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  • Question about the evolution of interaction paradigm between web server program and content provider program?

    - by smwikipedia
    Hi experts, In my opinion, web server is responsible to deliver content to client. If it is static content like pictures and static html document, web server just deliver them as bitstream directly. If it is some dynamic content that is generated during processing client's request, the web server will not generate the conetnt itself but call some external proram to genearte the content. AFAIK, this kind of dynamice content generation technologies include the following: CGI ISAPI ... And from here, I noticed that: ...In IIS 7, modules replace ISAPI filters... Is there any others? Could anyone help me complete the above list and elabrate on or show some links to their evolution? I think it would be very helpful to understand application such as IIS, TomCat, and Apache. I once wrote a small CGI program, and though it serves as a content generator, it is still nothing but a normal standalone program. I call it normal because the CGI program has a main() entry point. But with the recenetly technology like ASP.NET, I am not writing complete program, but only some class library. Why does such radical change happens? Many thanks.

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  • C++0x rvalue references and temporaries

    - by Doug
    (I asked a variation of this question on comp.std.c++ but didn't get an answer.) Why does the call to f(arg) in this code call the const ref overload of f? void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } My intuition says that the f(string &&) overload should be chosen, because arg needs to be converted to a temporary no matter what, and the temporary matches the rvalue reference better than the lvalue reference. This is not what happens in GCC and MSVC. In at least G++ and MSVC, any lvalue does not bind to an rvalue reference argument, even if there is an intermediate temporary created. Indeed, if the const ref overload isn't present, the compilers diagnose an error. However, writing f(arg + 0) or f(std::string(arg)) does choose the rvalue reference overload as you would expect. From my reading of the C++0x standard, it seems like the implicit conversion of a const char * to a string should be considered when considering if f(string &&) is viable, just as when passing a const lvalue ref arguments. Section 13.3 (overload resolution) doesn't differentiate between rvalue refs and const references in too many places. Also, it seems that the rule that prevents lvalues from binding to rvalue references (13.3.3.1.4/3) shouldn't apply if there's an intermediate temporary - after all, it's perfectly safe to move from the temporary. Is this: Me misreading/misunderstand the standard, where the implemented behavior is the intended behavior, and there's some good reason why my example should behave the way it does? A mistake that the compiler vendors have somehow all made? Or a mistake based on common implementation strategies? Or a mistake in e.g. GCC (where this lvalue/rvalue reference binding rule was first implemented), that was copied by other vendors? A defect in the standard, or an unintended consequence, or something that should be clarified?

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  • Vertically Aligning Elements

    - by Naz
    I'm trying to understand how to center elements within a div. I have this basic code I am working with and am trying to get the 'This is a button' element to be in the center <body> <div style="width:960px;background-color:#d7d7d7;"> <div style=" width:400px; padding:10px; height:auto; background-color:#006699; display:inline-block; "> <p> Vivamus vel sapien. Praesent nisl tortor, laoreet eu, dapibus quis, egestas non, mauris. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Vivamus vel sapien. Praesent nisl tortor, laoreet eu, dapibus quis, egestas non, mauris. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus.</p> </div> <div style=" width:100px; padding:10px; height:auto; background-color:#b1b1b1; float:right; display:inline-block; margin:auto!important; vertical-align:middle; "> <p>This is a button</p> </div> </div> </body> It's essentially 1 div, divided into 2 with text on the left hand side and a 'This is a button' label to be in the center of the right side, but I can;t figure out how to get it to center, I've tried all sorts of methods. All help/advice is appreciated.

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  • UITableViewIndex Grows to Incorrect Bounds Unexpectedly

    - by chadburggraf
    I have a standard UITableView + UISearchDisplayController + UITableViewIndex setup. Everything works like a champ. Except, under very specific conditions, the index grows too long to display on the screen. Specifically, after ending a search and re-displaying the unfiltered, indexed table, the index sometimes grows too long. More specifically, this doesn't happen if I search then cancel. It only happens if I search, then push a view controller from the search table, then pop that view controller back to the still-searching table, then cancel the search, then re-search and then cancel that final search. After the end of the final search the index is too long. In portrait, the table view is reporting a height of 416 and the index a height of 404 under normal conditions. If I log from searchDisplayControllerDidEndSearch when the index is sized incorrectly, it is reporting a height of 620. I've tried everything from setLayout on the table and the index to manually re-sizing the frame. Nothing works (the manual re-size causes the correct height to be logged, but it doesn't change the display on screen). I was about to try re-sizing after a delay in case the cancel animation was interfering, but then I realized what an absurd situation I'm in and thought seeking help might be wise...

