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• iPhone application update (using Core Data on Sqlite)

  - by owen

  I have an app which is using Core Data on Sqlite, Now I have a update which has some DB structure changes say adding a new table I know when an app get updated, it updates the app binary only, nothing on document directory will be changed. When the app gets updated and launchs at the first time and run [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; It will find the difference between the data model and DB structure in Sqlite and will throw an exception and quit. Error: "The model used to open the store is incompatible with the one used to create the store" So, can anyone here give me some idea how to update an app when there is a DB structure change? I think we can run a DB script to create that new table when it launchs the update at the first time. But if there are other changes like changing the type of some fields or deleting some fields, and we need to migrate the old data, this is really a headache. In this case, Is the only way to do is creating a new app? Is there anyone tried something similar like this?

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• wrapping aspx user controls commands in a transaction

  - by Hans Gruber

  I'm working on heavily dynamic and configurable CMS system. Therefore, many pages are composed of a dynamically loaded set of user controls. To enable loose coupling between containers (pages) and children (user controls), all user controls are responsible for their own persistence. Each User Control is wired up to its data/service layer dependencies via IoC. They also implement an IPersistable interface, which allows the container .aspx page to issue a Save command to its children without knowledge of the number or exact nature of these user controls. Note: what follows is only pseudo-code: public class MyUserControl : IPersistable, IValidatable { public void Save() { throw new NotImplementedException(); } public bool IsValid() { throw new NotImplementedException(); } } public partial class MyPage { public void btnSave_Click(object sender, EventArgs e) { foreach (IValidatable control in Controls) { if (!control.IsValid) { throw new Exception("error"); } } foreach (IPersistable control in Controls) { if (!control.Save) { throw new Exception("error"); } } } } I'm thinking of using declarative transactions from the System.EnterpriseService namespace to wrap the btnSave_Click in a transaction in case of an exception, but I'm not sure how this might be achieved or any pitfalls to such an approach.

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• parse content away from structure in a binary file

  - by Jeff Godfrey

  Using C#, I need to read a packed binary file created using FORTRAN. The file is stored in an "Unformatted Sequential" format as described here (about half-way down the page in the "Unformatted Sequential Files" section): http://www.tacc.utexas.edu/services/userguides/intel8/fc/f_ug1/pggfmsp.htm As you can see from the URL, the file is organized into "chunks" of 130 bytes or less and includes 2 length bytes (inserted by the FORTRAN compiler) surrounding each chunk. So, I need to find an efficient way to parse the actual file payload away from the compiler-inserted formatting. Once I've extracted the actual payload from the file, I'll then need to parse it up into its varying data types. That'll be the next exercise. My first thoughts are to slurp up the entire file into a byte array using File.ReadAllBytes. Then, just iterate through the bytes, skipping the formatting and transferring the actual data to a second byte array. In the end, that second byte array should contain the actual file contents minus all the formatting, which I'd then need to go back through to get what I need. As I'm fairly new to C#, I thought there might be a better, more accepted way of tackling this. Also, in case it's helpful, these files could be fairly large (say 30MB), though most will be much smaller...

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• Getting response status code 0 in SmartGWT webservice call using json

  - by Girish

  I have developed application using SmartGWT, now i need to call webservice using json to another application which is deployed in another server for submitting username and password. When i make a request with url and POST method, getting the response status code as 0 and response text as blank. Here is my code, public void sendRequest() throws Exception { // Get login json data to be sent to server. String strData = createLoginReqPacket(); String url = "some url"; RequestBuilder builder = new RequestBuilder(RequestBuilder.POST, url); builder.setHeader("Content-Type", "application/json"); builder.setHeader("Content-Length", strData.length() + ""); Request response = builder.sendRequest(strData, new RequestCallback() { @Override public void onResponseReceived(Request request, Response response) { int statusCode = response.getStatusCode(); System.out.println("Response code ----"+response.getStatusCode()+""); if (statusCode == Response.SC_OK) { String responseBody = response.getText(); System.out.println("Respose :" + responseBody); // do something with the response } else { GWT.log("Response error at server side ----",null); // do in case of server error } }// end of method. @Override public void onError(Request request, Throwable exception) { GWT.log("**** Error in service call ******",null); }// end of method. }); builder.send(); }// end of send request. Please anybody knows the solution?? Give some reference code or links for this. Thanks.

