Swift：按排序描述符排序数组

Question

我正在使用coredata所以我需要为我的实体排序描述符

例如，Coordinate-entity具有此类func：

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

我在对CoreData执行获取请求时使用此方法，如下所示：

var request = NSFetchRequest(entityName: entityName)

request.sortDescriptors = T.sortDescriptors()

但是，当我有一个坐标数组作为另一个coredata对象的属性时，这是一个NSSet（即未分类）

为了解决这个问题，我将返回如下坐标：

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

使用NSArray只是为了获得sortedArrayUsingDescriptors -method感觉很难sortedArrayUsingDescriptors 。 是否有类似的方法直接在Swift数组，即Array<Coordinate>使用排序描述符？

谢谢！

Answer 1

Damien漂亮扩展的另一种方法可能是多播。

myArray = (myArray as NSArray).sortedArrayUsingDescriptors(tableView.sortDescriptors) as! Array

原始来源： NSHipster

Answer 2

没有内置方法，但您可以使用协议扩展添加它们：

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
        }
    }
}

但请注意，这仅在数组元素是类而不是结构时才有效，因为NSSortDescriptor compareObject方法需要符合AnyObject的参数

Answer 3

Swift 3版本@Darniel的回答

extension MutableCollection where Self : RandomAccessCollection {
    /// Sort `self` in-place using criteria stored in a NSSortDescriptors array
    public mutating func sort(sortDescriptors theSortDescs: [NSSortDescriptor]) {
        sort { by:
            for sortDesc in theSortDescs {
                switch sortDesc.compare($0, to: $1) {
                case .orderedAscending: return true
                case .orderedDescending: return false
                case .orderedSame: continue
                }
            }
            return false
        }

    }
}

extension Sequence where Iterator.Element : AnyObject {
    /// Return an `Array` containing the sorted elements of `source`
    /// using criteria stored in a NSSortDescriptors array.

    public func sorted(sortDescriptors theSortDescs: [NSSortDescriptor]) -> [Self.Iterator.Element] {
        return sorted {
            for sortDesc in theSortDescs {
                switch sortDesc.compare($0, to: $1) {
                case .orderedAscending: return true
                case .orderedDescending: return false
                case .orderedSame: continue
                }
            }
            return false
        }
    }
}