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  • Location of Embedly (JQuery-Preview) Results

    - by user749798
    Embedly/Jquery-Preview has been fantastic. However, I'm trying to change the location of the preview result, and having trouble. Right now, the result appears right below the input field...but I'd rather have it in a separate part of the page. Is there a way to do this? I've tried changing the location of the selector and loading divs, but that hasn't helped. It seems to ignore those divs and put it right below the submit button. Below is my code: <form accept-charset="UTF-8" action="private" class="new_comment" data-remote="true" id="new_comment" method="post"> <input class="photo_comm" id="comment_comment" name="comment[comment]" placeholder="add a comment or link..." size="30" type="text" /><span type="text" id="counter">1000</span> <input class="btn btn-primary btn-mini" data-disable-with="Submitting..." name="commit" type="submit" value="Post" /> </form> <!-- Placeholder that tells Preview where to put the loading icon--> <div class="loading"> <img src='http://embedly.github.com/jquery-preview/images/loading-rectangle.gif'> </div> <!-- Placeholder that tells Preview where to put the selector--> <div class="selector"></div> $('#comment_comment').preview({ key:'60f1dcdf3258476794784148a6eb65e7', // Sign up for a key: http://embed.ly/pricing selector : {type:'rich'}, preview : { submit : function(e, data){ e.preventDefault(); $.ajax({ dataType: 'script', url: this.form.attr('action'), type: 'POST', data: data }); }, }, autoplay : 0, maxwidth : 400, display : {display : 'rich'} });

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  • Should java try blocks be scoped as tightly as possible?

    - by isme
    I've been told that there is some overhead in using the Java try-catch mechanism. So, while it is necessary to put methods that throw checked exception within a try block to handle the possible exception, it is good practice performance-wise to limit the size of the try block to contain only those operations that could throw exceptions. I'm not so sure that this is a sensible conclusion. Consider the two implementations below of a function that processes a specified text file. Even if it is true that the first one incurs some unnecessary overhead, I find it much easier to follow. It is less clear where exactly the exceptions come from just from looking at statements, but the comments clearly show which statements are responsible. The second one is much longer and complicated than the first. In particular, the nice line-reading idiom of the first has to be mangled to fit the readLine call into a try block. What is the best practice for handling exceptions in a funcion where multiple exceptions could be thrown in its definition? This one contains all the processing code within the try block: void processFile(File f) { try { // construction of FileReader can throw FileNotFoundException BufferedReader in = new BufferedReader(new FileReader(f)); // call of readLine can throw IOException String line; while ((line = in.readLine()) != null) { process(line); } } catch (FileNotFoundException ex) { handle(ex); } catch (IOException ex) { handle(ex); } } This one contains only the methods that throw exceptions within try blocks: void processFile(File f) { FileReader reader; try { reader = new FileReader(f); } catch (FileNotFoundException ex) { handle(ex); return; } BufferedReader in = new BufferedReader(reader); String line; while (true) { try { line = in.readLine(); } catch (IOException ex) { handle(ex); break; } if (line == null) { break; } process(line); } }

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  • Comet (long polling) and XmlHttpRequest status

    - by chris_l
    I'm playing around a little bit with raw XmlHttpRequestObjects + Comet Long Polling. (Usually, I'd let GWT or another framework handle of this for me, but I want to learn more about it.) I wrote the following code: function longPoll() { var xhr = createXHR(); // Creates an XmlHttpRequestObject xhr.open('GET', 'LongPollServlet', true); xhr.onreadystatechange = function () { if (xhr.readyState == 4) { if (xhr.status == 200) { ... } if (xhr.status > 0) { longPoll(); } } } xhr.send(null); } ... <body onload="javascript:longPoll()">... I wrapped the longPoll() call in an if statement that checks for status > 0, because I encountered, that when I leave the page (by browsing somewhere else, or by reloading it), one last unnecessary comet call is sent. [And on Firefox, it even causes severe problems when doing a page reload, for some reason I don't fully understand yet.] Question: Is that status check the correct way to handle this problem, or is there a better solution?

