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• Characters in usernames that cause trouble

  - by acidzombie24

  I am testing out security and reliability issues on my site. I have made \n and \r illegal. I created a user with null in the name which caused my PM system to not message the user. However \b worked and \t didnt allow copy/paste to work correctly. The browser (firefox which i am testing with) copied the tab as a single space causing the name not to be the same thus not recognizing the username. Since i cant copy paste easily i'll probably disallow it. \f works as well although i do see a symbol in the title but nowhere else because of the \f. What else should i try? It appears 0-31 127-159 (i dont understand this range) are illegal. What characters in legal range might i want to disallow? I heard there was a 0 width character space. That may be something i want to disallow? What else is there?

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• SQL: Join multiple tables and get a grouped sum

  - by Scienceprodigy

  I have a database with 3 tables that have related data. One table has transactions, and the other two relate to transaction categories. Basically it's financial data, so each transaction has a category (i.e. "gasoline" for a gas purchase transaction). A short version of my Transactions table looks like this- Transactions Table: ________________________________ | ID | Type | Amount | Category | --------------------------------- I also have two more tables relating a category to a categories parent. So basically, every Category entry in the Transactions Table belongs to a parent category (i.e. "gasoline" would belong to say "Automotive Expenses"). For categories, and their parent, I have two tables - Category Children: ____________________________________________ | ID | Parent Category ID | Child Category | -------------------------------------------- Category Parent: ________________________ | ID | Parent Category | ------------------------ What I'm trying to do is query the database and have it return a total spending by parent category. To get "spending" the Type of transactions must be "Debit". I tried the following statement: SELECT category_parents.parent_category, SUM(amount) AS totals FROM (transactions INNER JOIN category_children ON transactions.category = 'category_children.child_category') INNER JOIN category_parents ON category_children.parent_category_id = category_parents._id WHERE trans_type = 'Debit' GROUP BY parent_category ORDER BY totals DESC but it gives me the following exception: 12-31 13:51:21.515: ERROR/Exception on query(4403): android.database.sqlite.SQLiteException: no such column: category_children.parent_category_id: , while compiling: SELECT category_parents.parent_category, SUM(amount) AS totals FROM (transactions INNER JOIN category_children ON transactions.category='category_children.child_category') INNER JOIN category_parents ON category_children.parent_category_id=category_parents._id where trans_type='Debit' group by parent_category order by totals desc Any help is appreciated. (EXTRA CREDIT: I also need to make another statement to do spending by child category, given the parent category)

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• Zend Framework: Zend_DB Error

  - by Sergio E.

  I'm trying to learn ZF, but got strange error after 20 minutes :) Fatal error: Uncaught exception 'Zend_Db_Adapter_Exception' with message 'Configuration array must have a key for 'dbname' that names the database instance' What does this error mean? I got DB information in my config file: resources.db.adapter=pdo_mysql resources.db.host=localhost resources.db.username=name resources.db.password=pass resources.db.dbname=name Any suggestions? EDIT: This is my model file /app/models/DbTable/Bands.php: class Model_DbTable_Bands extends Zend_Db_Table_Abstract { protected $_name = 'zend_bands'; } Index controller action: public function indexAction() { $albums = new Model_DbTable_Bands(); $this->view->albums = $albums->fetchAll(); } EDIT All codes: bootstrap.php protected function _initAutoload() { $autoloader = new Zend_Application_Module_Autoloader(array( 'namespace' => '', 'basePath' => dirname(__FILE__), )); return $autoloader; } protected function _initDoctype() { $this->bootstrap('view'); $view = $this->getResource('view'); $view->doctype('XHTML1_STRICT'); } public static function setupDatabase() { $config = self::$registry->configuration; $db = Zend_Db::factory($config->db); $db->query("SET NAMES 'utf8'"); self::$registry->database = $db; Zend_Db_Table::setDefaultAdapter($db); Zend_Db_Table_Abstract::setDefaultAdapter($db); } IndexController.php class IndexController extends Zend_Controller_Action { public function init() { /* Initialize action controller here */ } public function indexAction() { $albums = new Model_DbTable_Bands(); $this->view->albums = $albums->fetchAll(); } } configs/application.ini, changed database and provided password: [development : production] phpSettings.display_startup_errors = 1 phpSettings.display_errors = 1 db.adapter = PDO_MYSQL db.params.host = localhost db.params.username = root db.params.password = pedro db.params.dbname = test models/DbTable/Bands.php class Model_DbTable_Bands extends Zend_Db_Table_Abstract { protected $_name = 'cakephp_bands'; public function getAlbum($id) { $id = (int)$id; $row = $this->fetchRow('id = ' . $id); if (!$row) { throw new Exception("Count not find row $id"); } return $row->toArray(); } }

