lucas leitao - Page 10 - Developer IT

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Do you play Sudoku ?

- by Gilles Haro

Did you know that 11gR2 database could solve a Sudoku puzzle with a single query and, most of the time, and this in less than a second ? The following query shows you how ! Simply pass a flattened Sudoku grid to it a get the result instantaneously ! col "Solution" format a9 col "Problem" format a9 with Iteration( initialSudoku, Step, EmptyPosition ) as ( select initialSudoku, InitialSudoku, instr( InitialSudoku, '-' ) from ( select '--64----2--7-35--1--58-----27---3--4---------4--2---96-----27--7--58-6--3----18--' InitialSudoku from dual ) union all select initialSudoku , substr( Step, 1, EmptyPosition - 1 ) || OneDigit || substr( Step, EmptyPosition + 1 ) , instr( Step, '-', EmptyPosition + 1 ) from Iteration , ( select to_char( rownum ) OneDigit from dual connect by rownum <= 9 ) OneDigit where EmptyPosition > 0 and not exists ( select null from ( select rownum IsPossible from dual connect by rownum <= 9 ) where OneDigit = substr( Step, trunc( ( EmptyPosition - 1 ) / 9 ) * 9 + IsPossible, 1 ) -- One line must contain the 1-9 digits or OneDigit = substr( Step, mod( EmptyPosition - 1, 9 ) - 8 + IsPossible * 9, 1 ) -- One row must contain the 1-9 digits or OneDigit = substr( Step, mod( trunc( ( EmptyPosition - 1 ) / 3 ), 3 ) * 3 -- One square must contain the 1-9 digits + trunc( ( EmptyPosition - 1 ) / 27 ) * 27 + IsPossible + trunc( ( IsPossible - 1 ) / 3 ) * 6 , 1 ) ) ) select initialSudoku "Problem", Step "Solution" from Iteration where EmptyPosition = 0 ; The Magic thing behind this is called Recursive Subquery Factoring. The Oracle documentation gives the following definition: If a subquery_factoring_clause refers to its own query_name in the subquery that defines it, then the subquery_factoring_clause is said to be recursive. A recursive subquery_factoring_clause must contain two query blocks: the first is the anchor member and the second is the recursive member. The anchor member must appear before the recursive member, and it cannot reference query_name. The anchor member can be composed of one or more query blocks combined by the set operators: UNION ALL, UNION, INTERSECT or MINUS. The recursive member must follow the anchor member and must reference query_name exactly once. You must combine the recursive member with the anchor member using the UNION ALL set operator. This new feature is a replacement of this old Hierarchical Query feature that exists in Oracle since the days of Aladdin (well, at least, release 2 of the database in 1977). Everyone remembers the old syntax : select empno, ename, job, mgr, level from emp start with mgr is null connect by prior empno = mgr; that could/should be rewritten (but not as often as it should) as withT_Emp (empno, name, level) as ( select empno, ename, job, mgr, level from emp start with mgr is null connect by prior empno = mgr ) select * from T_Emp; which uses the "with" syntax, whose main advantage is to clarify the readability of the query. Although very efficient, this syntax had the disadvantage of being a Non-Ansi Sql Syntax. Ansi-Sql version of Hierarchical Query is called Recursive Subquery Factoring. As of 11gR2, Oracle got compliant with Ansi Sql and introduced Recursive Subquery Factoring. It is basically an extension of the "With" clause that enables recursion. Now, the new syntax for the query would be with T_Emp (empno, name, job, mgr, hierlevel) as ( select E.empno, E.ename, E.job, E.mgr, 1 from emp E where E.mgr is null union all select E.empno, E.ename, E.job, E.mgr, T.hierlevel + 1from emp E join T_Emp T on ( E.mgr = T.empno ) ) select * from T_Emp; The anchor member is a replacement for the "start with" The recursive member is processed through iterations. It joins the Source table (EMP) with the result from the Recursive Query itself (T_Emp) Each iteration works with the results of all its preceding iterations. Iteration 1 works on the results of the first query Iteration 2 works on the results of Iteration 1 and first query Iteration 3 works on the results of Iteration 1, Iteration 2 and first query. So, knowing that, the Sudoku query it self-explaining; The anchor member contains the "Problem" : The Initial Sudoku and the Position of the first "hole" in the grid. The recursive member tries to replace the considered hole with any of the 9 digit that would satisfy the 3 rules of sudoku Recursion progress through the grid until it is complete. Another example : Fibonaccy Numbers : un = (un-1) + (un-2) with Fib (u1, u2, depth) as (select 1, 1, 1 from dual union all select u1+u2, u1, depth+1 from Fib where depth<10) select u1 from Fib; Conclusion Oracle brings here a new feature (which, to be honest, already existed on other concurrent systems) and extends the power of the database to new boundaries. It’s now up to developers to try and test it and find more useful application than solving puzzles… But still, solving a Sudoku in less time it takes to say it remains impressive… Interesting links: You might be interested by the following links which cover different aspects of this feature Oracle Documentation Lucas Jellema 's Blog Fibonaci Numbers

