手动导入支持iOS10以下（iOS8，iOS9）

Kingfisher 最新版本 支持Swift5，但pod要求iOS10以上，

为了支持swfit5, pod 导入的时 要求最低使用 iOS 10 的系统，作者给出理由是iOS10以下的用户太少，找不到任何理由去支持。太任性了 哈哈！相信依旧给一部分iOS 开发造成一定的困扰。所以我找到以下方案解决既支持swift5又支持iOS10以下的系统，就是本地导入源码，不通过pod形式。

1.首先先创建一个新的工程，通过pod 把最新的版本的Kingfisher下载下来，从Pods 文件夹 找到源码，然后将源码拖到一个新的工程中。

2.把源码进行以下的修改，然后运行即可。

// MemoryStorage.swfit  75行
cleanTimer = .scheduledTimer(withTimeInterval: config.cleanInterval, repeats: true) { [weak self] _ in
                guard let self = self else { return }
                self.removeExpired()
             }
// 替换如下：
     cleanTimer = Timer.init(timeInterval: config.cleanInterval, target: self, selector: #selector(removeExpiredFunc), userInfo: nil, repeats: true)
          cleanTimer?.fire()  

并且在该类添加一个方法
 @objc func removeExpiredFunc()  {
        self.removeExpired()
      }        
     

// ImageModifier.swift  里面 96行
return image.imageFlippedForRightToLeftLayoutDirection()  
// 替换如下：
if #available(iOS 9.0, *) {
        return image.imageFlippedForRightToLeftLayoutDirection()
      } else {
        return image
      }

// ImageView+Kingfisher.swift  343行
view.centerXAnchor.constraint(
                    equalTo: base.centerXAnchor, constant: newIndicator.centerOffset.x).isActive = true
 view.centerYAnchor.constraint(
                    equalTo: base.centerYAnchor, constant: newIndicator.centerOffset.y).isActive = true
// 替换如下：
 if #available(iOS 9.0, *) {
                view.centerXAnchor.constraint(
                  equalTo: base.centerXAnchor, constant: newIndicator.centerOffset.x).isActive = true
                view.centerYAnchor.constraint(
                  equalTo: base.centerYAnchor, constant: newIndicator.centerOffset.y).isActive = true
              } else {
                // Fallback on earlier versions
                NSLayoutConstraint.activate([
                  NSLayoutConstraint(item: self, attribute: .centerX, relatedBy: .equal, toItem: base, attribute: .centerX, multiplier: 1, constant: newIndicator.centerOffset.x),
                  NSLayoutConstraint(item: self, attribute: .centerY, relatedBy: .equal, toItem: base, attribute: .centerY, multiplier: 1, constant: newIndicator.centerOffset.y),
                  
                  ])
              }

// Placeholder.swift 66行
centerXAnchor.constraint(equalTo: imageView.centerXAnchor).isActive = true
        centerYAnchor.constraint(equalTo: imageView.centerYAnchor).isActive = true
        heightAnchor.constraint(equalTo: imageView.heightAnchor).isActive = true
        widthAnchor.constraint(equalTo: imageView.widthAnchor).isActive = true
// 替换入下:
if #available(iOS 9.0, *) {
        centerXAnchor.constraint(equalTo: imageView.centerXAnchor).isActive = true
        centerYAnchor.constraint(equalTo: imageView.centerYAnchor).isActive = true
        heightAnchor.constraint(equalTo: imageView.heightAnchor).isActive = true
        widthAnchor.constraint(equalTo: imageView.widthAnchor).isActive = true
      } else {
        // Fallback on earlier versions
        NSLayoutConstraint.activate([
          NSLayoutConstraint(item: self, attribute: .centerX, relatedBy: .equal, toItem: imageView, attribute: .centerX, multiplier: 1, constant: 0),
          NSLayoutConstraint(item: self, attribute: .centerY, relatedBy: .equal, toItem: imageView, attribute: .centerY, multiplier: 1, constant: 0),
          NSLayoutConstraint(item: self, attribute: .height, relatedBy: .equal, toItem: imageView, attribute: .height, multiplier: 1, constant: 0),
          NSLayoutConstraint(item: self, attribute: .width, relatedBy: .equal, toItem: imageView, attribute: .width, multiplier: 1, constant: 0)
          ])
      }

// AnimatableImageView.swift 289行
if displayLink.preferredFramesPerSecond == 0 {
            duration = displayLink.duration
        } else {
            // Some devices (like iPad Pro 10.5) will have a different FPS.
            duration = 1.0 / Double(displayLink.preferredFramesPerSecond)
        }

// 替换如下：
 if #available(iOS 10.0, *) {
        if displayLink.preferredFramesPerSecond == 0 {
          duration = displayLink.duration
        } else {
          // Some devices (like iPad Pro 10.5) will have a different FPS.
          duration = 1.0 / Double(displayLink.preferredFramesPerSecond)
        }
      } else {
        duration = displayLink.duration
      }

PS:然后运行即可，有问题欢迎留言。