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• In Java it seems Public constructors are always a bad coding practice

  - by Adam Gent

  This maybe a controversial question and may not be suited for this forum (so I will not be insulted if you choose to close this question). It seems given the current capabilities of Java there is no reason to make constructors public ... ever. Friendly, private, protected are OK but public no. It seems that its almost always a better idea to provide a public static method for creating objects. Every Java Bean serialization technology (JAXB, Jackson, Spring etc...) can call a protected or private no-arg constructor. My questions are: I have never seen this practice decreed or written down anywhere? Maybe Bloch mentions it but I don't own is book. Is there a use case other than perhaps not being super DRY that I missed? EDIT: I explain why static methods are better. .1. For one you get better type inference. For example See Guava's http://code.google.com/p/guava-libraries/wiki/CollectionUtilitiesExplained .2. As a designer of the class you can later change what is returned with a static method. .3. Dealing with constructor inheritance is painful especially if you have to pre-calculate something.

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• Type result with Ternary operator in C#

  - by Vaccano

  I am trying to use the ternary operator, but I am getting hung up on the type it thinks the result should be. Below is an example that I have contrived to show the issue I am having: class Program { public static void OutputDateTime(DateTime? datetime) { Console.WriteLine(datetime); } public static bool IsDateTimeHappy(DateTime datetime) { if (DateTime.Compare(datetime, DateTime.Parse("1/1")) == 0) return true; return false; } static void Main(string[] args) { DateTime myDateTime = DateTime.Now; OutputDateTime(IsDateTimeHappy(myDateTime) ? null : myDateTime); Console.ReadLine(); ^ } | } | // This line has the compile issue ---------------+ On the line indicated above, I get the following compile error: Type of conditional expression cannot be determined because there is no implicit conversion between '< null ' and 'System.DateTime' I am confused because the parameter is a nullable type (DateTime?). Why does it need to convert at all? If it is null then use that, if it is a date time then use that. I was under the impression that: condition ? first_expression : second_expression; was the same as: if (condition) first_expression; else second_expression; Clearly this is not the case. What is the reasoning behind this? (NOTE: I know that if I make "myDateTime" a nullable DateTime then it will work. But why does it need it? As I stated earlier this is a contrived example. In my real example "myDateTime" is a data mapped value that cannot be made nullable.)

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• generating and unmarshalling java classes while unmarshalling input contains a DTD

  - by Hans Westerbeek

  Hi, For a Spring-based project, I have the following situation to solve: I have XML files coming in whose contents I will have to parse at runtime. Those XML files come with a DTD reference. I need to generate the classes that the unmarshaller churns out using the right at build time, using the Maven2 plugin for the unmarshalling library of choice. This is also not very hard to do, once I have generated an XSD from the DTD. I want to use spring-oxm's UnMarshaller interface to do the unmarshalling at runtime. This I understand how to do. The xml files come in with a DTD reference, and all unmarshalling libraries out there want to do unmarshalling based on an XSD. Now, as described in the castor documentation, I can convert the DTD to an XSD and keep it on the classpath. However, when an actual XML file comes into the system it will still have that DTD reference at the top, and there's nothing I can really do about that (except for string replacing which feels hacky in this case). Will this cause the unmarshaller, like Castor to fail? Am I right in suspecting that this DTD reference will cause the unmarshalling to fail? Could I do pure DTD-based unmarshalling? Or can this somehow be prevented by providing detailed configuration to the unmarshaller? Until now, I have tried castor, xmlbeans and xstream. Which would fit my purposes best? Has anyone else been in this situation? Did you also end up just doing manual DOM or SAX parsing?