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CodePlex Daily Summary for Friday, June 06, 2014

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CodePlex Daily Summary for Friday, December 03, 2010

CodePlex Daily Summary for Friday, December 03, 2010Popular ReleasesChronos WPF: Chronos v2.0 Beta 3: Release notes: Updated introduction document. Updated Visual Studio 2010 Extension (vsix) package. Added horizontal scrolling to the main window TaskBar. Added new styles for ListView, ListViewItem, GridViewColumnHeader, ... Added a new WindowViewModel class (allowing to fetch data). Added a new Navigate method (with several overloads) to the NavigationViewModel class (protected). Reimplemented Task usage for the WorkspaceViewModel.OnDelete method. Removed the reflection effect...MDownloader: MDownloader-0.15.26.7024: Fixed updater; Fixed MegauploadDJ - jQuery WebControls for ASP.NET: DJ 1.2: What is new? Update to support jQuery 1.4.2 Update to support jQuery ui 1.8.6 Update to Visual Studio 2010 New WebControls with samples added Autocomplete WebControl Button WebControl ToggleButt WebControl The example web site is including in source code project.LateBindingApi.Excel: LateBindingApi.Excel Release 0.7g: Unterschiede zur Vorgängerversion: - Zusätzliche Interior Properties - Group / Ungroup Methoden für Range - Bugfix COM Reference Handling für Application Objekt in einigen Klassen Release+Samples V0.7g: - Enthält Laufzeit DLL und Beispielprojekte Beispielprojekte: COMAddinExample - Demonstriert ein versionslos angebundenes COMAddin Example01 - Background Colors und Borders für Cells Example02 - Font Attributes undAlignment für Cells Example03 - Numberformats Example04 - Shapes, WordArts, P...ESRI ArcGIS Silverlight Toolkit: November 2010 - v2.1: ESRI ArcGIS Silverlight Toolkit v2.1 Added Windows Phone 7 build. New controls added: InfoWindow ChildPage (Windows Phone 7 only) See what's new here full details for : http://help.arcgis.com/en/webapi/silverlight/help/#/What_s_new_in_2_1/016600000025000000/ Note: Requires Visual Studio 2010, .NET 4.0 and Silverlight 4.0.ASP .NET MVC CMS (Content Management System): Atomic CMS 2.1.1: Atomic CMS 2.1.1 release notes Atomic CMS installation guide Winware: Winware 3.0 (.Net 4.0): Winware 3.0 is base on .Net 4.0 with C#. Please open it with Visual Studio 2010. This release contains a lab web application.UltimateJB: UltimateJB 2.02 PL3 KAKAROTO + CE-X-3.41 EvilSperm: Voici une version attendu avec impatience pour beaucoup : - La Version CEX341 pour pouvoir jouer avec des jeux demandant le firmware 3.50 ( certain ne fonctionne tous simplement pas ). - Pour l'instant le CEX341 n'est disponible qu'avec les PS3 en firmwares 3.41 !!! - La version PL3 KAKAROTO intégre ses dernières modification et intégre maintenant le firmware 3.30 !!! Conclusion : - UltimateJB CEX341 => Spoof le Firmware 3.41 en 3.50 ( facilite l'utilisation de certain jeux avec openManage...EnhSim: EnhSim 2.1.1: 2.1.1This release adds in the changes for 4.03a. To use this release, you must have the Microsoft Visual C++ 2010 Redistributable Package installed. This can be downloaded from http://www.microsoft.com/downloads/en/details.aspx?FamilyID=A7B7A05E-6DE6-4D3A-A423-37BF0912DB84 To use the GUI you must have the .NET 4.0 Framework installed. This can be downloaded from http://www.microsoft.com/downloads/en/details.aspx?FamilyID=9cfb2d51-5ff4-4491-b0e5-b386f32c0992 - Switched Searing Flames bac...AI: Initial 0.0.1: It’s simply just one code file; it simulates AI and machine in a simulated world. The AI has a little understanding of its body machine and parts, and able to use its feet to do actions just start and stop walking. The world is all of white with nothing but just the machine on a white planet. Colors, odors and position information make no sense. I’m previous C# programmer and I’m learning F# during this project, although I’m still not a good F# programmer, in this project I learning to prog...NKinect: NKinect Preview: Build features: Accelerometer reading Motor serial number property Realtime image update Realtime depth calculation Export to PLY (On