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• Alternatives to the Entity Framework for Serving/Consuming an OData Interface

  - by Egahn

  I'm researching how to set up an OData interface to our database. I would like to be able to pull/query data from our DB into Excel, as a start. Eventually I would like to have Excel run queries and pull data over HTTP from a remote client, including authentication, etc. I've set up a working (rickety) prototype so far, using the ADO.NET Entity Data Model wizard in Visual Studio, and VSTO to create a test Excel worksheet with a button to pull from that ADO.NET interface. This works OK so far, and I can query the DB using Linq through the entities/objects that are created by the ADO.NET EDM wizard. However, I have started to run into some problems with this approach. I've been finding the Entity Framework difficult to work with (and in fact, also difficult to research solutions to, as there's a lot of chaff out there regarding it and older versions of it). An example of this is my being unable to figure out how to set the SQL command timeout (as opposed to the HTTP request timeout) on the DataServiceContext object that the wizard generates for my schema, but that's not the point of my question. The real question I have is, if I want to use OData as my interface standard, am I stuck with the Entity Framework? Are there any other solutions out there (preferably open source) which can set up, serve and consume an OData interface, and are easier to work with and less bloated than the Entity Framework? I have seen mention of NHibernate as an alternative, but most of the comparison threads I've seen are a few years old. Are there any other alternatives out there now? Thanks very much!

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• querying huge database table takes too much of time in mysql

  - by Vijay

  Hi all, I am running sql queries on a mysql db table that has 110Mn+ unique records for whole day. Problem: Whenever I run any query with "where" clause it takes at least 30-40 mins. Since I want to generate most of data on the next day, I need access to whole db table. Could you please guide me to optimize / restructure the deployment model? Site description: mysql Ver 14.12 Distrib 5.0.24, for pc-linux-gnu (i686) using readline 5.0 4 GB RAM, Dual Core dual CPU 3GHz RHEL 3 my.cnf contents : [root@reports root]# cat /etc/my.cnf [mysqld] datadir=/data/mysql/data/ socket=/tmp/mysql.sock sort_buffer_size = 2000000 table_cache = 1024 key_buffer = 128M myisam_sort_buffer_size = 64M # Default to using old password format for compatibility with mysql 3.x # clients (those using the mysqlclient10 compatibility package). old_passwords=1 [mysql.server] user=mysql basedir=/data/mysql/data/ [mysqld_safe] err-log=/data/mysql/data/mysqld.log pid-file=/data/mysql/data/mysqld.pid [root@reports root]# DB table details: CREATE TABLE `RAW_LOG_20100504` ( `DT` date default NULL, `GATEWAY` varchar(15) default NULL, `USER` bigint(12) default NULL, `CACHE` varchar(12) default NULL, `TIMESTAMP` varchar(30) default NULL, `URL` varchar(60) default NULL, `VERSION` varchar(6) default NULL, `PROTOCOL` varchar(6) default NULL, `WEB_STATUS` int(5) default NULL, `BYTES_RETURNED` int(10) default NULL, `RTT` int(5) default NULL, `UA` varchar(100) default NULL, `REQ_SIZE` int(6) default NULL, `CONTENT_TYPE` varchar(50) default NULL, `CUST_TYPE` int(1) default NULL, `DEL_STATUS_DEVICE` int(1) default NULL, `IP` varchar(16) default NULL, `CP_FLAG` int(1) default NULL, `USER_LOCATE` bigint(15) default NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1 MAX_ROWS=200000000; Thanks in advance! Regards,

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• How much detail should be in a project plan or spec?

