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  • How to process signals in a Qt subclass?

    - by Jen
    How do I process a signal of in a subclass? Let's say my subclass is derived from QTextEdit and is interested in the signal textChanged. It seems silly to connect an object to itself, I should be able to simply override the textChange method -- but it isn't virtual. What is the accepted way to do this?

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  • Error handling in C++, constructors vs. regular methods

    - by Dennis Ritchie
    I have a cheesesales.txt CSV file with all of my recent cheese sales. I want to create a class CheeseSales that can do things like these: CheeseSales sales("cheesesales.txt"); //has no default constructor cout << sales.totalSales() << endl; sales.outputPieChart("piechart.pdf"); The above code assumes that no failures will happen. In reality, failures will take place. In this case, two kinds of failures could occur: Failure in the constructor: The file may not exist, may not have read-permissions, contain invalid/unparsable data, etc. Failure in the regular method: The file may already exist, there may not be write access, too little sales data available to create a pie chart, etc. My question is simply: How would you design this code to handle failures? One idea: Return a bool from the regular method indicating failure. Not sure how to deal with the constructor. How would seasoned C++ coders do these kinds of things?

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  • Whose fault is a NullReferenceException?

    - by stefan.at.wpf
    I'm currently working on a class which exposes an internal List through a property. The List shall and can be modified. The problem is, entries in the internal list could be set to null from outside the class. My code actually looks like this: class ClassWithList { List<object> _list = new List<object>(); // get accessor, which however returns the reference to the list, // therefore the list can be modified (this is intended) public List<object> Data { get { return _list; } } private void doSomeWorkWithTheList() { foreach(object obj in _list) // do some work with the objects in the list without checking for null. } } So now in the doSomeWorkWithTheList() I could always check whether the current list entry is null or I could just asume that the person using this class doesn't have the great idea to set entries to null. So finally the questions end up in: Whose fault is a NullReferenceException in this case? Is it the fault of the class developer not checking everything for null (which would make code generally - not only in this class - more complex) or is it the fault of the user of this class, as setting a List entry to null doesn't really make sense? I'd tend to generally not check values for null except in some really special cases. Is this a bad style or de facto standard / standard in praxis? I know there's probably no ultimate answer for this, I'm just missing enough experience for such thing and therefore wondering what other developers think about such cases and want to hear what's done in reality about checking null (or not).

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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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  • Mapping relationships from multiple databases in NHibernate

    - by mannish
    I have a multi-database application configured with NHibernate. The entities that correspond to tables from each database are in their own separate assemblies (an assembly per database if you will). I have a need/desire to relate an entity from one database to an entity of another database. Everything up to this point works as I want it to (the application handles multiple session factories, etc.). The relationship I want is many-to-one, but in reality my application only cares about one side of the relationship (for reasons that aren't relevant). The relevant entities are Project and PMProject, where a Project HAS A PMProject. When I map the many-to-one, I get the following error: NHibernate.MappingException: An association from the table PROJECTS refers to an unmapped class: SDMS.PPRM.PMProject The Project mapping itself reads (ignore the funky column naming; it's an Oracle db): <many-to-one name="PMProject" class="SDMS.PPRM.PMProject" column="PM_PROJECT_ID" cascade="none" /> In the class attribute, I'm referencing the appropriate assembly, but I get that error which seems to tell me it simply can't find the mapping file for PMProject. But that file exists (it's set as embedded resource), the session factory instantiation works without fail; so I'm at a loss on how to tell the Project mapping how/where to look for the appropriate mapping. Is there something I'm missing? A better way to go about this? Thanks in advance.

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  • How to test a site rigorously?

    - by Sarfraz
    Hello, I recently created a big portal site. It's time for putting it to test. How do you guys test a site rigorously? What are the ways and tools for that? Can we sort of mimic hundreds of virtual users visiting the site to see its load handling? The test should be for both security and speed Thanks in advance.

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  • I can't get my Android program to run correctly on an AVM in Eclipse

    - by Wes
    This is a simple question about getting started with developing Android apps using Eclipse. I have followed all the tutorials on the developer site for installing Eclipse, the SDK and the ADT plugin. When trying to run a simple Hello World program, everything seems to compile correctly, but then the virtual machine comes up empty. In the Console Window it reads: The program then just sits and my text never comes up. Any idea with what the problem could be?

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  • Finding the Column Index for a Specific Value

    - by Btibert3
    Hi All, I am having a brain cramp. Below is a toy dataset: df <- data.frame( id = 1:6, v1 = c("a", "a", "c", NA, "g", "h"), v2 = c("z", "y", "a", NA, "a", "g"), stringsAsFactors=F) I have a specific value that I want to find across a set of defined columns and I want to identify the position it is located in. The fields I am searching are characters and the trick is that the value I am looking for might not exist. In addition, null strings are also present in the dataset. Assuming I knew how to do this, the variable position indicates the values I would like returned. > df id v1 v2 position 1 1 a z 1 2 2 a y 1 3 3 c a 2 4 4 <NA> <NA> 99 5 5 g a 2 6 6 h g 99 The general rule is that I want to find the position of value "a", and if it is not located or if v1 is missing, then I want 99 returned. In this instance, I am searching across v1 and v2, but in reality, I have 10 different variables. It is also worth noting that the value I am searching for can only exist once across the 10 variables. What is the best way to generate this recode? Many thanks in advance.