demand) Control motor LED Control Kinect tiltMicrosoft - Domain Oriented N-Layered .NET 4.0 App Sample (Microsoft Spain): V1.0 - N-Layer DDD Sample App .NET 4.0: Required Software (Microsoft Base Software needed for Development environment) Visual Studio 2010 RTM & .NET 4.0 RTM (Final Versions) Expression Blend 4 SQL Server 2008 R2 Express/Standard/Enterprise Unity Application Block 2.0 - Published May 5th 2010 http://www.microsoft.com/downloads/en/details.aspx?FamilyID=2D24F179-E0A6-49D7-89C4-5B67D939F91B&displaylang=en http://unity.codeplex.com/releases/view/31277 PEX & MOLES 0.94.51023.0, 29/Oct/2010 - Visual Studio 2010 Power Tools http://re...Sense/Net Enterprise Portal & ECMS: SenseNet 6.0.1 Community Edition: Sense/Net 6.0.1 Community Edition This half year we have been working quite fiercely to bring you the long-awaited release of Sense/Net 6.0. Download this Community Edition to see what we have been up to. These months we have worked on getting the WebCMS capabilities of Sense/Net 6.0 up to par. New features include: New, powerful page and portlet editing experience. HTML and CSS cleanup, new, powerful site skinning system. Upgraded, lightning-fast indexing and query via Lucene. Limita...Minecraft GPS: Minecraft GPS 1.1.1: New Features Compass! New style. Set opacity on main window to allow overlay of Minecraft. Open World in any folder. Fixes Fixed style so listbox won't grow the window size. Fixed open file dialog issue on non-vista kernel machines.DotSpatial: DotSpatial 11-28-2001: This release introduces some exciting improvements. Support for big raster, both in display and changing the scheme. Faster raster scheme creation for all rasters. Caching of the "sample" values so once obtained the raster symbolizer dialog loads faster. Reprojection supported for raster and image classes. Affine transform fully supported for images and rasters, so skewed images are now possible. Projection uses better checks when loading unprojected layers. GDAL raster support f...Virtu: Virtu 0.9.0: Source Requirements.NET Framework 4 Visual Studio 2010 or Visual Studio 2010 Express Silverlight 4 Tools for Visual Studio 2010 Windows Phone 7 Developer Tools (which includes XNA Game Studio 4) Binaries RequirementsSilverlight 4 .NET Framework 4 XNA Framework 4SuperWebSocket: SuperWebSocket(60438): It is the first release of SuperWebSocket. Because it is base on SuperSocket, most features of SuperSocket are supported in SuperWebSocket. The source code include a LiveChat demo.Cropper: 1.9.4: Mostly fixes for issues with a few feature requests. Fixed Issues 2730 & 3638 & 14467 11044 11447 11448 11449 14665 Implemented Features 6123 11581PFC: PFC for PB 11.5: This is just a migration from the 11.0 code. No changes have been made yet (and they are needed) for it to work properly with 11.5.PDF Rider: PDF Rider 0.5: This release does not add any new feature for pdf manipulation, but enables automatic updates checking, so it is reccomended to install it in order to stay updated with next releases. Prerequisites * Microsoft Windows Operating Systems (XP - Vista - 7) * Microsoft .NET Framework 3.5 runtime * A PDF rendering software (i.e. Adobe Reader) that can be opened inside Internet Explorer. Installation instructionsChoose one of the following methods: 1. Download and run the "pdfRider0...New Projects.Net MVC Dialog Authentication Starter: .Net MVC Dialog Authentication Starter is the basic .Net MVC application starter template that has been modified to render the Register and Logon functionality via a modal dialog. It is developed using .Net MVC 2, Jquery 1.4.1, and Jquery UI 1.8.6..Net SQL Generator: Generation tool for random queries in SQL in the Windows environment. Can produce random queries, tables, deletes, and updates as well as generate random data for a table. Structured to allow easy adaptation for other SQL implementations as well.10010dshjlahfajhflkjhkjhherkjhfkja: 10010dshjlahfajhflkjhkjhherkjhfkjaBanshee: MOSS 2007 utility to detect authored links and headings in navigation structure of a site collection which point to the subweb's root instead of the subweb's welcome page. It's developed in C# and requires MOSS 2007 SP2 or later.Counter Strike Live Level editor: What is CSLIVE? A web browser based online 2d Shooter. It is clone of Counter Strike. Game supports the multiplayer game over internet or lan. And its Free to play! open souce! This project is still in development. Official open beta tests will be ran every day 20:00 - 21:00 +2GTCRM 2011 Style Templates: CRM 2011 Style Templates.DarkTimes: Having many projects at the sames time ? need an easy way to count those times ? here is a windows phone 7 app for