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• Login problem with php

  - by shinod

  I want to prevent multiple log in with same log in credentials simultaneously. So I made a column login_status and set it to 1 when some one logging in and change to 0 when logging out besides I set session after successful logged in. If user won't click on log out(in case of user close tab or because of some network problem) it doesn't update database and then one can't use that log in credentials again. So I use a ajax call to set current time stamp in database with related log in credentials and it is updated in each 2 minutes if user not navigate from that page. Then if some one attempts to log in with same log in credentials, it will check these time stamp if column login_status is 1, then if the time stamp is older than 3 minutes it allows the log in.Then it solving that problem. But the new problem is if user closes the tab or browser window and after 3 minutes one can log in with same log in credentials from somewhere and if the previous user open that page automatically it will log in as session is already set. How can I prevent this.

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• Undefined method `add' on a cucumber step that usually works.

  - by Josiah Kiehl

  I have a path defined: when /the admin home\s?page/ "/admin/" I have scenario that is passing: Scenario: Let admins see the admin homepage Given "pojo" is logged in And "pojo" is an "admin" And I am on the admin home page Then I should see "Hi there." And I have a scenario that is failing: Scenario: Review flagged photo Given "pojo" is logged in And "pojo" is an "admin" ...bunch of steps that create stuff in the database... And I am on the admin home page Then ... the rest of the steps The step that fails in the second one is "And I am on the admin home page" which passes just fine in the first scenario. Here's the error I get: And I am on the admin home page # features/step_definitions/web_steps.rb:18 undefined method `add' for {}:Hash (NoMethodError) ./app/controllers/admin_controller.rb:13:in `index' ./app/controllers/admin_controller.rb:11:in `each' ./app/controllers/admin_controller.rb:11:in `index' /usr/lib/ruby/1.8/benchmark.rb:308:in `realtime' ./features/step_definitions/web_steps.rb:19:in `/^(?:|I )am on (.+)$/' features/admin.feature:52:in `And I am on the admin home page' This is very odd... why would it be fine in the first case, and not in the second where the only difference are a bunch of steps that create records in the db? [edit] Here's the add stuff to database step: Given /^there is a "([^\"]*)" with the following:$/ do |model, table| model.constantize.create!(table.rows_hash) end

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• PHP, MySQL: mysql substitute for php in_array function

  - by Devner

  Hi all, Say if I have an array and I want to check if an element is a part of that array, I can go ahead and use in_array( needle, haystack ) to determine the results. I am trying to see the PHP equivalent of this for my purpose. Now you might have an instant answer for me and you might be tempted to say "Use IN". Yes, I can use IN, but that's not fetching the desired results. Let me explain with an example: I have a column called "pets" in DB table. For a record, it has a value: Cat, dog, Camel (Yes, the column data is a comma separated value). Consider that this row has an id of 1. Now I have a form where I can enter the value in the form input and use that value check against the value in the DB. So say I enter the following comma separated value in the form input: CAT, camel (yes, CAT is uppercase & intentional as some users tend to enter it that way). Now when I enter the above info in the form input and submit, I can collect the POST'ed info and use the following query: $search = $_POST['pets']; $sql = "SELECT id FROM table WHERE pets IN ('$search') "; The above query is not fetching me the row that already exists in the DB (remember the record which has Cat, dog, Camel as the value for the pets column?). I am trying to get the records to act as a superset and the values from the form input as subsets. So in this case I am expecting the id value to show up as the values exist in the column, but this is not happending. Now say if I enter just CAT as the form input and perform the search, it should show me the ID 1 row. Now say if I enter just camel, cAT as the form input and perform the search, it should show me the ID 1 row. How can I achieve the above? Thank you.

