iris/mvc/README.md

MVC Internals

• MakeHandler - accepts a function which accepts any input and outputs any result, and any optional values that will be used as binders, if needed they will be converted in order to be faster at serve-time. Returns a context/iris#Handler and a non-nil error if passed function cannot be wrapped to a raw context/iris#Handler
  • Struct fields with Struct Binding
  • Methods with Dynamic Binding
• Engine - The "manager" of the controllers and handlers, can be grouped and an Engine can have any number of children.
  • Engine#Bind Binds values to be used inside on one or more handlers and controllers
  • Engine#Handler - Creates and returns a new mvc handler, which accept any input parameters (calculated by the binders) and output any result which will be sent as a response to the HTTP Client. Calls the MakeHandler with the Engine's Dependencies.Values as the binders
  • Engine#Controller - Creates and activates a controller based on a struct which has the C as an embedded , anonymous, field and defines methods to be used as routes. Can accept any optional activator listeners in order to bind any custom routes or change the bindings, called once at startup.
• The highest level feature of this package is the Application which contains an iris.Party as its Router and an Engine. A new Application is created with New(iris.Party) and registers a new Engine for itself, Engines can be shared via the Application#NewChild or by manually creating an &Application{ Engine: engine, Router: subRouter }. The Application is being used to build complete mvc applications through controllers, it doesn't contain any method to convert mvc handlers to raw handlers, although its Engine can do that but it's not a common scenario.

Examples can be found at: https://github.com/kataras/iris/tree/master/_examples/mvc.

Binding

First of all, they can be binded to func input arguments (custom handlers) or struct fields (controllers). We will use the term Input for both of them.

// consume the user here as func input argument.
func myHandler(user User) {}

type myController struct {
    // consume the user here, as struct field.
    user User 
}

If the input is an interface then it will check if the binding is completed this interface and it will be binded as expected.

Two types of binders are supported:

Dynamic Binding

ReturnValue, should return a single value, no pointer to, if the consumer Input (struct field or func input argument) expects User then it will be binded on each request, this is a dynamic binding based on the Context.

type User struct {
    Username string
}

myBinder := func(ctx iris.Context) User {
    return User {
        Username: ctx.Params().Get("username"),
    }
}

myHandler := func(user User) {
    // ...
}

Static Binding

Static Value (Service), this is used to bind a value instance, like a service or a database connection.

// optional but we declare interface most of the times to 
// be easier to switch from production to testing or local and visa versa.
// If input is an interface then it will check if the binding is completed this interface
// and it will be binded as expected.
type Service interface { 
    Do() string
}

type myProductionService struct {
    text string
}
func (s *myProductionService) Do() string {
    return s.text
}

myService := &myProductionService{text: "something"}

myHandler := func(service Service) {
    // ...
}

Add Dependencies

For Handlers

MakeHandler is used to create a handler based on a function which can accept any input arguments and export any output arguments, the input arguments can be dynamic path parameters or custom binders.

h, err := MakeHandler(myHandler, reflect.ValueOf(myBinder))

Values passed in Dependencies are binded to all handlers and controllers that are expected a type of the returned value, in this case the myBinder indicates a dynamic/serve-time function which returns a User, as shown above.

m := NewEngine()
m.Dependencies.Add(myBinder)

h := m.Handler(myHandler)

For Controllers

app := iris.New()
m := NewEngine()
m.Dependencies.Add(myBinder)
m.Controller(app, new(myController))
// ...

sub := app.Party("/sub")
m := NewEngine()
m.Controller(sub, &myController{service: myService})

NewEngine().Controller(sub.Party("/subsub"), new(myController), func(b mvc.BeforeActivation) {
    b.Dependencies().Add(myService)
})