this ^^ --------------------- Vous avez plusieurs projets en même temps ? besoin d'un moyen simple de compter ces temps ? voici une appli windows phone 7 pour ca ^^DSN Export-o-Matic 3000: DSN Export-o-Matic 3000 is a Windows application which allows you to export ODBC DSN Registry settings to a .reg file which can then be imported on another computer. It is written in C#.NET using Visual C# 2010 Express Edition.DYSS Game and AGE Game Engine for XNA: Did You Slay Something? (Working title) and AGE Game Engine for XNA Developed by Lucas LoreggiaExeCryptorNetWrapper: .NET Wrapper for ExeCryptor product (serial number checking functionalities only)ffmpegYAG: ffmpegYAG is a GUI for the popular ffmpeg audio/video processing toolFluentScheduler: A task scheduler that uses fluent interface to configure schedules. Useful for running cron jobs/automated tasks from your application. General Purpose Hash Function Algorithms: The General Purpose Hash Functions Library has the following mix of additive and rotative general purpose string hashing algorithms. HD Web FileManager: Incercam sa facem un singur fisier asp.net care sa faca managementul fisierelor pe un server web.iConverter: iConverter ?????????????。 iConverter is a character transcoding encoding conversion tool.LHA Social Work: Source control host for http://lhasocialwork.org.Mega Puzzle WP7: Mega Puzzle its a Puzzle game in Silverlight that run in Windows Phone 7.It's developed in C#MTConnect Managed Agent SDK: The MTConnect Managed SDK provides an Agent object model to facilitate exposing MTConnect data from your machine tools.Nebula - Image Lock / Unlock Software: Nebula - Image ( Jpg / bmp ) file lock / unlock software designed for simply changing file extension, so that files will be visible on HDD but not unless you change the extension. Written in Perl + Compiled into exe.Pushing - A Sokoban like Puzzle game: Pushing is a C# port of a little hobby project I created some years ago in C++. It's a Sokoban like Puzzle game. The old C++ version was just a 2D/Pseudo 3D Game, the new C# version will be a real 3D Game.RESTController: Provides a base class implementation for a RESTful controller model. Provides common functionality for the basic controller actions of List, Show, New, Edit, and Delete. It's meant to remove as much of the redundant code for MVC controllers as possible.Scientific Calculator ZENO-5000: HTML 5, CSS 3, jQuery: Scientific Calculator ZENO-5000 is a lightweight web application (<40kb), utilizing latest HTML5/CSS3 features and client-side jQuery/Java scripting. Application does not include any graphic files. It is portable, capable of running in online/offline modes on PC/mobile devicesSCR-Airplane Autopilot System: Automatyczny pilot samolotu - projekt na zaliczenie przedmiotu Systemy Czasu RzeczywistegoScriptonite: A lightweight system for scripting gameplay events for games such as RPGs. After integrating Scriptonite into your project, you create scripted events using an incredibly simple scripting language. Intended for XNA, but should work anywhere.Shelf: Shelf is a .NET library of common extension methods.SQLite ADO.NET for Windows Phone: Windows Phone is missing SQLite. This project fixes that :) And does so by giving the community the interfaces we've grown to know and love; IDbConnection, IDbCommand, IDbTransaction and, IDbReader. Thanks so much to the pioneers before me who ported the c++ to c#!Tailf: Tailf is a C# implementation of the tail -f command available on unix/linux systems. Differently form other ports it does not lock the file in any way so it works even if other rename the file: this is expecially designed to works well with log4net rolling file appender.TeamBrain: TeamBrain helps project teams to centralise all knowledge about a project into a repository that is clean and a pleasure to use.TeamDev JQuery c# wrapper: C# jQuery Wrapper. Helps you to write correct jQuery functions in c# language. The code you write will be traduced into correct jQuery methods calls. VirtualEye: Virtual Eye...Win32 Registry Activity Monitor: A simple program written in Delphi that monitors registry activity on win32 systems. In short a registry key and class are statically added to the code, the program is then run and as changes are made by other applications to the key and all its sub keys the changes are logged anXamlCode: XamlCode provides support for embedding inline C# code directly in the xaml files to create simple value converters, value providers and validation rules. It's targeted mainly as a rapid WPF application development tool.

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An Introduction to Meteor

- by Stephen.Walther