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• Rolling back file moves, folder deletes and mysql queries

  - by Workoholic

  This has been bugging me all day and there is no end in sight. When the user of my php application adds a new update and something goes wrong, I need to be able to undo a complex batch of mixed commands. They can be mysql update and insert queries, file deletes and folder renaming and creations. I can track the status of all insert commands and undo them if an error is thrown. But how do I do this with the update statements? Is there a smart way (some design pattern?) to keep track of such changes both in the file structure and the database? My database tables are MyISAM. It would be easy to just convert everything to InnoDB, so that I can use transactions. That way I would only have to deal with the file and folder operations. Unfortunately, I cannot assume that all clients have InnoDB support. It would also require me to convert many tables in my database to InnoDB, which I am hesitant to do.

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• Seed has_many relation using mass assignment

  - by rnd

  Here are my two models: class Article < ActiveRecord::Base attr_accessible :content has_many :comments end class Comment < ActiveRecord::Base attr_accessible :content belongs_to :article end And I'm trying to seed the database in seed.rb using this code: Article.create( [{ content: "Hi! This is my first article!", comments: [{content: "It sucks"}, {content: "Best article ever!"}] }], without_protection: true) However rake db:seed gives me the following error message: rake aborted! Comment(#28467560) expected, got Hash(#13868840) Tasks: TOP => db:seed (See full trace by running task with --trace) It is possible to seed the database like this? If yes a follow-up question: I've searched some and it seems that to do this kind of (nested?) mass assignment I need to add 'accepts_nested_attributes_for' for the attributes I want to assign. (Possibly something like 'accepts_nested_attributes_for :article' for the Comment model) Is there a way to allow this similar to the 'without_protection: true'? Because I only want to accept this kind of mass assignment when seeding the database.

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• Compiling gstreamer plugin in windows

  - by utnapistim

  Hello all, My question: What is the correct way to compile a gstreamer plugin in windows, so that it will be accepted by gstreamer (actually Songbird on top of gstreamer). My setup: I have downloaded the songbird sources following the steps described here and I have a trunk/dependencies/windows-i686-msvc8 directory within my svn sources with all the gstreamer binaries. I have created a gstreamer empty plugin skeleton following the steps detailed in the GStreamer Plugin Writer's Guide, and compiled it against the gstreamer binaries in the Songbird dependencies folder. The compilation was done with VS2010 RC1 (Visual Studio 2008 yelded the same results), using an empty DLL project with the .h and .c files generated using the GStreamer Plugin Writer's Guide. The DLL was lined with libcpmt.lib, libcmt.lib, ws2_32.lib, gobject-2.0.lib, gthread-2.0.lib, gstreamer-0.10-0.lib, glib-2.0.lib, kernel32.lib, nspr4.lib and ignoring all default libraries. I have compiled the files as both .c and .cpp with the same results. Testing: I have installed the Songbird binaries corresponding to the correct svn version, then installed Songbird Developer Tools addon and used it to create an addon for testing my gstreamer plugin. Songbird will not load the pluggin. I have also tried to load it with gst-launch.exe from the trunk/dependencies/windows-i686-msvc8/[...] directory and that generated runtime error R6034: An application has made an attempt to load the C runtime library incorrectly. Most resources I found for this problem recommended restarting or reinstalling windows :(.