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  • Javascript when to show results

    - by Pete
    This is my Javascript below I want to show records on load and also show new records when added to the database showrecords(); displays the records in the database where abouts can I put this in my code where it will work correctly. `$(document).ready(function() { //showrecords() function showrecords() { $.ajax({ type: "POST", url: "demo_show.php", cache: false, success: function(html){ $("#display").after(html); document.getElementById('content').value=''; $("#flash").hide(); } }); } $(".comment_button").click(function() { var element = $(this); var test = $("#content").val(); var dataString = 'content='+ test; if(test=='') { alert("Please Enter Some Text"); } else { $("#flash").show(); $("#flash").fadeIn(400).html('<img src="http://tiggin.com/ajax-loader.gif" align="absmiddle">&nbsp;<span class="loading">Loading Comment...</span>'); $.ajax({ type: "POST", url: "demo_insert.php", data: dataString, cache: false, success: function(html){ // $("#display").after(html); document.getElementById('content').value=''; $("#flash").hide(); //Function for showing records //showrecords(); } }); } return false; }); }); `

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  • Inereritance of clousure objects and overriding of methods

    - by bobikk
    I need to extend a class, which is encapsulated in a closure. This base class is following: var PageController = (function(){ // private static variable var _current_view; return function(request, new_view) { ... // priveleged public function, which has access to the _current_view this.execute = function() { alert("PageController::execute"); } } })();` Inheritance is realised using the following function: function extend(subClass, superClass){ var F = function(){ }; F.prototype = superClass.prototype; subClass.prototype = new F(); subClass.prototype.constructor = subClass; subClass.superclass = superClass.prototype; StartController.cache = ''; if (superClass.prototype.constructor == Object.prototype.constructor) { superClass.prototype.constructor = superClass; } } I subclass the PageController: var StartController = function(request){ // calling the constructor of the super class StartController.superclass.constructor.call(this, request, 'start-view'); } // extending the objects extend(StartController, PageController); // overriding the PageController::execute StartController.prototype.execute = function() { alert('StartController::execute'); } Inheritance is working. I can call every PageController's method from StartController's instance. However, method overriding doesn't work: var startCont = new StartController(); startCont.execute(); alerts "PageController::execute". How should I override this method?

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  • .NET: How to pass value when subscribing to event and obtain it when the event is triggered (Dynamic

    - by Entrase
    The task is to create event handlers in runtime. I need the one method to be called with different parameter value for different events. The events and their number are only known in runtime. So I'm trying to generate dynamic methods, each of which will be assigned to some event, but in general they all just pass some value to an instance method and call it. It would be great if something similar could be done the easier way. I mean passing some value at subscribing stage and then obtaining it when the event is triggered. This is what I'm trying to do now: public class EventSource { public event EventHandler eventOne; public event EventHandler eventTwO; public event EventHandler eventThree; } public class EventListener { SubscribeForEvents() { BindingFlags flags = BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance; // Suppose we've already got EventInfo // and target source somewhere // so we can do eventInfo.AddEventHandler(target, delegate) // Now we need a delegate. int value = 42; Type tDelegate = eventInfo.EventHandlerType; // http://msdn.microsoft.com/en-us/library/ms228976(VS.95).aspx Type returnType = GetDelegateReturnType(tDelegate); DynamicMethod listener = new DynamicMethod("", null, GetDelegateParameterTypes(tDelegate), this.GetType()); ///////// Type[] callParameters = { typeof(int) }; MethodInfo method = this.GetType().GetMethod("ToCallFromDelegate", flags); ILGenerator generator = listener.GetILGenerator(); // No success in this mess. What's wrong? generator.Emit(OpCodes.Ldc_I4, value); generator.Emit(OpCodes.Call, method); generator.Emit(OpCodes.Pop); generator.Emit(OpCodes.Ret); ///////////// Delegate delegate = listener.CreateDelegate(tDelegate); eventInfo.AddEventHandler(target, delegate); // When triggered, there is InvalidProgramException } void ToCallFromDelegate(int value) { doSomething(); } }

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  • jQuery Ajax load images problem

    - by jackysee
    I have a code that would call $.load() to get an HTML fragment. In the fragment there will be a list of images and a script that would do some calculation based on the list size. The fragment looks like <div> <ul> <li><img .../></li> <li><img .../></li> ... </ul> </div> <script> //... script to do calculation on the list width </script> Originally, I use css's max-width to ensure that the image would not exceed 180px. But as IE has no max-width, I use the expression hack. However, it seems when the image are first load, the script cannot get a correct width of image list. Seems like the script load earlier than the CSS expression. If it is a new page, I can certainly call $(window).load() to ensure all the images are loaded. But what can I do in an ajax html fragment request?

