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Rails >= 3 comes with HTTP caching abilities out of the box. This uses the Cache-Control and ETag headers to control how long a client or intermediary (such as a CDN) can cache a page. In a controller action, use expires_in to set the length of caching for that action: def show @user = User....

Imagine the following situation: foo :: Show a => (a -> String) -> String -> Int -> IO () foo show' string int = do putStrLn (show' string) putStrLn (show' int) Here, we want to pass in a function that converts a value into a String, apply that function to both a string p...

To generate a new mailer, enter the following command rails generate mailer PostMailer This will generate a blank template file in app/mailers/post_mailer.rb named PostMailer class PostMailer < ApplicationMailer end Two layout files will also be generated for the email view, one for the...

added in GHC 7.8. OverloadedLists, similar to OverloadedStrings, allows list literals to be desugared as follows: [] -- fromListN 0 [] [x] -- fromListN 1 (x : []) [x .. ] -- fromList (enumFrom x) This comes handy when dealing with types such as Set, Vector and Maps. ['0'...

“Fat Model, Skinny Controller” refers to how the M and C parts of MVC ideally work together. Namely, any non-response-related logic should go in the model, ideally in a nice, testable method. Meanwhile, the “skinny” controller is simply a nice interface between the view and model. In practice, this...

GCD will guarantee that your singleton only gets instantiated once, even if called from multiple threads. Insert this into any class for a singleton instance called shared. + (instancetype)shared { // Variable that will point to the singleton instance. The `static` // modifier makes it ...

To differentiate between plural and singular strings, you can define a plural in your strings.xml file and list the different quantities, as shown in the example below: <?xml version="1.0" encoding="utf-8"?> <resources> <plurals name="hello_people&quo...

Given a file file.txt with the following content: line 1 line 2 line 3 You can add a new line after first matching line with the a command. For portable use the a command must be followed immediately by an escaped newline, with the text-to-append on its own line or lines. sed ' /line 2/a\ ...

xml of the Dialog: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="mat...

String filename = "image.png"; String imagePath = getExternalFilesDir() + "/" + filename; Picasso.with(context) .load(new File(imagePath)) .into(imageView);

Add below to your build.gradle out of android tag: // Apply plug-in to app. apply plugin: 'com.google.gms.google-services' Add below helper class to your util package: /** * Created by Andy */ public class GoogleSignInHelper implements GoogleApiClient.OnConnectionFailedListener, ...

Rails provides a lot of generators, for controllers too of course. You can generate a new controller by running this command in your app folder rails generate controller NAME [action action] [options] Note: You can also use rails g alias to invoke rails generate For example, to generate a cont...

You can rescue a RecordNotFound exception with a redirect instead of showing an error page: class ApplicationController < ActionController::Base # your other stuff rescue_from ActiveRecord::RecordNotFound do |exception| redirect_to root_path, 404, alert: I18n.t("errors.record...

Configuration files for rails can be found in config/environments/. By default rails has 3 environments, development, production and test. By editing each file you are editing the configuration for that environment only. Rails also has a configuration file in config/application.rb. This is a common...

Database configuration of a rails project lies in a file config/database.yml. If you create a project using rails new command and don't specify a database engine to be used then rails uses sqlite as the default database. A typical database.yml file with default configuration will look similar to fol...

Callbacks offer a way to extend the functionality of a function (or method) without changing its code. This approach is often used in modules (libraries / plugins), the code of which is not supposed to be changed. Suppose we have written the following function, calculating the sum of a given array ...

You can get a Model class from a Controller name this way (context is Controller class): class MyModelController < ActionController::Base # Returns corresponding model class for this controller # @return [ActiveRecord::Base] def corresponding_model_class # ... add some validation...

In the case of a multi-project gradle build, you may sometimes need to depend on another project in your build. To accomplish this, you'd enter the following in your project's dependencies: dependencies { compile project(':OtherProject') } Where ':OtherProject' is the gradle path for the p...

Testing your Active Record models through your command line interface is simple. Navigate to the app directory in your terminal and type in rails console to start the Rails console. From here, you can run active record methods on your database. For example, if you had a database schema with a User...

Consumable Managed Products are products that can be bought multiple times such as in-game currency, game lives, power-ups, etc. In this example, we are going to implement 4 different consumable managed products "item1", "item2", "item3", "item4". Steps in...