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• Problem with WHERE columnName = Data in MySQL query in C#

  - by Ryan Sullivan

  I have a C# webservice on a Windows Server that I am interfacing with on a linux server with PHP. The PHP grabs information from the database and then the page offers a "more information" button which then calls the webservice and passes in the name field of the record as a parameter. So i am using a WHERE statement in my query so I only pull the extra fields for that record. I am getting the error: System.Data.SqlClient.SqlException:Invalid column name '42' Where 42 is the value from the name field from the database. my query is string selectStr = "SELECT name, castNotes, triviaNotes FROM tableName WHERE name =\"" + show + "\""; I do not know if it is a problem with my query or something is wrong with the database, but here is the rest of my code for reference. NOTE: this all works perfectly when I grab all of the records, but I only want to grab the record that I ask my webservice for. public class ktvService : System.Web.Services.WebService { [WebMethod] public string moreInfo(string show) { string connectionStr = "MyConnectionString"; string selectStr = "SELECT name, castNotes, triviaNotes FROM tableName WHERE name =\"" + show + "\""; SqlConnection conn = new SqlConnection(connectionStr); SqlDataAdapter da = new SqlDataAdapter(selectStr, conn); DataSet ds = new DataSet(); da.Fill(ds, "tableName"); DataTable dt = ds.Tables["tableName"]; DataRow theShow = dt.Rows[0]; string response = "Name: " + theShow["name"].ToString() + "Cast: " + theShow["castNotes"].ToString() + " Trivia: " + theShow["triviaNotes"].ToString(); return response; } }

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• Using ember-resource with couchdb - how can i save my documents?

  - by Thomas Herrmann

  I am implementing an application using ember.js and couchdb. I choose ember-resource as database access layer because it nicely supports nested JSON documents. Since couchdb uses the attribute _rev for optimistic locking in every document, this attribute has to be updated in my application after saving the data to the couchdb. My idea to implement this is to reload the data right after saving to the database and get the new _rev back with the rest of the document. Here is my code for this: // Since we use CouchDB, we have to make sure that we invalidate and re-fetch // every document right after saving it. CouchDB uses an optimistic locking // scheme based on the attribute "_rev" in the documents, so we reload it in // order to have the correct _rev value. didSave: function() { this._super.apply(this, arguments); this.forceReload(); }, // reload resource after save is done, expire to make reload really do something forceReload: function() { this.expire(); // Everything OK up to this location Ember.run.next(this, function() { this.fetch() // Sub-Document is reset here, and *not* refetched! .fail(function(error) { App.displayError(error); }) .done(function() { App.log("App.Resource.forceReload fetch done, got revision " + self.get('_rev')); }); }); } This works for most cases, but if i have a nested model, the sub-model is replaced with the old version of the data just before the fetch is executed! Interestingly enough, the correct (updated) data is stored in the database and the wrong (old) data is in the memory model after the fetch, although the _rev attribut is correct (as well as all attributes of the main object). Here is a part of my object definition: App.TaskDefinition = App.Resource.define({ url: App.dbPrefix + 'courseware', schema: { id: String, _rev: String, type: String, name: String, comment: String, task: { type: 'App.Task', nested: true } } }); App.Task = App.Resource.define({ schema: { id: String, title: String, description: String, startImmediate: Boolean, holdOnComment: Boolean, ..... // other attributes and sub-objects } }); Any ideas where the problem might be? Thank's a lot for any suggestion! Kind regards, Thomas

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• Rails Binary Stream support

  - by Craig Walker

  I'm going to be starting a project soon that requires support for large-ish binary files. I'd like to use Ruby on Rails for the webapp, but I'm concerned with the BLOB support. In my experience with other languages, frameworks, and databases, BLOBs are often overlooked and thus have poor, difficult, and/or buggy functionality. Does RoR spport BLOBs adequately? Are there any gotchas that creep up once you're already committed to Rails? BTW: I want to be using PostgreSQL and/or MySQL as the backend database. Obviously, BLOB support in the underlying database is important. For the moment, I want to avoid focusing on the DB's BLOB capabilities; I'm more interested in how Rails itself reacts. Ideally, Rails should be hiding the details of the database from me, and so I should be able to switch from one to the other. If this is not the case (ie: there's some problem with using Rails with a particular DB) then please do mention it. UPDATE: Also, I'm not just talking about ActiveRecord here. I'll need to handle binary files on the HTTP side (file upload effectively). That means getting access to the appropriate HTTP headers and streams via Rails. I've updated the question title and description to reflect this.

