returns true if its receiver is a new model object that is one that has never

Returns true if its receiver is a new model object

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returns true if its receiver is a new model object, that is, one that has never been saved in the database. Such objects won’t have ID’s. Project 4.6. The dropdown menus for Release Date don’t allow adding movies released earlier than 2006. Modify it to allow movies as early as 1930. (Hint: check the documentation for the date_select helper used in the form.) Project 4.7. The description field of a movie was created as part of the initial migration, but cannot be edited. Make the necessary changes so that the description is visible and editable in the New and Edit views. Hint: you should only need to change two files. Project 4.8. Our current controller methods aren’t very robust: if the user manually enters a URI to Show a movie that doesn’t exist (for example /movies/99999 ), she will see an ugly exception message. Modify the show method in the controller so that if the requested movie doesn’t exist, the user is redirected to the Index view with a friendly message explaining that no movie with the given ID could be found. (Hint: use begin...rescue...end to rescue from ActiveRecord::RecordNotFound .) Project 4.9. Putting it all together exercise: Write and deploy a Rails app that scrapes some information from a Web page using Nokogiri’s XPath features, and turns it into an RSS feed using Builder. Verify that you can subscribe to the RSS feed in your browser or RSS news reader.
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5. SaaS Framework: Advanced Rails Kristen Nygaard (left, 1926–2002) and Ole-Johan Dahl (right, 1931–2002) shared the 2001 Turing Award for inventing fundamental OO concepts including objects, classes, and inheritance, and demonstrating them in Simula, the ancestor of every OO language. Programming is understanding. Kristen Nygaard
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5.1 DRYing Out MVC: Partials, Validations and Filters 5.2 Single Sign-On and Third-Party Authentication 5.3 Associations and Foreign Keys 5.4 Through-Associations 5.5 RESTful Routes for Associations 5.6 Composing Queries With Reusable Scopes 5.7 Fallacies and Pitfalls 5.8 Concluding Remarks: Languages, Productivity, and Beauty 5.9 To Learn More 5.10 Suggested Projects Concepts This chapter covers advanced features of Rails that you can use to make your code more DRY and concise, including how to reuse entire external services such as Twitter to integrate with your apps. Rails mechanisms such as controller filters, model lifecycle hooks, and model validations provide a limited form of aspect-oriented programming , which allows code about crosscutting concerns to be centralized in a single place and automatically called when needed. ActiveRecord associations use metaprogramming and reflection to map relationships among resources in your app, such as “belongs to” or “has many”, to queries that mirror those relationships in the app’s database. ActiveRecord scopes are composable “filters” you can define on your model data, enabling DRY reuse of model logic.
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5.1 DRYing Out MVC: Partials, Validations and Filters We’ll focus our discussion of DRYness on the three elements of MVC, starting with Views. As Section 6.6 explains, the partial is also the basic unit of view updating for JavaScript-enabled pages.
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  • Spring '19
  • Dr.Marcos

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