Sort Swift Array of Dictionaries by Value of a Key

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闹比i
闹比i 2021-02-07 05:45

I am attempting to sort a Swift array which is composed of dictionaries. I have prepared a working example below. The goal is to sort the entire array by the \"d\" element in t

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  •  囚心锁ツ
    2021-02-07 06:03

    To declare, if you need to keep it as AnyObject, you have to explicitly cast:

    var myArray = Array()
    var dict = Dictionary()
    
    dict["a"] = ("hickory" as! AnyObject)
    dict["b"] = ("dickory" as! AnyObject)
    dict["c"] = ("dock" as! AnyObject)
    dict["d"] = (6 as! AnyObject)
    
    myArray.append(dict as! AnyObject)
    
    dict["a"] = ("three" as! AnyObject)
    dict["b"] = ("blind" as! AnyObject)
    dict["c"] = ("mice" as! AnyObject)
    dict["d"] = (5 as! AnyObject)
    
    
    myArray.append(dict as! AnyObject)
    
    dict["a"] = ("larry" as! AnyObject)
    dict["b"] = ("moe" as! AnyObject)
    dict["c"] = ("curly" as! AnyObject)
    dict["d"] = (4 as! AnyObject)
    
    myArray.append(dict as! AnyObject)
    

    Without appending, you can do it like this:

    var myArray: [AnyObject] = [ ([
        "a" : ("hickory" as! AnyObject),
        "b" : ("dickory" as! AnyObject),
        "c" : ("dock" as! AnyObject),
        "d" : (6 as! AnyObject)
      ] as! AnyObject), ([
        "a" : ("three" as! AnyObject),
        "b" : ("blind" as! AnyObject),
        "c" : ("mice" as! AnyObject),
        "d" : (5 as! AnyObject)
      ] as! AnyObject), ([
        "a" : ("larry" as! AnyObject),
        "b" : ("moe" as! AnyObject),
        "c" : ("curly" as! AnyObject),
        "d" : (4 as! AnyObject)
      ] as! AnyObject)
    ]
    

    Which gives you the same result. Although, if only the value object in the dictionary needs to change, you don't need to cast the elements of the array:

    var myArray: [Dictionary] = [[
        "a" : ("hickory" as! AnyObject),
        "b" : ("dickory" as! AnyObject),
        "c" : ("dock" as! AnyObject),
        "d" : (6 as! AnyObject)
      ], [
        "a" : ("three" as! AnyObject),
        "b" : ("blind" as! AnyObject),
        "c" : ("mice" as! AnyObject),
        "d" : (5 as! AnyObject)
      ], [
        "a" : ("larry" as! AnyObject),
        "b" : ("moe" as! AnyObject),
        "c" : ("curly" as! AnyObject),
        "d" : (4 as! AnyObject)
      ]
    ]
    

    Then, to sort, you use the sort() closure, which sorts an Array in place. The closure you supply takes two arguments (named $0 and $1), and returns a Bool. The closure should return true if $0 is ordered before $1, or false if it comes after. To do this, you've got to cast an awful lot:

    //myArray starts as: [
    //  ["d": 6, "b": "dickory", "c": "dock", "a": "hickory"],
    //  ["d": 5, "b": "blind", "c": "mice", "a": "three"],
    //  ["d": 4, "b": "moe", "c": "curly", "a": "larry"]
    //]
    
    myArray.sort{
      (($0 as! Dictionary)["d"] as? Int) < (($1 as! Dictionary)["d"] as? Int)
    }
    
    //myArray is now: [
    //  ["d": 4, "b": "moe", "c": "curly", "a": "larry"],
    //  ["d": 5, "b": "blind", "c": "mice", "a": "three"],
    //  ["d": 6, "b": "dickory", "c": "dock", "a": "hickory"]
    //]
    

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