iOS NSData.write(toFile) 在将 zip 写入 cacheDirectory 时返回 false

Question

>我正在尝试下载一个zip文件，并在解压缩之前将其写入cacheDirectory。但是，write(toFile：( 总是返回 false：

import Foundation
func downloadFile(url: URL, completion: @escaping (Result<Data>) -> Void) {
print("starting dqueue to download " + url.absoluteString)
DispatchQueue.global(qos: .background).async {
print("Starting download")
let data = NSData.init(contentsOf: url)
if data == nil {
print("Data nil!")
}
// Find cache
print("Got data!")
let paths = NSSearchPathForDirectoriesInDomains(.cachesDirectory, .userDomainMask, true)
let path = paths[0]
let dataPath = URL(fileURLWithPath: path).appendingPathComponent("mod.zip")
if (FileManager.default.fileExists(atPath: dataPath.absoluteString)) {
print("File already exists!")
}
// Save data
print("Saving to " + dataPath.absoluteString)
if (data?.write(toFile: dataPath.absoluteString, atomically: true) ?? false) {
if (FileManager.default.fileExists(atPath: dataPath.absoluteString)) {
print("exists!")
} else {
print("does not exist!")
}
if (FileManager.default.isWritableFile(atPath: dataPath.absoluteString)) {
print("Writable")
}else {
print("Not Writable")
}
DispatchQueue.main.async {
print("This is run on the main queue, after the previous code in outer block")
}
} else {
print("Failed to write to file!")
}
}
}

以下是日志输出：

starting dqueue to download https://github.com/minetest-mods/armor_monoid/archive/c7988a3dae32f2c1cb93fde31d9e53222a205eea.zip
Starting download
Got data!
Saving to file:///var/mobile/Containers/Data/Application/E734C574-1E94-44CB-9A6E-2AE1C8850E88/Library/Caches/mod.zip
Failed to write to file!

我试过：

• 创建目录(它已存在(
• 将原子更改为假(无影响(
• 尝试查看权限(找不到任何文档(
• 阅读并尝试以下问题：
  • 无法写入应用程序支持目录中的文件
  • iOS：无法将文件保存到"应用程序支持"文件夹，但可以保存到"文档">
  • 写入文件不起作用

我正在使用Xcode v9.0 beta 2(9M137d(和iPad Air 2(iOS 11.0 15A5318g(

Answer 1

您需要使用relativePath而不是absoluteString。

试试这个(我试过了，它奏效了(：

import Foundation
func downloadFile(url: URL, completion: @escaping (Result<Data>) -> Void) {
print("starting dqueue to download " + url.absoluteString)
DispatchQueue.global(qos: .background).async {
print("Starting download")
let data = NSData.init(contentsOf: url)
if data == nil {
print("Data nil!")
}
// Find cache
print("Got data!")
let paths = NSSearchPathForDirectoriesInDomains(.cachesDirectory, .userDomainMask, true)
let path = paths[0]
let dataPath = URL(fileURLWithPath: path).appendingPathComponent("mod.zip")
if (FileManager.default.fileExists(atPath: dataPath.relativePath)) {
print("File already exists!")
}
// Save data
print("Saving to " + dataPath.relativePath)
if (data?.write(toFile: dataPath.relativePath, atomically: true) ?? false) {
if (FileManager.default.fileExists(atPath: dataPath.relativePath)) {
print("exists!")
} else {
print("does not exist!")
}
if (FileManager.default.isWritableFile(atPath: dataPath.relativePath)) {
print("Writable")
}else {
print("Not Writable")
}
DispatchQueue.main.async {
print("This is run on the main queue, after the previous code in outer block")
}
} else {
print("Failed to write to file!")
}
}
}