Method constructor

lib/associations/belongs-to-many.js:58–220

(source, target, options)

 */
class BelongsToMany extends Association {
  constructor(source, target, options) {
    super(source, target, options);

    if (this.options.through === undefined || this.options.through === true || this.options.through === null) {
      throw new AssociationError(`${source.name}.belongsToMany(${target.name}) requires through option, pass either a string or a model`);
    }

    if (!this.options.through.model) {
      this.options.through = {
        model: options.through
      };
    }

    this.associationType = 'BelongsToMany';
    this.targetAssociation = null;
    this.sequelize = source.sequelize;
    this.through = { ...this.options.through };
    this.isMultiAssociation = true;
    this.doubleLinked = false;

    if (!this.as && this.isSelfAssociation) {
      throw new AssociationError('\'as\' must be defined for many-to-many self-associations');
    }

    if (this.as) {
      this.isAliased = true;

      if (_.isPlainObject(this.as)) {
        this.options.name = this.as;
        this.as = this.as.plural;
      } else {
        this.options.name = {
          plural: this.as,
          singular: Utils.singularize(this.as)
        };
      }
    } else {
      this.as = this.target.options.name.plural;
      this.options.name = this.target.options.name;
    }

    this.combinedTableName = Utils.combineTableNames(
      this.source.tableName,
      this.isSelfAssociation ? this.as || this.target.tableName : this.target.tableName
    );

    /*
    * If self association, this is the target association - Unless we find a pairing association
    */
    if (this.isSelfAssociation) {
      this.targetAssociation = this;
    }

    /*
    * Find paired association (if exists)
    */
    _.each(this.target.associations, association => {
      if (association.associationType !== 'BelongsToMany') return;