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  • callbacks via objective-c selectors

    - by codemonkey
    I have a "BSjax" class that I wrote that lets me make async calls to our server to get json result sets, etc using the ASIHTTPRequest class. I set it up so that the BSjax class parses my server's json response, then passes control back to the calling view controller via this call: [[self delegate] performSelectorOnMainThread:@selector(bsRequestFinished:) withObject:self waitUntilDone:YES]; ... where "bsRequestFinished" is the callback method in the calling view controller. This all worked fine and well until I realized that some pages are going to need to make different types of requests... i.e. I'll want to do different types of things in that callback function depending on which type of request was made. To me it seems like being able to pass different callback function names to my BSjax class would be the cleanest fix... but I'm having trouble (and am not even sure if it's possible) to pass in a variable that holds the callback function name and then replace the call above with something like this: [[self delegate] performSelectorOnMainThread:@selector(self.variableCallbackFunctionName) withObject:self waitUntilDone:YES]; ... where "self.variableCallbackFunctionName" is set by the calling view controller when it calls BSjax to make a new request. Is this even possible? If so, advisable? If not, alternatives? EDIT: Note that whatever fix I arrive at will need to take into account the reality that this class is making async requests... so I need to make sure that the callback function processing is correctly tied to the specific requests... as I can't rely on FIFO processing sequence.

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  • Using parameterized function calls in SELECT statements. SQL Server

    - by geekzlla
    I have taken over some code from a previous developer and have come across this SQL statement that calls several SQL functions. As you can see, the function calls in the select statement pass a parameter to the function. How does the SQL statement know what value to replace the variable with? For the below sample, how does the query engine know what to replace nDeptID with when it calls, fn_SelDeptName_DeptID(nDeptID) nDeptID IS a column in table Note. SELECT STATEMENT: SELECT nCustomerID AS [Customer ID], nJobID AS [Job ID], dbo.fn_SelDeptName_DeptID(nDeptID) AS Department, nJobTaskID AS JobTaskID, dbo.fn_SelDeptTaskDesc_OpenTask(nJobID, nJobTaskID) AS Task, nStandardNoteID AS StandardNoteID, dbo.fn_SelNoteTypeDesc(nNoteID) AS [Note Type], dbo.fn_SelGPAStandardNote(nStandardNoteID) AS [Standard Note], nEntryDate AS [Entry Date], nUserName as [Added By], nType AS Type, nNote AS Note FROM Note WHERE nJobID = 844261 ORDER BY nJobID, Task, [Entry Date] ====================== Function fn_SelDeptName_DeptID: ALTER FUNCTION [dbo].[fn_SelDeptName_DeptID] (@iDeptID int) RETURNS varchar(25) -- Used by DataCollection for Job Tracking -- if the Deptartment isnt found return an empty string BEGIN -- Return the Department name for the given DeptID. DECLARE @strDeptName varchar(25) IF @iDeptID = 0 SET @strDeptName = '' ELSE BEGIN SET @strDeptName = (SELECT dName FROM Department WHERE dDeptID = @iDeptID) IF (@strDeptName IS NULL) SET @strDeptName = '' END RETURN @strDeptName END ========================== Thanks in advance.

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  • How to create a generic list in this wierd case in c#

    - by Marc Bettex
    Hello, In my program, I have a class A which is extended by B, C and many more classes. I have a method GetInstance() which returns a instance of B or C (or of one of the other child), but I don't know which one, so the return type of the method is A. In the method CreateGenericList(), I have a variable v of type A, which is in fact either a B, a C or another child type and I want to create a generic list of the proper type, i.e. List<B> if v is a B or List<C> if v is a C, ... Currently I do it by using reflection, which works, but this is extremely slow. I wanted to know if there is another way to to it, which doesn't use reflection. Here is an example of the code of my problem: class A { } class B : A { } class C : A { } // More childs of A. class Program { static A GetInstance() { // returns an instance of B or C } static void CreateGenericList() { A v = Program.GetInstance(); IList genericList = // Here I want an instance of List<B> or List<C> or ... depending of the real type of v, not a List<A>. } } I tried the following hack. I call the following method, hoping the type inferencer will guess the type of model, but it doesn't work and return a List<A>. I believe that because c# is statically typed, T is resolved as A and not as the real type of model at runtime. static List<T> CreateGenericListFromModel<T>(T model) where T : A { return new List<T> (); } Does anybody have a solution to that problem that doesn't use reflection or that it is impossible to solve that problem without reflection? Thank you very much, Marc