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• How can I get the user object from a service in Symfony2

  - by pogo

  My site is using a third party service for authentication as well as other bits of functionality so I have setup a service that does all the API calls for me and it's this service that I need to be able to access the user object. I've tried injecting the security.context service into my API service but I get a ServiceCircularReferenceException because my user authentication provider references the API service (it has to in order to authenticate the user). So I get a chain of security.context -> authentication provider -> user provider -> API service -> security.context I'm struggling to this of another way of getting the user object and I can't see any obvious way of splitting up this chain. My configs are all defined in config.yml, here are the relevant bits myapp.database: class: Pogo\MyAppBundle\Service\DatabaseService arguments: siteid: %siteid% entityManager: "@doctrine.orm.entity_manager" myapp.apiservice: class: Pogo\MyAppBundle\Service\TicketingService arguments: entityManager: "@myapp.database" myapp.user_provider: class: Pogo\MyAppBundle\Service\APIUserProvider arguments: entityManager: "@myapp.database" ticketingAdapter: "@myapp.apiservice" securityContext: "@security.context" myapp.authenticationprovider: class: Pogo\MyAppBundle\Service\APIAuthenticationProvider arguments: userChecker: "@security.user_checker" encoderFactory: "@security.encoder_factory" userProvider: "@myapp.user_provider" myapp.user_provider is the service that I've defined as my user provider service in security.yml which I presume is how it's being referenced by security.context

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• SQL Server 2005 Reporting Services (x64) on Windows 2K8 -> CleanCurrentUserName() not found

  - by Steven Pardo

  I have installed SQL Server 2005 three times now on the same box. I cleaned up registry settings, files, you name it. All along I have been trying to install SQL Server 2005 Database and Reporting Services (x64) on a Windows 2008 Server. I have also applied the SP3 patch. Installing and Restarting the Server at every point. I have installed multiple instances (SQLDEV64, SQLQA64, SQLSTAGE64) of the Database and Reporting Services. I started to go through the Reporting Services Configuration manager, installing the Reporting Database along with setting up IIS. When I go test the website I get the following and there lies my question. How can I get around this error? http://localhost/reportserver Reporting Services Error -------------------------------------------------------------------------------- An internal error occurred on the report server. See the error log for more details. (rsInternalError) Method not found: 'Void Microsoft.ReportingServices.Diagnostics.UserUtil.CleanCurrentUserName()'. -------------------------------------------------------------------------------- SQL Server Reporting Services Any help would be greatly appreciated.

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• New Rails deployment half working...not sure why?

  - by Meltemi

  I'm in the final stages of going round trip through the entire Rails cycle: development - test - production (on an external server). I'm very close...but seeing some errors with the production version and don't know enough about Rails' "magic" to troubleshoot it yet... all seems well and I can load my app by going to www.mydomain.com/rails and it seems to work...I can interact with my app and create new objects in my database. However, when I go to www.mydomain.com/rails/ (difference is the trailing slash) i get a webpage that just says "Index from public" on it?!? I don't know where that's coming from? index.html is long removed from public. this may or may not be related to why I can't access, say, the first record in one of my classes by calling its controller like so: www.mydomain.com/rails/mycontroller/1 . and yes, there are records in the database. anyway, something's askew. it works fine on development box. but, only half working on production server. anyone know what might be causing this? this app is running on the server box (not development) Installed Passenger on server to serve app via Apache modified my httpd.conf with Passenger's stuff (headache but finally got it to respond) loaded schema into the production database: rake db:schema:load RAILS_ENV=production

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• SQLce DAL Linq to Sql or EntityFramework

  - by bretddog

  Hi, I'm learning databases, using SqlCe, and need business object to database mapping. Currently I try to decide if to use Linq to Sql, or EntityFramework. (I understand a bit L2S, but haven't familiarized with EF yet) The program will only be debeloped and used by myself, so I have good control of the priorities: I don't need to consider potential change of database type or data storage type, as I'm quite certain SQLce will stay sufficient. I DO expect continued development and changes to the data scheme while the program is in active use; change business object properties (Hence database columns), and possibly overall table scheme. So old data must be transported to new scheme. I also want to keep a decent degree of layer separation DAL/BLL, although this may not be necessary, it is good for me to learn these principles. My question is: With these priorities, would I have any benefit by choosing either Linq2Sql vs. EntityFramwork? (and please explain why) Btw, the project involves very simple table scheme with only 4-5 tables and very simple relations. Thanks!

