Controllers

Controller is responsible for handling incoming request, validate user inputs, call appropriate application logic behind and returns the response for that request. The response would be different content types based on request such as HTML, JSON, XML, Text, Binary, File, etc.

Table of Contents

• How to create a Controller in aah framework?
• Extending aah Controller

How to create a Controller in aah framework?

A Controller is any struct type that embeds the aah.Context (Note: this is not a standard package context.Context). The controller gets access to -

• Request
• Response
• Reply Builder
• Subject
• Session
• i18n Message
• Reverse URL
• View Arg
• Is Static Route

// Examples

// App controller
type AppController struct {
  *aah.Context
}

// User Controller
type UserController struct {
  *aah.Context
}

// OR

// Indirectly using `aah.Context` in User Controller
type UserController struct {
  AppController
}

Request

Request contains processed incoming request details such as Params, Content Type, Locale, Client IP (aka Remote IP/Address) Accept Content Type, Accept Encoding, Raw request object, etc.

• To learn more about Request attributes and methods click here.
• To learn more about Params attributes and methods click here

Response

Response implements interface of http.CloseNotifier, http.Flusher, http.Hijacker, http.Pusher and handy methods.

Note:

• It is recommend to use Reply builder to compose your response.
• If you’re using cxt.Res directly to send reply/response, don’t forget to call Reply().Done() so that framework will not intervene with your response.

Reply Builder

aah provides intuitive way to compose response using Reply() builder in chained method calls. To learn more click here

Subject

A aah Subject instance represents both security state and operations for a single application user. These operations include:

• Authorization (access control)
• Session access
• Logout

Read more about Subject,

Session

In aah framework default session mode is stateless, of-course via configuration you can enable stateful. Framework does HMAC sign and AES encryption to secure session data.

It is perfect for Web and API application-

• Web requires to persist state info between the HTTP request
• API doesn’t requires state info between the HTTP request.

To learn more about Session object click here.

i18n Message

i18n messages is for internationalization and localization. To learn more click here.

Reverse URL

aah framework provides a convenient way to create reverse route URL via two methods.

• ReverseURL - method generates the URL for given route name (defined in the routes.conf) and arguments.
• ReverseURLm - method generates the URL for given route name (defined in the routes.conf) and map of named arguments. Remaining provided values added as URL Query parameters.

// let's say route named `login` has path `/login.html`
ReverseURL("login")

// Output
"//<host-name:port-no-if-present>/login.html"


// let's say route named `user_info` has path `/v1/users/:userId`
ReverseURL("user_info", 100001)

// Output
"//<host-name:port-no-if-present>/v1/users/100001"


// let's say route named 'product_info' has path `/product/:productId`
ReverseURLm("product_info", map[string]interface{}{
  "id": "5564HFGFG56207",
  "lang": "es",
})

// Output
"//<host-name:port-no-if-present>/product/5564HFGFG56207?lang=es"

View Arg

AddViewArg method adds the given key and value into View Arguments. These values are accessible on templates. Chained call is possible. Also you can supply bunch of values via Reply().Ok().HTML(aah.Data{ ... }).

u.AddViewArg("Username", "Jeevanandam M.").
  AddViewArg("UserId", "e5f0396dfc504a949d9f9e2c511a779c")

Is Static Route

aah.Context enables you to identify the current incoming request is static or application route using IsStaticRoute() method. For e.g: if you have register custom NotFound handler in the route config, this method is very handy.

// true - static route
// false - application route
a.IsStaticRoute()

Extending aah Controller

A Controller is any struct type that embeds the aah.Context directly or indirectly. You can extend the controller for your need.

Note: when extending a controller via indirectly, embedding is not a pointer.

Example

// App controller
type AppController struct {
  *aah.Context
}

// User Controller
type UserController struct {
  AppController
}