What is the Swift 3 equivalent of NSURL.URLByAppendingPathComponent()?

问题

I'm following a basic tutorial on building a simple iOS app in Swift.

It is written in Swift 2.x, and I work with XCode 8 Beta and Swift 3.

The tutorial suggests using NSFileManager to find a data directory. Class names have changed, so the auto-fixed Swift 3 looks like this:

static let DocumentsDirectory = FileManager().urlsForDirectory(.documentDirectory, inDomains:.userDomainMask).first!
static let ArchiveURL = DocumentsDirectory.URLByAppendingPathComponent("meals")

However, Xcode now complains that

Value of type 'URL' has no member 'URLByAddingPathComponent'

I am unable to find out what the method is called now.

The NSURL Class Reference doesn't contain any hints as to how to address it from Swift 3

• What is the new method name?

• Where do I have to go to find a complete class reference for Swift 3 (or, the Swift 3 interface to the library the URL class is defined in - I still don't completely understand the nomenclature) so I can research these myself in the future?

回答1:

As of Xcode 8 beta 4, it is named appendingPathComponent(_:), and does not throw.

static let archiveURL = documentsDirectory.appendingPathComponent("meals")

Also as Leo Dabus points out in the comments, your documentsDirectory property will need changing to use urls(for:in:) in beta 4:

static let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]

^{(Note that I've made your property names lowerCamelCase, as per the Swift API design guidelines. I would also recommend using FileManager.default, rather than creating a new instance.)}

You can take a look at Apple's latest API reference guide to see the API naming changes that have taken place in Swift 3.

回答2:

It has now changed to appendingPathComponent(_:) and it throws, so you need to wrap it in do - catch block

do {
  let archiveURL = try documentsDirectory?.appendingPathComponent("meals")
} catch {
  print(error)
}

Update

As per Xcode 8 beta 4, the appendingpathcomponent(_:) do not throw error.

For relevant info see answer by @Hamish

回答3:

func appendingPathComponent(String)

=> Returns a new URL made by appending a path component to the original URL.

static let archiveURL = documentsDirectory?.appendingPathComponent("meals")

If it is directory:

func appendingPathComponent(String, isDirectory: Bool)

=> Returns a new URL made by appending a path component to the original URL, along with a trailing slash if the component is designated a directory.

static let archiveURL = documentsDirectory?.appendingPathComponent("meals", isDirectory: true)

来源：https://stackoverflow.com/questions/38812240/what-is-the-swift-3-equivalent-of-nsurl-urlbyappendingpathcomponent