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• @PrePersist with entity inheritance

  - by gerry

  I'm having some problems with inheritance and the @PrePersist annotation. My source code looks like the following: _the 'base' class with the annotated updateDates() method: @javax.persistence.Entity @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS) public class Base implements Serializable{ ... @Id @GeneratedValue protected Long id; ... @Column(nullable=false) @Temporal(TemporalType.TIMESTAMP) private Date creationDate; @Column(nullable=false) @Temporal(TemporalType.TIMESTAMP) private Date lastModificationDate; ... public Date getCreationDate() { return creationDate; } public void setCreationDate(Date creationDate) { this.creationDate = creationDate; } public Date getLastModificationDate() { return lastModificationDate; } public void setLastModificationDate(Date lastModificationDate) { this.lastModificationDate = lastModificationDate; } ... @PrePersist protected void updateDates() { if (creationDate == null) { creationDate = new Date(); } lastModificationDate = new Date(); } } _ now the 'Child' class that should inherit all methods "and annotations" from the base class: @javax.persistence.Entity @NamedQueries({ @NamedQuery(name=Sensor.QUERY_FIND_ALL, query="SELECT s FROM Sensor s") }) public class Sensor extends Entity { ... // additional attributes @Column(nullable=false) protected String value; ... // additional getters, setters ... } If I store/persist instances of the Base class to the database, everything works fine. The dates are getting updated. But now, if I want to persist a child instance, the database throws the following exception: MySQLIntegrityConstraintViolationException: Column 'CREATIONDATE' cannot be null So, in my opinion, this is caused because in Child the method "@PrePersist protected void updateDates()" is not called/invoked before persisting the instances to the database. What is wrong with my code?

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• Silverlight RIA Services - Showing columns from multiple tables

  - by Villager

  Hello, I have been evaluating Silverlight and .NET RIA Services for my company. I am trying to decide if it is right for us. For the most part, I like it. But, I see one item that I am surprised that I cannot do easily. Because of this, I'm guessing I'm doing some thing wrong. To demonstrate, I have two database tables: Order ----- ID CustomerID OrderDate OrderNumber Customer -------- ID FirstName LastName Address When I create my Domain Service class, I select both of these tables. On the Silverlight application, I drag-and-drop the Order entity from the Data Sources page to my Silverlight page. When I do this, a DataGrid is added with all of the properties in the Order entity. In reality though, I would like the DataGrid to show: Order.OrderNumber Order.OrderDate Customer.FirstName Customer.LastName Because this information is spread across multiple tables, I'm not sure how to use RIA Services to show them in my Silverlight application. What is the recommended way to do this? Should I add a view in my database? Can I do it without touching the database? Thank you,

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• NUnit integration programmatically with spring

  - by harkon

  Hi! I have a component based architecture framework designed and I use NUnit for isolated testing - okay so far. Now I want to enable integration tests. Therefore the tests use real implementations of the existing components. Each element of the component has a life cycle (init, start and stop) and I created a NUnit component. In the start section the Console runner of the NUnit will be executed. Okay - now if I have a test fixture class in my dlls in the execution path the runner exectues them - fine! But: And this is crucial! Each to be tested implementation exists so far in the process and I want to use this instances for testing. If I use NUnit runner in the current way each instance will be created twice - and above all: I have a spring container and a implementation registry. Via this registry I can get access to all instances in the processes. But how do I give the test fixture access to the existing registry? Good: I can start the component architecture framework in the startup of the nunit runner - but this is not what I want. My guide is the apache Cactus framework (with JUnit and tomcat, JBoss etc.) Can someone help? Thanks a lot! Check: http://cone.codeplex.com

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• Grabbing rows from MySql where current date is in between start date and end date (Check if current date lies between start date and end date)