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  • How i change the Enabled= attribute via a preloaded field

    - by user1904656
    I want to modify the PXUIField Enabled=false/true using an existing boolean field #region LastBatNbr public abstract class lastBatNbr : PX.Data.IBqlField { } protected String _LastBatNbr; [PXDBString(10, IsFixed = true)] [PXUIField(DisplayName = "Last Batch Nbr")] public virtual String LastBatNbr { get { return this._LastBatNbr; } set { this._LastBatNbr = value; } } #endregion

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  • writing to an ioport resulting in segfaults...

    - by Sniperchild
    I'm writing for an atmel at91sam9260 arm 9 cored single board computer [glomation gesbc9260] Using request_mem_region(0xFFFFFC00,0x100,"name"); //port range runs from fc00 to fcff that works fine and shows up in /proc/iomem then i try to write to the last bit of the port at fc20 with writel(0x1, 0xFFFFFC20); and i segfault...specifically "unable to handle kernel paging request at virtual address fffffc20. I'm of the mind that i'm not allocating the right memory space... any helpful insight would be great...

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  • RTTI and Portability in C++

    - by Joshua
    If a compiler doesn't "support" RTTI, does that mean that the compiler can not handle class hierarchies that have virtual functions in them? Or have I been misunderstanding the literature about how RTTI isn't portable, and the issues lie elsewhere?

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  • jquery animated buttons that just wont behave

    - by TJ Sherrill
    Ok I have a inline list of buttons. <ul id="nav"> <li class="home"><a href="#">Menu Item</a></li> <li class="contact"><a href="#">Menu Item</a></li> <li class="about"><a href="#">Menu Item</a></li> </ul> .home{ position:absolute; bottom:0; background-image:url(../img/menu/single_line.png); background-repeat:no-repeat; height:34px; width:134px; } .home_hover{ position:absolute; bottom:0; background-image:url(../img/menu/single_line_over.png); background-repeat:no-repeat; height:70px; width:134px; } $(document).ready(function(){ $("#nav .home").mouseover(function(){ $(this).toggleClass("home_hover").slideToggle("slow"); return false; }).mouseout(function(){ $(this).toggleClass("home_hover").slideToggle("slow"); return false; }); }); Each menu item has a background image, and then when its hovered the background image is replaced by a taller image. Ultimately I am trying to build a simple menu where on mouseover the menu item appears to slide up. But in reality Jquery can animate the toggleClass with slideToggle. The problem is that this current code doesn't behave right. It jumps up and down, because the text is moving. I am pretty new to Jquery so any help is greatly appreciated. I also loaded this up at http://gasworks.ravennainteractive.com/result/ thanks

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  • How to lock files in a tomcat web application?

    - by yankee
    The Java manual says: The locks held on a particular file by a single Java virtual machine do not overlap. The overlaps method may be used to test whether a candidate lock range overlaps an existing lock. I guess that if I lock a file in a tomcat web application I can't be sure that every call to this application is done by a different JVM, can I? So how can I lock files within my tomcat application in a reliable way?

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  • Resources for writing kernel in C

    - by anon
    I don't want to write my own boot loader -- happy to use Grub. I just want to implement pre-emptive multi threading, a basic file system, and virtual memory. I want something that can run on top of qemu. What's a good resource (book / tutorial) for accomplishing this goal? Thanks!

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  • Merge computed data from two tables back into one of them

    - by Tyler McHenry
    I have the following situation (as a reduced example). Two tables, Measures1 and Measures2, each of which store an ID, a Weight in grams, and optionally a Volume in fluid onces. (In reality, Measures1 has a good deal of other data that is irrelevant here) Contents of Measures1: +----+----------+--------+ | ID | Weight | Volume | +----+----------+--------+ | 1 | 100.0000 | NULL | | 2 | 200.0000 | NULL | | 3 | 150.0000 | NULL | | 4 | 325.0000 | NULL | +----+----------+--------+ Contents of Measures2: +----+----------+----------+ | ID | Weight | Volume | +----+----------+----------+ | 1 | 75.0000 | 10.0000 | | 2 | 400.0000 | 64.0000 | | 3 | 100.0000 | 22.0000 | | 4 | 500.0000 | 100.0000 | +----+----------+----------+ These tables describe equivalent weights and volumes of a substance. E.g. 10 fluid ounces of substance 1 weighs 75 grams. The IDs are related: ID 1 in Measures1 is the same substance as ID 1 in Measures2. What I want to do is fill in the NULL volumes in Measures1 using the information in Measures2, but keeping the weights from Measures1 (then, ultimately, I can drop the Measures2 table, as it will be redundant). For the sake of simplicity, assume that all volumes in Measures1 are NULL and all volumes in Measures2 are not. I can compute the volumes I want to fill in with the following query: SELECT Measures1.ID, Measures1.Weight, (Measures2.Volume * (Measures1.Weight / Measures2.Weight)) AS DesiredVolume FROM Measures1 JOIN Measures2 ON Measures1.ID = Measures2.ID; Producing: +----+----------+-----------------+ | ID | Weight | DesiredVolume | +----+----------+-----------------+ | 4 | 325.0000 | 65.000000000000 | | 3 | 150.0000 | 33.000000000000 | | 2 | 200.0000 | 32.000000000000 | | 1 | 100.0000 | 13.333333333333 | +----+----------+-----------------+ But I am at a loss for how to actually insert these computed values into the Measures1 table. Preferably, I would like to be able to do it with a single query, rather than writing a script or stored procedure that iterates through every ID in Measures1. But even then I am worried that this might not be possible because the MySQL documentation says that you can't use a table in an UPDATE query and a SELECT subquery at the same time, and I think any solution would need to do that. I know that one workaround might be to create a new table with the results of the above query (also selecting all of the other non-Volume fields in Measures1) and then drop both tables and replace Measures1 with the newly-created table, but I was wondering if there was any better way to do it that I am missing.

