流程图（完整代码见文末）

屏幕快照 2019-06-18 下午4.07.24.png 屏幕快照 2019-06-18 下午4.37.19.png 屏幕快照 2019-06-18 下午4.38.13.png 屏幕快照 2019-06-18 下午4.38.53.png 屏幕快照 2019-06-18 下午4.44.51.png

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一.在 info.plist 中设置获取照片的权限，主要是要描述 App 获取照片权限用于做什么

屏幕快照 2019-06-18 下午4.34.27.png
屏幕快照 2019-06-18 下午4.31.22.png

如果不在 info.plist 中设置，在点击 「选择照片」的按钮时会报错，见上图

---

二.声明一个 ImagePickerController, 并设置其代理为当前的 VC

    
    func presentPhotoPickerController() {
        let myPickerController = UIImagePickerController()
        myPickerController.allowsEditing = true
        myPickerController.delegate = self
        myPickerController.sourceType = .photoLibrary
        self.present(myPickerController, animated: true, completion: nil)
        
    }
    

设置代理 myPickerController.delegate = self 时会报错，要在class PickImageViewController 后面同时添加 UIImagePickerControllerDelegate, UINavigationControllerDelegate

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三. 实现 UIImagePickerControllerDelegate 的方法

    /* ----- UIImagePickerControllerDelegate ----- */
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
        if let image = info[UIImagePickerController.InfoKey.editedImage] as? UIImage {
            self.UserImageView.image = image
        } else if let image = info[UIImagePickerController.InfoKey.originalImage] as? UIImage {
            self.UserImageView.image = image
        }
        dismiss(animated: true, completion: nil)
    }
    
    func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
        dismiss(animated: true, completion: nil)
    }

第一个方法主要是获取用户选择的图片，并设置 UserImageView 的图片
第二个方法主要是点击「选择图片」按钮之后跳转到图片选择界面之后不选择图片，点击取消时，dismiss。

---

四.用户点击「选择图片」时触发

    @IBAction func chooseImage(_ sender: UIButton) {
        if UIImagePickerController.isSourceTypeAvailable(.photoLibrary) {
            PHPhotoLibrary.requestAuthorization { (status) in
                switch status {
                case .authorized: self.presentPhotoPickerController()
                case .notDetermined:
                    if status == PHAuthorizationStatus.authorized {
                        self.presentPhotoPickerController()
                    }
                case .denied:
                    let alert = UIAlertController(title: "没有权限获取照片信息", message: "照片权限已被拒绝，请开启权限后再更改照片", preferredStyle: .alert)
                    let confirmAction = UIAlertAction(title: "去设置", style: .default, handler: { (goSettingAction) in
                        DispatchQueue.main.async {
                            let url = URL(string: UIApplication.openSettingsURLString)!
                            UIApplication.shared.open(url, options: [:])
                        }
                    })
                    let cancelAction = UIAlertAction(title: "取消", style: .cancel)
                    alert.addAction(confirmAction)
                    alert.addAction(cancelAction)
                    self.present(alert, animated: true)
                case .restricted: let alert = UIAlertController(title: "权限限制", message: "照片的获取被限制了无法获取", preferredStyle: .alert)
                    let okAction = UIAlertAction(title: "好的", style: .default)
                    alert.addAction(okAction)
                    self.present(alert, animated: true)
                default: break
                }
            }
        }
    }

---

完整代码

import UIKit
import Photos

class PickImageViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate{

   @IBOutlet weak var UserImageView: UIImageView!
   
   override func viewDidLoad() {
       super.viewDidLoad()
   }
   
   func presentPhotoPickerController() {
       let myPickerController = UIImagePickerController()
       myPickerController.allowsEditing = true
       myPickerController.delegate = self
       myPickerController.sourceType = .photoLibrary
       self.present(myPickerController, animated: true, completion: nil)
       
   }
   
   @IBAction func chooseImage(_ sender: UIButton) {
       if UIImagePickerController.isSourceTypeAvailable(.photoLibrary) {
           PHPhotoLibrary.requestAuthorization { (status) in
               switch status {
               case .authorized: self.presentPhotoPickerController()
               case .notDetermined:
                   if status == PHAuthorizationStatus.authorized {
                       self.presentPhotoPickerController()
                   }
               case .denied:
                   let alert = UIAlertController(title: "没有权限获取照片信息", message: "照片权限已被拒绝，请开启权限后再更改照片", preferredStyle: .alert)
                   let confirmAction = UIAlertAction(title: "去设置", style: .default, handler: { (goSettingAction) in
                       DispatchQueue.main.async {
                           let url = URL(string: UIApplication.openSettingsURLString)!
                           UIApplication.shared.open(url, options: [:])
                       }
                   })
                   let cancelAction = UIAlertAction(title: "取消", style: .cancel)
                   alert.addAction(confirmAction)
                   alert.addAction(cancelAction)
                   self.present(alert, animated: true)
               case .restricted: let alert = UIAlertController(title: "权限限制", message: "照片的获取被限制了无法获取", preferredStyle: .alert)
                   let okAction = UIAlertAction(title: "好的", style: .default)
                   alert.addAction(okAction)
                   self.present(alert, animated: true)
               default: break
               }
           }
       }
   }
   
   /* ----- UIImagePickerControllerDelegate ----- */
   func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
       if let image = info[UIImagePickerController.InfoKey.editedImage] as? UIImage {
           self.UserImageView.image = image
       } else if let image = info[UIImagePickerController.InfoKey.originalImage] as? UIImage {
           self.UserImageView.image = image
       }
       dismiss(animated: true, completion: nil)
   }
   
   func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
       dismiss(animated: true, completion: nil)
   }
}


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补充

如果需要上传图像，可以压缩图片

guard let imageData = image.jpegData(compressionQuality: 0.2) else { return }