如何在Swift 3.0中使用SDWebImage完成块？
我使用SDWebImage下载图像。 如果成功下载图像，我想进一步操作。
cell.appIcon.sd_setImage(with: url, placeholderImage: UIImage.init(named: "App-Default"), completed: {(image: UIImage!, error: NSError!, cacheType: SDImageCacheType, imageURL: URL!) -> Void in // Perform operation. }) 但是我收到了错误：
无法将类型’（UIImage！，NSError！，SDImageCacheType，URL！） – > Void’的值转换为预期的参数类型’SDExternalCompletionBlock？’
终于解决了。
cell.appIcon.sd_setImage(with: url!, placeholderImage: UIImage(named: "App-Default"),options: SDWebImageOptions(rawValue: 0), completed: { (image, error, cacheType, imageURL) in // Perform operation. })
SWIFT 4版本
cell.appIcon.sd_setImage(with: url, placeholderImage: UIImage(named: "App-Default"),options: SDWebImageOptions(rawValue: 0), completed: { image, error, cacheType, imageURL in // your rest code })
重要！ 在必要时，不要忘记将自我发送为弱或无主（如此[自我弱] / [自己未拥有]）到块，以避免保留周期。
例：
cell.appIcon.sd_setImage( with: url, placeholderImage: UIImage(named: "App-Default"), options: SDWebImageOptions(rawValue: 0), completed: { [self weak] image, error, cacheType, imageURL in guard let selfNotNil = self else { return } // your rest code } )
根据你正在使用的框架中的typedef ：
typedef void(^SDExternalCompletionBlock)(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL);
SDExternalCompletionBlock由_Nullable指示的可选参数组成。 因此，您的代码应该像这样写：
cell.appIcon.sd_setImage(with: url, placeholderImage: UIImage.init(named: "App-Default"), completed: {(image: UIImage?, error: NSError?, cacheType: SDImageCacheType, imageURL: URL?) -> Void in // Perform operation. })
由于编译器知道完成块参数的类型（来自函数声明），您可以更简洁地编写代码，并且（IMO）更容易阅读，如下所示：
cell.appIcon.sd_setImage(with: url, placeholderImage: UIImage(named: "App-Default"), completed: { (image, error, cacheType, imageURL) in // Perform operation. })
这个也适用于swift 3：
cell.appIcon.sd_setImage(with: url, placeholderImage: UIImage(named: "App-Default"), options: []) { (image, error, imageCacheType, imageUrl) in // Perform your operations here. }
cell.appIcon.sd_setImage(with: url, placeholderImage: UIImage(named: "App-Default"),options: SDWebImageOptions(rawValue: 0), completed: { (img, err, cacheType, imgURL) in // code })
试试这个，希望这会很好