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• Are there solutions for streamlining the update of legacy code in multiple places?

  - by ccomet

  I'm working in some old code which was originally designed for handling two different kinds of files. I was recently tasked with adding a new kind of file to this code. Most of my problems were solved by filling out an extensive XML file with a new entry that handled everything from what lists were named to how the file is written in plural lower case. But this ended up being insufficient, as there were maybe 50 different places in 24 different code files where I had to update hardcoded switch-statements that only branched for the original two file types. Unfortunately there is no consistency in this; there are methods which operate half from the XML file, and half off of hardcode. Some of the files which look like they would operate off of the XML file don't, and some that I would expect that I'd need to update the hardcode don't need it. So the only way to find the majority of these is to run through testing the whole system when only part of it is operational, finding that one step to fix (when I'm lucky that error logging actually tells me what is going on), and then running the whole thing again. This wastes time testing the parts of the code which are already confirmed to work, time better spent testing the new parts I have to add on top of it all. It's a hassle and a half, and to my luck I can expect that I will have to add yet another new kind of file in the near future. Are there any solutions out there which can aid in this kind of endeavour? Something which I can input some parameters of current features, document what points in a whole code project actually need to be updated, and run something nice the next time I need to add a new feature to the code. It needn't even be fully automated, something that'll help me navigate straight to the specific points in everything and maybe even record what kind of parameters need to be loaded. Doubt it matters specifically, but the code is comprised of ASP.NET pages, some ASP.NET controls, hundreds of C# code files, and a handful of additional XML files. It's all currently in a couple big Visual Studio 2008 projects.

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• How to hold payment in paygate for a while?

  - by Fero

  HI all, I have a query regarding holding the payment in PAYGATE PAYMENT GATEWAY. Here is the problem in brief. I am doing a website where the payment should be made only a certain members buy the product. For Example if there is an iPhone in my site, then that particular phone must be buy by certain quantities which given by admin. It may be done one by one user or a single user can buy all the quantities at a single time. In this case as a developer how can i able to hold the payment which received by user? Because i don't want to receive the payments until the certain quantities bought. Because if certain quantities were not buy i need to refund the money to their account. We don't like to do this process. That's why we are looking for holding the payment. Is it possible or what is the best way to solve this problem? Please let me know what is you professional opinion? thanks in advance... Please let me know what is you professional opinion?

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• Potential g++ template bug?

  - by Evan Teran

  I've encountered some code which I think should compile, but doesn't. So I'm hoping some of the local standards experts here at SO can help :-). I basically have some code which resembles this: #include <iostream> template <class T = int> class A { public: class U { }; public: U f() const { return U(); } }; // test either the work around or the code I want... #ifndef USE_FIX template <class T> bool operator==(const typename A<T>::U &x, int y) { return true; } #else typedef A<int> AI; bool operator==(const AI::U &x, int y) { return true; } #endif int main() { A<int> a; std::cout << (a.f() == 1) << std::endl; } So, to describe what is going on here. I have a class template (A) which has an internal class (U) and at least one member function which can return an instance of that internal class (f()). Then I am attempting to create an operator== function which compares this internal type to some other type (in this case an int, but it doesn't seem to matter). When USE_FIX is not defined I get the following error: test.cc: In function 'int main()': test.cc:27:25: error: no match for 'operator==' in 'a.A<T>::f [with T = int]() == 1' Which seems odd, because I am clearly (I think) defining a templated operator== which should cover this, in fact if I just do a little of the work for the compiler (enable USE_FIX), then I no longer get an error. Unfortunately, the "fix" doesn't work generically, only for a specific instantiation of the template. Is this supposed to work as I expected? Or is this simply not allowed? BTW: if it matters I am using gcc 4.5.2.

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• How can I create a properly sizing QWebView?

