is-valid-instance/README.md

Returns true if a value is a valid instance of Base.

# is-valid-instance [![NPM version](https://img.shields.io/npm/v/is-valid-instance.svg?style=flat)](https://www.npmjs.com/package/is-valid-instance) [![NPM monthly downloads](https://img.shields.io/npm/dm/is-valid-instance.svg?style=flat)](https://npmjs.org/package/is-valid-instance)  [![NPM total downloads](https://img.shields.io/npm/dt/is-valid-instance.svg?style=flat)](https://npmjs.org/package/is-valid-instance) [![Linux Build Status](https://img.shields.io/travis/jonschlinkert/is-valid-instance.svg?style=flat&label=Travis)](https://travis-ci.org/jonschlinkert/is-valid-instance)

> Returns true if a value is a valid instance of Base.

## Install

Install with [npm](https://www.npmjs.com/):

```sh
$ npm install --save is-valid-instance
```

## Usage

Use in your [base](https://github.com/node-base/base) plugin to ensure that the plugin is registered on a valid instance.

```js
var isValidInstance = require('is-valid-instance');

function plugin(app) {
  if (!isValidInstance(app)) return;
  // do plugin stauff
}
```

## API

**Params**

* `val` **{Object}**
* `names` **{Array|Function}**: One or more names to check for on the given instance. Example `app` will check for `app.isApp === true` or `app._name === 'app'`.
* `fn` **{Function}**: Custom function for validating the instance.
* `returns` **{Boolean}**

**Example**

```js
function plugin(app) {
  if (!isValidInstance(app)) return;
  // do plugin stuff
}
```

## Examples

**Collection instance**

Return true if the instance is a [templates](https://github.com/jonschlinkert/templates) view-collection (`views`):

```js
function plugin(collection) {
  if (!isValidInstance(collection, ['views'])) {
    // optionally return the plugin function so the plugin is re-tried on 
    // each instance until it finds the correct one
    return plugin;
  }
  // do plugin stauff
}
```

**View instance**

Return true if the instance is a [templates](https://github.com/jonschlinkert/templates) view:

```js
function plugin(view) {
  if (!isValidInstance(view, ['view'])) {
    return plugin;
  }
  // do plugin stauff
}
```

**View instance**

Return true if the instance is either "app" or "collection":

```js
function plugin(app) {
  if (!isValidInstance(app, ['app', 'collection'])) {
    return plugin;
  }
  // do plugin stauff
}
```

## About

### Related projects

* [base-app](https://www.npmjs.com/package/base-app): Starting point for creating a base application, with a few light plugins for running tasks… [more](https://github.com/node-base/base-app) | [homepage](https://github.com/node-base/base-app "Starting point for creating a base application, with a few light plugins for running tasks and writing to the file system, and a functional CLI.")
* [base-plugins](https://www.npmjs.com/package/base-plugins): Upgrade's plugin support in base applications to allow plugins to be called any time after… [more](https://github.com/node-base/base-plugins) | [homepage](https://github.com/node-base/base-plugins "Upgrade's plugin support in base applications to allow plugins to be called any time after init.")
* [base](https://www.npmjs.com/package/base): base is the foundation for creating modular, unit testable and highly pluggable node.js applications, starting… [more](https://github.com/node-base/base) | [homepage](https://github.com/node-base/base "base is the foundation for creating modular, unit testable and highly pluggable node.js applications, starting with a handful of common methods, like `set`, `get`, `del` and `use`.")

### Contributing

Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).

### Building docs

_(This project's readme.md is generated by [verb](https://github.com/verbose/verb-generate-readme), please don't edit the readme directly. Any changes to the readme must be made in the [.verb.md](.verb.md) readme template.)_

To generate the readme, run the following command:

```sh
$ npm install -g verbose/verb#dev verb-generate-readme && verb
```

### Running tests

Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:

```sh
$ npm install && npm test
```

### Author

**Jon Schlinkert**

* [github/jonschlinkert](https://github.com/jonschlinkert)
* [twitter/jonschlinkert](https://twitter.com/jonschlinkert)

### License

Copyright © 2017, [Jon Schlinkert](https://github.com/jonschlinkert).
Released under the [MIT License](LICENSE).

***

_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.4.3, on March 24, 2017._