iOS8, Swift: fileURLWithPath - missing argument for parameter error

问题

I am trying to append subdirectory to documents directory using method:

class func fileURLWithPath(path: String) -> NSURL?`

code:

let applicationDocumentsDirectory:String = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as NSString
let storesDirectory:NSURL = NSURL.fileURLWithPath(applicationDocumentsDirectory).URLByAppendingPathComponent("Stores")

Getting error

missing argument for parameter 'isDirectory' in call.

I don't really get it, why compiler requires this parameter? It isn't mentioned in the interface?

Thnanx in advance

回答1:

The problem is that you're trying to chain methods when there are optionals in the chain.

NSURL.fileURLWithPath(applicationDocumentsDirectory) returns NSURL? type. When you try to execute method URLByAppendingPathComponent on it, it throws a compiler error.

I know it's kind of sucks that the compiler error is totally unrelated to the real cause, but it's just a beauty of current Swift version.

Use ! to unwrap and it's gonna work properly:

let storesDirectory:NSURL = 
NSURL.fileURLWithPath(applicationDocumentsDirectory)!
     .URLByAppendingPathComponent(NFConstants.NFCoreDataStringIdentifiers.CoreDataStoresPathComponent.rawValue)

Of course force unwrapping the optional is potentially crashy, so even better use if let idiom:

if let baseUrl = NSURL.fileURLWithPath(applicationDocumentsDirectory) {
    let storeURL = baseUrl.URLByAppendingPathComponent(NFConstants.NFCoreDataStringIdentifiers.CoreDataStoresPathComponent.rawValue)
}

来源：https://stackoverflow.com/questions/27627116/ios8-swift-fileurlwithpath-missing-argument-for-parameter-error

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ios

swift

nsurl