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  • Are there any downsides in using C++ for network daemons?

    - by badcat
    Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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  • in Rails, with check_box_tag, how do I keep the checkboxes checked after submitting query?

    - by Sebastien Paquet
    Ok, I know this is for the Saas course and people have been asking questions related to that as well but i've spent a lot of time trying and reading and I'm stuck. First of all, When you have a model called Movie, is it better to use Ratings as a model and associate them or just keep Ratings in an array floating in space(!). Second, here's what I have now in my controller: def index @movies = Movie.where(params[:ratings].present? ? {:rating => (params[:ratings].keys)} : {}).order(params[:sort]) @sort = params[:sort] @ratings = Ratings.all end Now, I decided to create a Ratings model since I thought It would be better. Here's my view: = form_tag movies_path, :method => :get do Include: - @ratings.each do |rating| = rating.rating = check_box_tag "ratings[#{rating.rating}]" = submit_tag "Refresh" I tried everything that is related to using a conditional ternary inside the checkbox tag ending with " .include?(rating) ? true : "" I tried everything that's supposed to work but it doesn't. I don't want the exact answer, I just need guidance.Thanks in advance!

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  • How to calculate the normal of points on a 3D cubic Bézier curve given normals for its start and end points?

    - by Robert
    I'm trying to render a "3D ribbon" using a single 3D cubic Bézier curve to describe it (the width of the ribbon is some constant). The first and last control points have a normal vector associated with them (which are always perpendicular to the tangents at those points, and describe the surface normal of the ribbon at those points), and I'm trying to smoothly interpolate the normal vector over the course of the curve. For example, given a curve which forms the letter 'C', with the first and last control points both having surface normals pointing upwards, the ribbon should start flat, parallel to the ground, slowly turn, and then end flat again, facing the same way as the first control point. To do this "smoothly", it would have to face outwards half-way through the curve. At the moment (for this case), I've only been able to get all the surfaces facing upwards (and not outwards in the middle), which creates an ugly transition in the middle. It's quite hard to explain, I've attached some images below of this example with what it currently looks like (all surfaces facing upwards, sharp flip in the middle) and what it should look like (smooth transition, surfaces slowly rotate round). Silver faces represent the front, black faces the back. Incorrect, what it currently looks like: Correct, what it should look like: All I really need is to be able to calculate this "hybrid normal vector" for any point on the 3D cubic bézier curve, and I can generate the polygons no problem, but I can't work out how to get them to smoothly rotate round as depicted. Completely stuck as to how to proceed!

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  • Terminal-based snake game: input thread manipulates output

    - by enlightened
    I'm writing a snake game for the terminal, i.e. output via print. The following works just fine: while status[snake_monad] do print to_string draw canvas, compose_all([ frame, specs, snake_to_hash(snake[snake_monad]) ]) turn! snake_monad, get_dir move! snake_monad, specs sleep 0.25 end But I don't want the turn!ing to block, of course. So I put it into a new Thread and let it loop: Thread.new do loop do turn! snake_monad, get_dir end end while status[snake_monad] do ... # no turn! here ... end Which also works logically (the snake is turning), but the output is somehow interspersed with newlines. As soon as I kill the input thread (^C) it looks normal again. So why and how does the thread have any effect on my output? And how do I work around this issue? (I don't know much about threads, even less about them in ruby. Input and output concurrently on the same terminal make the matter worse, I guess...) Also (not really important): Wanting my program as pure as possible, would it be somewhat easily possible to get the input non-blockingly while passing everything around? Thank you!

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  • Why doesn't the Java Collections API include a Graph implementation?

    - by dvanaria
    I’m currently learning the Java Collections API and feel I have a good understanding of the basics, but I’ve never understood why this standard API doesn’t include a Graph implementation. The three base classes are easily understandable (List, Set, and Map) and all their implementations in the API are mostly straightforward and consistent. Considering how often graphs come up as a potential way to model a given problem, this just doesn’t make sense to me (it’s possible it does exist in the API and I’m not looking in the right place of course). Steve Yegge suggests in one of his blog posts that a programmer should consider graphs first when attacking a problem, and if the problem domain doesn’t fit naturally into this data structure, only then consider the alternative structures. My first guess is that there is no universal way to represent graphs, or that their interfaces may not be generic enough for an API implementation to be useful? But if you strip down a graph to its basic components (vertices and a set of edges that connect some or all of the vertices) and consider the ways that graphs are commonly constructed (methods like addVertex(v) and insertEdge(v1, v2)) it seems that a generic Graph implementation would be possible and useful. Thanks for helping me understand this better.