  - by DeanMc

  I have an issue that I feel many programmers can relate to... I have worked on many small scale projects. After my initial paper brain storm I tend to start coding. What I come up with is usually a rough working model of the actual application. I design in a disconnected fashion so I am talking about underlying code libraries, user interfaces are the last thing as the library usually dictates what is needed in the UI. As my projects get bigger I worry that so should my "spec" or design document. The above paragraph, from my investigations, is echoed all across the internet in one fashion or another. When a UI is concerned there is a bit more information but it is UI specific and does not relate to code libraries. What I am beginning to realise is that maybe code is code is code. It seems from my extensive research that there is no 1:1 mapping between a design document and the code. When I need to research a topic I dump information into OneNote and from there I prioritise features into versions and then into related chunks so that development runs in a fairly linear fashion, my tasks tend to look like so: Implement Binary File Reader Implement Binary File Writer Create Object to encapsulate Data for expression to the caller Now any programmer worth his salt is aware that between those three to do items could be a potential wall of code that could expand out to multiple files. I have tried to map the complete code process for each task but I simply don't think it can be done effectively. By the time one mangles pseudo code it is essentially code anyway so the time investment is negated. So my question is this: Am I right in assuming that the best documentation is the code itself. We are all in agreement that a high level overview is needed. How high should this be? Do you design to statement, class or concept level? What works for you?

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• How to load entities into readonly collections using the entity framework

  - by Anton P

  I have a POCO domain model which is wired up to the entity framework using the new ObjectContext class. public class Product { private ICollection<Photo> _photos; public Product() { _photos = new Collection<Photo>(); } public int Id { get; set; } public string Name { get; set; } public virtual IEnumerable<Photo> Photos { get { return _photos; } } public void AddPhoto(Photo photo) { //Some biz logic //... _photos.Add(photo); } } In the above example i have set the Photos collection type to IEnumerable as this will make it read only. The only way to add/remove photos is through the public methods. The problem with this is that the Entity Framework cannot load the Photo entities into the IEnumerable collection as it's not of type ICollection. By changing the type to ICollection will allow callers to call the Add mentod on the collection itself which is not good. What are my options?

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• Hierarchical/Nested Database Structure for Comments

  - by Stephen Melrose

  Hi, I'm trying to figure out the best approach for a database schema for comments. The problem I'm having is that the comments system will need to allow nested/hierarchical comments, and I'm not sure how to design this out properly. My requirements are, Comments can be made on comments, so I need to store the tree hierarchy I need to be able to query the comments in the tree hierarchy order, but efficiently, preferably in a fast single query, but I don't know if this is possible I'd need to make some wierd queries, e.g. pull out the latest 5 root comments, and a maximum of 3 children for each one of those I read an article on the MySQL website on this very subject, http://dev.mysql.com/tech-resources/articles/hierarchical-data.html The "Nested Set Model" in theory sounds like it will do what I need, except I'm worried about querying the thing, and also inserting. If this is the right approach, How would I do my 3rd requirement above? If I have 2000 comments, and I add a new sub-comment on the first comment, that will be a LOT of updating to do. This doesn't seem right to me? Or is there a better approach for the type of data I'm wanting to store and query? Thank you

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• PHP Object References in Frameworks

  - by bigstylee

  Before I dive into the disscusion part a quick question; Is there a method to determine if a variable is a reference to another variable/object? For example $foo = 'Hello World'; $bar = &$foo; echo (is_reference($bar) ? 'Is reference' : 'Is orginal'; I have been using PHP5 for a few years now (personal use only) and I would say I am moderately reversed on the topic of Object Orientated implementation. However the concept of Model View Controller Framework is fairly new to me. I have looked a number of tutorials and looked at some of the open source frameworks (mainly CodeIgnitor) to get a better understanding how everything fits together. I am starting to appreciate the real benefits of using this type of structure. I am used to implementing object referencing in the following technique. class Foo{ public $var = 'Hello World!'; } class Bar{ public function __construct(){ global $Foo; echo $Foo->var; } } $Foo = new Foo; $Bar = new Bar; I was surprised to see that CodeIgnitor and Yii pass referencs of objects and can be accessed via the following method: $this->load->view('argument') The immediate advantage I can see is a lot less code and more user friendly. But I do wonder if it is more efficient as these frameworks are presumably optimised? Or simply to make the code more user friendly? This was an interesting article Do not use PHP references.

