Sharing Code With Views

As of CouchDB 1.1.0, its possible to share code between views (map/reduce functions) and other parts of your couchapp by putting the modules in the views/lib directory. To add a new directory of modules in Kanso, you need to edit the kanso.json configuration file, so it looks something like the following:

    "name": "myapp",
    "load": "lib/app",
    "modules": ["lib", "views"],
    "templates": "templates",
    "attachments": "static"

Note that you can use either a single string or an array of strings to represent modules directories (same goes for attachments). Once you've added the views directory to kanso.json, create the views and views/lib and add your shared module code in there:


exports.fn = function () {
    return 42;

Using shared modules

When using a module inside a view, you need to remember that views are not context-aware like list, show or update functions. They do not have access to their surrounding scope. Each map or reduce function needs to be completely self-contained so CouchDB can detect when it has changed and update the index. Because of this, you need to make sure you require the shared module inside the function:

exports.example_view = {
    map: function (doc) {
        // this must be placed *inside* the map function
        var example = require('views/lib/example');
        if (doc.num) {
            emit(doc._id, example.fn());

After pushing these changes and making sure you have some example documents, requesting this view should give results similar to the following:

    "total_rows": 2,
    "offset": 0,
    "rows": [
            "id": "cfe0bf4ac09fd7cf1efad645d2abf376",
            "key": "cfe0bf4ac09fd7cf1efad645d2abf376",
            "value": 42
            "id": "cfe0bf4ac09fd7cf1efad645d2abfd85",
            "key": "cfe0bf4ac09fd7cf1efad645d2abfd85",
            "value": 42

The value of each row is the result of calling example.fn(). In other modules in your application, you can require the new example module by doing require('views/lib/example').

One thing to be aware of, is that changes to the new module will trigger a re-indexing of the relevant views. Make sure you only put code essential to your views inside the views/lib directory.