用于表视图的Swift排序字典

Question

I have a dictionary that I will use for populating a table:

["struvite":716,"calcium_oxalate":388,"urate":217,"calcium_phosphate":30,"silica":21,"compound":41]

I understand that dictionaries are, by definition, not sorted, and that tableView works on Arrays, not dictionaries.

So my problem is two fold. I need to sort this data by value and place it in an array so I can easily get it into a table. I found this answer for sorting but it seems out of date for Swift 2.

The result I'm looking for would be something like this:

---

struvite (716)

calcium_oxalate (388)

urate (217)

compound (41)

calcium_phosphate (30)

silica (21)

---

Where each line is an element of the array and they appear in descending order by what was once their value in the dictionary. Once it's in an array, I can get it into a table.

Answer 1

let dict = ["struvite": 716, "calcium_oxalate": 388, "urate": 217, "calcium_phosphate": 30, "silica": 21, "compound": 41]
let test = dict.sort { $0.1 > $1.1 }

Result is:

[("struvite", 716), ("calcium_oxalate", 388), ("urate", 217), ("compound", 41), ("calcium_phosphate", 30), ("silica", 21)]

You can access this and assign it to your cells like this:

let name = test[indexPath.row].0
let number = test[indexPath.row].1

Answer 2

The easy to reay way to do this in swift would be something along these lines, supposed that dictionary : [String:Int] .

struct Compound : Equatable, Comparable {
   let name : String
   let value : Int
}
func ==(x : Compound, y : Compound) -> Bool {
   return x.value == y.value
}
func <(x : Compound, y : Compound) -> Bool {
   return x.value < y.value
}

var compounds = [Compound]()
for (key, value) in dictionary {
   compounds.append(Compound(name: key, value: value)
}
let sorted = compounds.sort(>)

Answer 3

Starting with your example:

let dict = ["struvite":716,"calcium_oxalate":388,"urate":217,"calcium_phosphate":30,"silica":21,"compound":41]

This part will sort from the biggest and actually transform dictionary to array of tupples:

let sortedTupples = dict.sort { (lhs, rhs) -> Bool in
    return lhs.1 > rhs.1
}

This will result in exact form that you want, it's an array of strings:

let arrayOfStringsFromTupples = sortedTupples.map { "\($0.0) (\($0.1))" }

Map function maps each tupple entry into defined in clojure type, and here we've just created on string object, but actually it could be any different object.

In short

let dict = ["struvite":716,"calcium_oxalate":388,"urate":217,"calcium_phosphate":30,"silica":21,"compound":41]
let allInOne = dict.sort { (lhs, rhs) -> Bool in
    return lhs.1 > rhs.1
}.map { "\($0.0) (\($0.1))" }