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  • Are there good reasons not to use an ORM?

    - by hangy
    During my apprenticeship, I have used NHibernate for some smaller projects which I mostly coded and designed on my own. Now, before starting some bigger project, the discussion arose how to design data access and whether or not to use an ORM layer. As I am still in my apprenticeship and still consider myself a beginner in enterprise programming, I did not really try to push in my opinion, which is that using an object relational mapper to the database can ease development quite a lot. The other coders in the development team are much more experienced than me, so I think I will just do what they say. :-) However, I do not completely understand two of the main reasons for not using NHibernate or a similar project: One can just build one’s own data access objects with SQL queries and copy those queries out of Microsoft SQL Server Management Studio. Debugging an ORM can be hard. So, of course I could just build my data access layer with a lot of SELECTs etc, but here I miss the advantage of automatic joins, lazy-loading proxy classes and a lower maintenance effort if a table gets a new column or a column gets renamed. (Updating numerous SELECT, INSERT and UPDATE queries vs. updating the mapping config and possibly refactoring the business classes and DTOs.) Also, using NHibernate you can run into unforeseen problems if you do not know the framework very well. That could be, for example, trusting the Table.hbm.xml where you set a string’s length to be automatically validated. However, I can also imagine similar bugs in a “simple” SqlConnection query based data access layer. Finally, are those arguments mentioned above really a good reason not to utilise an ORM for a non-trivial database based enterprise application? Are there probably other arguments they/I might have missed? (I should probably add that I think this is like the first “big” .NET/C# based application which will require teamwork. Good practices, which are seen as pretty normal on Stack Overflow, such as unit testing or continuous integration, are non-existing here up to now.)

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  • JQuery: how to store records id for data from ajax query in dynamicly created html elements

    - by grapkulec
    Probably question title is rather cryptic but I will try to explain myself here so please bare with me :) Let's assume this configuration: server-side is PHP application responding for requests with data (list of items, single item details, etc.) in json format client-side is JQuery application sending ajax request to that PHP app and creating html content corresponding with received data So, for example: client requests "list of all animals with names staring with 'A'", gets the json response from server, and for every "animal" creates some html gizmo like div with animal description or something like that. It doesn't really matter what html element it will be but it has to point exactly to specific record by "containing" id of that record. And here is my dilemma: is it good solution to use "id" property for that? So it would be like: <div id="10" class="animal"> <p> This is animal of very mysterious kind... </p> </div> <div id="11" class="animal"> <p> And this one is very common to our country... </p> </div> where id="10" is of course indication that this is representation of record with id = 10. Or maybe I should store this record id in some custom made tag like <record_id>10</record_id> and leave an "id" strictly for what it was meant to be (css selector)? I need that record id for further stuff like updating database with some user input or deleting some of "animals" or creating new ones or anything that will be needed. All manipulations will be done with JQuery and ajax requests and responses will be visualized also with dynamic creation of html interface. I'm sure that somebody had to deal with that kind of stuff before so I would be grateful for some tips on that topic.

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  • Unity: Replace registered type with another type at runtime

    - by gehho
    We have a scenario where the user can choose between different hardware at runtime. In the background we have several different hardware classes which all implement an IHardware interface. We would like to use Unity to register the currently selected hardware instance for this interface. However, when the user selects another hardware, this would require us to replace this registration at runtime. The following example might make this clearer: public interface IHardware { // some methods... } public class HardwareA : IHardware { // ... } public class HardwareB : IHardware { // ... } container.RegisterInstance<IHardware>(new HardwareA()); // user selects new hardware somewhere in the configuration... // the following is invalid code, but can it be achieved another way? container.ReplaceInstance<IHardware>(new HardwareB()); Can this behavior be achieved somehow? BTW: I am completely aware that instances which have already been resolved from the container will not be replaced with the new instances, of course. We would take care of that ourselves by forcing them to resolve the instance once again.

