比较 Swift 中的 AnyObject [英] Comparing AnyObject in Swift

问题描述

我无法将此 Objective-C 代码移植到 Swift.代码必须按照给定的 property 对目录的内容进行排序.

I'm having trouble porting this Objective-C code to Swift. The code must sort the contents of a directory by a given property.

NSArray *contents = [fileManager contentsOfDirectoryAtURL:directoryURL includingPropertiesForKeys:@[property] options:kNilOptions error:&error];
if (!contents) return nil;
contents = [contents sortedArrayUsingComparator:^NSComparisonResult(NSURL *url1, NSURL *url2) {
    id value1;
    if ([url1 getResourceValue:&value1 forKey:property error:nil]) return NSOrderedAscending;
    id value2;
    if ([url2 getResourceValue:&value2 forKey:property error:nil]) return NSOrderedDescending;
    return [value1 compare:value2];
}];
return contents

到目前为止我的 Swift 版本:

My Swift version so far:

if let contents = fileManager.contentsOfDirectoryAtURL(directoryURL, includingPropertiesForKeys: [property], options: NSDirectoryEnumerationOptions.allZeros, error: &error) as? [NSURL] {

    let sortedContents = contents.sorted({(URL1 : NSURL, URL2 : NSURL) -> Bool in

        var value1 : AnyObject?
        if !URL1.getResourceValue(&value1, forKey: property, error: nil) { return true }
        var value2 : AnyObject?
        if !URL2.getResourceValue(&value2, forKey: property, error: nil) { return false }
        // How do I compare AnyObject?
        return false
        })
    return sortedContents
} else {
    return nil
}

特别是，我不知道如何比较两个 AnyObject 对象.我不能向下转换到 Comparable 协议，因为它没有被标记为 @objc 并且显然我不能用可选的链接语法调用 compare (错误:后缀?"的操作数应该有可选类型；类型是NSComparisonResult").

Particularly, I don't know how to compare two AnyObject objects. I can't downcast to the Comparable protocol because it's not marked as @objc and apparently I can't call compare with optional chaining syntax (error: Operand of postfix '?' should have optional type; type is 'NSComparisonResult').

当然，总是有将值向下转换为 String、NSDate 和 NSNumber 的蛮力方法:

Of course, there's always the brute-force approach of downcasting the values to String, NSDate and NSNumber:

if let string1 = value1 as? String {
    if let string2 = value2 as? String {
        return string1 < string2
    }
}
if let date1 = value1 as? NSDate {
    if let date2 = value2 as? NSDate {
        return date1.compare(date2) == NSComparisonResult.OrderedAscending
    }
}

// And so on...

return false

有没有更好的方法?

推荐答案

除非它们确实是 AnyObject(即，它们可以是快速的事物)将它们声明(或强制转换)为 NSObject 代替.

Unless they really are AnyObject (ie., they can be swift things) declare them (or cast them) to NSObject instead.

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