The goal of this blog post is to give you a brief introduction to Meteor which is a framework for building Single Page Apps. In this blog entry, I provide a walkthrough of building a simple Movie database app. What is special about Meteor? Meteor has two jaw-dropping features: Live HTML – If you make any changes to the HTML, CSS, JavaScript, or data on the server then every client shows the changes automatically without a browser refresh. For example, if you change the background color of a page to yellow then every open browser will show the new yellow background color without a refresh. Or, if you add a new movie to a collection of movies, then every open browser will display the new movie automatically. With Live HTML, users no longer need a refresh button. Changes to an application happen everywhere automatically without any effort. The Meteor framework handles all of the messy details of keeping all of the clients in sync with the server for you. Latency Compensation – When you modify data on the client, these modifications appear as if they happened on the server without any delay. For example, if you create a new movie then the movie appears instantly. However, that is all an illusion. In the background, Meteor updates the database with the new movie. If, for whatever reason, the movie cannot be added to the database then Meteor removes the movie from the client automatically. Latency compensation is extremely important for creating a responsive web application. You want the user to be able to make instant modifications in the browser and the framework to handle the details of updating the database without slowing down the user. Installing Meteor Meteor is licensed under the open-source MIT license and you can start building production apps with the framework right now. Be warned that Meteor is still in the “early preview” stage. It has not reached a 1.0 release. According to the Meteor FAQ, Meteor will reach version 1.0 in “More than a month, less than a year.” Don’t be scared away by that. You should be aware that, unlike most open source projects, Meteor has financial backing. The Meteor project received an $11.2 million round of financing from Andreessen Horowitz. So, it would be a good bet that this project will reach the 1.0 mark. And, if it doesn’t, the framework as it exists right now is still very powerful. Meteor runs on top of Node.js. You write Meteor apps by writing JavaScript which runs both on the client and on the server. You can build Meteor apps on Windows, Mac, or Linux (Although the support for Windows is still officially unofficial). If you want to install Meteor on Windows then download the MSI from the following URL: http://win.meteor.com/ If you want to install Meteor on Mac/Linux then run the following CURL command from your terminal: curl https://install.meteor.com | /bin/sh Meteor will install all of its dependencies automatically including Node.js. However, I recommend that you install Node.js before installing Meteor by installing Node.js from the following address: http://nodejs.org/ If you let Meteor install Node.js then Meteor won’t install NPM which is the standard package manager for Node.js. If you install Node.js and then you install Meteor then you get NPM automatically. Creating a New Meteor App To get a sense of how Meteor works, I am going to walk through the steps required to create a simple Movie database app. Our app will display a list of movies and contain a form for creating a new movie. The first thing that we need to do is create our new Meteor app. Open a command prompt/terminal window and execute the following command: Meteor create MovieApp After you execute this command, you should see something like the following: Follow the instructions: execute cd MovieApp to change to your MovieApp directory, and run the meteor command. Executing the meteor command starts Meteor on port 3000. Open up your favorite web browser and navigate to http://localhost:3000 and you should see the default Meteor Hello World page: Open up your favorite development environment to see what the Meteor app looks like. Open the MovieApp folder which we just created. Here’s what the MovieApp looks like in Visual Studio 2012: Notice that our MovieApp contains three files named MovieApp.css, MovieApp.html, and MovieApp.js. In other words, it contains a Cascading Style Sheet file, an HTML file, and a JavaScript file. Just for fun, let’s see how the Live HTML feature works. Open up multiple browsers and point each browser at http://localhost:3000. Now, open the MovieApp.html page and modify the text “Hello World!” to “Hello Cruel World!” and save the change. The text in all