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  • In-order tree traversal

    - by Chris S
    I have the following text from an academic course I took a while ago about in-order traversal (they also call it pancaking) of a binary tree (not BST): In-order tree traversal Draw a line around the outside of the tree. Start to the left of the root, and go around the outside of the tree, to end up to the right of the root. Stay as close to the tree as possible, but do not cross the tree. (Think of the tree — its branches and nodes — as a solid barrier.) The order of the nodes is the order in which this line passes underneath them. If you are unsure as to when you go “underneath” a node, remember that a node “to the left” always comes first. Here's the example used (slightly different tree from below) However when I do a search on google, I get a conflicting definition. For example the wikipedia example: Inorder traversal sequence: A, B, C, D, E, F, G, H, I (leftchild,rootnode,right node) But according to (my understanding of) definition #1, this should be A, B, D, C, E, F, G, I, H Can anyone clarify which definition is correct? They might be both describing different traversal methods, but happen to be using the same name. I'm having trouble believing the peer-reviewed academic text is wrong, but can't be certain.

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  • ASP.NET server data persistence

    - by Wayne Werner
    Hi, I'm not really sure exactly how the question should be phrased, so please be patient if I ask the wrong thing. I'm writing an ASP.NET application using VB as the code behind language. I have a data access class that connects to the DB to run the query (parameterized, of course), and another class to perform the validation tasks - I access this class from my aspx page. What I would like is to be able to store the data server side and wait for the user to choose from a few options based on the validity of the data. But unless my understanding is completely off, having persistent data objects on the server will give problems when multiple users connect? My ultimate goal is that once the data has been validated the end user can't modify it. Currently I'm validating the data, but I still have to retrieve it from the web form AFTER the user says OK, which obviously leaves open the possibility of injecting bad data either accidentally (unlikely) or on purpose (also unlikely for the use, but I'd prefer not to take the chance). So am I completely off in my understanding? If so, can someone point me to a resource that provides some instructions on keeping persistent data on the server, or provide instruction? Thanks!

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  • Best practices for encrypting continuous/small UDP data

    - by temp
    Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (no waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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  • Setting Nullable Integer to String Containing Nothing yields 0

    - by Brian MacKay
    I've been pulling my hair out over some unexpected behavior from nullable integers. If I set an Integer to Nothing, it becomes Nothing as expected. If I set an Integer? to a String that is Nothing, it becomes 0! Of course I get this whether I explicitly cast the String to Integer? or not. I realize I could work around this pretty easily but I want to know what I'm missing. Dim NullString As String = Nothing Dim NullableInt As Integer? = CType(NullString, Integer?) 'Expected NullableInt to be Nothing, but it's 0! NullableInt = Nothing 'This works -- NullableInt now contains Nothing. How is this EDIT: Previously I had my code up here so without the explicit conversion to 'Integer?' and everyone seemed to be fixated on that. I want to be clear that this is not an issue that would have been caught by Option Strict On -- check out the accepted answer. This is a quirk of the string-to-integer conversion rules which predate nullable types, but still impact them.

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  • Deploying a Rails app on an Ubuntu server using Git

    - by NudeCanalTroll
    I'm completely new to Linux, but today I find myself setting up a server (Ubuntu 10.04 LTS lucid) from scratch to host a Rails application. Anyway, I managed to get a Rails app up and running on the server itself, but I had to scrap that because I want to use Git. So I setup a git repository on the server, then pushed all the code from my local machine to the repository. Buuuut, of course Git doesn't actually store the files themselves in the repository -- all the code for my Rails app is now only on my local machine. How am I supposed to tell the server to host that? Right now my solution is to have the server use git to pull the code from its own repository. That's the code I'll host for all the world to see. In order to update the code, I guess I'll have to do something like this: Update the code on my local machine. Do some git adds, git commits, and a git push. On the server, do a git pull to update the code. So my question is, am I doing this the right way? enter code here

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  • Can i change the view without changing the controller?