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  • rookie MySql question about paging; Is one query enough?

    - by Camran
    I have managed to get paging to work, almost. I want to display to the user, total nr of records found, and the currently displayed records. Ex: 4000 found, displaying 0-100. I am testing this with the nr 2 (because I don't have that many records, have like 20). So I am using LIMIT $start, $nr_results; Do I have to make two queries in order to display the results the way I want, one query fetching all records and then make a mysql_num_rows to get all records, then the one with the LIMIT ? I have this: mysql_num_rows($qry_result); $total_pages = ceil($num_total / $res_per_page); //$res_per_page==2 and $num_total = 2 if ($p - 10 < 1) { $pagemin=1; } else { $pagemin = $p - 10; } if ($p + 10 $total_pages) { $pagemax = $total_pages; } else { $pagemax = $p + 10; } Here is the query: SELECT mt.*, fordon.*, boende.*, elektronik.*, business.*, hem_inredning.*, hobby.* FROM classified mt LEFT JOIN fordon ON fordon.classified_id = mt.classified_id LEFT JOIN boende ON boende.classified_id = mt.classified_id LEFT JOIN elektronik ON elektronik.classified_id = mt.classified_id LEFT JOIN business ON business.classified_id = mt.classified_id LEFT JOIN hem_inredning ON hem_inredning.classified_id = mt.classified_id LEFT JOIN hobby ON hobby.classified_id = mt.classified_id ORDER BY modify_date DESC LIMIT 0, 2 Thanks, if you need more input let me know. Basically Q is, do I have to make two queries?

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  • Correct Delphi compiler switches to stop in the user's code, not my component's

    - by Jeremy Mullin
    I'm modifying our VCL components so the end user's application links to our dcu files, instead of building our source code each time. We have everything working, but I want the debugger to stop on the user's code when an exception is raised. At first it would stop in our dcu and open the CPU window. I was able to prevent that by removing debug info from the dcu files. But now it still doesn't stop in the users code (like DevExpress libraries and others do). The following screencast is a short example. The first time I cause an exception in the DevExpress code, and the debugger correctly stops in my button event. The second time I cause an exception in my components, but the debugger doesn't have my button event on the call stack, and doesn't show me where the problem was. Any ideas why? http://screencast.com/t/NjhlOTRk Currently building the DCU's with these options: -$W+ -$D- -h -w -q Update: The TDataSet methods in between my component and the button event seem to cause this behavior. If I instead call a direct method of my table, I get the expected behavior. I'm guessing there isn't anything I can do about this, but I'm still curious why it happens.

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  • Linker error: wants C++ virtual base class destructor

    - by jdmuys
    Hi, I have a link error where the linker complains that my concrete class's destructor is calling its abstract superclass destructor, the code of which is missing. This is using GCC 4.2 on Mac OS X from XCode. I saw http://stackoverflow.com/questions/307352/g-undefined-reference-to-typeinfo but it's not quite the same thing. Here is the linker error message: Undefined symbols: "ConnectionPool::~ConnectionPool()", referenced from: AlwaysConnectedConnectionZPool::~AlwaysConnectedConnectionZPool()in RKConnector.o ld: symbol(s) not found collect2: ld returned 1 exit status Here is the abstract base class declaration: class ConnectionPool { public: static ConnectionPool* newPool(std::string h, short p, std::string u, std::string pw, std::string b); virtual ~ConnectionPool() =0; virtual int keepAlive() =0; virtual int disconnect() =0; virtual sql::Connection * getConnection(char *compression_scheme = NULL) =0; virtual void releaseConnection(sql::Connection * theConnection) =0; }; Here is the concrete class declaration: class AlwaysConnectedConnectionZPool: public ConnectionPool { protected: <snip data members> public: AlwaysConnectedConnectionZPool(std::string h, short p, std::string u, std::string pw, std::string b); virtual ~AlwaysConnectedConnectionZPool(); virtual int keepAlive(); // will make sure the connection doesn't time out. Call regularly virtual int disconnect(); // disconnects/destroys all connections. virtual sql::Connection * getConnection(char *compression_scheme = NULL); virtual void releaseConnection(sql::Connection * theConnection); }; Needless to say, all those members are implemented. Here is the destructor: AlwaysConnectedConnectionZPool::~AlwaysConnectedConnectionZPool() { printf("AlwaysConnectedConnectionZPool destructor call"); // nothing to destruct in fact } and also maybe the factory routine: ConnectionPool* ConnectionPool::newPool(std::string h, short p, std::string u, std::string pw, std::string b) { return new AlwaysConnectedConnectionZPool(h, p, u, pw, b); } I can fix this by artificially making my abstract base class concrete. But I'd rather do something better. Any idea? Thanks

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  • std::string insert method has ambiguous overloads?

