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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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  • MySQL - Calculating fields on the fly vs storing calculated data

    - by Christian Varga
    Hi Everyone, I apologise if this has been asked before, but I can't seem to find an answer to a question that I have about calculating on the fly vs storing fields in a database. I read a few articles that suggested it was preferable to calculate when you can, but I would just like to know if that still applies to the following 2 examples. Example 1. Say you are storing data relating to a car. You store the fuel tank size in litres, and how many litres it uses per 100km. You also want to know how many KMs it can travel, which can be calculated from the tank size and economy. I see 2 ways of doing this: When a car is added or updated, calculate the amount of KMs and store this as a static field in the database. Every time a car is accessed, calculate the amount of KMs on the fly. Because the cars economy/tank size doesn't change (although it could be edited), the KMs is a pretty static value. I don't see why we would calculate it every single time the car is accessed. Wouldn't this waste cpu time as opposed to simply storing it in a separate field in the database and calculating only when a car is added or updated? My next example, which is almost an entirely different question (but on the same topic), relates to counting children. Let's say we have a app which has categories and items. We have a view where we display all the categories, and a count of all the items inside each category. Again, I'm wondering what's better. To perform a MySQL query to count all the items in each category every single time the page is accessed? Or store the count in a field in the categories table and update when an item is added / deleted? I know it is redundant to store anything that can be calculated, but I worry that calculating fields or counting records might be slow as opposed to storing the data in a field. If it's not then please let me know, I just want to learn about when to use either method. On a small scale I guess it wouldn't matter either way, but apps like Facebook, would they really count the amount of friends you have every time someone views your profile or would they just store it as a field? I'd appreciate any responses to both of these scenarios, and any resource that might explain the benefits of calculating vs storing. Thanks in advance, Christian

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  • Perl - Calling subclass constructor from superclass (OO)

    - by Emmel
    This may turn out to be an embarrassingly stupid question, but better than potentially creating embarrassingly stupid code. :-) This is an OO design question, really. Let's say I have an object class 'Foos' that represents a set of dynamic configuration elements, which are obtained by querying a command on disk, 'mycrazyfoos -getconfig'. Let's say that there are two categories of behavior that I want 'Foos' objects to have: Existing ones: one is, query ones that exist in the command output I just mentioned (/usr/bin/mycrazyfoos -getconfig`. Make modifications to existing ones via shelling out commands. Create new ones that don't exist; new 'crazyfoos', using a complex set of /usr/bin/mycrazyfoos commands and parameters. Here I'm not really just querying, but actually running a bunch of system() commands. Affecting changes. Here's my class structure: Foos.pm package Foos, which has a new($hashref-{name = 'myfooname',) constructor that takes a 'crazyfoo NAME' and then queries the existence of that NAME to see if it already exists (by shelling out and running the mycrazyfoos command above). If that crazyfoo already exists, return a Foos::Existing object. Any changes to this object requires shelling out, running commands and getting confirmation that everything ran okay. If this is the way to go, then the new() constructor needs to have a test to see which subclass constructor to use (if that even makes sense in this context). Here are the subclasses: Foos/Existing.pm As mentioned above, this is for when a Foos object already exists. Foos/Pending.pm This is an object that will be created if, in the above, the 'crazyfoo NAME' doesn't actually exist. In this case, the new() constructor above will be checked for additional parameters, and it will go ahead and, when called using -create() shell out using system() and create a new object... possibly returning an 'Existing' one... OR As I type this out, I am realizing it is perhaps it's better to have a single: (an alternative arrangement) Foos class, that has a -new() that takes just a name -create() that takes additional creation parameters -delete(), -change() and other params that affect ones that exist; that will have to just be checked dynamically. So here we are, two main directions to go with this. I'm curious which would be the more intelligent way to go.

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  • jquery and mobile browser compatiblity?