  - by Jordan Parker

  I'm trying to select from the database to get the "campaigns" that dates fall into the month. So far i've been successful in grabbing rows that starts or ends inside the current month. What I need to do now is select rows that start in one month and ends a few months down the line ( EG: It's the 3rd month in the year, and there's a "campaign" that runs from the 1st month until the 5th. other example There is a "campaign" that runs from 2012 until 2013 ) I'm hoping there is some way to select via MySql all rows in which a capaign may run. If not should I grab all data in the database and only show the ones that run via the current month. I have already made a function that displays all the days inbetween each date inside an array, which is called "dateRange". I've also created another which shows how many days the campaign runs for called "runTime". Select all (Obviously) $result = mysql_query("SELECT * FROM campaign"); Select Starting This Month $result = mysql_query("SELECT * FROM campaign WHERE YEAR( START ) = YEAR( CURDATE( ) ) AND MONTH( START ) = MONTH( CURDATE( ) )"); Select Ending This Month $result = mysql_query("SELECT * FROM campaign WHERE YEAR( END ) = YEAR( CURDATE( ) ) AND MONTH( END ) = MONTH( CURDATE( ) ) LIMIT 0 , 30"); Code sample while($row = mysql_fetch_array($result)) { $dateArray = dateRange($row['start'], $row['end']); echo "<h3>" . $row['campname'] . "</h3> Start " . $row['start'] . "<br /> End " . $row['end']; echo runTime($row['start'], $row['end']); print_r($dateArray); } In regards to the dates, MySql database only holds start date and end date of the campaign.

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• NHibernate listener/event to replace object before insert/update

  - by vIceBerg

  Hi! I have a Company class which have a collection of Address. Here's my Address class:(written top of my head): public class Address { public string Civic; public string Street; public City City; } This is the City class: public class City { public int Id; public string Name; public string SearchableName{ get { //code } } } Address is persisted in his own table and have a reference to the city's ID. City are also persisted in is own table. The City's SearchableName is used to prevent some mistakes in the city the user type. For example, if the city name is "Montréal", the searchable name will be "montreal". If the city name is "St. John", the searchable name will be "stjohn", etc. It's used mainly to to search and to prevent having multiple cities with a typo in it. When I save an address, I want an listener/event to check if the city is already in the database. If so, cancel the insert and replace the user's city with the database one. I would like the same behavior with updates. I tried this: public bool OnPreInsert(PreInsertEvent @event) { City entity = (@event.Entity as City); if (entity != null) { if (entity.Id == 0) { var city = (from c in @event.Session.Linq<City>() where c.SearchableName == entity.SearchableName select c).SingleOrDefault(); if (city != null) { //don't know what to do here return true; } } } return false; } But if there's already a City in the database, I don't know what to do. @event.Entity is readonly, if I set @event.Entity.Id, I get an "null identifier" exception. I tried to trap insert/update on Address and on Company, but the City if the first one to get inserted (it's logic...) Any thoughts? Thanks

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• Avoid loading unnecessary data from db into objects (web pages)

  - by GmGr

  Really newbie question coming up. Is there a standard (or good) way to deal with not needing all of the information that a database table contains loaded into every associated object. I'm thinking in the context of web pages where you're only going to use the objects to build a single page rather than an application with longer lived objects. For example, lets say you have an Article table containing id, title, author, date, summary and fullContents fields. You don't need the fullContents to be loaded into the associated objects if you're just showing a page containing a list of articles with their summaries. On the other hand if you're displaying a specific article you might want every field loaded for that one article and maybe just the titles for the other articles (e.g. for display in a recent articles sidebar). Some techniques I can think of: Don't worry about it, just load everything from the database every time. Have several different, possibly inherited, classes for each table and create the appropriate one for the situation (e.g. SummaryArticle, FullArticle). Use one class but set unused properties to null at creation if that field is not needed and be careful. Give the objects access to the database so they can load some fields on demand. Something else? All of the above seem to have fairly major disadvantages. I'm fairly new to programming, very new to OOP and totally new to databases so I might be completely missing the obvious answer here. :)