    - by Ian Boyd
    Pretend1 there is a place to type in a name:     Name: __________________ When the text box changes, the value is absorbed into the controller, who stores it in data model. Business rules require that a name be entered: if there is no text entered the TextBox should be colored something in the view to indicate baddness; otherwise it can be whatever color the view likes. The TextBox contains a String, the controller handles a String, and the model stores a String. Now lets say i want to improve the view. There is a new kind of text box2 that can be fed not only string-based keyboard input, but also an image. The view (currently) knows how to determine if the image is in the proper format to perform the processing required to extract text out of it. If there is text, then that text can be fed to the controller, who feeds it to the data model. But if the image is invalid, e.g.3 wrong file format invalid dimensions invalid bit depth unhandled or unknown encoding format missing or incorrectly located registration marks contents not recognizable the view can show something to the user that the image is bad. But the telling the user that something is bad is supposed to be the job of the controller. i'm, of course, not going to re-write the controller to handle Image based text-input (e.g. image based names). a. the code is binary locked inside a GUI widget4 b. there other views besides this one, i'm not going to impose a particular view onto the controller c. i just don't wanna. If i have to change things outside of this UI improvement, then i'll just leave the UI unimproved5 So what's the thinking on having different views for the same Model and Controller? Nitpicker's Corner 1 contrived hypothetical example 2 e.g. bar code, g-mask, ocr 3 contrived hypothetical reasons 4 or hardware of a USB bar-code scanner 5 forcing the user to continue to use a DateTimePicker rather than a TextBox

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  • What is the correct stage to use for Google Guice in production in an application server?

    - by Yishai
    It seems like a strange question (the obvious answer would Production, duh), but if you read the java docs: /** * We want fast startup times at the expense of runtime performance and some up front error * checking. */ DEVELOPMENT, /** * We want to catch errors as early as possible and take performance hits up front. */ PRODUCTION Assuming a scenario where you have a stateless call to an application server, the initial receiving method (or there abouts) creates the injector new every call. If there all of the module bindings are not needed in a given call, then it would seem to have been better to use the Development stage (which is the default) and not take the performance hit upfront, because you may never take it at all, and here the distinction between "upfront" and "runtime performance" is kind of moot, as it is one call. Of course the downside of this would appear to be that you would lose the error checking, causing potential code paths to cause a problem by surprise. So the question boils down to are the assumptions in the above correct? Will you save performance on a large set of modules when the given lifetime of an injector is one call?

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  • C# "Rename" Property in Derived Class

    - by Eric
    When you read this you'll be awfully tempted to give advice like "this is a bad idea for the following reason..." Bear with me. I know there are other ways to approach this. This question should be considered trivia. Lets say you have a class "Transaction" that has properties common to all transactions such as Invoice, Purchase Order, and Sales Receipt. Let's take the simple example of Transaction "Amount", which is the most important monetary amount for a given transaction. public class Transaction { public double Amount { get; set; } public TxnTypeEnum TransactionType { get; set; } } This Amount may have a more specific name in a derived type... at least in the real world. For example, the following values are all actually the same thing: Transaction - Amount Invoice - Subtotal PurchaseOrder - Total Sales Receipt - Amount So now I want a derived class "Invoice" that has a Subtotal rather than the generically-named Amount. Ideally both of the following would be true: In an instance of Transaction, the Amount property would be visible. In an instance of Invoice, the Amount property would be hidden, but the Subtotal property would refer to it internally. Invoice looks like this: public class Invoice : Transaction { new private double? Amount { get { return base.Amount; } set { base.Amount = value; } } // This property should hide the generic property "Amount" on Transaction public double? SubTotal { get { return Amount; } set { Amount = value; } } public double RemainingBalance { get; set; } } But of course Transaction.Amount is still visible on any instance of Invoice. Thanks for taking a look!

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  • What is the most common way to use a middleware in node with express and connect

    - by Bernhard
    Thinking about the correct way, how to make use of middlewares in a node.js web project using express and connect which is growing up at the moment. Of course there are middlewares right now wich has to pass or extend requests globally but in a lot of cases there are special jobs like prepare incoming data and in this case the middleware would only work for a set of http-methods and routes. I've a component based architecture and each component brings it's own middleware layer which can implement those for requests this component can handle. On app startup any required component is loaded and prepared. Is it a good idea to bind the middleware code execution to URLs to keep cpu load lower or is it better to use middlewares only for global purposes? Here's some dummy how an url related middleware look like. app.use(function(req, res, next) { // Check if requested route is a part of the current component // or if the middleware should be passed on any request if (APP.controller.groups.Component.isExpectedRoute(req) || APP.controller.groups.Component.getConfig().MIDDLEWARE_PASS_ALL === true) { // Execute the midleware code here console.log('This is a route which should be afected by middleware'); ... next(); }else{ next(); } });

