throw 如何在 Swift 中通过'startAccessingSecurityScopedResource()' 声明？

Question

我会通过当前文件选择器导入数据。我正在查看开发文档并遵循它，并且存在一个问题。当我不在警卫的条件语句中时，我将收到一个错误，但 'throw' 不可用。你如何解决这个问题？

func startAccessingSecurityScopedResource() -> Bool

用法

    func presentDocument(at documentURL: URL) {


        // Start accessing a security-scoped resource.
        guard documentURL.startAccessingSecurityScopedResource() else {
            throw IXError.fileAcessFailed // Error is not handled because the enclosing function is not declared 'throws'
            return
        }

由于未声明封闭函数，因此未处理错误 '投掷'

我尝试了guard let，但失败了。

        guard let Acess = documentURL.startAccessingSecurityScopedResource() else { //Initializer for conditional binding must have Optional type, not 'Bool'
            throw IXError.fileAcessFailed // Error is not handled because the enclosing function is not declared 'throws'
            return
        }

IXError

public enum IXError: Error {
    ...
}

************************************编辑开始 ************* *************************************

我根据答案添加了throws，但是使用它的函数出错了。

    func documentBrowser(_ controller: UIDocumentBrowserViewController, didPickDocumentURLs documentURLs: [URL]) {
        guard let sourceURL = documentURLs.first else { return }
        presentDocument(at: sourceURL) // Call can throw, but it is not marked with 'try' and the error is not handled
    }
...
    func documentBrowser(_ controller: UIDocumentBrowserViewController, didImportDocumentAt sourceURL: URL, toDestinationURL destinationURL: URL) {
        presentDocument(at: destinationURL) // Call can throw, but it is not marked with 'try' and the error is not handled
    }
...
    func presentDocument(at documentURL: URL) throws {

        guard documentURL.startAccessingSecurityScopedResource() else {
            throw IXError.fileAcessFailed
            return
        }

Error 是 Call 可以抛出，但没有标上 'try' 和错误 不处理

Answer 1

错误未处理，因为封闭函数未声明为“抛出”

这是指您的presentDocument 函数。像这样声明它：

func presentDocument(at documentURL: URL) throws {
...
}