of the browsers should update automatically without a browser refresh. Pretty amazing, right? Controlling Where JavaScript Executes You write a Meteor app using JavaScript. Some of the JavaScript executes on the client (the browser) and some of the JavaScript executes on the server and some of the JavaScript executes in both places. For a super simple app, you can use the Meteor.isServer and Meteor.isClient properties to control where your JavaScript code executes. For example, the following JavaScript contains a section of code which executes on the server and a section of code which executes in the browser: if (Meteor.isClient) { console.log("Hello Browser!"); } if (Meteor.isServer) { console.log("Hello Server!"); } console.log("Hello Browser and Server!"); When you run the app, the message “Hello Browser!” is written to the browser JavaScript console. The message “Hello Server!” is written to the command/terminal window where you ran Meteor. Finally, the message “Hello Browser and Server!” is execute on both the browser and server and the message appears in both places. For simple apps, using Meteor.isClient and Meteor.isServer to control where JavaScript executes is fine. For more complex apps, you should create separate folders for your server and client code. Here are the folders which you can use in a Meteor app: · client – This folder contains any JavaScript which executes only on the client. · server – This folder contains any JavaScript which executes only on the server. · common – This folder contains any JavaScript code which executes on both the client and server. · lib – This folder contains any JavaScript files which you want to execute before any other JavaScript files. · public – This folder contains static application assets such as images. For the Movie App, we need the client, server, and common folders. Delete the existing MovieApp.js, MovieApp.html, and MovieApp.css files. We will create new files in the right locations later in this walkthrough. Combining HTML, CSS, and JavaScript Files Meteor combines all of your JavaScript files, and all of your Cascading Style Sheet files, and all of your HTML files automatically. If you want to create one humongous JavaScript file which contains all of the code for your app then that is your business. However, if you want to build a more maintainable application, then you should break your JavaScript files into many separate JavaScript files and let Meteor combine them for you. Meteor also combines all of your HTML files into a single file. HTML files are allowed to have the following top-level elements: <head> — All <head> files are combined into a single <head> and served with the initial page load. <body> — All <body> files are combined into a single <body> and served with the initial page load. <template> — All <template> files are compiled into JavaScript templates. Because you are creating a single page app, a Meteor app typically will contain a single HTML file for the <head> and <body> content. However, a Meteor app typically will contain several template files. In other words, all of the interesting stuff happens within the <template> files. Displaying a List of Movies Let me start building the Movie App by displaying a list of movies. In order to display a list of movies, we need to create the following four files: · client\movies.html – Contains the HTML for the <head> and <body> of the page for the Movie app. · client\moviesTemplate.html – Contains the HTML template for displaying the list of movies. · client\movies.js – Contains the JavaScript for supplying data to the moviesTemplate. · server\movies.js – Contains the JavaScript for seeding the database with movies. After you create these files, your folder structure should looks like this: Here’s what the client\movies.html file looks like: <head> <title>My Movie App</title> </head> <body> <h1>Movies</h1> {{> moviesTemplate }} </body> Notice that it contains <head> and <body> top-level elements. The <body> element includes the moviesTemplate with the syntax {{> moviesTemplate }}. The moviesTemplate is defined in the client/moviesTemplate.html file: <template name="moviesTemplate"> <ul> {{#each movies}} <li> {{title}} </li> {{/each}} </ul> </template> By default, Meteor uses the Handlebars templating library. In the moviesTemplate above, Handlebars is used to loop through each of the movies using {{#each}}…{{/each}} and display the title for each movie using {{title}}. The client\movies.js JavaScript file is used to bind the moviesTemplate to the Movies collection on the client. Here’s what this JavaScript file looks like: // Declare client Movies collection Movies = new