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• Access 2007 and Special/Unicode Characters in SQL

  - by blockcipher

  I have a small Access 2007 database that I need to be able to import data from an existing spreadsheet and put it into our new relational model. For the most part this seems to work pretty well. Part of the process is attempting to see if a record already exists in a target table using SQL. For example, if I extract book information out of the current row in the spreadsheet, it may contain a title and abstract. I use SQL to get the ID of a matching record, if it exists. This works fine except when I have data that's in a non-English language. In this case, it seems that there is some punctuation that is causing me problems. At least I think it's punctuation as I do have some fields that do not have punctuation and are non-English that do not give me any problems. Is there a built-in function that can escape these characters? Currently I have a small function that will escape the single quote character, but that isn't enough. Or, is there a list of Unicode characters that can interfere with how SQL wants data quoted? Thanks in advance.

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• How to manage data access / preloading efficiently using web services in C# ?

  - by Amadeus45

  Hello all, Ok, this is very "generic" question. We currently have a SQL Server database for which we need to develop an application in ASP.NET with will contain all the business logic in C# Web Services. The thing is that, architecturally speaking, I'm not sure how to design the web service and the data management. There are many things to consider : We need have very rapid access to data. Right now, we have over a million "sales" and "purchases" record from which we need to often calculate and load the current stock for a given day according to a serie of parameter. I'm not sure how we should preload the data and keep the data in the Web Service. Doing a stock calculation within a SQL query will be very lengthy. They currently have a stock calculation application that preloads all sales and purchases for the day and afterwards calculate the stock on the code-side. We want to develop powerful reporting tools. We want to implement a "pivot table" but not sure how to implement it and have good performances. For the reasons above, I'm not sure how to design the data model. Anybody can give me any guidelines on how to start, or from their personnal experiences (what have you done in the past ?) I'm not sure if it's possible to make a bounty even though the question is new (I'd put 300 rep on it, since I really need something). If you know how, let me know. Thanks

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• Returning Database Blobs in TurboGears 2.x / FCGI / Lighttpd extremely slow

  - by Tom

  Hey everyone, I am running a TG2 App on lighttpd via flup/fastcgi. We are reading images (~30kb each) from BlobFields in a MySQL database and return those images with a custom mime type via a controller method. Caching these images on the hard disk makes no sense because they change with every request, the only reason we cache these in the DB is that creating these images is quite expensive and the data used to create the images is also present in plain text on the website. Now to the problem itself: When returning such an image, things get extremely slow. The code runs totally fine on paster itself with no visible delay, but as soon as its running via fcgi/lighttpd the described phenomenon happens. I profiled the method of my controller that returns my blob, and the entire method runs in a few miliseconds, but when "return" executes, the entire app hangs for roughly 10 seconds. We could not reproduce the same error with PHP on FCGI. This only seems to happen with Turbogears or Pylons. Here for your consideration the concerned piece of source code: @expose(content_type=CUSTOM_CONTENT_TYPE) def return_img(self, img_id): """ Return a DB persisted image when requested """ img = model.Images.by_id(img_id) #get image from DB response.headers['content-type'] = 'image/png' return img.data # this causes the app to hang for 10 seconds

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• Remove duplicate records/objects uniquely identified by multiple attributes

  - by keruilin

  I have a model called HeroStatus with the following attributes: id user_id recordable_type hero_type (can be NULL!) recordable_id created_at There are over 100 hero_statuses, and a user can have many hero_statuses, but can't have the same hero_status more than once. A user's hero_status is uniquely identified by the combination of recordable_type + hero_type + recordable_id. What I'm trying to say essentially is that there can't be a duplicate hero_status for a specific user. Unfortunately, I didn't have a validation in place to assure this, so I got some duplicate hero_statuses for users after I made some code changes. For example: user_id = 18 recordable_type = 'Evil' hero_type = 'Halitosis' recordable_id = 1 created_at = '2010-05-03 18:30:30' user_id = 18 recordable_type = 'Evil' hero_type = 'Halitosis' recordable_id = 1 created_at = '2009-03-03 15:30:00' user_id = 18 recordable_type = 'Good' hero_type = 'Hugs' recordable_id = 1 created_at = '2009-02-03 12:30:00' user_id = 18 recordable_type = 'Good' hero_type = NULL recordable_id = 2 created_at = '2009-012-03 08:30:00' (Last two are not a dups obviously. First two are.) So what I want to do is get rid of the duplicate hero_status. Which one? The one with the most-recent date. I have three questions: How do I remove the duplicates using a SQL-only approach? How do I remove the duplicates using a pure Ruby solution? Something similar to this: http://stackoverflow.com/questions/2790004/removing-duplicate-objects. How do I put a validation in place to prevent duplicate entries in the future?

