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Remove duplicate doc content 

Duplicates http://docs.strongloop.com/display/DOC/Remote+methods+and+hooks.
Some of this belongs in JSDoc ultimately.
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Rand McKinney 2014-06-03 15:34:28 -07:00
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## Remote methods and hooks
You can expose a Model's instance and static methods to clients. A remote method must accept a callback with the conventional `fn(err, result, ...)` signature.
### Static Methods
#### loopback.remoteMethod(fn, [options])
Expose a remote method.
```js
Product.stats = function(fn) {
var statsResult = {
totalPurchased: 123456
};
var err = null;
// callback with an error and the result
fn(err, statsResult);
}
loopback.remoteMethod(
Product.stats,
{
returns: {arg: 'stats', type: 'object'},
http: {path: '/info', verb: 'get'}
}
);
```
**Options**
The options argument is a JSON object, described in the following table.
| Option | Required? | Description |
| ----- | ----- | ----- |
| accepts | No | Describes the remote method's arguments; See <a href="#argdesc">Argument description</a>. The `callback` argument is assumed; do not specify. |
| returns | No | Describes the remote method's callback arguments; See <a href="#argdesc">Argument description</a>. The `err` argument is assumed; do not specify. |
| http | No | HTTP routing information: <ul><li> **http.path**: path (relative to the model) at which the method is exposed. May be a path fragment (for example, `/:myArg`) that will be populated by an arg of the same name in the `accepts` description. For example, the `stats` method above will be at the whole path `/products/stats`.</li><li> **http.verb**: HTTP method (verb) from which the method is available (one of: get, post, put, del, or all).</li></ul>
| description | No | A text description of the method. This is used by API documentation generators like Swagger.
<a name="argdesc"></a>
**Argument description**
The arguments description defines either a single argument as an object or an ordered set of arguments as an array. Each individual argument has keys for:
* arg: argument name
* type: argument datatype; must be a [loopback type](http://wiki.strongloop.com/display/DOC/LoopBack+types).
* required: Boolean value indicating if argument is required.
* root: For callback arguments: set this property to `true` if your function
has a single callback argument to use as the root object
returned to remote caller. Otherwise the root object returned is a map (argument-name to argument-value).
* http: For input arguments: a function or an object describing mapping from HTTP request
to the argument value, as explained <a href="#argdesc-http">below</a>.
For example, a single argument, specified as an object:
```js
{arg: 'myArg', type: 'number'}
```
Multiple arguments, specified as an array:
```js
[
{arg: 'arg1', type: 'number', required: true},
{arg: 'arg2', type: 'array'}
]
```
<a name="argdesc-http"></a>
**HTTP mapping of input arguments**
There are two ways to specify HTTP mapping for input parameters (what the method accepts):
* Provide an object with a `source` property
* Specify a custom mapping function
To use the first way to specify HTTP mapping for input parameters, provide an object with a `source` property
that has one of the values shown in the following table.
| Value of source property | Description |
|---|---|
| body | The whole request body is used as the value. |
| form | The value is looked up using `req.param`, which searches route arguments, the request body and the query string.|
| query | An alias for form (see above). |
| path | An alias for form (see above). |
| req | The whole HTTP reqest object is used as the value. |
For example, an argument getting the whole request body as the value:
```js
{ arg: 'data', type: 'object', http: { source: 'body' } }
```
The use the second way to specify HTTP mapping for input parameters, specify a custom mapping function
that looks like this:
```js
{
arg: 'custom',
type: 'number',
http: function(ctx) {
// ctx is LoopBack Context object
// 1. Get the HTTP request object as provided by Express
var req = ctx.req;
// 2. Get 'a' and 'b' from query string or form data
// and return their sum as the value
return +req.param('a') + req.param('b');
}
}
```
If you don't specify a mapping, LoopBack will determine the value
as follows (assuming `name` as the name of the input parameter to resolve):
1. If there is a HTTP request parameter `args` with a JSON content,
then the value of `args['name']` is used if it is defined.
2. Otherwise `req.param('name')` is returned.
### Remote hooks
A _remote hook_ enables you to execute a function before or after a remote method is called by a client.
The `beforeRemote` function runs before the remote method and `afterRemote` runs after.
```js
// *.save === prototype.save
User.beforeRemote('*.save', function(ctx, user, next) {
if(ctx.req.accessToken) {
next();
} else {
next(new Error('must be logged in to update'))
}
});
User.afterRemote('*.save', function(ctx, user, next) {
console.log('user has been saved', user);
next();
});
```
***NOTE***: The second argument to the hook(`user` in the above example) is the `ctx.result` which is not always available.
Remote hooks also support wildcards. Run a function before any remote method is called.
```js
// ** will match both prototype.* and *.*
User.beforeRemote('**', function(ctx, user, next) {
console.log(ctx.methodString, 'was invoked remotely'); // users.prototype.save was invoked remotely
next();
});
```
Other wildcard examples
```js
// run before any static method eg. User.find
User.beforeRemote('*', ...);
// run before any instance method eg. User.prototype.save
User.beforeRemote('prototype.*', ...);
// prevent password hashes from being sent to clients
User.afterRemote('**', function (ctx, user, next) {
if(ctx.result) {
if(Array.isArray(ctx.result)) {
ctx.result.forEach(function (result) {
result.password = undefined;
});
} else {
ctx.result.password = undefined;
}
}
next();
});
```
### Context
Remote hooks are provided with a Context `ctx` object which contains transport specific data (eg. for http: `req` and `res`). The `ctx` object also has a set of consistent apis across transports.
#### ctx.req.accessToken
The `accessToken` of the user calling the method remotely. **Note:** this is undefined if the remote method is not invoked by a logged in user (or other principal).
#### ctx.result
During `afterRemote` hooks, `ctx.result` will contain the data about to be sent to a client. Modify this object to transform data before it is sent.
#### REST
When [loopback.rest](#loopbackrest) is used the following additional `ctx` properties are available.
##### ctx.req
The express ServerRequest object. [See full documentation](http://expressjs.com/api.html#req).
##### ctx.res
The express ServerResponse object. [See full documentation](http://expressjs.com/api.html#res).