  - by chacham15

  I want to make a QWebView appear expanding to the width and height so that ideally it will have no scroll bars. Some websites may have fixed widths that wont allow this, but I am not concerned with those. In any case, I cannot do as I wish because QWebView implements sizeHint as follows: QSize QWebView::sizeHint() const { return QSize(800, 600); // ####... } This is incorrect on a number of levels. 1. It doesnt at all take into account the size of the actual web page. 2. It doesnt take into account that the height and width are related to each other. (To prove #2 think about text in web pages that wraps to the next line.) As a simple fix I tried to do (where QResizingWebView extends QWebView): QSize QResizingWebView::sizeHint() const{ return this-page()-mainFrame()-contentsSize(); } While this is closer to the result, it also has 2 flaws. 1. It doesnt take into account the relation between the displayed width/height. 2. this->page()->mainFrame()->contentsSize() is inaccurate from what I can tell from my preliminary testing (it has returned heights larger than it should under many cases, although this may be related to #1). Does anyone have any tips to fix this?

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• Apps with lable XYZ could not be found

  - by HWM-Rocker

  Hello folks, today I ran into an error and have no clue how to fix it. Error: App with label XYZ could not be found. Are you sure your INSTALLED_APPS setting is correct? Where XYZ stands for the app-name that I am trying to reset. This error shows up every time I try to reset it (manage.py reset XYZ). Show all the sql code works. Even manage.py validate shows no error. I already commented out every single line of code in the models.py that I touched the last three monts. (function by function, model by model) And even if there are no models left I get this error. Here http://code.djangoproject.com/ticket/10706 I found a bugreport about this error. I also applied one the patches to allocate the error, it raises an exception so you have a trace back, but even there is no sign in what of my files the error occurred. I don't want to paste my code right now, because it is nearly 1000 lines of code in the file I edited the most. If someone of you had the same error please tell me were I can look for the problem. In that case I can post the important part of the source. Otherwise it would be too much at once. Thank you for helping!!!

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• Why thread in background is not waiting for task to complete?

  - by Haris Hasan

  I am playing with async await feature of C#. Things work as expected when I use it with UI thread. But when I use it in a non-UI thread it doesn't work as expected. Consider the code below private void Click_Button(object sender, RoutedEventArgs e) { var bg = new BackgroundWorker(); bg.DoWork += BgDoWork; bg.RunWorkerCompleted += BgOnRunWorkerCompleted; bg.RunWorkerAsync(); } private void BgOnRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs runWorkerCompletedEventArgs) { } private async void BgDoWork(object sender, DoWorkEventArgs doWorkEventArgs) { await Method(); } private static async Task Method() { for (int i = int.MinValue; i < int.MaxValue; i++) { var http = new HttpClient(); var tsk = await http.GetAsync("http://www.ebay.com"); } } When I execute this code, background thread don't wait for long running task in Method to complete. Instead it instantly executes the BgOnRunWorkerCompleted after calling Method. Why is that so? What am I missing here? P.S: I am not interested in alternate ways or correct ways of doing this. I want to know what is actually happening behind the scene in this case? Why is it not waiting?

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• How do I launch background jobs w/ paramiko?

  - by sophacles

  Here is my scenario: I am trying to automate some tasks using Paramiko. The tasks need to be started in this order (using the notation (host, task)): (A, 1), (B, 2), (C, 2), (A,3), (B,3) -- essentially starting servers and clients for some testing in the correct order. Further, because in the tests networking may get mucked up, and because I need some of the output from the tests, I would like to just redirect output to a file. In similar scenarios the common response is to use 'screen -m -d' or to use 'nohup'. However with paramiko's exec_cmd, nohup doesn't actually exit. Using: bash -c -l nohup test_cmd & doesnt work either, exec_cmd still blocks to process end. In the screen case, output redirection doesn't work very well, (actually, doesnt work at all the best I can figure out). So, after all that explanation, my question is: is there an easy elegant way to detach processes and capture output in such a way as to end paramiko's exec_cmd blocking? Update The dtach command works nicely for this!