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• Ajax Auto Complete in ASP.Net MVC project - How to display a an object's name but actually save it's

  - by Ben

  I have implemented the Ajax Autocomplete feature in my application using a web service file that querys my database and it works great. One problem I am having is allowing the user to see the item's name, as that's what they are typing in the textbox, but when they select it, it saves the item's ID number instead of the actual name. I want it to behave much like a dropdown list, where I can specify what is seen and entered vs. what is actually saved in the database (in this case, the product ID instead of it's name.) I have this text box in my view, along with the script: <script type="text/javascript"> Sys.Application.add_init(function() { $create( AjaxControlToolkit.AutoCompleteBehavior, { serviceMethod: 'ProductSearch', servicePath: '/ProductService.asmx', minimumPrefixLength: 1, completionSetCount: 10 }, null, null, $get('ProductID')) }); </script> <p> <label for="ProductID">Product:</label> <%= Html.TextBox("ProductID", Model.Products)%> <%= Html.ValidationMessage("ProductID", "*")%> </p> Here's what is in my asmx file: public class ProductService : System.Web.Services.WebService { [WebMethod] public string[] ProductSearch(string prefixText, int count) { MyDataContext db = new MyDataContext(); string[] products = (from product in db.Products where product.ProductName.StartsWith(prefixText) select product.ProductName).Take(count).ToArray(); return products; } } Can anyone help me figure this out? I'm using this so they can just start typing instead of having a dropdown list that's a mile long...

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• Using Cucumber With Modular Sinatra Apps

  - by Rob Conery

  I'm building out a medium-sized application using Sinatra and all was well when I had a single app.rb file and I followed Aslak's guidance up on Github: http://wiki.github.com/aslakhellesoy/cucumber/sinatra As the app grew a bit larger and the app.rb file started to bulge, I refactored out a lot of of the bits into "middleware" style modules using Sinatra::Base, mapping things using a rack-up file (config.ru) etc. The app works nicely - but my specs blew up as there was no more app.rb file for webrat to run against (as defined in the link above). I've tried to find examples on how to work this - and I think I'm just not used to the internal guts of Cuke just yet as I can't find a single way to have it cover all the apps. I tried just pointing to "config.ru" instead of app.rb - but that doesn't work. What I ended up doing - which is completely hackish - is to have a separate app.rb file in my support directory, which has all the requires stuff so I can at least test the model stuff. I can also specify routes in there - but that's not at all what I want to do. So - the question is: how can I get Cucumber to properly work with the modular app approach?

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• What is the best way to store site configuration data?

  - by DaveDev

  I have a question about storing site configuration data. We have a platform for web applications. The idea is that different clients can have their data hosted and displayed on their own site which sits on top of this platform. Each site has a configuration which determines which panels relevant to the client appear on which pages. The system was originally designed to keep all the configuration data for each site in a database. When the site is loaded all the configuration data is loaded into a SiteConfiguration object, and the clients panels are generated based on the content of this object. This works, but I find it very difficult to work with to apply change requests or add new sites because there is so much data to sift through and it's difficult maintain a mental model of the site and its configuration. Recently I've been tasked with developing a subset of some of the sites to be generated as PDF documents for printing. I decided to take a different approach to how I would define the configuration in that instead of storing configuration data in the database, I wrote XML files to contain the data. I find it much easier to work with because instead of reading meaningless rows of data which are related to other meaningless rows of data, I have meaningful documents with semantic, readable information with the relationships defined by visually understandable element nesting. So now with these 2 approaches to storing site configuration data, I'd like to get the opinions of people more experienced in dealing with this issue on dealing with these two approaches. What is the best way of storing site configuration data? Is there a better way than the two ways I outlined here? note: StackOverflow is telling me the question appears to be subjective and is likely to be closed. I'm not trying to be subjective. I'd like to know how best to approach this issue next time and if people with industry experience on this could provide some input.