    - by sdg
    Environment: VS2005 C++ using STLPort 5.1.4. Compiling the following code snippet: std::string copied = "asdf"; char ch = 's'; copied.insert(0,1,ch); I receive an error: Error 1 error C2668: 'stlpx_std::basic_string<_CharT,_Traits,_Alloc>::insert' : ambiguous call to overloaded function It appears that the problem is the insert method call on the string object. The two defined overloads are void insert ( iterator p, size_t n, char c ); string& insert ( size_t pos1, size_t n, char c ); But given that STLPort uses a simple char* as its iterator, the literal zero in the insert method in my code is ambiguous. So while I can easily overcome the problem by hinting such as copied.insert(size_t(0),1,ch); My question is: is this overloading and possible ambiguity intentional in the specification? Or more likely an unintended side-effect of the specific STLPort implementation? (Note that the Microsoft-supplied STL does not have this problem as it has a class for the iterator, instead of a naked pointer)

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  • JSF: Avoid nested update calls

    - by dhroove
    I don't know if I am on right track or not still asking this question. I my JSF project I have this tree structure: <p:tree id="resourcesTree" value="#{someBean.root}" var="node" selectionMode="single" styleClass="no-border" selection="#{someBean.selectedNode}" dynamic="true"> <p:ajax listener="#{someBean.onNodeSelect}" update=":centerPanel :tableForm :tabForm" event="select" onstart="statusDialog.show();" oncomplete="statusDialog.hide();" /> <p:treeNode id="resourcesTreeNode" > <h:outputText value="#{node}" id="lblNode" /> </p:treeNode> </p:tree> I have to update this tree after I added something or delete something.. But whenever I update this still its nested update also call I mean to say it also call to update these components ":centerPanel :tableForm :tabForm"... This give me error that :tableForm not found in view because this forms load in my central panel and this tree is in my right panel.. So when I am doing some operation on tree is it not always that :tableForm is in my central panel.. (I mean design is something like this only) So now my question is that can I put some condition or there is any way so that I can specify when to update nested components also and when not.... In nut shell is there any way to update only :resoucesTree is such a way that nested updates are not called so that I can avoid error... Thanks in advance.

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  • Creating a simple command line interface (CLI) using a python server (TCP sock) and few scripts

    - by VN44CA
    I have a Linux box and I want to be able to telnet into it (port 77557) and run few required commands without having to access to the whole Linux box. So, I have a server listening on that port, and echos the entered command on the screen. (for now) Telnet 192.168.1.100 77557 Trying 192.168.1.100... Connected to 192.168.1.100. Escape character is '^]'. hello<br /> You typed: "hello"<br /> NOW: I want to create lot of commands that each take some args and have error codes. Anyone has done this before? It would be great if I can have the server upon initialization go through each directory and execute the init.py file and in turn, the init.py file of each command call into a main template lib API (e.g. RegisterMe()) and register themselves with the server as function call backs. At least this is how I would do it in C/C++. But I want the best Pythonic way of doing this. /cmd/ /cmd/myreboot/ /cmd/myreboot/ini.py (note underscore don't show for some reason) /cmd/mylist/ /cmd/mylist/init.py ... etc IN: /cmd/myreboot/_ini_.py: from myMainCommand import RegisterMe RegisterMe(name="reboot",args=Arglist, usage="Use this to reboot the box", desc="blabla") So, repeating this creates a list of commands and when you enter the command in the telnet session, then the server goes through the list, matches the command and passed the args to that command and the command does the job and print the success or failure to stdout. Thx

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  • Deep Zoom in Ajax - Possible? Any examples out there?

