使用Composition的通用JavaScript模型

Question

I am currently working on a Node.js application with a couple of JavaScript model like this:

function Role(data) {
  this.data = data;
  ...
}

Role.prototype.save = function(...) {...}

Role.findById = function(...) {...}
Role.findAll = function(...) {...}

All of them are using the same (similar) logic for most of the functions, but some need a different implementation for saving and so on. So my idea was to refactor them by using some kind of composition. My current solution is a combination of using inheritance for the prototype functions and an Adapter for the static functions. It looks like this.

var _adapter = new DatabaseAdapter(SCHEMA, TABLE, Role);

function Role(data) {
  Model.call(this, _adapter, Role._attributes)
  this.data = data;
  ...
}

Role._attributes = {
  name: ''
}

Role.prototype.save = function(...) {...}

Role.findById = function(...) {
  _adapter.findById(...);
}

Role.findAll = function(...)
{
  _adapter.findAll(...)
}

But, I am not really happy with my current solution, because the developers need to know a lot of implementation details to create a new Model. So, I hope someone could show me a better approach to solve my problem.

Thanks, Hendrik

Edit After some research I came up with the following solution:

Role model:

 Role.schema = 'db-schema-name';
 Role.table = 'db-table-name';
 Role.attributes = { /* attributes of the model */ }

 Role.prototype.save = genericSaveFunc;

 Role.findById = genericFindByIdFunc;
 ...

generic save:

 function genericSaveFunc(...) {
   if (this.id) {
     // handle update
     // attributes in 'this' will be updated 
   } else {
     // handle create
     // attributes in 'this' will be updated 
   }
 }

static generic function findById:

 function genericFindByIdFunc(...) {
   /* use this.schema && this.table to create correct SELECT statement */
 }

The model creation could be wrapped into a factory function. The good part of this solution is the simple creation of new models with different kind of functionality (eg only add save and findById to a model). But I don't know if it is a good idea to rely on the calling context of the generic functions?

Answer 1

Since your using a prototype-based language. There is no need to try to do class-inheritance. Take a look at stampit it will make it very easy for you to do composition the JavaScript way :)