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• Can't log in with a valid password using Authlogic and Ruby on Rails?

  - by kbighorse

  We support a bit of an unusual scheme. We don't require a password on User creation, and use password_resets to add a password to the user later, on demand. The problem is, once a password is created, the console indicates the password is valid: user.valid_password? 'test' = true but in my UserSessions controller, @user_session.save returns false using the same password. What am I not seeing? Kimball UPDATE: Providing more details, here is the output when saving the new password: Processing PasswordResetsController#update (for 127.0.0.1 at 2011-01-31 14:01:12) [PUT] Parameters: {"commit"="Update password", "action"="update", "_method"="put", "authenticity_token"="PQD4+eIREKBfHR3/fleWuQSEtZd7RIvl7khSYo5eXe0=", "id"="v3iWW5eD9P9frbEQDvxp", "controller"="password_resets", "user"={"password"="johnwayne"}} The applicable SQL is: UPDATE users SET updated_at = '2011-01-31 22:01:12', crypted_password = 'blah', perishable_token = 'blah', password_salt = 'blah', persistence_token = 'blah' WHERE id = 580 I don't see an error per se, @user_session.save just returns false, as if the password didn't match. I skip validating passwords in the User model: class User < ActiveRecord::Base acts_as_authentic do |c| c.validate_password_field = false end Here's the simplified controller code: def create logger.info("SAVED SESSION? #{@user_session.save}") end which outputs: Processing UserSessionsController#create (for 127.0.0.1 at 2011-01-31 14:16:59) [POST] Parameters: {"commit"="Login", "user_session"={"remember_me"="0", "password"="johnwayne", "email"="[email protected]"}, "action"="create", "authenticity_token"="PQD4+eIREKBfHR3/fleWuQSEtZd7RIvl7khSYo5eXe0=", "controller"="user_sessions"} User Columns (2.2ms) SHOW FIELDS FROM users User Load (3.7ms) SELECT * FROM users WHERE (users.email = '[email protected]') ORDER BY email ASC LIMIT 1 SAVED SESSION? false CACHE (0.0ms) SELECT * FROM users WHERE (users.email = '[email protected]') ORDER BY email ASC LIMIT 1 Redirected to http://localhost:3000/login Lastly, the console indicates that the new password is valid: $ u.valid_password? 'johnwayne' = true Would love to do it all in the console, is there a way to load UserSession controller and call methods directly? Kimball

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• Is there an ORM that supports composition w/o Joins

  - by Ken Downs

  EDIT: Changed title from "inheritance" to "composition". Left body of question unchanged. I'm curious if there is an ORM tool that supports inheritance w/o creating separate tables that have to be joined. Simple example. Assume a table of customers, with a Bill-to address, and a table of vendors, with a remit-to address. Keep it simple and assume one address each, not a child table of addresses for each. These addresses will have a handful of values in common: address 1, address 2, city, state/province, postal code. So let's say I'd have a class "addressBlock" and I want the customers and vendors to inherit from this class, and possibly from other classes. But I do not want separate tables that have to be joined, I want the columns in the customer and vendor tables respectively. Is there an ORM that supports this? The closest question I have found on StackOverflow that might be the same question is linked below, but I can't quite figure if the OP is asking what I am asking. He seems to be asking about foregoing inheritance precisely because there will be multiple tables. I'm looking for the case where you can use inheritance w/o generating the multiple tables. Model inheritance approach with Django's ORM

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• C++ Switch won't compile with externally defined variable used as case

