Swift：按排序描述符排序数组 [英] Swift: Sort Array by sort descriptors

问题描述

我正在使用coredata，所以我需要为我的实体排序描述符

I am using coredata so I need sort descriptors for my entities

例如，一个协调中心实体有这个类func：

For example, a Coordinate-entity has this class func:

class func sortDescriptors() -> Array<NSSortDescriptor>
{
    return [NSSortDescriptor(key: "sequence", ascending: true)]
}

我使用这个当向CoreData进行获取请求时：

I am using this when doing fetch-requests to CoreData like this:

var request = NSFetchRequest(entityName: entityName)

request.sortDescriptors = T.sortDescriptors()

然而，当我有一个坐标数组作为另一个coredata对象上的属性时，这是一个NSSet（Ie未排序）

However, when I have an array of coordinates as a property on another coredata object, this is an NSSet (I.e. unsorted)

为了解决这个问题，像这样：

To solve this, I am returning the coordinates like this:

return NSArray(array: coordinates!).sortedArrayUsingDescriptors(Coordinate.sortDescriptors()) as? Array<Coordinate>

这感觉很丑陋，使用NSArray只是为了获得 sortedArrayUsingDescriptors -method。有一个类似的方法，直接在Swift数组，即。 Array< Coordinate> 使用排序描述符？

Which feels ugly, to use an NSArray just to get the sortedArrayUsingDescriptors-method. Is there a similar way to do this directly on a Swift-array, I.e. Array<Coordinate> by using sort descriptors?

谢谢！

推荐答案

没有内置的方法，但您可以使用协议扩展添加它们：

There is no built-in method for this, but you can add them using protocol extension:

extension MutableCollectionType where Index : RandomAccessIndexType, Generator.Element : AnyObject {
    /// Sort `self` in-place using criteria stored in a NSSortDescriptors array
    public mutating func sortInPlace(sortDescriptors theSortDescs: [NSSortDescriptor]) {
        sortInPlace {
            for sortDesc in theSortDescs {
                switch sortDesc.compareObject($0, toObject: $1) {
                case .OrderedAscending: return true
                case .OrderedDescending: return false
                case .OrderedSame: continue
                }
            }
            return false
        }
    }
}

extension SequenceType where Generator.Element : AnyObject {
    /// Return an `Array` containing the sorted elements of `source`
    /// using criteria stored in a NSSortDescriptors array.
    @warn_unused_result
    public func sort(sortDescriptors theSortDescs: [NSSortDescriptor]) -> [Self.Generator.Element] {
        return sort {
            for sortDesc in theSortDescs {
                switch sortDesc.compareObject($0, toObject: $1) {
                case .OrderedAscending: return true
                case .OrderedDescending: return false
                case .OrderedSame: continue
                }
            }
            return false
        }
    }
}

<需要符合AnyObject

But note that this will work only when the array elements are classes, not structures, as NSSortDescriptor compareObject method requires arguments conforming to AnyObject

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