ios - Swift 按键排序字典数组，其中值是可选的 AnyObject

Question

我直接从 Parse 中提取一系列字典并将它们显示在表格中。所以我真的很想使用我收到的数据结构(下面结构奇怪的字典)。

A PFObject 是 [String : AnyObject?] 并且我希望能够按任意键排序，所以我不知道对象类型和键可能某些词典中没有。因为在 Parse 中，如果你不给一个属性一个值，它就根本不存在。例如:

[
    {
        "ObjectId" : "1",
        "Name" : "Frank",
        "Age" : 32
    },
    {
        "ObjectId" : "2",
        "Name" : "Bill"
    },
    {
        "ObjectId" : "3",
        "Age" : 18
    }
    {
        "ObjectId" : "4",
        "Name" : "Susan",
        "Age" : 47
    }

]

我希望缺少键的字典总是排在排序后的字典之后。一个例子:

原始表:

ObjectId   Name       Age
1          Frank      32
2          Bill     
3                     18
4          Susan      47

按名称排序:

ObjectId   Name       Age
2          Bill       
1          Frank      32
4          Susan      47
3                     18

由于我对数据模型没有太多控制权，而且它在整个应用程序中的使用受到限制，所以我更愿意专注于算法解决方案而不是结构性解决方案。

我想出了一个方法来做到这一点，但它似乎效率低下且缓慢，我确信有人可以做得更好。

//dataModel is an array of dictionary objects used as my table source
//sort mode is NSComparisonResult ascending or descending
//propertyName is the dictionary key

        //first filter out any objects that dont have this key
        let filteredFirstHalf = dataModel.filter({ $0[propertyName] != nil })
        let filteredSecondHalf = dataModel.filter({ $0[propertyName] == nil })

        //sort the dictionaries that have the key
        let sortedAndFiltered = filteredFirstHalf { some1, some2 in

            if let one = some1[propertyName] as? NSDate, two = some2[propertyName] as? NSDate {
                return one.compare(two) == sortMode
            } else if let one = some1[propertyName] as? String, two = some2[propertyName] as? String {
                return one.compare(two) == sortMode
            } else if let one = some1[propertyName] as? NSNumber, two = some2[propertyName] as? NSNumber {
                return one.compare(two) == sortMode
            } else {
                fatalError("filteredFirstHalf shouldn't be here")
            }
        }

        //this will always put the blanks behind the sorted
        dataModel = sortedAndFiltered + filteredSecondHalf

谢谢!

Answer 1

Swift 无法比较任何两个对象。您必须先将它们转换为特定类型:

let arr: [[String: Any]] = [
    ["Name" : "Frank", "Age" : 32],
    ["Name" : "Bill"],
    ["Age" : 18],
    ["Name" : "Susan", "Age" : 47]
]

let key = "Name" // The key you want to sort by

let result = arr.sort {
    switch ($0[key], $1[key]) {
        case (nil, nil), (_, nil):
            return true
        case (nil, _):
            return false
        case let (lhs as String, rhs as String):
            return lhs < rhs
        case let (lhs as Int, rhs as Int):
            return  lhs < rhs
        // Add more for Double, Date, etc.
        default:
            return true
    }
}

print(result)

如果有多个字典没有指定key的值，它们将被放在result数组的末尾，但它们的相对顺序是不确定的。