Results

Actions must return a revel.Result, which handles the response generation. It adheres to a simple interface:

type Result interface {
	Apply(req *Request, resp *Response)
}

revel.Controller provides a couple methods to produce Results: * Render, RenderTemplate - render a template, passing arguments. * RenderJson, RenderXml - serialize a structure to json or xml. * RenderText - return a plaintext response. * Redirect - redirect to another action or URL * RenderFile - return a file, generally to be downloaded as an attachment. * RenderError - return a 500 response that renders the errors/500.html template. * NotFound - return a 404 response that renders the errors/404.html template. * Todo - return a stub response (500)

Additionally, the developer may define their own revel.Result and return that.

Setting the Status Code / Content Type

Each built-in Result has a default Status Code and Content Type. To override those defaults, simply set those properties on the response:

func (c App) Action() revel.Result {
	c.Response.Status = http.StatusTeapot
	c.Response.ContentType = "application/dishware"
	return c.Render()
}

Render

Called within an action (e.g. “Controller.Action”), mvc.Controller.Render does two things: 1. Adds all arguments to the controller’s RenderArgs, using their local identifier as the key. 2. Executes the template “views/Controller/Action.html”, passing in the controller’s “RenderArgs” as the data map.

If unsuccessful (e.g. it could not find the template), it returns an ErrorResult instead.

This allows the developer to write:

func (c MyApp) Action() revel.Result {
	myValue := calculateValue()
	return c.Render(myValue)
}

and to use “myValue” in their template. This is usually more convenient than constructing an explicit map, since in many cases the data will need to be handled as a local variable anyway.

Note: Revel looks at the calling method name to determine the Template path and to look up the argument names. Therefore, c.Render() may only be called from Actions.

RenderJson / RenderXml

The application may call RenderJson or RenderXml and pass in any Go type (usually a struct). Revel will serialize it using json.Marshal or xml.Marshal.

If results.pretty=true in app.conf, serialization will be done using MarshalIndent instead, to produce nicely indented output for human consumption.

Redirect

A helper function is provided for generating redirects. It may be used in two ways.

Redirect to an action with no arguments: <pre class="prettyprint lang-go"> return c.Redirect(Hotels.Settings)

</pre> This form is useful as it provides a degree of type safety and independence from the routing. (It generates the URL automatically.)

Redirect to a formatted string: <pre class="prettyprint lang-go"> return c.Redirect(“/hotels/%d/settings”, hotelId)

</pre> This form is necessary to pass arguments.

It returns a 302 (Temporary Redirect) status code.

Adding your own Result

Here is an example of adding a simple Result.

Create this type:

type Html string

func (r Html) Apply(req *Request, resp *Response) {
	resp.WriteHeader(http.StatusOK, "text/html")
	resp.Out.Write([]byte(r))
}

Then use it in an action:

func (c *App) Action() revel.Result {
	return Html("<html><body>Hello World</body></html>")
}

Status Codes

Each Result will set a status code by default. You can override the default status code by setting one yourself:

func (c *App) CreateEntity() revel.Result {
	c.Response.Status = 201
	return c.Render()
}