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• Account confirmation email sent as SPAM

  - by praveen

  I am using PHPMailer to send a confirmation email for newly registered users in my social network. But I found out most of them have ended up in user's spam list. (Hotmail and Yahoo). How to avoid this? This is my script $mail=new PHPMailer(); $mail->IsSMTP(); $mail->SMTPAuth = mSMTPAuth(); $mail->SMTPSecure = mSMTPSecure(); $mail->Host = mHost(); $mail->Port = mPort(); $mail->Username = mUsername(); $mail->Password = mPassword(); $mail->From = mFrom(); $mail->FromName = "SiteName"; $mail->Subject = "SiteName New Account Activation"; $mail->IsHTML(true); $mail->WordWrap = 50; $mail->Body = "<h2>Welcome to " .$sitename. " " .$username. "! </h2><br><br>"; $mail->Body .= "Please click on the link below to verify your email address:<br><br>"; $mail->Body .= "<a href='".$base. "verify.php?a=" .$gen_key."'>".$base. "verify.php?a=" .$gen_key."</a>"; $mail->Body .= "<br><br>Regards<br>"; $mail->AltBody = "Welcome to " .$sitename. " " .$username. "!\n\nTo verify your email address, please click on the link below:\n\n".$base. "verify.php?a=" .$gen_key; $mail->AddAddress($email); $mail->Send(); $mail->ClearAddresses();

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• MemoryStream, XmlTextWriter and Warning 4 CA2202 : Microsoft.Usage

  - by rasx

  The Run Code Analysis command in Visual Studio 2010 Ultimate returns a warning when seeing a certain pattern with MemoryStream and XmlTextWriter. This is the warning: Warning 7 CA2202 : Microsoft.Usage : Object 'ms' can be disposed more than once in method 'KinteWritePages.GetXPathDocument(DbConnection)'. To avoid generating a System.ObjectDisposedException you should not call Dispose more than one time on an object.: Lines: 421 C:\Visual Studio 2010\Projects\Songhay.DataAccess.KinteWritePages\KinteWritePages.cs 421 Songhay.DataAccess.KinteWritePages This is the form: static XPathDocument GetXPathDocument(DbConnection connection) { XPathDocument xpDoc = null; var ms = new MemoryStream(); try { using(XmlTextWriter writer = new XmlTextWriter(ms, Encoding.UTF8)) { using(DbDataReader reader = CommonReader.GetReader(connection, Resources.KinteRssSql)) { writer.WriteStartDocument(); writer.WriteStartElement("data"); do { while(reader.Read()) { writer.WriteStartElement("item"); for(int i = 0; i < reader.FieldCount; i++) { writer.WriteRaw(String.Format("<{0}>{1}</{0}>", reader.GetName(i), reader[i].ToString())); } writer.WriteFullEndElement(); } } while(reader.NextResult()); writer.WriteFullEndElement(); writer.WriteEndDocument(); writer.Flush(); ms.Position = 0; xpDoc = new XPathDocument(ms); } } } finally { ms.Dispose(); } return xpDoc; } The same kind of warning is produced for this form: XPathDocument xpDoc = null; using(var ms = new MemoryStream()) { using(XmlTextWriter writer = new XmlTextWriter(ms, Encoding.UTF8)) { using(DbDataReader reader = CommonReader.GetReader(connection, Resources.KinteRssSql)) { //... } } } return xpDoc; By the way, the following form produces another warning: XPathDocument xpDoc = null; var ms = new MemoryStream(); using(XmlTextWriter writer = new XmlTextWriter(ms, Encoding.UTF8)) { using(DbDataReader reader = CommonReader.GetReader(connection, Resources.KinteRssSql)) { //... } } return xpDoc; The above produces the warning: Warning 7 CA2000 : Microsoft.Reliability : In method 'KinteWritePages.GetXPathDocument(DbConnection)', object 'ms' is not disposed along all exception paths. Call System.IDisposable.Dispose on object 'ms' before all references to it are out of scope. C:\Visual Studio 2010\Projects\Songhay.DataAccess.KinteWritePages\KinteWritePages.cs 383 Songhay.DataAccess.KinteWritePages In addition to the following, what are my options?: Supress warning CA2202. Supress warning CA2000 and hope that Microsoft is disposing of MemoryStream (because Reflector is not showing me the source code). Rewrite my legacy code to recognize the wonderful XDocument and LINQ to XML.

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• Loading external pngs into an AS2 swf that is loaded into an AS3 swf wrapper

  - by James Fassett

  I have a Wrapper SWF that loads a series of AS2 movies. Each AS2 movie loads a series of .png files. AS3_wrapper.swf |-> AS2_1.swf |-> image_1.png |-> image_2.png |-> AS2_2.swf |-> image_1.png |-> image_2.png Inside of the AS2 I listen for the load of the pngs using onLoadInit and update my UI. This works fine for the first AS2 swf. But when I load the second AS2 swf the onLoadInit isn't triggered for the pngs. My guess is that the images are in a cache or something like that. I put a random string on the end of the request to try and avoid the cache but that doesn't seem to work. The code in the as2 looks roughly like this: var flagLoader:MovieClipLoader = new MovieClipLoader(); var listener:Object = new Object(); listener.onLoadInit = Delegate.create(this, handleImageLoad); flagLoader.addListener(listener); var row:MovieClip = frame1["row" + (numLoaded + 1)]; flagLoader.loadClip(predictionData[numLoaded].flag + "?r="+Math.random(), row.flag); I'm making sure to load only one image at a time (I've read anecdotal evidence loading more than one thing at a time can confuse the MovieClipLoader). For the first as2 file everything works great. When I load the second as2 file the handleImageLoad never gets called. Update: Even more perplexing is if I reload the first AS2 movie (after the second AS2 movie fails to load the images) the first AS2 movie loads the images again fine. Update 2: After trying to change from using a MovieClipLoader to polling (as was helpfully suggested) I have found some more evidence that is relevant. When I load the first AS2 files and trace from the top level clip it prints out _root. The second AS2 file when loaded traces the same _root. This lead me to check if they were clashing on names and they are. Both have a child called frame. The first one, when I trace it comes out as _root.frame as expected. The second AS2 file traces _level0.instance3.instance118.instance111.frame. I'm guessing this is related to the problem. Flash is keeping the _root of the two files the same but it is changing the locations of their children (for subsequently loaded files that have children with the same names). So either the onLoad is going to the wrong clip or the events about it loading are.