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  • How to remove the port number from a url string

    - by Brono The Vibrator
    I have the following code snippet: string tmp = String.Format("javascript:window.open('{0}');", url); ClientScript.RegisterClientScriptBlock(this.GetType(), "NewWindow", tmp); the url generated by this code include the port number and I think that is happening becasue port 80 is used by the website and in this code I am trying to load a page from a virtual directory of the website. Any ideas on how to supress the port number in the url string generated by this code?

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  • What are possible causes of IDirect3DVertexBuffer9::Lock failing?

    - by Suma
    In error reports from some I have quite often seen following behaviour: IDirect3DVertexBuffer9::Lock fails, returned error code is D3DERR_NOTAVAILABLE. Once this happens, quite frequently (but not always) it is followed by CreateTexture or CreateVertexBuffer failing with error D3DERR_OUTOFVIDEOMEMORY. What are possible reasons for vertex buffer lock failure? Could virtual memory address space exhausted, or what?

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  • How do I add a servlet to an existing website with IIS7 and Tomcat6?

    - by jabe
    I've configured IIS7 and Tomcat6 successfully with the isapi redirector. I can get my servlets from tomcat's examples, and also my own servlets running from localhost. http://localhost/examples/servlets/ works fine for the supplied tomcat examples. How do i add servlets to existing web sites? I've tried adding a virtual directory to my website, the same way i did for the Default Website, but i get 404 errors thanks

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  • how to run web application in another machine?

    - by angel ansari
    hi, I want to run my web application in another machine.My problem is that i have already created virtual directory in iis 7.5 and add web application in it. Its running in my machine properly but i am trying it run in another machine through url and add the ip address along port number but its not found the web page.Plz help me .

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  • how do I best create a set of list classes to match my business objects

    - by ken-forslund
    I'm a bit fuzzy on the best way to solve the problem of needing a list for each of my business objects that implements some overridden functions. Here's the setup: I have a baseObject that sets up database, and has its proper Dispose() method All my other business objects inherit from it, and if necessary, override Dispose() Some of these classes also contain arrays (lists) of other objects. So I create a class that holds a List of these. I'm aware I could just use the generic List, but that doesn't let me add extra features like Dispose() so it will loop through and clean up. So if I had objects called User, Project and Schedule, I would create UserList, ProjectList, ScheduleList. In the past, I have simply had these inherit from List< with the appropriate class named and then written the pile of common functions I wanted it to have, like Dispose(). this meant I would verify by hand, that each of these List classes had the same set of methods. Some of these classes had pretty simple versions of these methods that could have been inherited from a base list class. I could write an interface, to force me to ensure that each of my List classes has the same functions, but interfaces don't let me write common base functions that SOME of the lists might override. I had tried to write a baseObjectList that inherited from List, and then make my other Lists inherit from that, but there are issues with that (which is really why I came here). One of which was trying to use the Find() method with a predicate. I've simplified the problem down to just a discussion of Dispose() method on the list that loops through and disposes its contents, but in reality, I have several other common functions that I want all my lists to have. What's the best practice to solve this organizational matter?

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  • JQuery - Set TBODY

    - by Villager
    Hello, I have a table defined as follows: <table id="myTable" cellpadding="0" cellspacing="0"> <thead><tr> <th>Date</th> <th>First Name</th> <th>Last Name</th> </tr></thead> <tbody> <!-- rows will go here --> </tbody> </table> I am trying to dynamically populate 'myTable' at runtime via JavaScript. To accomodate for this, I am using JQuery. I want to write some HTML into the tbody element within 'myTable'. However, I am having problems understanding how to do this with the selectors. I know that I can get 'myTable' using: $("#myTable") I know that I can set the HTML of myTable by using the following: $("#myTable").html(someHtmlString); However, that sets the HTML of the entire table. In reality, I just want to set the HTML within the TBODY of 'myTable'. How do I do this with JQuery? Thank you!

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