  - by C Nielsen

  I'm writing C++ using the MinGW GNU compiler and the problem occurs when I try to use an externally defined integer variable as a case in a switch statement. I get the following compiler error: "case label does not reduce to an integer constant". Because I've defined the integer variable as extern I believe that it should compile, does anyone know what the problem may be? Below is an example: test.cpp #include <iostream> #include "x_def.h" int main() { std::cout << "Main Entered" << std::endl; switch(0) { case test_int: std::cout << "Case X" << std::endl; break; default: std::cout << "Case Default" << std::endl; break; } return 0; } x_def.h extern const int test_int; x_def.cpp const int test_int = 0; This code will compile correctly on Visual C++ 2008. Furthermore a Montanan friend of mine checked the ISO C++ standard and it appears that any const-integer expression should work. Is this possibly a compiler bug or have I missed something obvious? Here's my compiler version information: Reading specs from C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/specs Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-synchronization --enable-libstdcxx-debug Thread model: win32 gcc version 3.4.5 (mingw-vista special r3)

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• Silverlight 4 ComboBox - Binding to Nullable data (tried TargetNullValue but not working as expected)

  - by Laurence

  (Please note - I am a Silverlight beginner and am looking for the simplest solution here, e.g. that doesn't involve writing/installing a replacement for the ComboBox control!) This is an issue with a Silverlight 4 application that uses the View Model (MVVM) approach. I have a simple form for editing a "Product" object. Product has a CategoryID property which is nullable (int?). A ComboBox is used to view and set the CategoryID - this is bound to an ObservableCollection of Categories. Product also has number of non-nullable properties bound to TextBoxes. I want the user to see "N/A" in the ComboBox for a product with no category, and to be use this "N/A" option to set CategoryID to null. So, I manually added a Category object with CategoryID=0 and CategoryName="N/A" to the collection; then I set TargetNullValue=0 in the SelectedValue Binding of the ComboBox. My thinking was - when the ComboBox SelectedValue was bound to a null CategoryID it would substitute zero, and therefore select the "N/A" option. When editing a Product with a non-null CategoryID, everything works. However when a null CategoryID is found, two problems occur: No option is selected in the ComboBox (its blank) The ComboBox binding seems broken from this point onwards - any Product I subsequently edit (incl. ones with a non-null CategoryID) have nothing selected in the ComboBox (its still populated with all categories - just no selected item). I've seen reports of problem #2 (here, here) but I was under the impression that #1 should have worked. What am I missing to get the "N/A" option to be selected? XAML for ComboBox: <ComboBox x:Name="cboCategory" ItemsSource="{Binding colCategories, Mode=OneWay}" SelectedValuePath="CategoryID" DisplayMemberPath="CategoryName" SelectedValue="{Binding CurrentProduct.CategoryID, Mode=TwoWay, TargetNullValue=0}" Height="24" Width="344"></ComboBox>

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• In my cakephp project the save function is not working?

  - by Faheem

  My controller action is: function add() { if (!empty($this-data)) { $this-Customer-create(); if ($this-Customer-save($this-data)) { $this-Session-setFlash('A new Customer has been added'); $this-redirect(array('action'='index')); } else { $this-Session-setFlash('The customer cannot be added this time. Try again later.'); $this-redirect(array('action'='index')); } } } My model is: class Customer extends AppModel { var $name = 'Customer'; var $validate = array( 'name' = array( 'length'= array( 'rule' = array('between', 4,50), 'message' = 'Name must be minimum 4 and maximum 50 characters long.' ), 'checkUnique'= array( 'rule' = 'isUnique', 'message' = 'This Name is already registered' ) )); and this is my view: create('Customer',array('action'='add'));? input('Customer.name'); echo $form-input('Customer.balance',array('type'='hidden','default'=0)); ? end('Submit');? every time I submit the form it splashes: The customer cannot be added this time. Try again later.