Meteor.Collection("movies"); // Bind moviesTemplate to Movies collection Template.moviesTemplate.movies = function () { return Movies.find(); }; The Movies collection is a client-side proxy for the server-side Movies database collection. Whenever you want to interact with the collection of Movies stored in the database, you use the Movies collection instead of communicating back to the server. The moviesTemplate is bound to the Movies collection by assigning a function to the Template.moviesTemplate.movies property. The function simply returns all of the movies from the Movies collection. The final file which we need is the server-side server\movies.js file: // Declare server Movies collection Movies = new Meteor.Collection("movies"); // Seed the movie database with a few movies Meteor.startup(function () { if (Movies.find().count() == 0) { Movies.insert({ title: "Star Wars", director: "Lucas" }); Movies.insert({ title: "Memento", director: "Nolan" }); Movies.insert({ title: "King Kong", director: "Jackson" }); } }); The server\movies.js file does two things. First, it declares the server-side Meteor Movies collection. When you declare a server-side Meteor collection, a collection is created in the MongoDB database associated with your Meteor app automatically (Meteor uses MongoDB as its database automatically). Second, the server\movies.js file seeds the Movies collection (MongoDB collection) with three movies. Seeding the database gives us some movies to look at when we open the Movies app in a browser. Creating New Movies Let me modify the Movies Database App so that we can add new movies to the database of movies. First, I need to create a new template file – named client\movieForm.html – which contains an HTML form for creating a new movie: <template name="movieForm"> <fieldset> <legend>Add New Movie</legend> <form> <div> <label> Title: <input id="title" /> </label> </div> <div> <label> Director: <input id="director" /> </label> </div> <div> <input type="submit" value="Add Movie" /> </div> </form> </fieldset> </template> In order for the new form to show up, I need to modify the client\movies.html file to include the movieForm.html template. Notice that I added {{> movieForm }} to the client\movies.html file: <head> <title>My Movie App</title> </head> <body> <h1>Movies</h1> {{> moviesTemplate }} {{> movieForm }} </body> After I make these modifications, our Movie app will display the form: The next step is to handle the submit event for the movie form. Below, I’ve modified the client\movies.js file so that it contains a handler for the submit event raised when you submit the form contained in the movieForm.html template: // Declare client Movies collection Movies = new Meteor.Collection("movies"); // Bind moviesTemplate to Movies collection Template.moviesTemplate.movies = function () { return Movies.find(); }; // Handle movieForm events Template.movieForm.events = { 'submit': function (e, tmpl) { // Don't postback e.preventDefault(); // create the new movie var newMovie = { title: tmpl.find("#title").value, director: tmpl.find("#director").value }; // add the movie to the db Movies.insert(newMovie); } }; The Template.movieForm.events property contains an event map which maps event names to handlers. In this case, I am mapping the form submit event to an anonymous function which handles the event. In the event handler, I am first preventing a postback by calling e.preventDefault(). This is a single page app, no postbacks are allowed! Next, I am grabbing the new movie from the HTML form. I’m taking advantage of the template find() method to retrieve the form field values. Finally, I am calling Movies.insert() to insert the new movie into the Movies collection. Here, I am explicitly inserting the new movie into the client-side Movies collection. Meteor inserts the new movie into the server-side Movies collection behind the scenes. When Meteor inserts the movie into the server-side collection, the new movie is added to the MongoDB database associated with the Movies app automatically. If server-side insertion fails for whatever reasons – for example, your internet connection is lost – then Meteor will remove the movie from the client-side Movies collection automatically. In other words, Meteor takes care of keeping the client Movies collection and the server Movies collection in sync. If you open multiple browsers, and add movies, then you should notice that all of the movies appear on all of the open browser automatically. You don’t need to refresh individual browsers to update the client-side Movies collection. Meteor keeps everything synchronized between the browsers and server for you. Removing the Insecure Module