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• Avoiding Redundancies in XML documents

  - by MarceloRamires

  I was working with a certain XML where there were no redundancies <person> <eye> <eye_info> <eye_color> blue </eye_color> </eye_info> </eye> <hair> <hair_info> <hair_color> blue </hair_color> </hair_info> </hair> </person> As you can see, the sub-tag eye-color makes reference to eye in it's name, so there was no need to avoid redundancies, I could get the eye color in a single line after loading the XML into a dataset: dataset.ReadXml(path); value = dataset.Tables("eye_info").Rows(0)("eye_color"); I do realise it's not the smartest way of doing so, and this situation I'm having now wasn't unforeseen. Now, let's say I have to read xml's that are in this format: <person> <eye> <info> <color> blue </color> </info> </eye> <hair> <info> <color> blue </color> </info> </hair> </person> So If I try to call it like this: dataset.ReadXml(path); value = dataset.Tables("info").Rows(0)("color"); There will be a redundancy, because I could only go as far as one up level to identify a single field in a XML with my previous method, and the 'disambiguator' is three levels above. Is there a practical way to reach with no mistake a single field given all the above (or at least a few) fields ?

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• A couple questions using fwrite/fread with data structures

  - by Nazgulled

  Hi, I'm using fwrite() and fread() for the first time to write some data structures to disk and I have a couple of questions about best practices and proper ways of doing things. What I'm writing to disk (so I can later read it back) is all user profiles inserted in a Graph structure. Each graph vertex is of the following type: typedef struct sUserProfile { char name[NAME_SZ]; char address[ADDRESS_SZ]; int socialNumber; char password[PASSWORD_SZ]; HashTable *mailbox; short msgCount; } UserProfile; And this is how I'm currently writing all the profiles to disk: void ioWriteNetworkState(SocialNetwork *social) { Vertex *currPtr = social->usersNetwork->vertices; UserProfile *user; FILE *fp = fopen("save/profiles.dat", "w"); if(!fp) { perror("fopen"); exit(EXIT_FAILURE); } fwrite(&(social->usersCount), sizeof(int), 1, fp); while(currPtr) { user = (UserProfile*)currPtr->value; fwrite(&(user->socialNumber), sizeof(int), 1, fp); fwrite(user->name, sizeof(char)*strlen(user->name), 1, fp); fwrite(user->address, sizeof(char)*strlen(user->address), 1, fp); fwrite(user->password, sizeof(char)*strlen(user->password), 1, fp); fwrite(&(user->msgCount), sizeof(short), 1, fp); break; currPtr = currPtr->next; } fclose(fp); } Notes: The first fwrite() you see will write the total user count in the graph so I know how much data I need to read back. The break is there for testing purposes. There's thousands of users and I'm still experimenting with the code. My questions: After reading this I decided to use fwrite() on each element instead of writing the whole structure. I also avoid writing the pointer to to the mailbox as I don't need to save that pointer. So, is this the way to go? Multiple fwrite()'s instead of a global one for the whole structure? Isn't that slower? How do I read back this content? I know I have to use fread() but I don't know the size of the strings, cause I used strlen() to write them. I could write the output of strlen() before writing the string, but is there any better way without extra writes?

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• IE6 Bug - Div within Anchor tag: inline images not links

  - by thorn100

  I'm trying to get everything in the anchor tag to be a clickable link. Unfortunately, in IE6 (which is the only browser I'm concerned with currently), the only thing that isn't a clickable link are the inline images. I know that it's not valid html to put a div inside of an anchor but it's not my markup and I've been asked to avoid changing it. Any suggestions to altering the CSS to enable the images as clickable links? If changing the markup is the only solution... any suggestions there? My initial thought was to set the image as a background of it's parent (.ph-item-featured-img), although I'm unclear if that will solve the problem. Thanks! <div class="tab-panel-init clear ui-tabs-panel ui-widget-content ui-corner-bottom" id="ph-flashlights"> <a href="#" class="last ph-item-featured clear"> <div class="ph-item-featured-img"> <img src="#"> &nbsp; </div> <strong> PRODUCT CODE </strong> <p> PRODUCT CODE Heavy Duty Aluminum Led Flashlight </p> <span>Learn more &gt;</span> </a> <a href="#" class="last ph-item-featured clear"> <div class="ph-item-featured-img"> <img src="#"> &nbsp; </div> <strong> PRODUCT CODE </strong> <p> PRODUCT CODE Heavy Duty Aluminum Led Flashlight </p> <span>Learn more &gt;</span> </a> </div>

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• Is there any reasonable use of a function returning an anonymous struct?

  - by Akanksh

  Here is an (artificial) example of using a function that returns an anonymous struct and does "something" useful: #include <iostream> template<typename T> T* func( T* t, float a, float b ) { if(!t) { t = new T; t->a = a; t->b = b; } else { t->a += a; t->b += b; } return t; } struct { float a, b; }* foo(float a, float b) { if(a==0) return 0; return func(foo(a-1,b), a, b); } int main() { std::cout << foo(5,6)->a << std::endl; std::cout << foo(5,6)->b << std::endl; void* v = (void*)(foo(5,6)); float* f = (float*)(v); //[1] delete f now because I know struct is floats only. std::cout << f[0] << std::endl; std::cout << f[1] << std::endl; delete[] f; return 0; } There are a few points I would like to discuss: As is apparent, this code leaks, is there anyway I can NOT leak without knowing what the underlying struct definition is? see Comment [1]. I have to return a pointer to an anonymous struct so I can create an instance of the object within the templatized function func, can I do something similar without returning a pointer? I guess the most important, is there ANY (real-world) use for this at all? As the example given above leaks and is admittedly contrived. By the way, what the function foo(a,b) does is, to return a struct containing two numbers, the sum of all numbers from 1 to a and the product of a and b. EDIT: Maybe the line new T could use a boost::shared_ptr somehow to avoid leaks, but I haven't tried that. Would that work?