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• how to Compute the average probe length for success and failure - Linear probe (Hash Tables)

  - by fang_dejavu

  hi everyone, I'm doing an assignment for my Data Structures class. we were asked to to study linear probing with load factors of .1, .2 , .3, ...., and .9. The formula for testing is: The average probe length using linear probing is roughly Success-- ( 1 + 1/(1-L)**2)/2 or Failure-- (1+1(1-L))/2. we are required to find the theoretical using the formula above which I did(just plug the load factor in the formula), then we have to calculate the empirical (which I not quite sure how to do). here is the rest of the requirements **For each load factor, 10,000 randomly generated positive ints between 1 and 50000 (inclusive) will be inserted into a table of the "right" size, where "right" is strictly based upon the load factor you are testing. Repeats are allowed. Be sure that your formula for randomly generated ints is correct. There is a class called Random in java.util. USE it! After a table of the right (based upon L) size is loaded with 10,000 ints, do 100 searches of newly generated random ints from the range of 1 to 50000. Compute the average probe length for each of the two formulas and indicate the denominators used in each calculationSo, for example, each test for a .5 load would have a table of size approximately 20,000 (adjusted to be prime) and similarly each test for a .9 load would have a table of approximate size 10,000/.9 (again adjusted to be prime). The program should run displaying the various load factors tested, the average probe for each search (the two denominators used to compute the averages will add to 100), and the theoretical answers using the formula above. .** how do I calculate the empirical success?

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• What is the best approach to 2D collision detection on the iPhone?

  - by Magic Bullet Dave

  Been working on this problem of collision detection and there appears to be 3 main approaches I could take: Sprite and mask approach. (AND the overlap of the sprites and check for a non-zero number in the resulting sprite pixel data). Bounding circles, rectangles or polygons. (Create one or more shapes that enclose the sprites and do the basic maths to check for overlaps). Use an existing sprite library. The first approach, even though it would have been the way I would have done it in the old days of 16x16 sprite blocks, it appears that there just isn’t an easy way of getting at the individual image pixel data and/or alpha channel within Quartz (or OPENGL for that matter). Detecting the overlap of the bounding box is easy, but then creating a 3rd image from the overlap and then testing it for pixels is complicated and my gut feel is that even if we could get it to work would be slow. Am I missing something neat here? The second approach involves dividing up our sprites into several polygons and testing them for overlaps. The more polygons the more accurate the collision detection. The benefit is that it is fast, and can be accurate. The downside is it makes the sprite creation more complicated. i.e., we have to create the polygons for each sprite. For speed the best approach is to create a tree of polygons. The 3rd approach I’m not sure about as it involves buying code (or using an open source licence). I am not sure what the best library to use is or whether this would make life easier or give us a problem integrating this into our app. So in short I am favouring the polygon and tree approach and would appreciate you views on this before I go and write lots of code. Best regards Dave

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• Encapsulate update method inside of object or have method which accepts an object to update

  - by Tom

  Hi, I actually have 2 questions related to each other: I have an object (class) called, say MyClass which holds data from my database. Currently I have a list of these objects ( List < MyClass ) that resides in a singleton in a "communal area". I feel it's easier to manage the data this way and I fail to see how passing a class around from object to object is beneficial over a singleton (I would be happy if someone can tell me why). Anyway, the data may change in the database from outside my program and so I have to update the data every so often. To update the list of the MyClass I have a method called say, Update, written in another class which accepts a list of MyClass. This updates all the instances of MyClass in the list. However would it be better instead to encapulate the Update() method inside the MyClass object, so instead I would say foreach(MyClass obj in MyClassList) { obj.update(); } What is a better implementation and why? The update method requires a XML reader. I have written an XML reader class which is basically a wrapper over the standard XML reader the language natively provides which provides application specific data collection. Should the XML reader class be in anyway in the "inheritance path" of the MyClass object - the MyClass objects inherits from the XML reader because it uses a few methods. I can't see why it should. I don't like the idea of declaring an instance of the XML Reader class inside of MyClass and an MyClass object is meant to be a simple "record" from the database and I feel giving it loads of methods, other object instances is a bit messy. Perhaps my XML reader class should be static but C#'s native XMLReader isn't static.? Any comments would be greatly appreciated Thanks Thomas