    - by Phil
    I have an idea to implement a deep zoom type interface hosted in a browser for sports training data (speed, distance, heart rate etc.) However, rather than images I actually want to zoom into a hierarchy of information. For example, the initial display would contain a grid of years - hover over 2008, for example, and spin the mouse wheel (or click) will zoom into that year but during the zoom I want 2008 to fade out and be replaced with a calendar of months. Again zoom into a month and the months are replaced with the months calendar, zoom into a day and you finally see a chart with the training data plotted on it. All the time only dates with actual data would be highlighted in some fashion. My question is whether this would even be possible and whether anyone has seen examples of this already. I'm imagining that most of the time the next level of information could be cached in the browser (in fact, because this is calendar-based, I can calculate most of that and cache the dates to be highlighted.) I could also zoom into an empty chart whilst an Ajax thread is fetching the data to display. I've never tried anything like this before and I'm especially interested in whether DHTML would be capable of this sort of zoom (I suspect not and I would have to resort to Silverlight) and whether the Ajax execution would be uninterrupted whilst the browser rendering thread is kept busy zooming.

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  • Function with parameter type that has a copy-constructor with non-const ref chosen?

    - by Johannes Schaub - litb
    Some time ago I was confused by the following behavior of some code when I wanted to write a is_callable<F, Args...> trait. Overload resolution won't call functions accepting arguments by non-const ref, right? Why doesn't it reject in the following because the constructor wants a Test&? I expected it to take f(int)! struct Test { Test() { } // I want Test not be copyable from rvalues! Test(Test&) { } // But it's convertible to int operator int() { return 0; } }; void f(int) { } void f(Test) { } struct WorksFine { }; struct Slurper { Slurper(WorksFine&) { } }; struct Eater { Eater(WorksFine) { } }; void g(Slurper) { } void g(Eater) { } // chooses this, as expected int main() { // Error, why? f(Test()); // But this works, why? g(WorksFine()); } Error message is m.cpp: In function 'int main()': m.cpp:33:11: error: no matching function for call to 'Test::Test(Test)' m.cpp:5:3: note: candidates are: Test::Test(Test&) m.cpp:2:3: note: Test::Test() m.cpp:33:11: error: initializing argument 1 of 'void f(Test)' Can you please explain why one works but the other doesn't?

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  • problem with fork()

    - by john
    I'm writing a shell which forks, with the parent reading the input and the child process parsing and executing it with execvp. pseudocode of main method: do{ pid = fork(); print pid; if (p<0) { error; exit; } if (p>0) { wait for child to finish; read input; } else { call function to parse input; exit; } }while condition return; what happens is that i never seem to enter the child process (pid printed is always positive, i never enter the else). however, if i don't call the parse function and just have else exit, i do correctly enter parent and child alternatingly. full code: int main(int argc, char *argv[]){ char input[500]; pid_t p; int firstrun = 1; do{ p = fork(); printf("PID: %d", p); if (p < 0) {printf("Error forking"); exit(-1);} if (p > 0){ wait(NULL); firstrun = 0; printf("\n> "); bzero(input, 500); fflush(stdout); read(0, input, 499); input[strlen(input)-1] = '\0'; } else exit(0); else { if (parse(input) != 0 && firstrun != 1) { printf("Error parsing"); exit(-1); } exit(0); } }while(strcmp(input, "exit") != 0); return 0; }

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  • Checking for nil in view in Ruby on Rails

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

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  • Converting Generic Type into reference type after checking its type using GetType(). How ?

    - by Shantanu Gupta
    i am trying to call a function that is defined in a class RFIDeas_Wrapper(dll being used). But when i checked for type of reader and after that i used it to call function it shows me error Cannot convert type T to RFIDeas_Wrapper. EDIT private List<string> GetTagCollection<T>(T Reader) { TagCollection = new List<string>(); if (Reader.GetType() == typeof(RFIDeas_Wrapper)) { ((RFIDeas_Wrapper)Reader).OpenDevice(); // here Reader is of type RFIDeas_Wrapper //, but i m not able to convert Reader into its datatype. string Tag_Id = ((RFIDeas_Wrapper)Reader).TagID(); //Adds Valid Tag Ids into the collection if(Tag_Id!="0") TagCollection.Add(Tag_Id); } else if (Reader.GetType() == typeof(AlienReader)) TagCollection = ((AlienReader)Reader).TagCollection; return TagCollection; } ((RFIDeas_Wrapper)Reader).OpenDevice(); , ((AlienReader)Reader).TagCollection; I want this line to be executed without any issue. As Reader will always be of the type i m specifying. How to make compiler understand the same thing.