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• MS Access 2003 - Option Group frame: can I add text boxes that are part of the frame instead of rad

  - by Justin

  Ok so this maybe a simple/silly question but I don't know so here goes: In access let's say I want to have a frame control, so I click the option group button and add it to the desgin surface. However, I am not wanting to use this as a option group with radio button selection, instead I would like to add text boxes instead the frame, so that when I reference the frame, it references every control instead of it, hence the text boxes, cbo boxes, etc.....just as it would if they were radio option selections. So can you do this? I want whatever controls I add inside the frame to be easily referenced (i.e. make all controls visible just by using frameExample.visible = true) so that I can build my own tab control groupings..... can this be done? Thanks! EDIT: What I am trying to accomplish is having a form that includes a collection of controls (input controls - cbo boxes, text boxes, etc), that serve as the Main record information. These are saved to a table via an INSERT statement on button_click because this form is unbound. Next I have 8 categories that are relative per each main record (and data that goes along with it). Each of these categories could have a sub form area and a button click that bring it's relative form into the sub form area. These sub forms would be unbound as well as I would just save data via SQL statement. So i know I could accomplish this by running the insert statement from the parent form, on the main collection control's data that would create the KeyID number, then run a SQL statement that would turn around and load that KeyID number right back onto the page in a hidden text box. Then when I click one of the sub forms and load its relative collection of controls, I could then save that data along with KeyID for each of these sub-forms/tables. SO...... I was wondering if instead you could define these controls as a collection so that you could hide and make visible all the ones you need on button clicks and avoid the need for additional forms (subs). I know that if a user enters data into a text box, and then somewhere along the way that box becomes hidden, the data still exists in it and still ends up in the SQL statement.... So I want all these controls to exist on the same form, but I thought what is I could encapsulate them into a frame like an option group, then I could call the frame and all the relative controls would be called up (made visible) as needed. Sorry for the long explanation but I thought it would help.

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• Is ResourceBundle fallback resolution broken in Resin3x?

  - by LES2

  Given the following ResourceBundle properties files: messages.properties messages_en.properties messages_es.properties messages_{some locale}.properties Note: messages.properties contains all the messages for the default locale. messages_en.properties is really empty - it's just there for correctness. messages_en.properties will fall back to messages.properties! And given the following config params in web.xml: <context-param> <param-name>javax.servlet.jsp.jstl.fmt.localizationContext</param-name> <param-value>messages</param-value> </context-param> <context-param> <param-name>javax.servlet.jsp.jstl.fmt.fallbackLocale</param-name> <param-value>en</param-value> </context-param> I would expect that if the chosen locale is 'es', and a resource is not translated in 'es', then it would fall back to 'en', and finally to 'messages.properties' (since messages_en.properties is empty). This is how things work in Jetty. I've also tested this on WebSphere. Resin Is the Problem The problem is when I get to Resin (3.0.23). Fallback resolution does not work at all! In order to get an messages to display, I must do the following: Rename messages.properties to messages_en.properties (essentially, swap the contents of messages.properties and messages_en.properties) Make sure ever key in messages_en.properties is also defined in messages_{every other locale}.properties (even if the exact same). If I don't do this, I get "???some.key???" in the JSPs. Please help! This is perplexing. -- LES SOLUTION Add following to pom.xml (if you're using maven) ... <properties> <taglibs.version>1.1.2</taglibs.version> </properties> ... <!-- Resin ships with a crappy JSTL implementation that doesn't work with fallback locales for resource bundles correctly; we therefore include our own JSTL implementation in the WAR, and avoid this problem. This can be removed if the target container is not resin. --> <dependency> <groupId>taglibs</groupId> <artifactId>standard</artifactId> <version>${taglibs.version}</version> <scope>compile</scope> </dependency>

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• JavaScript: Given an offset and substring length in an HTML string, what is the parent node?

  - by Bungle

  My current project requires locating an array of strings within an element's text content, then wrapping those matching strings in <a> elements using JavaScript (requirements simplified here for clarity). I need to avoid jQuery if at all possible - at least including the full library. For example, given this block of HTML: <div> <p>This is a paragraph of text used as an example in this Stack Overflow question.</p> </div> and this array of strings to match: ['paragraph', 'example'] I would need to arrive at this: <div> <p>This is a <a href="http://www.example.com/">paragraph</a> of text used as an <a href="http://www.example.com/">example</a> in this Stack Overflow question.</p> </div> I've arrived at a solution to this by using the innerHTML() method and some string manipulation - basically using the offsets (via indexOf()) and lengths of the strings in the array to break the HTML string apart at the appropriate character offsets and insert <a href="http://www.example.com/"> and </a> tags where needed. However, an additional requirement has me stumped. I'm not allowed to wrap any matched strings in <a> elements if they're already in one, or if they're a descendant of a heading element (<h1> to <h6>). So, given the same array of strings above and this block of HTML (the term matching has to be case-insensitive, by the way): <div> <h1>Example</a> <p>This is a <a href="http://www.example.com/">paragraph of text</a> used as an example in this Stack Overflow question.</p> </div> I would need to disregard both the occurrence of "Example" in the <h1> element, and the "paragraph" in <a href="http://www.example.com/">paragraph of text</a>. This suggests to me that I have to determine which node each matched string is in, and then traverse its ancestors until I hit <body>, checking to see if I encounter a <a> or <h_> node along the way. Firstly, does this sound reasonable? Is there a simpler or more obvious approach that I've failed to consider? It doesn't seem like regular expressions or another string-based comparison to find bounding tags would be robust - I'm thinking of issues like self-closing elements, irregularly nested tags, etc. There's also this... Secondly, is this possible, and if so, how would I approach it?