To make it easier to develop and debug a new Meteor app, by default, you can modify the database directly from the client. For example, you can delete all of the data in the database by opening up your browser console window and executing multiple Movies.remove() commands. Obviously, enabling anyone to modify your database from the browser is not a good idea in a production application. Before you make a Meteor app public, you should first run the meteor remove insecure command from a command/terminal window: Running meteor remove insecure removes the insecure package from the Movie app. Unfortunately, it also breaks our Movie app. We’ll get an “Access denied” error in our browser console whenever we try to insert a new movie. No worries. I’ll fix this issue in the next section. Creating Meteor Methods By taking advantage of Meteor Methods, you can create methods which can be invoked on both the client and the server. By taking advantage of Meteor Methods you can: 1. Perform form validation on both the client and the server. For example, even if an evil hacker bypasses your client code, you can still prevent the hacker from submitting an invalid value for a form field by enforcing validation on the server. 2. Simulate database operations on the client but actually perform the operations on the server. Let me show you how we can modify our Movie app so it uses Meteor Methods to insert a new movie. First, we need to create a new file named common\methods.js which contains the definition of our Meteor Methods: Meteor.methods({ addMovie: function (newMovie) { // Perform form validation if (newMovie.title == "") { throw new Meteor.Error(413, "Missing title!"); } if (newMovie.director == "") { throw new Meteor.Error(413, "Missing director!"); } // Insert movie (simulate on client, do it on server) return Movies.insert(newMovie); } }); The addMovie() method is called from both the client and the server. This method does two things. First, it performs some basic validation. If you don’t enter a title or you don’t enter a director then an error is thrown. Second, the addMovie() method inserts the new movie into the Movies collection. When called on the client, inserting the new movie into the Movies collection just updates the collection. When called on the server, inserting the new movie into the Movies collection causes the database (MongoDB) to be updated with the new movie. You must add the common\methods.js file to the common folder so it will get executed on both the client and the server. Our folder structure now looks like this: We actually call the addMovie() method within our client code in the client\movies.js file. Here’s what the updated file looks like: // Declare client Movies collection Movies = new Meteor.Collection("movies"); // Bind moviesTemplate to Movies collection Template.moviesTemplate.movies = function () { return Movies.find(); }; // Handle movieForm events Template.movieForm.events = { 'submit': function (e, tmpl) { // Don't postback e.preventDefault(); // create the new movie var newMovie = { title: tmpl.find("#title").value, director: tmpl.find("#director").value }; // add the movie to the db Meteor.call( "addMovie", newMovie, function (err, result) { if (err) { alert("Could not add movie " + err.reason); } } ); } }; The addMovie() method is called – on both the client and the server – by calling the Meteor.call() method. This method accepts the following parameters: · The string name of the method to call. · The data to pass to the method (You can actually pass multiple params for the data if you like). · A callback function to invoke after the method completes. In the JavaScript code above, the addMovie() method is called with the new movie retrieved from the HTML form. The callback checks for an error. If there is an error then the error reason is displayed in an alert (please don’t use alerts for validation errors in a production app because they are ugly!). Summary The goal of this blog post was to provide you with a brief walk through of a simple Meteor app. I showed you how you can create a simple Movie Database app which enables you to display a list of movies and create new movies. I also explained why it is important to remove the Meteor insecure package from a production app. I showed you how to use Meteor Methods to insert data into the database instead of doing it directly from the client. I’m very impressed with the Meteor framework. The support for Live HTML and Latency Compensation are required features for many real world Single Page Apps but implementing these features by hand is not easy. Meteor makes it easy.

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