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• [MySQL/PHP] Avoid using RAND()

  - by Andrew Ellis

  So... I have never had a need to do a random SELECT on a MySQL DB until this project I'm working on. After researching it seems the general populous says that using RAND() is a bad idea. I found an article that explains how to do another type of random select. Basically, if I want to select 5 random elements, I should do the following (I'm using the Kohana framework here)? If not, what is a better solution? Thanks, Andrew <?php final class Offers extends Model { /** * Loads a random set of offers. * * @param integer $limit * @return array */ public function random_offers($limit = 5) { // Find the highest offer_id $sql = ' SELECT MAX(offer_id) AS max_offer_id FROM offers '; $max_offer_id = DB::query(Database::SELECT, $sql) ->execute($this->_db) ->get('max_offer_id'); // Check to make sure we're not trying to load more offers // than there really is... if ($max_offer_id < $limit) { $limit = $max_offer_id; } $used = array(); $ids = ''; for ($i = 0; $i < $limit; ) { $rand = mt_rand(1, $max_offer_id); if (!isset($used[$rand])) { // Flag the ID as used $used[$rand] = TRUE; // Set the ID if ($i > 0) $ids .= ','; $ids .= $rand; ++$i; } } $sql = ' SELECT offer_id, offer_name FROM offers WHERE offer_id IN(:ids) '; $offers = DB::query(Database::SELECT, $sql) ->param(':ids', $ids) ->as_object(); ->execute($this->_db); return $offers; } }

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• Checking for nil in view in Ruby on Rails

  - by seaneshbaugh

  I've been working with Rails for a while now and one thing I find myself constantly doing is checking to see if some attribute or object is nil in my view code before I display it. I'm starting to wonder if this is always the best idea. My rationale so far has been that since my application(s) rely on user input unexpected things can occur. If I've learned one thing from programming in general it's that users inputting things the programmer didn't think of is one of the biggest sources of run-time errors. By checking for nil values I'm hoping to sidestep that and have my views gracefully handle the problem. The thing is though I typically for various reasons have similar nil or invalid value checks in either my model or controller code. I wouldn't call it code duplication in the strictest sense, but it just doesn't seem very DRY. If I've already checked for nil objects in my controller is it okay if my view just assumes the object truly isn't nil? For attributes that can be nil that are displayed it makes sense to me to check every time, but for the objects themselves I'm not sure what is the best practice. Here's a simplified, but typical example of what I'm talking about: controller code def show @item = Item.find_by_id(params[:id]) @folders = Folder.find(:all, :order => 'display_order') if @item == nil or @item.folder == nil redirect_to(root_url) and return end end view code <% if @item != nil %> display the item's attributes here <% if @item.folder != nil %> <%= link_to @item.folder.name, folder_path(@item.folder) %> <% end %> <% else %> Oops! Looks like something went horribly wrong! <% end %> Is this a good idea or is it just silly?

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• Creating futures using Apple's GCD

  - by jer

  I'm working on a library which implements the actor model on top of Grand Central Dispatch (specifically the C level API libdispatch). Basically a brief overview of my system is as such: Communication happens between actors using messages Multicast communication only (one actor to many actors) Senders and receivers are decoupled from one another using a blackboard where messages are pushed to. Messages are sent in the default queue asynchronously using dispatch_group_async() once a message gets pushed onto the blackboard. I'm trying to implement futures in the language right now, so I've created a new type which holds some information: A group of its own The value being 'returned' However, I have a problem since dispatch_block_t is of type void (^)(void) so it doesn't return anything. So my idea of in my future_new() function of setting up another group which can be used to execute a block returning a result, which I can store in my "value" member in my future_t structure, isn't going to work. The rest of the futures implementation is very clear, except it all depends on being able to get the value into the future back from the actor, acting on the message. When using the library, it would greatly reduce its usefulness if I had to ask users (and myself) to be aware when futures were going to be used by other parts of the system—It just isn't practical. I'm wondering if anyone can think of a way around this?

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• Problems with rails and saving to the database.

