在 Swift 中从闭包内调用异步共享实例方法的语法

Question

我在使用闭包中调用共享实例方法的语法时遇到问题：

这是我的代码：

func getContactImage (contact:Contacts, completion:@escaping (_ myimage: UIImage)->()){//open 1 method
    var animg = UIImage(named:"default.png")!

    let surl = "https://~/contactimage.png"
    Utilities.shared.downloadImage(surl: surl as NSString, completion: image as UIImage ->Void in animg = img) 
    completion(animg)
}

行 Utilities.shared.downloadImage 给出了几个错误，包括：

Cannot convert value of type 'UIAccessibilityTraits' (aka 'UInt64') to type 'UIImage' in coercion

共享实例方法如下所示：

@objc func downloadImage(surl: NSString, completion : @escaping (UIImage) -> Void ) {
    //download image
}

从闭包中调用共享实例方法的正确语法是什么？

Answer 1

使用

Utilities.shared.downloadImage(surl) {  (img) in

  // use img here
}

也改函数

@objc func downloadImage(_ surl: String, completion : @escaping (UIImage) -> Void ) { }

func getContactImage (contact:Contacts, completion:@escaping (_ myimage: UIImage)->()){//open 1 method
    var animg = UIImage(named:"default.png")!

    let surl = "https://~/contactimage.png"

    Utilities.shared.downloadImage(surl) { (img) in 
       completion(img)
     }
}

顺便说一句，鼓励使用 SDWebImage

在 Swift 中从闭包内调用异步共享实例方法的语法

Syntax to Call Asynchronous Shared Instance Method from Within Closure in Swift

singleton

closures

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swift