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  • How can I format Custom Data and display in autocomplete when source is an DB

    - by Andres Scarpone
    so I'm trying to get some info in the auto-complete widget like it's shown in the JQuery UI demo Demo, the only problem is they use a variable that they fill with the data they want to show, I instead want to access the data and the different description and stuff using a Data Base in MySQL, for this I have changed the source to use another php page that looks up the info. here is the code for the Auto-complete, I really don't understand the methods so I haven't changed it from the basic search. This is the JS: $(document).ready((function(){ $( "#completa" ).autocomplete({ source: "buscar.php", minLength: 1, focus: function (event, ui){ $("#completa").val(ui.item.val); return false; }; })); This is what I have in buscar.php: <?php $conec = mysql_connect(localhost, root, admin); if(!$conec) { die(mysql_error()); } else { $bd = mysql_select_db("ve_test",$conec ); if(!$bd) { die(mysql_error()); } } $termino = trim(strip_tags($_GET['term']));//Obtener el termino que envia el autocompletar $qstring = "SELECT name, descripcion FROM VE_table WHERE name LIKE '%".$termino."%'"; $result = mysql_query($qstring);//Solicitud a la Base de Datos while ($row = mysql_fetch_array($result,MYSQL_ASSOC))//Realizar un LOOP sobre los valores obtenidos { $row['value']=htmlentities(stripslashes($row['name'])); $row_set[] = $row;//build an array } echo json_encode($row_set);//Enviar los datos al autocompletar en codificacion JSON, Altamente Necesario. ?

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  • Accessing global variables of custom controls in ASP.NET

    - by CL4NCY
    Hi, I have built lots of custom asp.net controls which work really well separately but I want to somehow allow global access to all their variables from anywhere on the page. I have a central control called the ContentManager which I can use to store these variables. The problem I have is that all the controls are bound at different times so I only want the variables available after they're bound. For example I have many custom repeaters on the page which when bound I want to add a reference in the content manager so all their variables are then available to use. <Custom:ContentManager ID="cm" runat="server"/> <Custom:Repeater ID="r1" runat="server"/> <Custom:Repeater ID="r2" runat="server"/> <Custom:Repeater ID="r3" runat="server"/> Then I want a tag which can access all variables from any of these controls. <%= cm.controls["r1"].Items[0]["name"] %> The problem with this is that the variable isn't available until the repeater is bound so I might need to use events to push out the value to tags on the page like so: <Custom:Var ID="v1" control="r1" value="Items[0]["name"]" runat="server"/> Is this possible or can you recommend a better approach?

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  • Is there a way to get the PREMATCH ($`) and POSTMATCH ($') from pcrecpp?

    - by Eric Peers
    Is there a way to obtain the C++ equivalent of Perl's PREMATCH ($`) and POSTMATCH ($') from pcrecpp? I would be happy with a string, a char *, or pairs indices/startpos+length that point at this. StringPiece seems like it might accomplish part of this, but I'm not certain how to get it. in perl: $_ = "Hello world"; if (/lo\s/) { $pre = $`; #should be "Hel" $post = $'; #should be "world" } in C++ I would have something like: string mystr = "Hello world"; //do I need to map this in a StringPiece? if (pcrecpp::RE("lo\s").PartialMatch(mystr)) { //should I use Consume or FindAndConsume? //What should I do here to get pre+post matches??? } pcre plainjane c seems to have the ability to return the vector with the matches including the "end" portion of the string, so I could theoretically extract such a pre/post variable, but that seems like a lot of work. I like the simplicty of the pcrecpp interface. Suggestions? Thanks! --Eric

