问题
I'm trying to get path to Documents folder with code:
var documentsPath = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory:0,NSSearchPathDomainMask:0,true)
but Xcode gives error: Cannot convert expression's type 'AnyObject[]!' to type 'NSSearchPathDirectory'
I'm trying to understand what is wrong in the code.
回答1:
Apparently, the compiler thinks NSSearchPathDirectory:0 is an array, and of course it expects the type NSSearchPathDirectory instead. Certainly not a helpful error message.
But as to the reasons:
First, you are confusing the argument names and types. Take a look at the function definition:
func NSSearchPathForDirectoriesInDomains(
directory: NSSearchPathDirectory,
domainMask: NSSearchPathDomainMask,
expandTilde: Bool) -> AnyObject[]!
directoryanddomainMaskare the names, you are using the types, but you should leave them out for functions anyway. They are used primarily in methods.- Also, Swift is strongly typed, so you shouldn't just use 0. Use the enum's value instead.
- And finally, it returns an array, not just a single path.
So that leaves us with (updated for Swift 2.0):
let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0]
and for Swift 3:
let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
回答2:
Swift 3.0 and 4.0
Directly getting first element from an array will potentially cause exception if the path is not found. So calling first and then unwrap is the better solution
if let documentsPathString = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first {
//This gives you the string formed path
}
if let documentsPathURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {
//This gives you the URL of the path
}
回答3:
The modern recommendation is to use NSURLs for files and directories instead of NSString based paths:
So to get the Document directory for the app as an NSURL:
func databaseURL() -> NSURL? {
let fileManager = NSFileManager.defaultManager()
let urls = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
if let documentDirectory: NSURL = urls.first as? NSURL {
// This is where the database should be in the documents directory
let finalDatabaseURL = documentDirectory.URLByAppendingPathComponent("items.db")
if finalDatabaseURL.checkResourceIsReachableAndReturnError(nil) {
// The file already exists, so just return the URL
return finalDatabaseURL
} else {
// Copy the initial file from the application bundle to the documents directory
if let bundleURL = NSBundle.mainBundle().URLForResource("items", withExtension: "db") {
let success = fileManager.copyItemAtURL(bundleURL, toURL: finalDatabaseURL, error: nil)
if success {
return finalDatabaseURL
} else {
println("Couldn't copy file to final location!")
}
} else {
println("Couldn't find initial database in the bundle!")
}
}
} else {
println("Couldn't get documents directory!")
}
return nil
}
This has rudimentary error handling, as that sort of depends on what your application will do in such cases. But this uses file URLs and a more modern api to return the database URL, copying the initial version out of the bundle if it does not already exist, or a nil in case of error.
回答4:
Xcode 8.2.1 • Swift 3.0.2
let documentDirectoryURL = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
Xcode 7.1.1 • Swift 2.1
let documentDirectoryURL = try! NSFileManager.defaultManager().URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: true)
回答5:
Usually I prefeer to use this extension:
Swift 3.x and Swift 4.0:
extension FileManager {
class func documentsDir() -> String {
var paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true) as [String]
return paths[0]
}
class func cachesDir() -> String {
var paths = NSSearchPathForDirectoriesInDomains(.cachesDirectory, .userDomainMask, true) as [String]
return paths[0]
}
}
Swift 2.x:
extension NSFileManager {
class func documentsDir() -> String {
var paths = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true) as [String]
return paths[0]
}
class func cachesDir() -> String {
var paths = NSSearchPathForDirectoriesInDomains(.CachesDirectory, .UserDomainMask, true) as [String]
return paths[0]
}
}
回答6:
For everyone who looks example that works with Swift 2.2, Abizern code with modern do try catch handle of error
func databaseURL() -> NSURL? {
let fileManager = NSFileManager.defaultManager()
let urls = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
if let documentDirectory:NSURL = urls.first { // No use of as? NSURL because let urls returns array of NSURL
// This is where the database should be in the documents directory
let finalDatabaseURL = documentDirectory.URLByAppendingPathComponent("OurFile.plist")
if finalDatabaseURL.checkResourceIsReachableAndReturnError(nil) {
// The file already exists, so just return the URL
return finalDatabaseURL
} else {
// Copy the initial file from the application bundle to the documents directory
if let bundleURL = NSBundle.mainBundle().URLForResource("OurFile", withExtension: "plist") {
do {
try fileManager.copyItemAtURL(bundleURL, toURL: finalDatabaseURL)
} catch let error as NSError {// Handle the error
print("Couldn't copy file to final location! Error:\(error.localisedDescription)")
}
} else {
print("Couldn't find initial database in the bundle!")
}
}
} else {
print("Couldn't get documents directory!")
}
return nil
}
Update I've missed that new swift 2.0 have guard(Ruby unless analog), so with guard it is much shorter and more readable
func databaseURL() -> NSURL? {
let fileManager = NSFileManager.defaultManager()
let urls = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
// If array of path is empty the document folder not found
guard urls.count != 0 else {
return nil
}
let finalDatabaseURL = urls.first!.URLByAppendingPathComponent("OurFile.plist")
// Check if file reachable, and if reacheble just return path
guard finalDatabaseURL.checkResourceIsReachableAndReturnError(nil) else {
// Check if file is exists in bundle folder
if let bundleURL = NSBundle.mainBundle().URLForResource("OurFile", withExtension: "plist") {
// if exist we will copy it
do {
try fileManager.copyItemAtURL(bundleURL, toURL: finalDatabaseURL)
} catch let error as NSError { // Handle the error
print("File copy failed! Error:\(error.localizedDescription)")
}
} else {
print("Our file not exist in bundle folder")
return nil
}
return finalDatabaseURL
}
return finalDatabaseURL
}
回答7:
More convenient Swift 3 method:
let documentsUrl = FileManager.default.urls(for: .documentDirectory,
in: .userDomainMask).first!
回答8:
Xcode 8b4 Swift 3.0
let paths = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.userDomainMask, true)
回答9:
Usually i prefer like below in swift 3, because i can add file name and create a file easily
let fileManager = FileManager.default
if let documentsURL = fileManager.urls(for: .documentDirectory, in: .userDomainMask).first {
let databasePath = documentsURL.appendingPathComponent("db.sqlite3").path
print("directory path:", documentsURL.path)
print("database path:", databasePath)
if !fileManager.fileExists(atPath: databasePath) {
fileManager.createFile(atPath: databasePath, contents: nil, attributes: nil)
}
}
来源：https://stackoverflow.com/questions/24055146/how-to-find-nsdocumentdirectory-in-swift