    - by fractalbit
    I want to build a relatively simple version of my site for mobile phones but i will definately need javascript and jquery for many functions. Googling didn't help to find an answer. How is compatibility of jquery with popular browsers in mobile phones? I am talking for smartphones. For example the deafult browsers for these platforms Windows mobile 6+ Android 1.5+ iphone 3g and let's add opera mobile. Has anyone tried it?

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  • Colud not open connection to the host error in telnet

    - by hima
    I am using telnet tk2smtp.msn.com 25 command from the command prompt to connect to the specific port on tk2smtp but its showing Could not open connection to the host error in command prompt. I installed Telnet Client in my machine . Let me know if there are any other things to be configured for this

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  • How do you return stolen packets back to Netfilter

    - by meg18019
    Let's say I have intercepted a packet from Netfilter and subsequently returned NF_STOLEN. At some point I want to re-inject that packet back to, in this case, the TCP stream it came from. I want to do this from Kernel space. So far I have been unable to find a way to do this. Thanks for the help.

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  • how to know whether file is downloaded by user or not?

    - by user251336
    hi all, I have a functionality where a user is given file to download. It works fine. BUT - 1. How to know whether user has downloaded a file or cancelled it? 2. After downloading I wat to redirect current page to another one that is also not happening. Please let me know if any one of you have any idea about it. (I am doing it in Joomla) Regards, Shahu

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  • Returning superclass of return type from remote EJB method

    - by fish
    Let's say I have remote interface A: @Remote public interface A { public Response doSomething(); } And implementation: @Stateless public class B implements A { public BeeResponse doSomething() {...} } Where: BeeResponse extends Response. Response is located in the EJB-API jar and BeeResponse is in the implementation jar. Response and BeeResponse have different serialVersionUID. My assumption is that the unmarshalling of the response from B will fail, am I correct?

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  • PHP Get only a part of the full path

    - by Adrian
    Hello, I would like to know how can I subtract only a part of the full path: I get the full path of the current folder: $dbc_root = getcwd(); // That will return let's say "/home/USER/public_html/test2" I want to select only "/public_html/test2" How can I do it? Thanks!

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  • What is the best practice to segment c#.net projects based on a single base project

    - by Anthony
    Honestly, I can't word my question any better without describing it. I have a base project (with all its glory, dlls, resources etc) which is a CMS. I need to use this project as a base for othe custom bake projects. This base project is to be maintained and updated among all custom bake projects. I use subversion (Collabnet and Tortise SVN) I have two questions: 1 - Can I use subversion to share the base project among other projects What I mean here is can I "Checkout" the base project into another "Checked Out" project and have both update and commit seperatley. So, to paint a picture, let's say I am working on a custom project and I modify the core/base prject in some way (which I know will suit the others) can I then commit those changes and upon doing so when I update the base project in the other "Checked out" resources will it pull the changes? In short, I would like not to have to manually deploy updated core files whenever I make changes into each seperate project. 2 - If I create a custom file (let's say an webcontrol or aspx page etc) can I have it compile seperatley from the base project Another tricky one to explain. When I publish my web application it creates DLLs based on the namespaces of projects attached to it. So I may have a number of DLLs including the "Website's" namespace DLL, which could simply be website. I want to be able to make a seperate, custom, control which does not compile into those DLLs as the custom files should not rely on those DLLS to run. Is it as simple to set a seperate namespace for those files like CustomFiles.ProjectName for example? Think of the whole idea as adding modules to the .NET project, I don't want the module's code in any of the core DLLs but I do need for module to be able to access the core dlls. (There is no need for the core project to access the module code as it should be one way only in theory, though I reckon it woould not be possible anyway without using JSON/SOAP or something like that, maybe I am wrong.) I want to create a pluggable environment much like that of Joomla/Wordpress as since PHP generally doesn't have to be compiled first I see this is the reason why all this is possible/easy. The idea is to allow pluggable themes, modules etc etc. (I haven't tried simply adding .NET themes after compile/publish but I am assuming this is possible anyway? OR does the compiler need to reference items in the files?)

