如何在Swift文件目录中检查文件是否存在?

How to check if a file exists in the Documents directory in Swift?

如何在Swift文件目录中检查文件是否存在?

I am using [ .writeFilePath ] method to save an image into the Documents directory and I want to load it every time the app is launched. But I have a default image if there is no saved image.

我正在使用[. writefilepath]方法将图像保存到Documents目录中，我想在每次启动应用程序时加载它。但是如果没有保存图像，我有一个默认的图像。

But I just cant get my head around how to use the [ func fileExistsAtPath(_:) ] function. Could someone give an example of using the function with a path argument passed into it.

但是我不知道怎么使用[func fileExistsAtPath(_:)]函数。是否有人能给出一个使用带有传入路径参数的函数的例子。

I believe I don't need to paste any code in there as this is a generic question. Any help will be much appreciated.

我认为我不需要在那里粘贴任何代码，因为这是一个通用的问题。如有任何帮助，我们将不胜感激。

Cheers

干杯

8 个解决方案

#1

Swift 4.x version

斯威夫特4。x版本

    let path = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
    let url = NSURL(fileURLWithPath: path)
    if let pathComponent = url.appendingPathComponent("nameOfFileHere") {
        let filePath = pathComponent.path
        let fileManager = FileManager.default
        if fileManager.fileExists(atPath: filePath) {
            print("FILE AVAILABLE")
        } else {
            print("FILE NOT AVAILABLE")
        }
    } else {
        print("FILE PATH NOT AVAILABLE")
    }

Swift 3.x version

斯威夫特3。x版本

    let path = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
    let url = URL(fileURLWithPath: path)

    let filePath = url.appendingPathComponent("nameOfFileHere").path
    let fileManager = FileManager.default
    if fileManager.fileExists(atPath: filePath) {
        print("FILE AVAILABLE")
    } else {
        print("FILE NOT AVAILABLE")
    }

Swift 2.x version, need to use URLByAppendingPathComponent

斯威夫特2。x版本，需要使用URLByAppendingPathComponent

    let path = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as String
    let url = NSURL(fileURLWithPath: path)
    let filePath = url.URLByAppendingPathComponent("nameOfFileHere").path!
    let fileManager = NSFileManager.defaultManager()
    if fileManager.fileExistsAtPath(filePath) {
        print("FILE AVAILABLE")
    } else {
        print("FILE NOT AVAILABLE")
    }

#2

Check the below code:

检查下面的代码:

Swift 1.2

斯威夫特1.2

let paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as String

let getImagePath = paths.stringByAppendingPathComponent("SavedFile.jpg")

let checkValidation = NSFileManager.defaultManager()

if (checkValidation.fileExistsAtPath(getImagePath))
{
    println("FILE AVAILABLE");
}
else
{
    println("FILE NOT AVAILABLE");
}

Swift 2.0

斯威夫特2.0

let paths = NSURL(fileURLWithPath: NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0])
let getImagePath = paths.URLByAppendingPathComponent("SavedFile.jpg")

let checkValidation = NSFileManager.defaultManager()

if (checkValidation.fileExistsAtPath("\(getImagePath)"))
{
    print("FILE AVAILABLE");
}
else
{
    print("FILE NOT AVAILABLE");
}

#3

Nowadays (2016) Apple recommends more and more to use the URL related API of NSURL, NSFileManager etc.

现在(2016)苹果公司建议越来越多的使用NSURL、NSFileManager等的URL相关API。

To get the documents directory in iOS and Swift 2 use

使用iOS和Swift 2获取文档目录

let documentDirectoryURL = try! NSFileManager.defaultManager().URLForDirectory(.DocumentDirectory, 
                                 inDomain: .UserDomainMask, 
                        appropriateForURL: nil, 
                                   create: true)

The try! is safe in this case because this standard directory is guaranteed to exist.

试一试!在这种情况下是安全的，因为这个标准目录保证存在。

Then append the appropriate path component for example an sqlite file

然后附加适当的路径组件，例如一个sqlite文件

let databaseURL = documentDirectoryURL.URLByAppendingPathComponent("MyDataBase.sqlite")

Now check if the file exists with checkResourceIsReachableAndReturnError of NSURL.

现在检查这个文件是否存在NSURL的checkresourceis可及andreturnerror。

let fileExists = databaseURL.checkResourceIsReachableAndReturnError(nil)

If you need the error pass the NSError pointer to the parameter.