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  • jQuery each loop - using variables

    - by Sam
    I have a list of products. Each product has a title and a review link. Currently the titles link directly to the individual product page, and the review links go elsewhere. I'd like to use a jquery each loop to cycle through each li, take the href from the title (the first link), and apply it to the review link (the second link), so they both point to the product page. Simplified code would be as follows: <ul> <li><a href="product1.html">Product 1</a><a href="review1.html">Review 1</a></li> <li><a href="product2.html">Product 2</a><a href="review2.html">Review 2</a></li> <li><a href="product3.html">Product 3</a><a href="review3.html">Review 3</a></li> </ul> I thought it would be something like the following: $("li").each(function(){ var link = $("a:eq(0)").attr('href'); $("a:eq(1)").attr("href", link); }); But it always uses the same variable "link". Can someone help me out?

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  • php request variables assigning $_GEt

    - by chris
    if you take a look at a previous question http://stackoverflow.com/questions/2690742/mod-rewrite-title-slugs-and-htaccess I am using the solution that Col. Shrapnel proposed- but when i assign values to $_GET in the actual file and not from a request the code doesnt work. It defaults away from the file as if the $_GET variables are not set The code I have come up with is- if(!empty($_GET['cat'])){ $_GET['target'] = "category"; if(isset($_GET['page'])){ $_GET['pageID'] = $_GET['page']; } $URL_query = "SELECT category_id FROM cats WHERE slug = '".$_GET['cat']."';"; $URL_result = mysql_query($URL_query); $URL_array = mysql_fetch_array($URL_result); $_GET['category_id'] = $URL_array['category_id']; }elseif($_GET['product']){ $_GET['target'] = "product"; $URL_query = "SELECT product_id FROM products WHERE slug = '".$_GET['product']."';"; $URL_result = mysql_query($URL_query); $URL_array = mysql_fetch_array($URL_result); print_r($URL_array); $_GET['product_id'] = $URL_array['product_id']; The original variable string that im trying to represent is /cart.php?Target=product&product_id=16142&category_id=249 And i'm trying to build the query string variables with code and including cart.php so i can use cleaner URL's So I have product/product-title-with-clean-url/ going to slug.php?product=slug Then the slug searches the db for a record with the matching slug and returns the product_id as in the code above.Then built the query string and include cart.php

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  • How does scope in Javascript work?

    - by Jim
    I can not understand how scoping works in Javascript. E.g. <html> <head> <script>var userName = "George"; </script> </head> <body> ...... <script> document.write('Name = ' + userName); </script> </body> </html> The variable userName is declared in another "section" of a script. As I understand it the browser renders html and executes code in the order it finds it. So how does userName in the second script tag gets resolved? Does it go to a global setting? Anything I declare earlier is global? I noticed the same happens if I do something like: <html> <head> <script> do { var userName = "George"; //bla } while (someCondition); </script> </head> <body> ...... <script> document.write('Name = ' + userName); </script> </body> </html> Even when userName is declared inside {} it is still resolved in the second script. How is that possible?

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  • How to change CSS color values in real-time off a javascript slider?

    - by bflora
    I'm making a page where the user gets a javascript slider that goes from 0 to 100 and can use it to set the opacity of a div on the page. I want the opacity of that div to change in real-time as they work the slider. I've not done this before. What's the best approach? There cursor in the slider displays the slider's current value as you move it. It seems to be that I just need to find a way to display that value in any arbitrary other place on the page so I can display it in the style settings for the div. The .js file that generates the slider has a line that (I think) is setting the current value in the cursor: $(this).children(".ui-slider-handle", context).html(parseInt(settings[index]['default'])); TO get this changing number to display somewhere else at the same time, do I just need to add a div somewhere and then add a line like this? $("#newDivId").children(".ui-slider-handle", context).html(parseInt(settings[index]['default'])); That seems like it would give me the number showing up in a div. How then would I get it into a form I could put into the style settings for a div? If this was a php variable, I would do something like this, style="opacity:<?php print $value ?>;" What would be the .js equivalent?