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• TFS Folders - Getting them to work like Subversion "Trunk/Tags/Branches"

  - by Sam Schutte

  I recently started using Team Foundation Server, and am having some trouble getting it to work the way I want it to. I've used Subversion for a couple years now, and love the way it works. I always set up three folders under each project, Trunk, Tags, and Branches. When I'm working on a project, all my code lives under a folder called "C:\dev\projectname". This "projectname" folder can be made to point to either trunk, or any of the branches or tags using Subversion (with the switch command). Now that I'm using TFS (my client's system), I'd like things to work the same way. I created a "Trunk" folder with my project in it, and mapped "Project/Trunk/Website" to "c:\dev\Website". Now, I want to make a release under the "tags" folder (located in "Project/Tags/Version 1.0/Website", and TFS is giving me the following error when I execute the branch command: "No appropriate mapping exists for $Project/tags/Version 1.0/Website" From what I can find on the internet, TFS expects you to have a mapping to your hard drive at the root of the project (the "Project" folder in my case), and then have all the source code that lives in trunk, tags and branches all pulled down to your hard drive. This sucks because it requires way too much stuff on your hard drive, and even worse, when you are working in a solution in Visual Studio, you won't be able to pull down "Version 2.0" and have all your project references to other projects work, because they'll all be pointing to "trunk" folders under the main folder, not just the main folder itself. What I want to do is have the root "Project/Website" folder on my hard drive, and be able to have it point to (mapped to) either tags, branches, or trunk, depending on what i'm doing, without having to screw around with fixing Visual Studio project references. Ideas?

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• WM_NOTIFY and superclass chaining issue in Win32

  - by DasMonkeyman

  For reference I'm using the window superclass method outlined in this article. The specific issue occurs if I want to handle WM_NOTIFY messages (i.e. for custom drawing) from the base control in the superclass I either need to reflect them back from the parent window or set my own window as the parent (passed inside CREATESTRUCT for WM_(NC)CREATE to the base class). This method works fine if I have a single superclass. If I superclass my superclass then I run into a problem. Now 3 WindowProcs are operating in the same HWND, and when I reflect WM_NOTIFY messages (or have them sent to myself from the parent trick above) they always go to the outermost (most derived) WindowProc. I have no way to tell if they're messages intended for the inner superclass (base messages are supposed to go to the first superclass) or messages intended for the outer superclass (messages from the inner superclass are intended for the outer superclass). These messages are indistinguishable because they all come from the same HWND with the same control ID. Is there any way to resolve this without creating a new window to encapsulate each level of inheritance? Sorry about the wall of text. It's a difficult concept to explain. Here's a diagram. single superclass: SuperA::WindowProc() - Base::WindowProc()---\ ^--------WM_NOTIFY(Base)--------/ superclass of a superclass: SuperB::WindowProc() - SuperA::WindowProc() - Base::WindowProc()---\ ^--------WM_NOTIFY(Base)--------+-----------------------/ ^--------WM_NOTIFY(A)-----------/ The WM_NOTIFY messages in the second case all come from the same HWND and control ID, so I cannot distinguish between the messages intended for SuperA (from Base) and messages intended for SuperB (from SuperA). Any ideas?

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• Can I return JSON from an .asmx Web Service if the ContentType is not JSON?

