ios - How to get one column from my database into dictionary using Swift3 -

i want insert name column database dictionary sort , add sections tableview. have function store names database , return mutablearray , function return array of dictionary. don't know why mutablearray nil, way i'v managed values when try sorted dictionary , got return value of type : [string, [string]] instead of [string: [string]]

my code:

let sharedinstance = modelmanager()     class modelmanager: nsobject {  var database: fmdatabase? = nil  class func getinstance() -> modelmanager {     if(sharedinstance.database == nil)     {         sharedinstance.database = fmdatabase(path: util.getpath("test3.sqlite"))     }     return sharedinstance }  func getallcrimesnames() -> nsmutablearray {    // part1: database mutablearray     sharedinstance.database!.open()     let resultset: fmresultset! = sharedinstance.database!.executequery("select * crimetable", withargumentsin: nil)     let marrcrimesinfo : nsmutablearray = nsmutablearray()     if (resultset != nil) {         while resultset.next() {             let crimesinfo : nameinfo = nameinfo()             crimesinfo.name = resultset.string(forcolumn: "name")             marrcrimesinfo.add(crimesinfo)         }     }      sharedinstance.database!.close()     return marrcrimesinfo }  } 

part 2: mutablearray dictionary , sort it

class sectiondata {  var marrcrimesnames : nsmutablearray!   func getcrimesnames() {     marrcrimesnames = nsmutablearray()     marrcrimesnames = modelmanager.getinstance().getallcrimesnames() }   func getsectionsfromdata() -> [string: [string]] {      var sectiondictionary =  [string: [string]]()      if marrcrimesnames != nil {   // reason nil!      let crime: nameinfo = marrcrimesnames.object(at: 0) as! nameinfo     _ = crime.name     var firstletter: [string] = []      crime in marrcrimesnames {         firstletter.append((crime anyobject).name)     }      let characters = array(set(firstletter.flatmap({ $0.characters.first })))      character in characters.map({ string($0) }) {         sectiondictionary[character] = firstletter.filter({ $0.hasprefix(character) })     }      //var sortedsectiondictionary = array(sectiondictionary.keys).sorted()   // return [string, [string]] instead of [string: [string]]      }     return sectiondictionary } 

}

i know it's lot i'm missing simple , need here. thank all...

it doesn't make sense sort dictionary. dictionaries unordered.

my guess want table's data represented sorted array of sections. each section represented struct 2 fields, 1 first letter , 1 array of names in section.

you can convert sectiondictionary, maps first letters arrays of names, sorted array of section structs using code this:

struct crimenamesection {     let firstletter: string     let names: [string] }  func getsectionsfromdata() -> [crimenamesection] {     // make sure marrcrimesnames non-nil     guard marrcrimesnames != nil else {         return []     }      // add each name dictionary mapping first letters name arrays     var sectiondictionary =  [string : [string]]()     crime in marrcrimesnames {         let crime = crime as! nameinfo         let firstchar = string(crime.name[crime.name.startindex])         if var names = sectiondictionary[firstchar] {             names.append(crime.name)             sectiondictionary[firstchar] = names         } else {             sectiondictionary[firstchar] = [crime.name]         }     }      // convert sectiondictionary sorted array of crimenamesections     let sections = sectiondictionary.map { (key, value) in         return crimenamesection(firstletter: key, names: value)     }     let sortedsections = sections.sorted { $0.firstletter < $1.firstletter }      return sortedsections }