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  • Creating a dynamic two-column iOS spinning wheel with HTML/Javascript

    - by JSW189
    I am trying to create a dynamic two-column spinning wheel for iOS Safari using this HTML/Javascript wheel. However, I am having trouble getting the value of the first column to change the results of the second column. I have tried using an if statement to get the value of the first variable (var beverage) and add the value of the second column correspondingly. Does anybody know what I am doing wrong/if there is a better approach? function openBirthDate() { var beverage = { 1:'Coffee', 2:'Soda' }; //THIS IS WHERE I'M HAVING TROUBLE var results = SpinningWheel.getSelectedValues(); if (results.values === 1) { var company = { 1:'Starbucks', 2:'Dunkin Donuts' }; } else { var company = { 1:'Coke', 2:'Pepsi' }; } var size = { 1:'Tall', 2:'Grande', 3:'Venti' }; SpinningWheel.addSlot(type, '', 1); SpinningWheel.addSlot(company, '', 1); SpinningWheel.addSlot(size, '', 1); SpinningWheel.setCancelAction(cancel); SpinningWheel.setDoneAction(done); SpinningWheel.open(); } function done() { var results = SpinningWheel.getSelectedValues(); document.getElementById('result').innerHTML = 'values: ' + results.values.join(' ') + '<br />keys: ' + results.keys.join(', '); } function cancel() { document.getElementById('result').innerHTML = 'cancelled!'; } window.addEventListener('load', function(){ setTimeout(function(){ window.scrollTo(0,0); }, 100); }, true);

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  • Using the <h2> as the title after sent?

    - by Delan Azabani
    Currently, I have a semi-dynamic system for my website's pages. head.php has all the tags before the content body, foot.php the tags after. Any page using the main theme will include head.php, then write the content, then output foot.php. Currently, to be able to set the title, I quickly set a variable $title before inclusion: <?php $title = 'Untitled document'; include_once '../head.php'; ?> <h2>Untitled document</h2> Content here... <?php include_once '../foot.php'; ?> So that in head.php... <title><?php echo $title; ?> | Delan Azabani</title> However, this seems kludgy as the title is most of the time, the same as the content of the h2 tag. Is there a way I can get PHP to read the content of h2, track back and insert it, then send the whole thing at the end?

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  • How do actually castings work at the CLR level?

    - by devoured elysium
    When doing an upcast or downcast, what does really happen behind the scenes? I had the idea that when doing something as: string myString = "abc"; object myObject = myString; string myStringBack = (string)myObject; the cast in the last line would have as only purpose tell the compiler we are safe we are not doing anything wrong. So, I had the idea that actually no casting code would be embedded in the code itself. It seems I was wrong: .maxstack 1 .locals init ( [0] string myString, [1] object myObject, [2] string myStringBack) L_0000: nop L_0001: ldstr "abc" L_0006: stloc.0 L_0007: ldloc.0 L_0008: stloc.1 L_0009: ldloc.1 L_000a: castclass string L_000f: stloc.2 L_0010: ret Why does the CLR need something like castclass string? There are two possible implementations for a downcast: You require a castclass something. When you get to the line of code that does an castclass, the CLR tries to make the cast. But then, what would happen had I ommited the castclass string line and tried to run the code? You don't require a castclass. As all reference types have a similar internal structure, if you try to use a string on an Form instance, it will throw an exception of wrong usage (because it detects a Form is not a string or any of its subtypes). Also, is the following statamente from C# 4.0 in a Nutshell correct? Upcasting and downcasting between compatible reference types performs reference conversions: a new reference is created that points to the same object. Does it really create a new reference? I thought it'd be the same reference, only stored in a different type of variable. Thanks

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  • R: Are there any alternatives to loops for subsetting from an optimization standpoint?

