belongsTo method

Future<OneToMany> belongsTo(String parentTable, { String? foreignKey, String? parentKey, })

If foreignKey is not specified, foreignKey will be issumed as the first column which contains parent table name the in the child table. e.g for a car belonging to a user, foreignKey will be assumed as user_id which includes the name of parentTable.

If parentKey is not specified, parentKey will be assumed as the word which is after _(underscore) of foreginKey. For example, in the case of foreign key user_id, id will be parentKey.

class Car extends Model with OneToOne{
 Future<Car?> getUser() async {
    var user = await belongsTo('users');
  }
}

Implementation

Future<OneToMany> belongsTo(String parentTable,
    {String? foreignKey, String? parentKey}) async {
  String? _foreignKey;
  String? _parentKey;
  String childTable = eloquent.tableName;
  List<Map<String, dynamic>> foreignKeys =
      (await eloquent.getForeignKeys(table: childTable))
          .where((element) => element['table'] == parentTable)
          .toList();
  if (foreignKeys.isEmpty) {
    throw Exception(
        'There is no foreign key related to $parentTable in $tableName');
  }

  Map<String, dynamic>? foreignInfo;
  if (foreignKeys.length > 1 && foreignKey == null) {
    throw Exception(
        'Please specify foreign key since there are more than one foreign keys in $tableName');
  }

  if (foreignKey == null) {
    foreignInfo = foreignKeys.first;
    _foreignKey = foreignInfo['from'];
  } else {
    if (foreignKeys
        .where((element) => element['from'] == foreignKey)
        .isEmpty) {
      throw Exception('foreign Key not found');
    }
    foreignInfo = foreignKeys.firstWhere(
        (element) => element['from'] == foreignKey,
        orElse: () => {});
    _foreignKey = foreignKey;
  }

  if (parentKey == null) {
    _parentKey = foreignInfo['to'];
  } else {
    List<String> columNames =
        await eloquent.getColumnNames(table: parentTable);
    if (!columNames.contains(parentKey)) {
      throw Exception('parent key not found in parent table');
    }
    _parentKey = parentKey;
  }

  query =
      '$parentTable table1, $childTable table2 WHERE table2.$_foreignKey = table1.$_parentKey AND table2.${eloquent.getPrimaryColumn} = "$primaryValue"';
  return this;
}