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• Variable sized packet structs with vectors

  - by Rev316

  Lately I've been diving into network programming, and I'm having some difficulty constructing a packet with a variable "data" property. Several prior questions have helped tremendously, but I'm still lacking some implementation details. I'm trying to avoid using variable sized arrays, and just use a vector. But I can't get it to be transmitted correctly, and I believe it's somewhere during serialization. Now for some code. Packet Header class Packet { public: void* Serialize(); bool Deserialize(void *message); unsigned int sender_id; unsigned int sequence_number; std::vector<char> data; }; Packet ImpL typedef struct { unsigned int sender_id; unsigned int sequence_number; std::vector<char> data; } Packet; void* Packet::Serialize(int size) { Packet* p = (Packet *) malloc(8 + 30); p->sender_id = htonl(this->sender_id); p->sequence_number = htonl(this->sequence_number); p->data.assign(size,'&'); //just for testing purposes } bool Packet::Deserialize(void *message) { Packet *s = (Packet*)message; this->sender_id = ntohl(s->sender_id); this->sequence_number = ntohl(s->sequence_number); this->data = s->data; } During execution, I simply create a packet, assign it's members, and send/receive accordingly. The above methods are only responsible for serialization. Unfortunately, the data never gets transferred. Couple of things to point out here. I'm guessing the malloc is wrong, but I'm not sure how else to compute it (i.e. what other value it would be). Other than that, I'm unsure of the proper way to use a vector in this fashion, and would love for someone to show me how (code examples please!) :) Edit: I've awarded the question to the most comprehensive answer regarding the implementation with a vector data property. Appreciate all the responses!

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• How can I create specialized builders for semantic layout in rails?

  - by Paul Alexander

  This is how I'd like to write markup in say index.html.erb <%= page_for "Super Cool Page" do |p| %> <%= p.header do %> Ruby is Cool <% end %> <%= p.body do %> Witty discourse on Ruby. <% end %> <% if page.has_sidebar? %> <%= p.sidebar do %> <ul><li>Option 1</li></ul> <% end %> <% end %> <% end %> Which would output <div class="page"> <header><h1>Super Cool Page</h1></header> <section> Witty discourse on Ruby. </section> </div> and when page.has_sidebar? is true <div class="page"> <header><h1>Super Cool Page</h1></header> <asside><ul><li>Option 1</li></ul></asside> <section> Witty discourse on Ruby. </section> </div> I've taken a look at the FormHelper class in rails for guidance, but it seems like I'd have to duplicate a lot of work which I'm trying to avoid. I'm really just trying to figure out where to hang the classes/modules/methods in the framework and whit kind of object |p| should be. My first inclination was to create a PageBuilder class that implements header, body and sidebar methods. But I got stuck on the rendering pipeline to get everything output just right. Is there a gem that already provides this type of semantic generation? If not I'd love any insight on how to set this up.

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• JDBC CommunicationsException with MySQL Database

  - by Dominik Siebel

  I'm having a little trouble with my MySQL- Connection- Pooling. This is the case: Different jobs are scheduled via Quartz. All jobs connect to different databases which works fine the whole day while the nightly scheduled jobs fail with a CommunicationsException... Quartz-Jobs: Job1 runs 0 0 6,10,14,18 * * ? Job2 runs 0 30 10,18 * * ? Job3 runs 0 0 5 * * ? As you can see the last job runs at 18 taking about 1 hour to run. The first job at 5am is the one that fails. I already tried all kinds of parameter-combinations in my resource config this is the one I am running right now: <!-- Database 1 (MySQL) --> <Resource auth="Container" driverClassName="com.mysql.jdbc.Driver" maxActive="100" maxIdle="30" maxWait="10000" removeAbandoned="true" removeAbandonedTimeout="60" logAbandoned="true" type="javax.sql.DataSource" name="jdbc/appDbProd" username="****" password="****" url="jdbc:mysql://127.0.0.1:3306/appDbProd?autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=UTF-8" testWhileIdle="true" testOnBorrow="true" testOnReturn="true" validationQuery="SELECT 1" timeBetweenEvictionRunsMillis="1800000" /> <!-- Database 2 (MySQL) --> <Resource auth="Container" driverClassName="com.mysql.jdbc.Driver" maxActive="100" maxIdle="30" maxWait="10000" removeAbandoned="true" removeAbandonedTimeout="60" logAbandoned="true" type="javax.sql.DataSource" name="jdbc/prodDbCopy" username="****" password="****" url="jdbc:mysql://127.0.0.1:3306/prodDbCopy?autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=UTF-8" testWhileIdle="true" testOnBorrow="true" testOnReturn="true" validationQuery="SELECT 1" timeBetweenEvictionRunsMillis="1800000" /> <!-- Database 3 (MSSQL)--> <Resource auth="Container" driverClassName="net.sourceforge.jtds.jdbc.Driver" maxActive="30" maxIdle="30" maxWait="100" removeAbandoned="true" removeAbandonedTimeout="60" logAbandoned="true" name="jdbc/catalogDb" username="****" password="****" type="javax.sql.DataSource" url="jdbc:jtds:sqlserver://127.0.0.1:1433;databaseName=catalog;useNdTLMv2=false" testWhileIdle="true" testOnBorrow="true" testOnReturn="true" validationQuery="SELECT 1" timeBetweenEvictionRunsMillis="1800000" /> For obvious reasons I changed IPs, Usernames and Passwords but they can be assumed to be correct, seeing that the application runs successfully the whole day. The most annoying thing is: The first job that runs first queries Database2 successfully but fails to query Database1 for some reason (CommunicationsException): Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 39,376,539 milliseconds ago. The last packet sent successfully to the server was 39,376,539 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem. Any ideas? Thanks!

