Grouping the list of based on the model view data-CodePudding

I want to convert my model view list to JSON format using the map.

 @override void initState() { 
/// model view data in list 
List<Model> data = [ 
Model('A', 'php'); 
Model('A', 'flutter', 'engineer1'); 
Model('A', 'flutter', 'engineer2'); 
Model('B', 'c sharp', 'engineer1'); 
Model('B', 'c sharp', 'engineer2'); 
Model('B', 'dot net', 'engineer2'); 
Model('B', 'php', 'engineer2');
Model('C', 'php', 'engineer2');
Model('C', 'php', 'engineer1'); ];
} 

/// model class 
Class Model{ 
Model(this.team, this.projectName, this.engineersName); 
String team; 
String projectName; 
String engineersName; 
}

Excepted output:
A team is occurred 3 times but it will show only one time, now A is KEY. And the A team have 2 project names(php, flutter). The flutter occurred 2 times but it will show only one time. The flutter have 2 engineers(engineer1, engineer2). Same method to team B and C.

When hover on the map variable it will shows KEY by VALUE.
A - {php,flutter{engineer1, engineer2}} 
B - {c sharp{engineer1, engineer2}, dot net{engineer1}, php{engineer2}} 
C - {php{engineer2, engineer1}}

I tried this way:

@override 
void initState() { 
/// Here I grouping a only team.(A, B, C). 
Map group = {}; 
For(var element in data){ 
var existingValue = group[element.team]; 
group[element.team] = existingValue; 
//// Here I tried to change the map type, but I can't to group a team wise formation. 
}}

My Output: When I hover on the group variable(Map group = {};), it shows the 3 Keys only. That is A, B, C. The values are not added. Because the map default type is Map<dynamic, dynamic>.

I tried to add the php and flutter values for A key. But I can't to add the list of values to map value. So, I changed to the map type Map<dynamic, List<Map<dynamic, dynamic>>>. It occurred null exception.

*I don't know how to group the project name and engineer name to hierarchy by based on teams.

If there is any other way to achieve this problem? *

CodePudding user response：

Is this what you like?

import "package:collection/collection.dart";

void main(List<String> arguments) {
  List<Model> data = [
    Model('A', 'php'),
    Model('A', 'flutter', 'engineer1'),
    Model('A', 'flutter', 'engineer2'),
    Model('B', 'c sharp', 'engineer1'),
    Model('B', 'c sharp', 'engineer2'),
    Model('B', 'dot net', 'engineer2'),
    Model('B', 'php', 'engineer2'),
    Model('C', 'php', 'engineer2'),
    Model('C', 'php', 'engineer1')
  ];

  var group = groupBy(data, (Model e) => e.team).map((key, value) => MapEntry(
      key,
      groupBy(value, (Model e) => e.projectName).map((key, value) =>
          MapEntry(key, value.map((e) => e.engineersName).whereNotNull()))));

  print(group);
}

class Model {
  String? team;
  String? projectName;
  String? engineersName;

  Model([this.team, this.projectName, this.engineersName]);
}

Output:

{A: {php: (), flutter: (engineer1, engineer2)}, B: {c sharp: (engineer1, engineer2), dot net: (engineer2), php: (engineer2)}, C: {php: (engineer2, engineer1)}}

CodePudding user response：

Love Ivo's answer. Here is an attempt at explicitly defining the data types and going about this task. Here is an example running on dartpad.dev/ where I have used the class defined below to get the output you likely need

class ModelNeeded {


 final List<Model> models;

  const ModelNeeded({required this.models});
  
 Map<String,Map<String,Set<String>>> toObject(){
    Map<String,Map<String,Set<String>>> object = {};
    // This will return a Map which has a key that is the team A,B,C
    for(var model in models){
      // If the key exists i.e team entry exists
       if(object.containsKey(model._team)){
         // Get data 
         Map data = object[model._team] as Map;
     
     //Check if project exists in data
     if(data.containsKey(model._projectName)){
       // Get engineers data
       Set engineers = data[model._projectName] as Set<String>;
       // Since this is a set the engineer can be added directly 
       engineers.add(model._engineerName);
     }
     // If project doesnt exist in data 
     // Create project
     else {
       data[model._projectName] = <String>{}..add(model._engineerName);
     }

   }
  else {
    // Create 
    object[model._team] = {
      model._projectName : <String>{}..add(model._engineerName)
    };
  }
  
}
return object;


  }
}