Mapping Multiple Lists in Flutter/Dart? - list

Question

I have SWIFT code where I've mapped a set of lists with equal number of elements where 1 was a list of ints and they were mapped in descending order. Here is my SWIFT Code...
class Video
{
let videoID: String
let rank: Int
let title: String
let imageString: String
init(videoID: String, rank: Int, title: String, imageString: String)
{
self.videoID = videoID
self.rank = rank
self.title = title
self.imageString = imageString
}
}
var videos = [Video]()
videos.sort { $0.rank < $1.rank }
self.vidTitleArray = videos.map { $0.title }
self.vidRankArray = videos.map { $0.rank }
self.vidIdArray = videos.map { $0.videoID }
self.vidImageArray = videos.map { $0.imageString }
Here is where I am in Flutter, but I'm getting errors going forward...
class videos{
String videoId;
int rank;
String title;
String imageString;
videos(this.videoId, this.rank, this.title, this.imageString);
}
How do I make a list from the class constructor then rearrange all elements in descending order mapped to rank?
***** OPTION *****
Here is my code without using a Video class. I got it to rank correctly using a SplayTreeMap but if Value is ever the same it only brings back 1 node. Is there a way to map all 4 maps descending with Value?
Map myMap = event.data.snapshot.value; //store each map
var titles = myMap.values;
List onesTitles = new List();
List onesIds = new List();
List onesImages = new List();
List onesRank = new List();
for (var items in titles) {
onesTitles.add(items['vidTitle']);
onesIds.add(items['vidId']);
onesImages.add(items['vidImage']);
onesRank.add(items['Value']);
}
names = onesTitles;
ids = onesIds;
numbers = onesRank;
vidImages = onesImages;

Answer 1

You can use List.sort() for that purpose, I have created a custom example where I hard coded 3 instances of your Videos class, and then added them in my build method in a List in ascending order. Using List.sort() and compareTo, I was able to rearrange them in an descending order.
List<Videos> myList = [_firstVideos, _secondVideos, _thirdVideos];
sort() {
for (var video in myList) {
print(video.rank); ///prints 1 2 3
}
myList.sort((y, x) => x.rank.compareTo(y.rank));
for (var video in myList) {
print(video.rank); ///prints 3 2 1
}
}
...
import 'package:flutter/material.dart';
void main(){
runApp(new MaterialApp(home: new MyApp(),));
}
class MyApp extends StatelessWidget {
Videos _firstVideos = new Videos(
videoId: "0001",
rank: 1,
title: "My First Video",
imageString: "My First Image",
);
Videos _secondVideos = new Videos(
videoId: "0002",
rank: 2,
title: "My Seocnd Video",
imageString: "My Second Image",
);
Videos _thirdVideos = new Videos(
videoId: "0003",
rank: 3,
title: "My Third Video",
imageString: "My Third Image",
);
#override
Widget build(BuildContext context) {
List<Videos> myList = [_firstVideos,_secondVideos,_thirdVideos];
sort()
{
myList.sort((y,x)=>x.rank.compareTo(y.rank));
print(myList[0].title);
}
return new Scaffold(
body: new Center(
child: new FlatButton(onPressed: sort, child: new Text("Sort")),
),
);
}
}
class Videos{
String videoId;
int rank;
String title;
String imageString;
Videos({this.videoId, this.rank, this.title, this.imageString});
}