iOS - 在 UIImageView 中从 Parse 检索并显示图像(Swift 1.2 错误) [英] iOS - Retrieve and display an image from Parse in UIImageView (Swift 1.2 Error)

问题描述

我之前一直在使用以下代码行从 Parse 后端检索图像以显示在我的应用程序中的 UIImageView 中:

I have previously been retrieving an image form my Parse backend to display in my app inside a UIImageView using the following lines of code:

let userPicture = PFUser.currentUser()["picture"] as PFFile

userPicture.getDataInBackgroundWithBlock { (imageData:NSData, error:NSError) -> Void in
    if (error == nil) {

            self.dpImage.image = UIImage(data:imageData)

    }
}

但我收到错误:

'任何对象?'不可转换为PFFile"；你的意思是使用作为！"强迫情绪低落?

'AnyObject?' is not convertible to 'PFFile'; did you mean to use 'as!' to force downcast?

有用"的 Apple fix-it 提示建议使用as！"更改，所以我添加了！，但随后出现错误:

The 'helpful' Apple fix-it tip suggests the "as!" change so I add in the !, but then I get the error:

'任何对象?'不可转换为PFFile"

'AnyObject?' is not convertible to 'PFFile'

使用 'getDataInBackgroundWithBlock' 部分，我也收到错误:

With the 'getDataInBackgroundWithBlock' section, I also get the error:

无法使用类型为 '((NSData, NSError) -> Void)' 的参数列表调用 'getDataInBackgroundWithBlock'

Cannot invoke 'getDataInBackgroundWithBlock' with an argument list of type '((NSData, NSError) -> Void)'

谁能解释一下如何使用 Swift 1.2 从 Parse 正确检索照片并在 UIImageView 中显示它?

Can someone please explain how to correctly retrieve a photo from Parse and display it in a UIImageView using Swift 1.2?

推荐答案

PFUser.currentUser() 返回可选类型 (Self?).所以你应该打开返回值以通过下标访问元素.

PFUser.currentUser() returns optional type (Self?). So you should unwrap return value to access element by subscript.

PFUser.currentUser()?["picture"]

而且下标得到的值也是可选类型.所以你应该使用可选绑定来转换值，因为类型转换可能会失败.

And the value got by subscript is also optional type. So you should use optional binding to cast the value because type casting may fail.

if let userPicture = PFUser.currentUser()?["picture"] as? PFFile {

getDataInBackgroundWithBlock() 方法的结果块的参数都是可选类型(NSData? 和 NSError?).所以你应该为参数指定可选类型，而不是 NSData 和 NSError.

And parameters of the result block of getDataInBackgroundWithBlock() method are both optional type (NSData? and NSError?). So you should specify optional type for the parameters, instead NSData and NSError.

userPicture.getDataInBackgroundWithBlock { (imageData: NSData?, error: NSError?) -> Void in

修改以上问题的代码如下:

The code modified the all above problems is below:

if let userPicture = PFUser.currentUser()?["picture"] as? PFFile {
    userPicture.getDataInBackgroundWithBlock { (imageData: NSData?, error: NSError?) -> Void in
        if (error == nil) {
            self.dpImage.image = UIImage(data:imageData)
        }
    }
}

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