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• How to convert a 32bpp image to an indexed format?

  - by Ed Swangren

  So here are the details (I am using C# BTW): I receive a 32bpp image (JPEG compressed) from a server. At some point, I would like to use the Palette property of a bitmap to color over-saturated pixels (brightness 240) red. To do so, I need to get the image into an indexed format. I have tried converting the image to a GIF, but I get quality loss. I have tried creating a new bitmap in an index format by these methods: // causes a "Parameter not valid" error Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Indexed) // no error, but the resulting image is black due to information loss I assume Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Format8bppIndexed) I am at a loss now. The data in this image is changed constantly by the user, so I don't want to manually set pixels that have a brightness 240 if I can avoid it. If I can set the palette once when the image is created, my work is done. If I am going about this the wrong way to begin with please let me know. EDIT: Thanks guys, here is some more detail on what I am attempting to accomplish. We are scanning a tissue slide at high resolution (pathology application). I write the interface to the actual scanner. We use a line-scan camera. To test the line rate of the camera, the user scans a very small portion and looks at the image. The image is displayed next to a track bar. When the user moves the track bar (adjusting line rate), I change the overall intensity of the image in an attempt to model what it would look like at the new line rate. I do this using an ImageAttributes and ColorMatrix object currently. When the user adjusts the track bar, I adjust the matrix. This does not give me per pixel information, but the performance is very nice. I could use LockBits and some unsafe code here, but I would rather not rewrite it if possible. When the new image is created, I would like for all pixels with a brightness value of 240 to be colored red. I was thinking that defining a palette for the bitmap up front would be a clean way of doing this.

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• Segmenting a double array of labels

  - by Ami

  The Problem: I have a large double array populated with various labels. Each element (cell) in the double array contains a set of labels and some elements in the double array may be empty. I need an algorithm to cluster elements in the double array into discrete segments. A segment is defined as a set of pixels that are adjacent within the double array and one label that all those pixels in the segment have in common. (Diagonal adjacency doesn't count and I'm not clustering empty cells). |-------|-------|------| | Jane | Joe | | | Jack | Jane | | |-------|-------|------| | Jane | Jane | | | | Joe | | |-------|-------|------| | | Jack | Jane | | | Joe | | |-------|-------|------| In the above arrangement of labels distributed over nine elements, the largest cluster is the “Jane” cluster occupying the four upper left cells. What I've Considered: I've considered iterating through every label of every cell in the double array and testing to see if the cell-label combination under inspection can be associated with a preexisting segment. If the element under inspection cannot be associated with a preexisting segment it becomes the first member of a new segment. If the label/cell combination can be associated with a preexisting segment it associates. Of course, to make this method reasonable I'd have to implement an elaborate hashing system. I'd have to keep track of all the cell-label combinations that stand adjacent to preexisting segments and are in the path of the incrementing indices that are iterating through the double array. This hash method would avoid having to iterate through every pixel in every preexisting segment to find an adjacency. Why I Don't Like it: As is, the above algorithm doesn't take into consideration the case where an element in the double array can be associated with two unique segments, one in the horizontal direction and one in the vertical direction. To handle these cases properly, I would need to implement a test for this specific case and then implement a method that will both associate the element under inspection with a segment and then concatenate the two adjacent identical segments. On the whole, this method and the intricate hashing system that it would require feels very inelegant. Additionally, I really only care about finding the large segments in the double array and I'm much more concerned with the speed of this algorithm than with the accuracy of the segmentation, so I'm looking for a better way. I assume there is some stochastic method for doing this that I haven't thought of. Any suggestions?

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• wget not behaving via IPC::Open3 vs bash

  - by Ryley

  I'm trying to stream a file from a remote website to a local command and am running into some problems when trying to detect errors. The code looks something like this: use IPC::Open3; my @cmd = ('wget','-O','-','http://10.10.1.72/index.php');#any website will do here my ($wget_pid,$wget_in,$wget_out,$wget_err); if (!($wget_pid = open3($wget_in,$wget_out,$wget_err,@cmd))){ print STDERR "failed to run open3\n"; exit(1) } close($wget_in); my @wget_outs = <$wget_out>; my @wget_errs = <$wget_err>; print STDERR "wget stderr: ".join('',@wget_errs); #page and errors outputted on the next line, seems wrong print STDERR "wget stdout: ".join('',@wget_outs); #clean up after this, not shown is running the filtering command, closing and waitpid'ing When I run that wget command directly from the command-line and redirect stderr to a file, something sane happens - the stdout will be the downloaded page, the stderr will contain the info about opening the given page. wget -O - http://10.10.1.72/index.php 2> stderr_test_file When I run wget via open3, I'm getting both the page and the info mixed together in stdout. What I expect is the loaded page in one stream and STDERR from wget in another. I can see I've simplified the code to the point where it's not clear why I want to use open3, but the general plan is that I wanted to stream stdout to another filtering program as I received it, and then at the end I was going to read the stderr from both wget and the filtering program to determine what, if anything went wrong. Other important things: I was trying to avoid writing the wget'd data to a file, then filtering that file to another file, then reading the output. It's key that I be able to see what went wrong, not just reading $? 8 (i.e. I have to tell the user, hey, that IP address is wrong, or isn't the right kind of website, or whatever). Finally, I'm choosing system/open3/exec over other perl-isms (i.e. backticks) because some of the input is provided by untrustworthy users.