    - by Adam
    A recurring analysis paradigm I encounter in my research is the need to subset based on all different group id values, performing statistical analysis on each group in turn, and putting the results in an output matrix for further processing/summarizing. How I typically do this in R is something like the following: data.mat <- read.csv("...") groupids <- unique(data.mat$ID) #Assume there are then 100 unique groups results <- matrix(rep("NA",300),ncol=3,nrow=100) for(i in 1:100) { tempmat <- subset(data.mat,ID==groupids[i]) #Run various stats on tempmat (correlations, regressions, etc), checking to #make sure this specific group doesn't have NAs in the variables I'm using #and assign results to x, y, and z, for example. results[i,1] <- x results[i,2] <- y results[i,3] <- z } This ends up working for me, but depending on the size of the data and the number of groups I'm working with, this can take up to three days. Besides branching out into parallel processing, is there any "trick" for making something like this run faster? For instance, converting the loops into something else (something like an apply with a function containing the stats I want to run inside the loop), or eliminating the need to actually assign the subset of data to a variable?

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  • XPath expression exception

    - by fftoolbar
    Hi I am not really sure if i am doing this right with XPath expression. I am trying to locate a text on DOM and this text is assingned to a variable. I have text stored in SQLite and i have retrievd the text and i am trying to locate it on the webpage which actually contains the text. so i ahve the following code: var searchText = dataset[x]['selectedText']; alert(dataset[x]['selectedText']); var res = googbar_frames[0].contentDocument.evaluate("//*[.=searchText]",googbar_frames[0].contentDocument.body,null,XPathResult.ANY_TYPE,null); alert(res.snapshotLength); And i get the following error. Error: Permission denied for <http://en.wikipedia.org> to call method XPathException.toString on <>. Error: Permission denied for <http://en.wikipedia.org> to call method XPathException.toString on <>. Have got the expression correct. I am trying to look for the text on DOM. Or am i going wrong somwehere? cheers

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  • Why does this asp.net mvc unit test fail?

    - by Brian McCord
    I have this unit test: [TestMethod] public void Delete_Post_Passes_With_State_4() { //Arrange ViewResult result = stateController.Delete( 4 ) as ViewResult; var model = (State)result.ViewData.Model; //Act RedirectToRouteResult redirectResult = stateController.Delete( model ) as RedirectToRouteResult; var newresult = stateController.Delete( 4 ) as ViewResult; var newmodel = (State)newresult.ViewData.Model; //Assert Assert.AreEqual( redirectResult.RouteValues["action"], "Index" ); Assert.IsNull( newmodel ); } Here are the two controller actions that handle deleting: // // GET: /State/Delete/5 public ActionResult Delete(int id) { var x = _stateService.GetById( id ); return View(x); } // // POST: /State/Delete/5 [HttpPost] public ActionResult Delete(State model) { try { if( model == null ) { return View( model ); } _stateService.Delete( model ); return RedirectToAction("Index"); } catch { return View( model ); } } What I can't figure out is why this test fails. I have verified that the record actually gets deleted from the list. If I set a break point in the Delete method on the line: var x = _stateService.GetById( id ); The GetById does indeed return a null just as it should, but when it gets back to the newresult variable in the test, the ViewData.Model is the deleted model. What am I doing wrong?

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  • cmd.exe Command Line Parsing of Environment Variables

    - by Artefacto
    I can't figure how to have cmd.exe not interpret something like %PATH% as an environment variable. Given this program: #include<stdio.h> #include<windows.h> int main(int argc, char *argv[]) { int i; printf("cmd line: %s\n", GetCommandLine()); for (i = 0; i < argc; i++) { printf("%d: %s\n", i, argv[i]); } return 0; } I have these different outputs according to the position of the arguments: >args "k\" o" "^%PATH^%" cmd line: args "k\" o" "%PATH%" 0: args 1: k" o 2: %PATH% >args "^%PATH^%" "k\" o" cmd line: args "^%PATH^%" "k\" o" 0: args 1: ^%PATH^% 2: k" o I guess it's because cmd.exe doesn't recognize the escaped \" and sees the escaped double quote as closing the first, leaving in the first case %PATH% unquoted. I say this, because if I don't quote the argument, it always works: >args ^%PATH^% "k\" o" cmd line: args %PATH% "k\" o" 0: args 1: %PATH% 2: k" o but then I can have no spaces...

