apis

Steps to create apis or handler functions

• Create one interface [resource]Service with all methods which had been implemented in [resource] service file.
  e.g.

  type userService interface{
      Get(rs app.RequestScope, email string) (*models.User, error)
      Count(rs app.RequestScope) (int, error)
      Create(rs app.RequestScope, model *models.User) error
      Update(rs app.RequestScope, email string, model *models.User) (*models.User, error)
      Delete(rs app.RequestScope, email string) error
      // these all methods **must** be defined in the service file
  }
  

• Create a Resourse, resourse is basically a entity or we can call it data store, it may be user collection or any collection.
  e.g.

  type userResource struct {
      service userService 
      // inject userService in the [user] resource
  }    
  

• Create a contructor or method to instantiate the service, basically this function will bind all layers and defines the end-points
  e.g.

  // ServeUserResource sets up the routing of user endpoints and the corresponding handlers.
  func ServeUserResource(rg *mux.Router, service userService) {
      // Create instance of userResource
      r := &userResource{service}
      rg.HandleFunc("/users/{email}", r.get).Methods("GET")
      rg.HandleFunc("/users", r.create).Methods("POST")
      rg.HandleFunc("/users/{email}", r.update).Methods("PUT")
      rg.HandleFunc("/users/{email}", r.delete).Methods("DELETE")
  }
  

  NOTE: this function expects a router object as first param, and service instance in second param
  This function should be called in main
  e.g.

  // Create a dao, to instantiate the service
  userDao := daos.NewUserDao()
  apis.ServeUserResource(r, services.NewUserService(userDao))
  

• Now Create the handler functions Methods, here we will not create a function rather we'll create methods, which will be specific to a resource. Each method will have resource as the receiver

  Basically it will be a handler function with a receiver

  Method signature:

    `func (rs userResourse) get(w http.ResponseWriter, r *http.Request)` 
  

        e.g.

  func (ur *userResource) create(w http.ResponseWriter, r *http.Request) {
      // Create requestScope obj
      rs := app.GetRequestScope(r)
      var x *models.User
      json.Unmarshal(rs.GetBody(), &x)
      
      // Call any service method using userResource
      err := ur.service.Create(rs, x)
  
      if err != nil {
          fmt.Fprintf(w, err.Error())
          return
      }
  
      fmt.Fprintf(w, "Done")
  }
  
  // Similarly we can create varoius handler with the resource as the receiver