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• Joomla - Force File Download / CSV Export

  - by lautaro.dragan

  I'm in need of help... this is my first time asking a question in SO, so please be kind :) I'm trying to force-download a file from php, so when the user hits a certain button, he gets a file download. The file is a csv (email, username) of all registered users. I decided to add this button to the admin users screen, as you can see in this screenshot. So I added the following code to the addToolbar function in administrator/components/com_users/views/users/view.html.php: JToolBarHelper::custom('users.export', 'export.png', 'export_f2.png', 'Exportar', false); This button is mapped to the following function in the com_users\controller\users.php controller: public function exportAllUsers() { ob_end_clean(); $app = JFactory::getApplication(); header("Content-type: text/csv"); header("Content-Disposition: attachment; filename=ideary_users.csv"); header("Pragma: no-cache"); header("Expires: 0"); echo "email,name\n"; $model = $this->getModel("Users"); $users = $model->getAllUsers(); foreach ($users as $user) { echo $user->email . ", " . ucwords(trim($user->name)) . "\r\n"; } $app->close(); } Now, this is actually working perfectly fine. The issue here is that after I download a file, if I hit any button in the admin that causes a POST, instead of it performing the action it should, it just downloads the file over again! For example: I hit the "Export" button "users.csv" downloads Then, I hit the "search" button "users.csv" downloads... what the hell? I'm guessing that when I hit the export button, a JS gets called and sets a form's action attribute to an URL... and expects a response or something, and then other button's are prevented from re-setting the form's action attribute. I can't think of any real solution for this, but I'd rather avoid hacks if possible. So, what would be the standard, elegant solution that joomla offers in this case?

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• SurfaceView for Camera Preview won't get destroyed when pressing Power-Botton

  - by for3st

  I want to implement a camera preview. For that I have a custom View CameraView extends ViewGroup that in the constructor programatically creates an surfaceView. I have the following components (higly simplified for beverity): ScannerFragment.java public View onCreateView(..) { //inflate view and get cameraView } public void onResume() { //open camera -> set rotation -> startPreview (in a thread) -> //set preview callback -> start decoding worker } public void onPause() { // stop decoding worker -> stop Preview -> release camera } CameraView.java extends ViewGroup public void setUpCalledInConstructor(Context context) { //create a surfaceview and add it to this viewgroup -> //get SurfaceHolder and set callback } /* SurfaceHolder.Callback */ public void surfaceCreated(SurfaceHolder holder) { camera.setPreviewDisplay(holder); } public void surfaceDestroyed(SurfaceHolder holder) { //NOTHING is done here } public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) { camera.getParameters().setPreviewSize(previewSize.width, previewSize.height); } fragment_scanner.xml <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent"> <com.myapp.camera.CameraView android:id="@+id/cameraPreview" android:layout_width="match_parent" android:layout_height="match_parent"/> </RelativeLayout> I think I have set the lifecycle correct (getting resources onResume(), releasing it onPause() roughly said) and the following works just fine: pressing home and returning pressing Taskswitcher and returning rotation But one thing doesn't work and that is when I press the power-button on the device and then return to the camera-preview. The result is: the preview is stuck with the image that was last captured before button was pressed. If I rotate it works fine again, since it will get through the lifecycle. After some research I found out that this is probably due to the fact that surfaceView won't get destroyed when the power-button is pressed, i.e. SurfaceHolder.Callback.surfaceDestroyed(SurfaceHolder holder) won't be called. And in fact when I compare the (very verbose) log output of the home-button-case and the power-button-case it's the same except that 'surfaceDestroyed' won't get called. So far I found no solution whatsoever to work around it. I purposely avoid any resource cleaning code in my surfaceDestroyed(), but this does not help. My idea was to manually destroy the surfaceView like asked in this question but this seems not possible. I also tested other applications with surfaceViews/cameras and they don't seem to have this issue. So I would appreciate any hints or tips on that.

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• Android Facebook SDK : post message without showing facebook page

  - by someone_ smiley

  I am trying to integrate Facebook to my Android app for social post. I have downloaded latest Facebook sdk from here and apply all setup require to post to facebook. Now i can post to facebook. But problem is that, when i run sample program from facebook sdk, a browser like page is open and user have to enter message himself there. but i dont want this page to showed up. i want a fixed message to post directly without opening facebook dialog box. But if there is noway to avoid this, please tell me how can i fixed certain part of message so that user can't modified it. Thanks in Advance Edit: this is message i got after using this project 04-10 11:44:34.691: I/dalvikvm(719): Failed resolving Lnet/xeomax/TestRocket/TestRocket; interface 22 'Lnet/xeomax/FBRocket/LoginListener;' 04-10 11:44:34.691: W/dalvikvm(719): Link of class 'Lnet/xeomax/TestRocket/TestRocket;' failed 04-10 11:44:34.691: D/AndroidRuntime(719): Shutting down VM 04-10 11:44:34.701: W/dalvikvm(719): threadid=1: thread exiting with uncaught exception (group=0x40015560) 04-10 11:44:34.781: E/AndroidRuntime(719): FATAL EXCEPTION: main 04-10 11:44:34.781: E/AndroidRuntime(719): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{net.xeomax.TestRocket/net.xeomax.TestRocket.TestRocket}: java.lang.ClassNotFoundException: net.xeomax.TestRocket.TestRocket in loader dalvik.system.PathClassLoader[/data/app/net.xeomax.TestRocket-1.apk] 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.os.Handler.dispatchMessage(Handler.java:99) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.os.Looper.loop(Looper.java:130) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.main(ActivityThread.java:3683) 04-10 11:44:34.781: E/AndroidRuntime(719): at java.lang.reflect.Method.invokeNative(Native Method) 04-10 11:44:34.781: E/AndroidRuntime(719): at java.lang.reflect.Method.invoke(Method.java:507) 04-10 11:44:34.781: E/AndroidRuntime(719): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 04-10 11:44:34.781: E/AndroidRuntime(719): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 04-10 11:44:34.781: E/AndroidRuntime(719): at dalvik.system.NativeStart.main(Native Method) 04-10 11:44:34.781: E/AndroidRuntime(719): Caused by: java.lang.ClassNotFoundException: net.xeomax.TestRocket.TestRocket in loader dalvik.system.PathClassLoader[/data/app/net.xeomax.TestRocket-1.apk] 04-10 11:44:34.781: E/AndroidRuntime(719): at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240) 04-10 11:44:34.781: E/AndroidRuntime(719): at java.lang.ClassLoader.loadClass(ClassLoader.java:551) 04-10 11:44:34.781: E/AndroidRuntime(719): at java.lang.ClassLoader.loadClass(ClassLoader.java:511) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561) 04-10 11:44:34.781: E/AndroidRuntime(719): ... 11 more

