prototype methods for attachment management

gistfile1.m

module.exports.afterModelCreate = function(Model) {
  Model = Model || {};
  
  Model.prototype.idAttribute = '_id'; // true for all TouchDB documents
  Model.prototype.config.Model = Model; // needed for fetch operations to initialize the collection from persistent store

  Model.prototype.attachmentNamed = function(name) {
    var doc = db.documentWithID(this.id);
    if (doc) {
      return doc.currentRevision.attachmentNamed(name);
    }
  };
  
  Model.prototype.addAttachment = function(name, contentType, content) {
    var doc = db.documentWithID(this.id);
    if (doc) {
      var rev = doc.newRevision();
      rev.addAttachment(name, contentType, content);
      rev.save();
    }
  };
  
  Model.prototype.removeAttachment = function(name) {
    var doc = db.documentWithID(this.id);
    if (doc) {
      var rev = doc.newRevision();
      rev.removeAttachment(name);
      rev.save();
    }
  };
  
  Model.prototype.attachmentNames = function() {
    var doc = db.documentWithID(this.id);
    return doc ? doc.attachmentNames : [];
  }
  
  return Model;
};