docs: describe http mapping of arguments
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@ -44,6 +44,12 @@ The arguments description defines either a single argument as an object or an or
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* arg: argument name
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* type: argument datatype; must be a[loopback type](http://wiki.strongloop.com/display/DOC/LoopBack+types).
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* required: Boolean value indicating if argument is required.
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* root: For callback arguments: set this property to true if your function
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has a single callback argument that should be used as the root object
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returned to remote caller. Otherwise a map (argument-name to argument-value)
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is returned.
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* http: For input arguments: a function or an object describing mapping from HTTP request
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to the argument value, as explained <a href="#argdesc-http">below</a>.
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For example, a single argument, specified as an object:
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@ -60,6 +66,57 @@ Multiple arguments, specified as an array:
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]
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```
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<a name="argdesc-http"></a>
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**HTTP mapping of input arguments**
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There are two ways how to specify HTTP mapping for input parameters (what the
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method accepts).
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The first way is to provide an object with a `source` property, that can have
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one of these values:
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| source | description |
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|---|---|
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| body | The whole request body is used as the value. |
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| form | The value is looked up using `req.param`, which searches route arguments, the request body and the query string.|
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| query | An alias for form (see above). |
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| path | An alias for form (see above). |
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| req | The whole HTTP reqest object is used as the value. |
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For example, an argument getting the whole request body as the value:
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```js
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{ arg: 'data', type: 'object', http: { source: 'body' } }
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```
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The second way is to specify your custom mapping function:
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```js
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{
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arg: 'custom',
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type: 'number',
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http: function(ctx) {
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// ctx is LoopBack Context object
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// 1. Get the HTTP request object as provided by Express
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var req = ctx.req;
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// 2. Get 'a' and 'b' from query string or form data
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// and return their sum as the value
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return +req.param('a') + req.param('b');
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}
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}
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```
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When there is no mapping specified, LoopBack will look up the value
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using the following algorithm (assuming `name` as the name of the input
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parameter to resolve):
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1. If there is a HTTP request parameter `args` with a JSON content,
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then its content is parsed and the value of `args['name']` is used
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if it is defined.
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2. Otherwise `req.param('name')` is returned.
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## Remote hooks
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Run a function before or after a remote method is called by a client.
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