  - by Grantismo

  I've been having some difficulty in understanding the source of a problem. Below is a listing of the model classes. Essentially the goal is to have the ability to add sentences to the end of the story, or to add stories to an existing sentence_block. Right now, I'm only attempting to allow users to add sentences, and automatically create a new sentence_block for the new sentence. class Story < ActiveRecord::Base has_many :sentence_blocks, :dependent => :destroy has_many :sentences, :through => :sentence_blocks accepts_nested_attributes_for :sentence_blocks end class SentenceBlock < ActiveRecord::Base belongs_to :story has_many :sentences, :dependent => :destroy end class Sentence < ActiveRecord::Base belongs_to :sentence_block def story @sentence_block = SentenceBlock.find(self.sentence_block_id) Story.find(@sentence_block.story_id) end end The problem is occurring when using the show method of the Story. The Story method is as follows, and the associated show method for a sentence is also included. Sentence.show def show @sentence = Sentence.find(params[:id]) respond_to do |format| format.html {redirect_to(@sentence.story)} format.xml { render :xml => @sentence } end end Story.show def show @story = Story.find(params[:id]) @sentence_block = @story.sentence_blocks.build @new_sentence = @sentence_block.sentences.build(params[:sentence]) respond_to do |format| if @new_sentence.content != nil and @new_sentence.sentence_block_id != nil and @sentence_block.save and @new_sentence.save flash[:notice] = 'Sentence was successfully added.' format.html # new.html.erb format.xml { render :xml => @story } else @sentence_block.destroy format.html format.xml { render :xml => @story } end end end I'm getting a "couldn't find Sentence_block without and id" error. So I'm assuming that for some reason the sentence_block isn't getting saved to the database. Can anyone help me with my understanding of the behavior and why I'm getting the error? I'm trying to ensure that every time the view depicts show for a story, an unnecessary sentence_block and sentence isn't created, unless someone submits the form, I'm not really sure how to accomplish this. Any help would be appreciated.

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• Postgres error with Sinatra/Haml/DataMapper on Heroku

  - by sevennineteen

  I'm trying to move a simple Sinatra app over to Heroku. Migration of the Ruby app code and existing MySQL database using Taps went smoothly, but I'm getting the following Postgres error: PostgresError - ERROR: operator does not exist: text = integer LINE 1: ...d_at", "post_id" FROM "comments" WHERE ("post_id" IN (4, 17,... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. It's evident that the problem is related to a type mismatch in the query, but this is being issued from a Haml template by the DataMapper ORM at a very high level of abstraction, so I'm not sure how I'd go about controlling this... Specifically, this seems to be throwing up on a call of p.comments from my Haml template, where p represents a given post. The Datamapper models are related as follows: class Post property :id, Serial ... has n, :comments end class Comment property :id, Serial ... belongs_to :post end This works fine on my local and current hosted environment using MySQL, but Postgres is clearly more strict. There must be hundreds of Datamapper & Haml apps running on Postgres DBs, and this model relationship is super-conventional, so hopefully someone has seen (and determined how to fix) this. Thanks!

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• Tree data in MySql database table

  - by Robert Koritnik

  I have a table that uses Adjacency list model for hierarchy storage. My most relevant columns in this table are therefore: ItemId // is auto_increment ParentId Level ParentTrail // in the form of "parentId/../parentId/itemId" then I created a before insert tigger, that populates columns Level and ParentTrail. Since the last column also includes current item's ID I had to use a trick in my trigger because auto_increment columns are not available in the before insert trigger. So I get that value from the information_schema.tables table. All works fine, until I try to write an update trigger, that would update my item and its descendants when the item changes its parent (ParentId has changed). But I can't make an update on my table inside the update trigger. All I can do is to change current record's values but not other's. I could use a separate table for hierarchy data, but that would mean that I would also have to create a view that would combine these two tables (1:1 relation) and I would like to avoid this is at all possible. Is there a way to have all these in the same table so that these fields (Level and ParetTrail) set/update themselves automagically using triggers?

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• Getting values from the html to the controller

  - by tina

  Hi, I'm trying to access the values a user introduces in a table from my controller. This table is NOT part of the model, and the view source code is something like: <table id="tableSeriales" summary="Seriales" class="servicesT" cellspacing="0" style="width: 100%"> <tr> <td class="servHd">Seriales</td> </tr> <tr id="t0"> <td class="servBodL"> <input id="0" type="text" value="1234" onkeypress = "return handleKeyPress(event, this.id);"/> <input id="1" type="text" value="578" onkeypress = "return handleKeyPress(event, this.id);"/> . . . </td> </tr> </table> How can I get those values (1234, 578) from the controller? Receiving a formcollection doesn't work since it does not get the table... Thank you.

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