mongoose-hook

Abstract mongoose plugin, allowing usage of 'pre' and 'post' hooks on internal direct wrappers to database API for all (including static) mongoose operations.

Installation

git clone [e-mail]:tarquas/mongoose-hook.git mongoose-hook

Package

{
  "mongoose-hook": "tarquas/mongoose-hook#40df5bac52"
}

Usage

Example: A plugin to mark every new document with some watermark (uses pre 'insert' hook):

mongoose-watermark.js

'use strict';
 
var
  hookPlugin = require('./mongoose-hook'),
  thisPlugin = {};
 
thisPlugin.pre = function(p, callback) {
  if (p.insert) {
    p.insert[this.watermarkPath] = this.watermarkValue;
  }
 
  callback();
};
 
module.exports = function(schema, opts) {
  schema.plugin(hookPlugin, {
    mongoose: opts.mongoose,
    pre: thisPlugin.pre,
    watermarkPath: opts.path || 'watermark',
    watermarkValue: opts.value
  });
};

Usage of plugin: adds a field to every new document, specifying which process ID created it:

watermark-example.js

var
  mongoose = require('mongoose'),
  watermarkPlugin = require('./mongoose-watermark');
  
mongoose.plugin(watermarkPlugin, {
  mongoose: mongoose,
  path: 'createdByProcess',
  value: process.pid
});

Notes

• Hook plugin must be provided with an exact instance of mongoose, where the processing models expected to be processed in opts parameter. The plugin correctly handles the hooking on multiple mongoose instances.

• Comparing the code above with the following:

schema.post('save', function(next) {
  this.createdByProcess = process.pid;
  next();
});

The difference is that post 'save' hook is not called for Model.create(...) method; the post 'insert' hook is called in either case, because mongoose calls underlying insert wrapper of database API anyway. Also, in example above p.insert may also refer to $setOnInsert object on upsert operation.

• this object, which is passed to hook function is an instance of mongoose.Collection. Please, refer to mongoose manuals for its API. Also, this plugin adds getModel() method to mongoose.Collection prototype, which returns a Model (made by mongoose.model()), which refers to given mongoose.Collection instance.