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  • Callback function and function pointer trouble in C++ for a BST

    - by Brendon C.
    I have to create a binary search tree which is templated and can deal with any data types, including abstract data types like objects. Since it is unknown what types of data an object might have and which data is going to be compared, the client side must create a comparison function and also a print function (because also not sure which data has to be printed). I have edited some C code which I was directed to and tried to template, but I cannot figure out how to configure the client display function. I suspect variable 'tree_node' of class BinarySearchTree has to be passed in, but I am not sure how to do this. For this program I'm creating an integer binary search tree and reading data from a file. Any help on the code or the problem would be greatly appreciated :) Main.cpp #include "BinarySearchTreeTemplated.h" #include <iostream> #include <fstream> #include <string> using namespace std; /*Comparison function*/ int cmp_fn(void *data1, void *data2) { if (*((int*)data1) > *((int*)data2)) return 1; else if (*((int*)data1) < *((int*)data2)) return -1; else return 0; } static void displayNode() //<--------NEED HELP HERE { if (node) cout << " " << *((int)node->data) } int main() { ifstream infile("rinput.txt"); BinarySearchTree<int> tree; while (true) { int tmp1; infile >> tmp1; if (infile.eof()) break; tree.insertRoot(tmp1); } return 0; } BinarySearchTree.h (a bit too big to format here) http://pastebin.com/4kSVrPhm

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  • cycle through spans on jquery click, removing the first-child

    - by jacob
    Basically, this advances to the next hidden span when clicked. The markup: <div id="facts"> <span>click to cycle</span> <span>fact 1</span> <span>fact 2</span> <span>fact 3</span> <span>fact 4</span> </div> The js: $(document).ready(function() { var current = 1; $('#facts span').click(function() { // Hide all of them $('#facts span').hide(); // Unhide the current one: $('#facts span:eq(' + (current % $('#facts span').length) + ')').show(); // Increment the variable console.log(current % 4); current++; }); // Unhide the first one on load $('#facts span:first-child').show(); });? What I'm trying to do now is remove the first span after it's been clicked, because it is not necessary for the user to see the 'click to cycle' instruction again.

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  • In SQL can I return a tables with a varying number of columns

    - by Matt
    I have a somewhat more complicated scenario, but I think it should be possible. I have a large SPROC whose result is a set of characteristics for a set of persons. So the Table would look something like this: Property | Client1 Client 2 Client3 ----------------------------------------------------------- Sex | M F M Age | 67 56 67 Income | Low Mid Low It's built using cursors, iterating over different datasets. The problem I am facing is that there is a varying number of Clients and Properties, so an equally valid result over different input sets might be: Property | Client1 Client 2 ------------------------------------------- Sex | M F Age | 67 56 Weight | 122 122 The different number of properties is easy, those are just extra rows. My problem is that I need to declare a temporary table with a varying number of columns. There could be 2 clients or 100. Every client in guaranteed to have every property ultimately listed. What SQL structure would statisfy this and how can I declare it and insert things into it? I can't just flip the columns and rows either because there is a variable number of each.

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  • jsf, richfaces, popup window

    - by Hubidubi
    Hi I would like to make a list-detail view with richfaces. There will be a link for every record in the list that should open a new window containing record details. I tried to implement the link this way: <a4j:commandLink oncomplete="window.open('/pages/serviceDetail.jsf','popupWindow', 'dependent=yes, menubar=no, toolbar=no, height=500, width=400')" actionListener="#{monitoringBean.recordDetail}" value="details" /> I use <a4j:keepAlive beanName="monitoringBean" ajaxOnly="false" /> for both the list and the detail page. recordDetail method fills the data of the selected record to a variable of the bean that I would like to display on the detail page. The problem is that keepalive doesn't work, so I get new bean instance on the detail page every time. So the the previously selected record from the other bean is not accessible here. Is there a way to pass parameter (id) to the detail page to handle record selection. Or is there any way to make keepalive work? (I this this would be the easiest). Thanks