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• Malformed Farsi characters on AWT

  - by jlover2010

  Hi As i started programming by jdk6, i had no problem in text components neither in awt nor in swing. But for labels or titles of awt components, yes : I couldn't have Farsi characters displayable on AWTs just as simple as Swing by typing them into the source code. lets check this SSCCE : import javax.swing.*; import java.awt.*; import java.io.*; import java.util.Properties; public class EmptyFarsiCharsOnAWT extends JFrame{ public EmptyFarsiCharsOnAWT() { super("????"); setDefaultCloseOperation(3); setVisible(rootPaneCheckingEnabled); } public static void main(String[] args) throws AWTException, IOException { JFrame jFrame = new EmptyFarsiCharsOnAWT(); MenuItem show ; // approach 1 = HardCoding : /* show = new MenuItem("\u0646\u0645\u0627\u06cc\u0634"); * */ // approach 2 = using simple utf-8 saved text file : /* BufferedReader in = new BufferedReader(new FileReader("farsiLabels.txt")); String showLabel = in.readLine(); in.close(); show = new MenuItem(showLabel); * */ // approach 3 = using properties file : FileReader in = new FileReader("farsiLabels.properties"); Properties farsiLabels = new Properties(); farsiLabels.load(in); show = new MenuItem(farsiLabels.getProperty("tray.show")); PopupMenu popUp = new PopupMenu(); popUp.add(show); // creating Tray object Image iconIamge = Toolkit.getDefaultToolkit().getImage("greenIcon.png"); TrayIcon trayIcon = new TrayIcon(iconIamge, null, popUp); SystemTray tray = SystemTray.getSystemTray(); tray.add(trayIcon); jFrame.setIconImage(iconIamge); } } Yes, i know each of three approaches in source code does right when you may test it from IDE , but if you make a JAR contains just this class, by means of NetBeans project clean&build ,you won't see the expected characters and will just get EMPTY/BLANK SQUARES ! Unfortunately, opposed to other situations i encountered before, here there is no way to avoid using awt and make use of Swing in this case. And this was just an SSCCE i made to show the problem and my recent (also first) application suffers from this subject. Note: it seems i can not attach anything, so the contents od the text file would be this: ????? and the contents of properties file: #Sun May 02 09:45:10 IRDT 2010 tray.show=????? but i don't think by giving you the unicode-scape sequence, these would be necessary any way... And i think should have to let you know I posted this question a while ago in SDN and "the Java Ranch" forums and other native forums and still I'm watching... By the way i am using latest version of Netbeans IDE... I will be so grateful if anybody has a solution to this damn AWT components never rendered any Farsi character for me... Thanks in advance

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• why is this rails association loading individually after an eager load?

  - by codeman73

  I'm trying to avoid the N+1 queries problem with eager loading, but it's not working. The associated models are still being loaded individually. Here are the relevant ActiveRecords and their relationships: class Player < ActiveRecord::Base has_one :tableau end Class Tableau < ActiveRecord::Base belongs_to :player has_many :tableau_cards has_many :deck_cards, :through => :tableau_cards end Class TableauCard < ActiveRecord::Base belongs_to :tableau belongs_to :deck_card, :include => :card end class DeckCard < ActiveRecord::Base belongs_to :card has_many :tableaus, :through => :tableau_cards end class Card < ActiveRecord::Base has_many :deck_cards end and the query I'm using is inside this method of Player: def tableau_contains(card_id) self.tableau.tableau_cards = TableauCard.find :all, :include => [ {:deck_card => (:card)}], :conditions => ['tableau_cards.tableau_id = ?', self.tableau.id] contains = false for tableau_card in self.tableau.tableau_cards # my logic here, looking at attributes of the Card model, with # tableau_card.deck_card.card; # individual loads of related Card models related to tableau_card are done here end return contains end Does it have to do with scope? This tableau_contains method is down a few method calls in a larger loop, where I originally tried doing the eager loading because there are several places where these same objects are looped through and examined. Then I eventually tried the code as it is above, with the load just before the loop, and I'm still seeing the individual SELECT queries for Card inside the tableau_cards loop in the log. I can see the eager-loading query with the IN clause just before the tableau_cards loop as well. EDIT: additional info below with the larger, outer loop Here's the larger loop. It is inside an observer on after_save def after_save(pa) @game = Game.find(turn.game_id, :include => :goals) @game.players = Player.find :all, :include => [ {:tableau => (:tableau_cards)}, :player_goals ], :conditions => ['players.game_id =?', @game.id] for player in @game.players player.tableau.tableau_cards = TableauCard.find :all, :include => [ {:deck_card => (:card)}], :conditions => ['tableau_cards.tableau_id = ?', player.tableau.id] if(player.tableau_contains(card)) ... end end end

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• Optimize date query for large child tables: GiST or GIN?

