Swift 2 ( executeFetchRequest ) : error handling

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As of Swift 2, Cocoa methods that produce errors are translated to Swift functions that throw an error.

Instead of an optional return value and an error parameter as in Swift 1.x:

var error : NSError?
if let result = context.executeFetchRequest(request, error: &error) {
    // success ...
    list = result
} else {
    // failure
    println("Fetch failed: \(error!.localizedDescription)")
}

in Swift 2 the method now returns a non-optional and throws an error
in the error case, which must be handled with try-catch:

do {
    list = try context.executeFetchRequest(request)
    // success ...
} catch let error as NSError {
    // failure
    print("Fetch failed: \(error.localizedDescription)")
}

For more information, see “Error Handling” in “Adopting Cocoa Design Patterns”
in the “Using Swift with Cocoa and Objective-C” documentation.

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