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• Call method immediately after object construction in LINQ query

  - by Steffen

  I've got some objects which implement this interface: public interface IRow { void Fill(DataRow dr); } Usually when I select something out of db, I go: public IEnumerable<IRow> SelectSomeRows { DataTable table = GetTableFromDatabase(); foreach (DataRow dr in table.Rows) { IRow row = new MySQLRow(); // Disregard the MySQLRow type, it's not important row.Fill(dr); yield return row; } } Now with .Net 4, I'd like to use AsParallel, and thus LINQ. I've done some testing on it, and it speeds up things alot (IRow.Fill uses Reflection, so it's hard on the CPU) Anyway my problem is, how do I go about creating a LINQ query, which calls Fills as part of the query, so it's properly parallelized? For testing performance I created a constructor which took the DataRow as argument, however I'd really love to avoid this if somehow possible. With the constructor in place, it's obviously simple enough: public IEnumerable<IRow> SelectSomeRowsParallel { DataTable table = GetTableFromDatabase(); return from DataRow dr in table.Rows.AsParallel() select new MySQLRow(dr); } However like I said, I'd really love to be able to just stuff my Fill method into the LINQ query, and thus not need the constructor overload.

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• how to handel failure mails using PHP?

  - by Navruk

  example:- If i sent a mail through gmail to this id "[email protected]" i got error like "Delivery to the following recipient failed permanently:" My question is:- If i sent using PHP mail function, how can i catch failure email id? code:- // To send HTML mail, the Content-type header must be set $headers = 'MIME-Version: 1.0' . "\r\n"; $headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n"; // Additional headers $headers .= 'To: Mary <[email protected]>, Kelly <[email protected]>' . "\r\n"; $headers .= 'From: Birthday Reminder <[email protected]>' . "\r\n"; $headers .= 'Cc: [email protected]' . "\r\n"; $headers .= 'Bcc: [email protected]' . "\r\n"; $to = "[email protected]"; $subject = "Testing"; $message = "Testing body"; mail($to, $subject, $message, $headers);

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• Why MSMQ won't send a space character?

  - by cyclotis04

  I'm exploring MSMQ services, and I wrote a simple console client-server application that sends each of the client's keystrokes to the server. Whenever hit a control character (DEL, ESC, INS, etc) the server understandably throws an error. However, whenever I type a space character, the server receives the packet but doesn't throw an error and doesn't display the space. Server: namespace QIM { class Program { const string QUEUE = @".\Private$\qim"; static MessageQueue _mq; static readonly object _mqLock = new object(); static XmlSerializer xs; static void Main(string[] args) { lock (_mqLock) { if (!MessageQueue.Exists(QUEUE)) _mq = MessageQueue.Create(QUEUE); else _mq = new MessageQueue(QUEUE); } xs = new XmlSerializer(typeof(string)); _mq.BeginReceive(new TimeSpan(0, 1, 0), new object(), OnReceive); while (Console.ReadKey().Key != ConsoleKey.Escape) { } } static void OnReceive(IAsyncResult result) { Message msg; lock (_mqLock) { try { msg = _mq.EndReceive(result); Console.Write("."); Console.Write(xs.Deserialize(msg.BodyStream)); } catch (Exception ex) { Console.Write(ex); } } _mq.BeginReceive(new TimeSpan(0, 1, 0), new object(), OnReceive); } } } Client: namespace QIM_Client { class Program { const string QUEUE = @".\Private$\qim"; static MessageQueue _mq; static void Main(string[] args) { if (!MessageQueue.Exists(QUEUE)) _mq = MessageQueue.Create(QUEUE); else _mq = new MessageQueue(QUEUE); ConsoleKeyInfo key = new ConsoleKeyInfo(); while (key.Key != ConsoleKey.Escape) { key = Console.ReadKey(); _mq.Send(key.KeyChar.ToString()); } } } } Client Input: Testing, Testing... Server Output: .T.e.s.t.i.n.g.,..T.e.s.t.i.n.g...... You'll notice that the space character sends a message, but the character isn't displayed.

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