  - by Dave Jarvis

  Problem 72 child tables, each having a year index and a station index, are defined as follows: CREATE TABLE climate.measurement_12_013 ( -- Inherited from table climate.measurement_12_013: id bigint NOT NULL DEFAULT nextval('climate.measurement_id_seq'::regclass), -- Inherited from table climate.measurement_12_013: station_id integer NOT NULL, -- Inherited from table climate.measurement_12_013: taken date NOT NULL, -- Inherited from table climate.measurement_12_013: amount numeric(8,2) NOT NULL, -- Inherited from table climate.measurement_12_013: category_id smallint NOT NULL, -- Inherited from table climate.measurement_12_013: flag character varying(1) NOT NULL DEFAULT ' '::character varying, CONSTRAINT measurement_12_013_category_id_check CHECK (category_id = 7), CONSTRAINT measurement_12_013_taken_check CHECK (date_part('month'::text, taken)::integer = 12) ) INHERITS (climate.measurement) CREATE INDEX measurement_12_013_s_idx ON climate.measurement_12_013 USING btree (station_id); CREATE INDEX measurement_12_013_y_idx ON climate.measurement_12_013 USING btree (date_part('year'::text, taken)); (Foreign key constraints to be added later.) The following query runs abysmally slow due to a full table scan: SELECT count(1) AS measurements, avg(m.amount) AS amount FROM climate.measurement m WHERE m.station_id IN ( SELECT s.id FROM climate.station s, climate.city c WHERE -- For one city ... -- c.id = 5182 AND -- Where stations are within an elevation range ... -- s.elevation BETWEEN 0 AND 3000 AND 6371.009 * SQRT( POW(RADIANS(c.latitude_decimal - s.latitude_decimal), 2) + (COS(RADIANS(c.latitude_decimal + s.latitude_decimal) / 2) * POW(RADIANS(c.longitude_decimal - s.longitude_decimal), 2)) ) <= 50 ) AND -- -- Begin extracting the data from the database. -- -- The data before 1900 is shaky; insufficient after 2009. -- extract( YEAR FROM m.taken ) BETWEEN 1900 AND 2009 AND -- Whittled down by category ... -- m.category_id = 1 AND m.taken BETWEEN -- Start date. (extract( YEAR FROM m.taken )||'-01-01')::date AND -- End date. Calculated by checking to see if the end date wraps -- into the next year. If it does, then add 1 to the current year. -- (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date GROUP BY extract( YEAR FROM m.taken ) The sluggishness comes from this part of the query: m.taken BETWEEN /* Start date. */ (extract( YEAR FROM m.taken )||'-01-01')::date AND /* End date. Calculated by checking to see if the end date wraps into the next year. If it does, then add 1 to the current year. */ (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date The HashAggregate from the plan shows a cost of 10006220141.11, which is, I suspect, on the astronomically huge side. There is a full table scan on the measurement table (itself having neither data nor indexes) being performed. The table aggregates 237 million rows from its child tables. Question What is the proper way to index the dates to avoid full table scans? Options I have considered: GIN GiST Rewrite the WHERE clause Separate year_taken, month_taken, and day_taken columns to the tables What are your thoughts? Thank you!

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• Available Coroutine Libraries in Java

  - by JUST MY correct OPINION

  I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7? Edited to add: Just to ensure that confusion is contained, this is a related question to my other one, but not the same. This one is looking for an existing implementation in a bid to avoid reinventing the wheel unnecessarily. The other one is a question relating to how one would go about implementing coroutines in Java should this question prove unanswerable. The intent is to keep different questions on different threads.

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• ASP.NET MVC Page - Viewstate for Confirm email field is getting erased on Registration Page if valid

  - by Rita

  Hi I have a Registaration page with the following fields Email, Confirm Email, Password and Confrim Password. On Register Button click and post the model to the server, the Model validates and if that Email is already Registered, it displays the Validation Error Message "User already Exists. Please Login or Register with a different email ID". While we are displaying this validation error message, I am loosing the value of "Confirm Email" field. So that the user has to reenter again and I want to avoid this. Here I don't have confirm_Email field in my Model. Is there something special that has to be done to remain Confirm Email value on the Page even in case of Validation failure? Appreciate your responses. Here is my Code: <% using (Html.BeginForm()) {%> <%= Html.ValidationSummary(false) %> <fieldset> <div class="cssform"> <p> <%= Html.LabelFor(model => model.Email)%><em>*</em> <%= Html.TextBoxFor(model => model.Email, new { @class = "required email" })%> <%= Html.ValidationMessageFor(model => model.Email)%> </p> <p> <%= Html.Label("Confirm email")%><em>*</em> <%= Html.TextBox("confirm_email")%> <%= Html.ValidationMessage("confirm_email") %> </p> <p> <%= Html.Label("Password")%><em>*</em> <%= Html.Password("Password", null, new { @class = "required" })%> <%= Html.ValidationMessage("Password")%><br /> (Note: Password should be minimum 6 characters) </p> <p> <%= Html.Label("Confirm Password")%><em>*</em> <%= Html.Password("confirm_password")%> <%= Html.ValidationMessage("confirm_password") %> </p><hr /> <p>Note: Confirmation email will be sent to the email address listed above.</p> </fieldset> <% } %>

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• Question about design (inheritance, polymorphism)

  - by Dan

  Hi, I have a question about a problem I'm struggling with. Hope you can bear with me. Imagine I have an Object class representing the base class of a hierarchy of physical objects. Later I inherit from it to create an Object1D, Object2D and Object3D classes. Each of these derived classes will have some specific methods and attributes. For example, the 3d object might have functionality to download a 3d model to be used by a renderer. So I'd have something like this: class Object {}; class Object1D : public Object { Point mPos; }; class Object2D : public Object { ... }; class Object3D : public Object { Model mModel; }; Now I'd have a separate class called Renderer, which simply takes an Object as argument and well, renders it :-) In a similar way, I'd like to support different kinds of renderers. For instance, I could have a default one that every object could rely on, and then provide other specific renderers for some kind of objects: class Renderer {}; // Default one class Renderer3D : public Renderer {}; And here comes my problem. A renderer class needs to get an Object as an argument, for example in the constructor in order to retrieve whatever data it needs to render the object. So far so good. But a Renderer3D would need to get an Object3D argument, in order to get not only the basic attributes but also the specific attributes of a 3d object. Constructors would look like this: CRenderer(Object& object); CRenderer3D(Object3D& object); Now how do I specify this in a generic way? Or better yet, is there a better way to design this? I know I could rely on RTTI or similar but I'd like to avoid this if possible as I feel there is probably a better way to deal with this. Thanks in advance!

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