SwiftUI 错误：无法转换“UIImage”类型的值？关闭结果类型“无效”

Posted 2023-03-08

【中文标题】SwiftUI 错误：无法转换“UIImage”类型的值？关闭结果类型“无效”

【英文标题】：SwiftUI Error : Cannot convert value of type 'UIImage?' to closure result type 'Void'

【发布时间】：2020-09-23 02:20:39

【问题描述】：

我收到以下 SwiftUI 错误：

var assetImage : UIImage? 
        if phphotoLibrary.authorizationStatus() == .authorized 
            let allPhotosOptions = PHFetchOptions()
            allPhotosOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: true)]
            let assetsFetchResults = PHAsset.fetchAssets(with: allPhotosOptions)
            if assetsFetchResults.count > 0 
                let asset = assetsFetchResults.lastObject
                if asset != nil 
                    let options = PHImageRequestOptions()
                    options.isNetworkAccessAllowed = true
                    options.version = .current
                    
                    PHCachingImageManager().requestImage(for: asset!, targetSize: CGSize(width: 64 * UIScreen.main.scale, height: 64 * UIScreen.main.scale), contentMode: .aspectFill, options: options, resultHandler:  img, _ in
                        DispatchQueue.main.async 
                            return img //Error Here
                        
                    )
                 else 
                    return nil
                
             else 
                return nil
            
        
        return nil
    

我收到以下错误：

Cannot convert value of type 'UIImage?' to closure result type 'Void'

【参考方案1】：

当您从 PHCachingImageManager 异步访问图像时，将其更改为带有 completionHandler 的方法，而不是计算属性。

func assetImage(_ completion: @escaping (UIImage?) -> Void) 
    if PHPhotoLibrary.authorizationStatus() == .authorized 
        let allPhotosOptions = PHFetchOptions()
        allPhotosOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: true)]
        let assetsFetchResults = PHAsset.fetchAssets(with: allPhotosOptions)
        if assetsFetchResults.count > 0 
            let asset = assetsFetchResults.lastObject
            if asset != nil 
                let options = PHImageRequestOptions()
                options.isNetworkAccessAllowed = true
                options.version = .current
                
                PHCachingImageManager().requestImage(for: asset!, targetSize: CGSize(width: 64 * UIScreen.main.scale, height: 64 * UIScreen.main.scale), contentMode: .aspectFill, options: options, resultHandler:  img, _ in
                    DispatchQueue.main.async 
                        completion(img)
                    
                )
             else 
                completion(nil)
            
         else 
            completion(nil)
        
     else 
        completion(nil)
    

用法

    self.assetImage  (image) in
        
    

【讨论】：

如何在 View body 中调用它？ var body: some View self.assetImage (image) in Image(uiImage: image!) 似乎不起作用。

@Gizmodo 请查看this 了解如何设置图像。