  - by Click Ahead

  I would like to post a form using ajax and jquery to a .asmx webservice and return the value from the webservice as JSON. I'm using ASP.NET 4.0. I know that in order to return JSON from a webservice the following needs to be set (1) dataType: "json" (2) contentType: "application/json; charset=utf-8", (3) type: "POST" (4) set the Data to something. I have tested this and it works fine (i.e. my webservice returns the data as JSON) if all *four are set*. But, lets say in my case I want to do a standard form post i.e. test1=value1&test2=value2 so the contentType is not JSON but I want back JSON {test1:value1}. This doesn't seem to work because the contentType is "application/x-www-form-urlencoded" not "application/json; charset=utf-8". Can anyone tell me why I can't do this? It seems crazy to me that you have to explicitly send JSON to get JSON back, yet if you don't use JSON (i.e. post urlencoded contenttype) then the webservice will return XML. Any insights are greatly appreciated :)

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• Efficient Method for Preventing Hotlinking via .htaccess

  - by Michael Robinson

  I need to confirm something before I go accuse someone of ... well I'd rather not say. The problem: We allow users to upload images and embed them within text on our site. In the past we allowed users to hotlink to our images as well, but due to server load we unfortunately had to stop this. Current "solution": The method the programmer used to solve our "too many connections" issue was to rename the file that receives and processes image requests (image_request.php) to image_request2.php, and replace the contents of the original with <?php header("HTTP/1.1 500 Internal Server Error") ; ?> Obviously this has caused all images with their src attribute pointing to the original image_request.php to be broken, and is also the wrong code to be sending in this case. Proposed solution: I feel a more elegant solution would be: In .htaccess If the request is for image_request.php Check referrer If referrer is not our site, send the appropriate header If referrer is our site, proceed to image_request.php and process image request What I would like to know is: Compared to simply returning a 500 for each request to image_request.php: How much more load would be incurred if we were to use my proposed alternative solution outlined above? Is there a better way to do this? Our main concern is that the site stays up. I am not willing to agree that breaking all internally linked images is the best / only way to solve this. I refuse to tell our users that because of something WE changed they must now manually change the embed code in all their previously uploaded content.

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• ActiveRecord exceptions not rescued

  - by zoopzoop

  I have the following code block: unless User.exist?(...) begin user = User.new(...) # Set more attributes of user user.save! rescue ActiveRecord::RecordInvalid, ActiveRecord::RecordNotUnique => e # Check if that user was created in the meantime user = User.exists?(...) raise e if user.nil? end end The reason is, as you can probably guess, that multiple processes might call this method at the same time to create the user (if it doesn't already exist), so while the first one enters the block and starts initializing a new user, setting the attributes and finally calling save!, the user might already be created. In that case I want to check again if the user exists and only raise the exception if it still doesn't (= if no other process has created it in the meantime). The problem is, that regularly ActiveRecord::RecordInvalid exceptions are raised from the save! and not rescued from the rescue block. Any ideas? EDIT: Alright, this is weird. I must be missing something. I refactored the code according to Simone's tip to look like this: unless User.find_by_email(...).present? # Here we know the user does not exist yet user = User.new(...) # Set more attributes of user unless user.save # User could not be saved for some reason, maybe created by another request? raise StandardError, "Could not create user for order #{self.id}." unless User.exists?(:email => ...) end end Now I got the following exception: ActiveRecord::RecordNotUnique: Mysql::DupEntry: Duplicate entry '[email protected]' for key 'index_users_on_email': INSERT INTO `users` ... thrown in the line where it says 'unless user.save'. How can that be? Rails thinks the user can be created because the email is unique but then the Mysql unique index prevents the insert? How likely is that? And how can it be avoided?

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• how to number t-rows ,when table generated using nested forloop in django templates

  - by stackover

  Hi, This part is from views.py results=[(A,[stuObj1,stuObj2,stuObj3]),(B,[stuObj4,stuObj5,stuObj6]),(C,[stuObj7,stuObj8])] for tup in results: total = tot+len(tup[1]) render_to_response(url,{'results':res , 'total':str(tot),}) this is template code: <th class="name">Name</th> <th class="id">Student ID</th> <th class="grade">Grade</th> {% for tup in results %} {% for student in tup|last %} {% with forloop.parentloop.counter as parentid%} {% with forloop.counter as centerid%} <tbody class="results-body"> <tr> <td>{{student.fname|lower|capfirst}} {{student.lname|lower|capfirst}}</td> <td>{{student.id}}</td> <td>{{tup|first}}</td> </tr> {% endfor %} {% endfor %} Now the problems am having are 1. numbering the rows. Here my problem is am not sure if i can do things like total=total-1 in the templates to get the numbered rows like <td>{{total}}</td> 2.applying css to tr:ever or odd. Whats happening in this case is everytime the loop is running the odd/even ordering is lost. these seems related problems. Any ideas would be great :)