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  • Questions about serving static files from a servlet

    - by Geo
    I'm very new to servlets. I'd like to serve some static files, some css and some javascript. Here's what I got so far: in web.xml: <servlet> <description></description> <display-name>StaticServlet</display-name> <servlet-name>StaticServlet</servlet-name> <servlet-class>StaticServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>StaticServlet</servlet-name> <url-pattern>/static/*</url-pattern> </servlet-mapping> I'm assuming in the StaticServlet I'd have to work with request.getPathInfo to see what was requested, get a mime type, read the file & write it to the client. If this is not the way to go, or is not a viable way of doing things, please suggest a better way. I'm not really sure where to place the static directory, because if I try to print new File(".") it gives me the directory of my Eclipse installation. Is there a way to find out the project's directory?

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  • Qt Creator CONFIG (debug, release) switches does NOT work

    - by killdaclick
    Problem: CONFIG(debug,debug|release) and CONFIG(release,deubg|release) are always evaluated wherever debug or release is choosen in Qt Creator 2.8.1 for Linux. My configuration in Qt Creator application (stock - default for new project): Projects->Build Settings->Debug Build Steps: qmake build configuration: Debug Effective qmake call: qmake2 proj.pro -r -spec linux-gnueabi-oe-g++ CONFIG+=debug Projects->Build Settings->Release Build Steps: qmake build configuration: Release Effective qmake call: qmake2 proj.pro -r -spec linux-gnueabi-oe-g++ My configuration in proj.pro: message(Variable CONFIG:) message($$CONFIG) CONFIG(debug,debug|release) { message(Debug build) } CONFIG(release,debug|release) { message(Release build) } Output on console for Debug: Project MESSAGE: Variable CONFIG: Project MESSAGE: lex yacc warn_on debug uic resources warn_on release incremental link_prl no_mocdepend release stl qt_no_framework debug console Project MESSAGE: Debug build Project MESSAGE: Release build Output on console for Release: Project MESSAGE: Variable CONFIG: Project MESSAGE: lex yacc warn_on uic resources warn_on release incremental link_prl no_mocdepend release stl qt_no_framework console Project MESSAGE: Debug build Project MESSAGE: Release build Under Windows 7 I didnt experienced any problem with such .pro configuration and it worked fine. I was desperate and modified .pro file: CONFIG = test message(Variable CONFIG:) message($$CONFIG) CONFIG(debug,debug|release) { message(Debug build) } CONFIG(release,debug|release) { message(Release build) } and I was suprised with the output: Project MESSAGE: Variable CONFIG: Project MESSAGE: test Project MESSAGE: Debug build Project MESSAGE: Release build so even if I completly clean CONFIG variable it still see debug and release configuration. What Im doing wrong?

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  • Doubts in executable and relocatable object file

    - by bala1486
    Hello, I have written a simple Hello World program. #include <stdio.h> int main() { printf("Hello World"); return 0; } I wanted to understand how the relocatable object file and executable file look like. The object file corresponding to the main function is 0000000000000000 <main>: 0: 55 push %rbp 1: 48 89 e5 mov %rsp,%rbp 4: bf 00 00 00 00 mov $0x0,%edi 9: b8 00 00 00 00 mov $0x0,%eax e: e8 00 00 00 00 callq 13 <main+0x13> 13: b8 00 00 00 00 mov $0x0,%eax 18: c9 leaveq 19: c3 retq Here the function call for printf is callq 13. One thing i don't understand is why is it 13. That means call the function at adresss 13, right??. 13 has the next instruction, right?? Please explain me what does this mean?? The executable code corresponding to main is 00000000004004cc <main>: 4004cc: 55 push %rbp 4004cd: 48 89 e5 mov %rsp,%rbp 4004d0: bf dc 05 40 00 mov $0x4005dc,%edi 4004d5: b8 00 00 00 00 mov $0x0,%eax 4004da: e8 e1 fe ff ff callq 4003c0 <printf@plt> 4004df: b8 00 00 00 00 mov $0x0,%eax 4004e4: c9 leaveq 4004e5: c3 retq Here it is callq 4003c0. But the binary instruction is e8 e1 fe ff ff. There is nothing that corresponds to 4003c0. What is that i am getting wrong? Thanks. Bala

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