如果需要错误，将NSError指针传递给参数。

var error : NSError?
let fileExists = databaseURL.checkResourceIsReachableAndReturnError(&error)
if !fileExists { print(error) }

Swift 3:

斯威夫特3:

In Swift 3 checkResourceIsReachable is marked as can throw

在Swift 3, checkresourceisable被标记为可以抛出。

do {
    let fileExists = try databaseURL.checkResourceIsReachable()
    // handle the boolean result
} catch let error as NSError {
    print(error)
}

To consider only the boolean return value and ignore the error use the nil-coalescing operator

要只考虑布尔返回值并忽略错误，请使用尼尔-合并操作符

let fileExists = (try? databaseURL.checkResourceIsReachable()) ?? false

#4

It's pretty user friendly. Just work with NSFileManager's defaultManager singleton and then use the fileExistsAtPath() method, which simply takes a string as an argument, and returns a Bool, allowing it to be placed directly in the if statement.

非常用户友好。只需使用NSFileManager的defaultManager singleton，然后使用fileExistsAtPath()方法，该方法只接受一个字符串作为参数，并返回一个Bool，允许它直接放在if语句中。

let paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
let documentDirectory = paths[0] as! String
let myFilePath = documentDirectory.stringByAppendingPathComponent("nameOfMyFile")

let manager = NSFileManager.defaultManager()
if (manager.fileExistsAtPath(myFilePath)) {
    // it's here!!
}

Note that the downcast to String isn't necessary in Swift 2.

注意，在Swift 2中，向下对字符串的转换不是必需的。

#5

An alternative/recommended Code Pattern in Swift 3 would be:

Swift 3中另一种/推荐的代码模式是:

1. Use URL instead of FileManager
2. 使用URL代替FileManager

3. Use of exception handling

   使用异常处理

   func verifyIfSqliteDBExists(){
       let docsDir     : URL       = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
       let dbPath      : URL       = docsDir.appendingPathComponent("database.sqlite")
   
       do{
           let sqliteExists : Bool = try dbPath.checkResourceIsReachable()
           print("An sqlite database exists at this path :: \(dbPath.path)")
   
       }catch{
           print("SQLite NOT Found at :: \(strDBPath)")
       }
   }
   

#6

For the benefit of Swift 3 beginners:

为了Swift 3初学者的利益:

1. Swift 3 has done away with most of the NextStep syntax
2. Swift 3取消了下一个步骤的大部分语法
3. So NSURL, NSFilemanager, NSSearchPathForDirectoriesInDomain are no longer used
4. 所以NSURL NSFilemanager NSSearchPathForDirectoriesInDomain不再被使用
5. Instead use URL and FileManager
6. 而是使用URL和FileManager
7. NSSearchPathForDirectoriesInDomain is not needed
8. 不需要NSSearchPathForDirectoriesInDomain
9. Instead use FileManager.default.urls
10. 而不是使用FileManager.default.urls

Here is a code sample to verify if a file named "database.sqlite" exists in application document directory:

这里有一个代码示例，用于验证一个名为“database”的文件。sqlite“存在于应用文档目录中:

func findIfSqliteDBExists(){

    let docsDir     : URL       = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
    let dbPath      : URL       = docsDir.appendingPathComponent("database.sqlite")
    let strDBPath   : String    = dbPath.path
    let fileManager : FileManager   = FileManager.default

    if fileManager.fileExists(atPath:strDBPath){
        print("An sqlite database exists at this path :: \(strDBPath)")
    }else{
        print("SQLite NOT Found at :: \(strDBPath)")
    }

}

#7

Very simple: If your path is a URL instance convert to string by 'path' method.

非常简单:如果您的路径是一个URL实例，通过“path”方法将其转换为字符串。

    let fileManager = FileManager.default
    var isDir: ObjCBool = false
    if fileManager.fileExists(atPath: yourURLPath.path, isDirectory: &isDir) {
        if isDir.boolValue {
            //it's a Directory path
        }else{
            //it's a File path
        }
    }

#8

You must add a "/" slash before filename, or you get path like ".../DocumentsFilename.jpg"

您必须在文件名之前添加“/”斜杠，否则您将获得“…/DocumentsFilename.jpg”之类的路径。