Context

The simplicity of app.Context

As you can see, every view in your app receives an app.Context object and we will be explaining it in detail here.

function Blog(ctx app.Context){
  /* do stuff with ctx */
}

Here is its structure:

type Context struct {
  Method     string              // GET, POST, PUT, DELETE
  Values     []string            // parsed pretty urls /path/1234/9876
  Params     map[string]string   // parsed query string /path?name=george&sex=male
  Form       map[string]string   // parsed all html fields after a form post
  Request   *http.Request        // request object if needed
  Response   http.ResponseWriter // response writer if needed
  User      *UserType            // appengine user for easy access
}

And here its functionality:

GetValue(key string) string                   // gets a value from the query string /path?name=george
DefValue(key string, def string) string       // gets a default value if it does not exists in the query string
Print(txt string)                             // prints to the console
Write(txt string)                             // writes to the response writer. useful for pages in plain text
Show(name string)                             // renders a static page without any data associated
Render(name string, data interface{})         // renders a template parsed with some dynamic data
NotFound(txt string)                          // shows an error page for resources not found in the server
Redirect(url string)                          // redirects to any route
SetHeader(key string, val string)             // sets headers to the http response
SetCookie(key string, val string, exp int64)  // sets cookies to store in the browser

To capture a value in the submitted query string:

name := ctx.GetValue("name")  // or
name := ctx.DefValue("name","Anonymous")

To show web pages from your templates:

ctx.Show("index")        // no data
ctx.Render("blog",data)  // with data

To redirect to the main page after a post:

ctx.Redirect("/")

As you can see, everything is easier with app.Context.