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  • C++: defining maximum/minimum limits for a class

    - by Luis
    Basically what the title says... I have created a class that models time slots in a variable-granularity daily schedule (where for example the first time slot is 30 minutes, but the second time slot can be 40 minutes); the first available slot starts at (a value comparable to) 1. What I want to do now is to define somehow the maximum and minimum allowable values that this class takes and I have two practical questions in order to do so: 1.- does it make sense to define absolute minimum and maximum in such a way for a custom class? Or better, does it suffice that a value always compares as lower-than any other possible value of the type, given the class's defined relational operators, to be defined the min? (and analogusly for the max) 2.- assuming the previous question has an answer modeled after "yes" (or "yes but ..."), how do I define such max/min? I know that there is std::numeric_limits<> but from what I read it is intended for "numeric types". Do I interpret that as meaning "represented as a number" or can I make a broader assumption like "represented with numbers" or "having a correspondence to integers"? After all, it would make sense to define the minimum and maximum for a date class, and maybe for a dictionary class, but numeric_limits may not be intended for those uses (I don't have much experience with it). Plus, numeric_limits has a lot of extra members and information that I don't know what to make with. If I don't use numeric_limits, what other well-known / widely-used mechanism does C++ offer to indicate the available range of values for a class?

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  • Prolog singleton variables in Python

    - by Rubens
    I'm working on a little set of scripts in python, and I came to this: line = "a b c d e f g" a, b, c, d, e, f, g = line.split() I'm quite aware of the fact that these are decisions taken during implementation, but shouldn't (or does) python offer something like: _, _, var_needed, _, _, another_var_needed, _ = line.split() as well as Prolog does offer, in order to exclude the famous singleton variables. I'm not sure, but wouldn't it avoid unnecessary allocation? Or creating references to the result of the split call does not count up as overhead? EDIT: Sorry, my point here is: in Prolog, as far as I'm concerned, in an expression like: test(L, N) :- test(L, 0, N). test([], N, N). test([_|T], M, N) :- V is M + 1, test(T, V, N). The variable represented by _ is not accessible, for what I suppose the reference to the value that does exist in the list [_|T] is not even created. But, in Python, if I use _, I can use the last value assigned to _, and also, I do suppose the assignment occurs for each of the variables _ -- which may be considered an overhead. My question here is if shouldn't there be (or if there is) a syntax to avoid such unnecessary attributions.

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  • Any problems with this C++ const reference accessor interface idiom?

    - by mskfisher
    I was converting a struct to a class so I could enforce a setter interface for my variables. I did not want to change all of the instances where the variable was read, though. So I converted this: struct foo_t { int x; float y; }; to this: class foo_t { int _x; float _y; public: foot_t() : x(_x), y(_y) { set(0, 0.0); } const int &x; const float &y; set(int x, float y) { _x = x; _y = y; } }; I'm interested in this because it seems to model C#'s idea of public read-only properties. Compiles fine, and I haven't seen any problems yet. Besides the boilerplate of associating the const references in the constructor, what are the downsides to this method? Any strange aliasing issues? Why haven't I seen this idiom before?

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  • Google AppEngine + Local JUnit Tests + Jersey framework + Embedded Jetty

    - by xamde
    I use Google Appengine for Java (GAE/J). On top, I use the Jersey REST-framework. Now i want to run local JUnit tests. The test sets up the local GAE development environment ( http://code.google.com/appengine/docs/java/tools/localunittesting.html ), launches an embedded Jetty server, and then fires requests to the server via HTTP and checks responses. Unfortunately, the Jersey/Jetty combo spawns new threads. GAE expects only one thread to run. In the end, I end up having either no datstore inside the Jersey-resources or multiple, having different datastore. As a workaround I initialise the GAE local env only once, put it in a static variable and inside the GAE resource I add many checks (This threads has no dev env? Re-use the static one). And these checks should of course only run inside JUnit tests.. (which I asked before: "How can I find out if code is running inside a JUnit test or not?" - I'm not allowed to post the link directly here :-|)

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