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  • How to implement geo-based data store and computation?

    - by Mickey Shine
    Well, let me explain this briefly: 1.I want to build a website that provides location based services, like http://fireeagle.yahoo.net/ . 2.I guess most of these services have something do with longitude and latitude. 3.Is there any particular database/datastore/data structures fit well for such apps? I mean easy to store longitude, latitude and easy to compute or easy to use. I am new to this and any feedbacks are welcome

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  • How to access table cells from jquery

    - by Sayem Ahmed
    Ok, I have a table which contains multiple rows. Each row contains some data and a hyperlink. When this link is clicked, I need to open up jquery's dialog form and let the user able to edit the data of the corresponding rows. So when the link is clicked, I need to access the values of the corresponding row cells from jquery. How can I do that ?

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  • ListView wont release focus in .NET CF 3.5

    - by roman
    I have a form with a ComboBox and a ListView, when I press the down key on the Dpad focus moves from ComboBox to the items in the listView. But then I cant get out of the ListView and focus on the ComboBox again, I can only go up and down in the ListView items, how do I let the user go back to the ComboBox?

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  • Why is it that I can include a header file in multiple cpp files that contains const int and not have a compiler error?

    - by tree
    Let's assume that I have files a.cpp b.cpp and file c.h. Both of the cpp files include the c.h file. The header file contains a bunch of const int definitions and when I compile them I get no errors and yet I can access those const as if they were global variables. So the question, why don't I get any compilation errors if I have multiple const definitions as well as these const int's having global-like scope?

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  • is it possible to extract all PDFs from a site

    - by deming
    given a URL like www.mysampleurl.com is it possible to crawl through the site and extract links for all PDFs that might exist? I've gotten the impression that Python is good for this kind of stuff. but is this feasible to do? how would one go about implementing something like this? also, assume that the site does not let you visit something like www.mysampleurl.com/files/

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  • How to create a windows service from java app

    - by ideasculptor
    I've just inherited a java application that needs to be installed as a service on XP and vista. It's been about 8 years since I've used windows in any form and I've never had to create a service, let alone from something like a java app (I've got a jar for the app and a single dependency jar - log4j). What is the magic necessary to make this run as a service? I've got the source, so code modifications, though preferably avoided, are possible.

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  • PHP - preg_replace with multiple matches

    - by Neil
    Let's say I have a string like: $text = "<object>item_id1a2b3</object>xxx<object>item_id4c5d6</object>" I want to convert it to: %ITEM:1a2b3xxx%ITEM:4c5d6 Here's what I've got: $text = preg_replace("/<object.*item_id([a-zA-Z0-9]+).*<\/object/","%ITEM:$1",$text); This isn't quite right, as the search is greedy. Thoughts? Thanks!

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  • Create, sort, and print a list of 100 random ints in the fewest chars of code

    - by TheSoftwareJedi
    What is the least amount of code you can write to create, sort (ascending), and print a list of 100 random positive integers? By least amount of code I mean characters contained in the entire source file, so get to minifying. I'm interested in seeing the answers using any and all programming languages. Let's try to keep one answer per language, edit the previous to correct or simplify. If you can't edit, comment?

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  • How to call the previous querystring parameter in .aspx

    - by Ingó Vals
    Let's say I have a ActionResult method that has a pageNumber parameter and a category parameter. The user should be able to set the category he's browsing which would be a ActionLink to the first page of that category. However if I have an another ActionLink where I go to the next page the category parameter would go back to default. How can I set the category parameter to be the same as on the previous page.

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  • Hide multiple PictureBox except clicked

    - by gadirzade
    HI Let me explain what i wont to do.I have a form and there is 10 picturebox on it.when I click one of them I wont to hide all other except clicked.It is possible that on click event of all of them hide others.but I ask for efficent way.forexample with a single function call from click event maybe

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