flash[:notice] in Rails

Flash[:notice] in Rails

In Ruby on Rails, flash is a special hash-like object used to store temporary messages that are intended to be displayed to the user after a redirect. The flash object is commonly used to show success, error, or informational messages that should be visible only once.

Using flash[:notice]

  • Purpose: flash[:notice] is typically used to display general success or informational messages.
  • Example Usage: It is often set in a controller action and then displayed in the view.

Setting a Flash Message

You set a flash message in a controller action. Here's how to do it:

class ArticlesController < ApplicationController def create @article = Article.new(article_params) if @article.save flash[:notice] = "Article was successfully created." redirect_to @article else render :new end end end

In this example, if the article is successfully created, a flash message is set and the user is redirected to the article's show page.

Displaying Flash Messages in Views

To display flash messages in your views, you can check for the presence of flash[:notice] and render it. Here's an example of how you might do it in your layout view (e.g., app/views/layouts/application.html.erb):

<!DOCTYPE html> <html> <head> <title>MyApp</title> <%= csrf_meta_tags %> <%= csp_meta_tag %> <%= stylesheet_link_tag "application", media: "all", "data-turbolinks-track": "reload" %> <%= javascript_pack_tag "application", "data-turbolinks-track": "reload" %> </head> <body> <% if flash[:notice] %> <div class="flash flash-notice"> <%= flash[:notice] %> </div> <% end %> <%= yield %> </body> </html>

In this layout file, if flash[:notice] is set, it will be displayed in a div with the class flash-notice.

Other Flash Types

In addition to flash[:notice], you can use other keys for different types of messages:

  • flash[:alert]: Typically used for error or warning messages.
  • flash[:error]: Sometimes used for error messages, though flash[:alert] is more conventional.

Example:

class ArticlesController < ApplicationController def destroy @article = Article.find(params[:id]) if @article.destroy flash[:notice] = "Article was successfully deleted." else flash[:alert] = "There was an error deleting the article." end redirect_to articles_path end end

And display it in the view similarly:

<% if flash[:alert] %> <div class="flash flash-alert"> <%= flash[:alert] %> </div> <% end %>

Clearing Flash Messages

Flash messages are only available for the next request. After they are displayed once, they are automatically cleared. If you need to clear a flash message before it is displayed, you can do so manually:

flash.now[:notice] = "This will not persist after redirect."

Use flash.now when you need to set a flash message that should be displayed in the current request and not persist after a redirect.

Summary

  • flash[:notice]: Use this to show informational or success messages.
  • Set Flash Messages: In the controller actions.
  • Display Flash Messages: In your views using conditional logic.
  • Other Flash Types: Use flash[:alert] or flash[:error] for different types of messages.

By using flash[:notice], you can provide feedback to users about the results of their actions in a Rails application.

Examples

  1. How to set a flash notice in a Rails controller action?

    # app/controllers/products_controller.rb class ProductsController < ApplicationController def create @product = Product.new(product_params) if @product.save flash[:notice] = 'Product was successfully created.' redirect_to @product else render :new end end end

    Description: This code sets a flash notice when a product is successfully created, which will be displayed on the redirected page.

  2. How to display flash notices in a Rails view?

    <!-- app/views/layouts/application.html.erb --> <!DOCTYPE html> <html> <head> <title>MyApp</title> <%= csrf_meta_tags %> <%= csp_meta_tag %> <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %> <%= javascript_pack_tag 'application', 'data-turbolinks-track': 'reload' %> </head> <body> <% if flash[:notice] %> <p class="flash-notice"><%= flash[:notice] %></p> <% end %> <%= yield %> </body> </html>

    Description: This code displays a flash notice in a layout view if flash[:notice] is present.

  3. How to set a flash notice for a Rails update action?

    # app/controllers/products_controller.rb class ProductsController < ApplicationController def update @product = Product.find(params[:id]) if @product.update(product_params) flash[:notice] = 'Product was successfully updated.' redirect_to @product else render :edit end end end

    Description: This code sets a flash notice when a product is successfully updated.

  4. How to use flash messages for error handling in Rails?

    # app/controllers/products_controller.rb class ProductsController < ApplicationController def create @product = Product.new(product_params) if @product.save flash[:notice] = 'Product was successfully created.' redirect_to @product else flash[:alert] = 'Error creating product. Please try again.' render :new end end end

    Description: This code uses flash[:alert] for error messages when creating a product fails.

  5. How to use flash messages with before_action in Rails?

    # app/controllers/products_controller.rb class ProductsController < ApplicationController before_action :set_product, only: [:show, :edit, :update, :destroy] def destroy if @product.destroy flash[:notice] = 'Product was successfully deleted.' else flash[:alert] = 'Error deleting product.' end redirect_to products_url end private def set_product @product = Product.find(params[:id]) end end

    Description: This code sets flash messages before redirecting after a product is destroyed, using before_action to find the product.

  6. How to handle flash notices with partials in Rails views?

    <!-- app/views/layouts/application.html.erb --> <body> <%= render 'shared/flash_messages' %> <%= yield %> </body> 
    <!-- app/views/shared/_flash_messages.html.erb --> <% flash.each do |type, message| %> <div class="flash <%= type %>"><%= message %></div> <% end %>

    Description: This code handles flash messages using a partial _flash_messages.html.erb, allowing for a reusable flash message display.

  7. How to clear flash messages after they are shown?

    # app/controllers/products_controller.rb class ProductsController < ApplicationController def show flash.discard end end

    Description: This code clears flash messages after they are displayed, so they won't persist on subsequent requests.

  8. How to use flash messages with JavaScript for notifications in Rails?

    # app/controllers/products_controller.rb class ProductsController < ApplicationController def create @product = Product.new(product_params) if @product.save flash.now[:notice] = 'Product was successfully created.' render js: "showNotification('#{flash[:notice]}');" else render :new end end end 
    // app/javascript/packs/application.js function showNotification(message) { alert(message); // Use a library or custom function for better UI }

    Description: This code shows flash messages using JavaScript, which can be customized for better user notifications.

  9. How to set multiple flash messages in a Rails action?

    # app/controllers/products_controller.rb class ProductsController < ApplicationController def create @product = Product.new(product_params) if @product.save flash[:notice] = 'Product was successfully created.' flash[:success] = 'Welcome to the products section!' redirect_to @product else flash[:alert] = 'Error creating product.' render :new end end end

    Description: This code demonstrates setting multiple flash messages, each with a different key.

  10. How to use custom flash types in Rails?

    # app/controllers/products_controller.rb class ProductsController < ApplicationController def create @product = Product.new(product_params) if @product.save flash[:success] = 'Product created successfully!' redirect_to @product else flash[:error] = 'Failed to create product.' render :new end end end 
    <!-- app/views/layouts/application.html.erb --> <body> <% if flash[:success] %> <p class="flash-success"><%= flash[:success] %></p> <% end %> <% if flash[:error] %> <p class="flash-error"><%= flash[:error] %></p> <% end %> <%= yield %> </body>

    Description: This code shows how to use custom flash types (:success, :error) and display them with specific styles in the view.

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