CODEWITHSUNDEEP
arraysobjectreflectiondarttype-conversion
Will Squire
Will Squire

Reputation: 6595

How to convert an object to array (map) in Dart?

How to convert an Object type to a Map type (array) in Dart, so the variables become key/value pairs?

Upvotes: 8

Views: 7518

Answers (2)

CedX
CedX

Reputation: 3987

Will convert recursively any JS object to a Dart map, list or scalar value:

/// js_interop.dart
import 'dart:js';

/// Converts the specified JavaScript [value] to a Dart instance.
dynamic convertToDart(value) {
  // Value types.
  if (value == null) return null;
  if (value is bool || value is num || value is DateTime || value is String) return value;

  // JsArray.
  if (value is Iterable) return value.map(convertToDart).toList();

  // JsObject.
  return new Map.fromIterable(getKeysOfObject(value), value: (key) => convertToDart(value[key]));
}

/// Gets the enumerable properties of the specified JavaScript [object].
List<String> getKeysOfObject(JsObject object) => (context['Object'] as JsFunction).callMethod('keys', [object]);

Usage:

/// config.js
window.$environment = 'staging';
window.$config = {
  name: 'FooBar',
  params: {
    assets: ['css', 'js'],
    forceSsl: true
  }
};

/// main.dart
import 'dart:js' as js;
import 'js_interop.dart';

void main() {
  var environment = convertToDart(js.context[r'$environment']);
  assert(environment is String);
  assert(environment == 'staging');

  var config = convertToDart(js.context[r'$config']);
  assert(config is Map<String, dynamic>);
  assert(config.length == 2);

  assert(config['name'] is String);
  assert(config['name'] == 'FooBar');

  assert(config['params'] is Map<String, dynamic>);
  assert(config['params'].length == 2);

  assert(config['params']['forceSsl'] is bool);
  assert(config['params']['forceSsl'] == true);

  assert(config['params']['assets'] is List<String>);
  assert(config['params']['assets'].length == 2);
  assert(config['params']['assets'].first == 'css');
  assert(config['params']['assets'].last == 'js');
}

Caveats: the created instance does not reflect the changes from the original JS object. If you need this feature, see: https://stackoverflow.com/a/20720378/1084485

Upvotes: 0

Will Squire
Will Squire

Reputation: 6595

/**
   * Uses refection (mirrors) to produce a Map (array) from an object's
   * variables. Making the variable name the key, and it's value the
   * value.
   */
  Map objectToMap(Object object)
  {
    // Mirror the particular instance (rather than the class itself)
    InstanceMirror instanceMirror = reflect(object);
    Map dataMapped = new Map();

    // Mirror the instance's class (type) to get the declarations
    for (var declaration in instanceMirror.type.declarations.values)
    {
      // If declaration is a type of variable, map variable name and value
      if (declaration is VariableMirror)
      {
        String variableName = MirrorSystem.getName(declaration.simpleName);
        String variableValue = instanceMirror.getField(declaration.simpleName).reflectee;

        dataMapped[variableName] = variableValue;
      }
    }

    return dataMapped;
  }

Upvotes: 2

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