检查文件是否已保存到磁盘？ [英] Check if file is already saved to disk?

问题描述

我从我的服务器下载文件，将它们保存到设备，并在我的应用程序中将它们显示给用户。我想实现检查以查看该文件是否已存在于设备上，以便我们可以跳过下载并显示，但我无法找到最佳方法。

I am downloading files from my server, saving them to device, and displaying them to the user in my app. I want to implement a check to see if the file already exists on the device so we can skip the download and just display, but I can't figure out the best way to do that.

我为每个文件创建一个唯一的fileName，然后将其转换为NSURL，如下所示：

I create a unique fileName for each file and then convert it to an NSURL like this:

NSString *fileString = [[NSString alloc] initWithString:[documentsDirectory stringByAppendingPathComponent:fileName]];
self.fileURL = [[NSURL alloc] initFileURLWithPath:fileString];

然后我写入文件并保存URL以供不久之后使用：

Then I write to file and save the URL for use shortly after:

[data writeToFile:fileString atomically:YES];
self.fileURL = [[NSURL alloc] initFileURLWithPath:fileString];

如何查看该文件或URL是否已存在？

How can I check if that File or URL already exists?

谢谢

推荐答案

NSFileManager有一种方法来检查路径中是否存在文件：

NSFileManager has a method to check if a file exists at a path:

[[NSFileManager defaultManager] fileExistsAtPath: fileString]

https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/nsfilemanager_Class/Reference/Reference.html#//apple_ref / doc / uid / 20000305-CHDDDDJG

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