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• Hiring my first employee

  - by Ady

  A few years ago I moved to a new job having been programming for 2 years using C#, however this new company was mainly using VB6. I made the case for .NET and won, but one of the consessions I had to make was to use VB.NET and not C# (understandable as most of the other developers were already using VB). Three years later it was time to move on, but when applying for jobs I couldn't get past the recruitment agents. I realised that when they were looking at the basic requirements (5 years experience) that they could not add 2 and 3 together to make 5. They were looking for 5 years in VB or C# not across both. Frustrated I decided to combine my skills with a designer friend and start my own company. After two years of hard graft we are now looking for our first employee (a programmer), and this question has hit me again, but now I see the employers perspective. Why take the risk of someone getting up to speed when you have thousands of applicants to choose from. So my question is this, if I define the requirements to be too narrow, I could miss the really great candidates. But if they are too broad it's going to take ages to go through them all. This will be our first 'employee' so the choice needs to be good, I can't afford to make a mistake and employ someone naff. Another option would be to choose a bright university graduate, and train them up (less of a risk because we can pay them less). What have others done in this situation, and what would you recommend I do?

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• Fetch the most viewed data in databases

  - by Erik Edgren

  I want to get the most viewed photo from the database but I don't know how I shall accomplish this. Here's my SQL at the moment: SELECT * FROM photos AS p, viewers AS v WHERE p.id = v.id_photo GROUP BY v.id_photo The databases: CREATE TABLE IF NOT EXISTS `photos` ( `id` int(10) NOT NULL AUTO_INCREMENT, `photo_filename` varchar(50) NOT NULL, `photo_camera` varchar(150) NOT NULL, `photo_taken` datetime NOT NULL, `photo_resolution` varchar(10) NOT NULL, `photo_exposure` varchar(10) NOT NULL, `photo_iso` varchar(3) NOT NULL, `photo_fnumber` varchar(10) NOT NULL, `photo_focallength` varchar(10) NOT NULL, `post_coordinates` text NOT NULL, `post_description` text NOT NULL, `post_uploaded` datetime NOT NULL, `post_edited` datetime NOT NULL, `checkbox_approxcoor` enum('0','1') NOT NULL DEFAULT '0', PRIMARY KEY (`id`), UNIQUE KEY `id` (`id`) ) CREATE TABLE IF NOT EXISTS `viewers` ( `id` int(10) NOT NULL AUTO_INCREMENT, `id_photo` int(10) DEFAULT '0', `ipaddress` text NOT NULL, `date_viewed` datetime NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `id` (`id`) ) The data in viewers looks like this: (1, 85, '3892a0ab97d6ff325f285b27b847070f', '2012-06-21 22:49:25'), (2, 84, '3892a0ab97d6ff325f285b27b847070f', '2012-06-21 22:49:25'), (3, 85, '3892a0ab97d6ff325f285b27b847070f', '2012-06-21 22:49:25'); One single row from the database for photos to understand how the rows looks like in this database: (85, 'P1170986.JPG', 'Panasonic DMC-LX3', '2012-06-19 18:00:40', '3968x2232', '10/8000', '80', '50/10', '51/10', '', '', '2012-06-19 18:45:17', '0000-00-00 00:00:00', '0') At the moment the SQL only prints the photo with ID 84. In this case it's wrong - it should print out the photo with ID 85. How can I fix this problem? Thanks in advance.

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