使用Rails中的表单将数据从视图传递到控制器

Question

I have been reading rails documents and guides all day and trying out different tutorials all day but nothing seems to help. I currently have a small app which has a stop table, a bus table and a schedule table. The schedule table is a rich join between bus and stop table. I understand the db and model part of rails clearly compared to the controllers and views.

My stop table has a id field, a longitude field, and a latitude field.

I basically want user to input a value for longitude and latitude and then do a query and find out the stop id by matching the user given longitude and latitude in the stop table.

What is the best way to achieve this? In my opinion i can create a form which will let user enter longitude and latitude and i can store that value in some variable and then do a query. I know exactly what i want to do but i don't know how to do it in rails. I am very frustrated and i would appreciate any input.

My code for form in index.html.erb

<%= form_for :welcome do |f| %>

    <%= f.label :longitude %><br>

    <%= f.text_field :longitude %>
    <br>
    <br>
    <%= f.label :latitude %><br>
    <%= f.text_field :latitude %>


  <p>
    <%= f.submit %>
  </p>
<% end %>

My code for controller

class WelcomeController < ApplicationController

  def index
     @long = params[:longitude]
     @lat =  params[:latitude]
  end


end

Please inform me if i am doing something wrong? Also how do i proceed from here onwards? I would really appreciate any help i have been stuck at this same point for the past 8 hours.

Answer 1

First of all, make sure you model is represented in the database, have you run a migration, can you post your schema?

If you are starting from scratch, you could run this command to get up and running quickly with the model:

bin/rails generate model Location latitude:string longitude:string

bin/rake db:migrate

UPDATE: If you don't need the user Location to persist in the database, you can use ActiveModel (skip the above). In the models folder create a location.rb file and create the ActiveModel:

class Location
  include ActiveModel::Model
  attr_accessor :latitude, :longitude
end

Now that Location model is in place, you'll need to save the latitude and longitude using a create method in the controller:

def create
  @location= Location.new(params[:location])

  @location.save
  redirect_to @location
end

UPDATE: now that you've captured the user location, you want to use this information to compare it to your Stop table in order to find the record that is relevant. Here, you'll want to do this work using resque (or other queue) or by making a call to a third-party API like Google maps for example, or use whatever algorithm you've come up with.

You also want to make sure that you have routes, the default CRUD routes can be achieved by:

Rails.application.routes.draw do

  resources :location
end

finally in your view (note I'm using the model name location instead of welcome):

<%= form_for :location do |f| %>
  <p>
    <%= f.label :latitude %><br>
    <%= f.text_field :latitude %>
  </p>

  <p>
    <%= f.label :longitude %><br>
    <%= f.text_area :longitude %>
  </p>

  <p>
    <%= f.submit %>
  </p>
<% end %>

Answer 2

If you want something with a little bit more features, you should try geokit-rails gem , this will let you query stops by coordinates, and get results even if the coordinates aren't exactly, right, it will fetch the closest stops.

• First check the gem page and check how to install the gem.

• Then add the mappable command in your stop model

   class Stop < ActiveRecord::Base acts_as_mappable end 

  note: check the options for acts_as_mappable cause you'll need to change some stuff, like default distance unit and default lat and lng column names

• Then now you could do a query in your controller like this

   class WelcomeController < ApplicationController def index lng = params[:longitude] lat = params[:latitude] Stop.within(5, origin: [lat, lng] end end 

  This will find all the bus stops that are within 5 miles (which is the default distance unit, can be changed to km) from the point you provided in the search

note : The params will probably be scoped inside a :welcome key, so it might be better to whitelist them using strong parameters

def bus_stop_params
  params.require(:welcome).permit(:latitude, :longitude)
end

Answer 3

If I can suggest something: watch this Railscast http://railscasts.com/episodes/273-geocoder?view=asciicast

This will help you achieve what you are looking for it a simpler manner than the route you currently are going down.

Basically what this episode entails is how to use a gem to convert place names to coordinates and vice-versa and even convert IP addresses to street addresses. The Geocoder gem can also find nearby locations with their distance and bearing and has many other useful features.