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  • Php - divide time period into equal intervals

    - by experc
    Hi! I am working on my php course project and for the past few days I have stucked at the point where I have to create php function which gets 5 parameters which represents information about the working time of some department - when the work starts/ends, when the lunchtime (or any other break) starts/ends and integer representing minutes into how small piecies we should divide time period. Besides - it's possible that there are not any breaks in the working time. The function should return all intervals from working time. function split_time_into_intervals($work_starts,$work_ends,$break_starts=null; $break_ends=null,$minutes_per_interval=60){ $intervals=array(); //all of the function code return $intervals; } So if I have the following parameters for the function function split_time_into_intervals("8:30","14:50","11:45"; "12:25"){ .. } I would like to retrieve the following array: $intervals[0]['starts']="8:30"; $intervals[0]['ends']="9:30"; $intervals[1]['starts']="9:30"; $intervals[1]['ends']="10:30"; $intervals[2]['starts']="10:30"; $intervals[2]['ends']="11:30"; $intervals[3]['starts']="11:30"; $intervals[3]['ends']="11:45"; //this interval was smaller than 60 minutes - because of the break (which starts at 11:45) $intervals[4]['starts']="12:25";//starts when the break ends $intervals[4]['ends']="13:25"; // interval is again 60 minutes $intervals[5]['starts']="13:25"; $intervals[5]['ends']="14:25"; $intervals[6]['starts']="14:25"; $intervals[6]['ends']="14:50"; //this period is shorter than 60 minutes - because work ends Any advises? I would apriciate any php (or C#) code regarding to this problem!

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  • Open source real life license examples: yours or others

    - by donpal
    I'm aware of the usual list of open source licenses, so I'm not even going to list it here. What I'd like to ask is about your open source projects (whether out or planned for the future), and why you're planning to choose a certain license over the other. Basically say I went for X license because I wanted Y and that other license didn't provide it for me. I understand that the language itself can make a difference in the choice of license: interpreted languages like PHP vs. compiled languages like Java. I'm mostly interested in hearing about PHP projects, but of course additional insights are welcome. You may even have chosen that particular language for a licensing reason. Ideally I want to hear answers from people who were involved in the actual project (i.e. your own project), because that usually means you've put some thought into the license yourself and understand the implications of that license. But examples of existing projects that aren't your own are OK. Please just say why you think that license was good/bad for them. But first-hand experience is preferred. Looking forward to hearing some informative input.

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  • MVC3 View For Loop values initialization

    - by Ryan
    So I have a for loop in my View that is supposed to render out the input boxes. Now inside these input boxes I want to put lables that disappear when you click on them. This is all simple. Now it's probably because my brain was wired for php first, and it has been difficult to get it to think in lambdas and object orientation, but I can't figure out how to do this: @{ for (int i = 0; i < 3; i++) { <div class="editor-label grid_2">User</div> Model.Users[i].UserFirstName = "First Name"; Model.Users[i].UserLastName = "Last Name"; Model.Users[i].UserEmailAddress = "Email Address"; <div class="grid_10"> @Html.TextBoxFor(m => Model.Users[i].UserFirstName, new { @class = "user-input" }) @Html.TextBoxFor(m => Model.Users[i].UserLastName, new { @class = "user-input" }) @Html.TextBoxFor(m => Model.Users[i].UserEmailAddress, new { @class = "user-input-long" }) @Html.CheckBoxFor(m => Model.Users[i].IsUserAdmin) <span>&nbsp;admin?</span> </div> <div class="clear"> </div> } } And initialize the values for the users. And you're probably thinking "Of course that won't work. You're going to get a Null Reference Exception", and you would be correct. I might need to initialize them somewhere else and I don't realize it but I'm just not sure. I've tried the [DefaultValue("First Name")] route and that doesn't work. I'm probably thinking about this wrong, but my brain is already shot from trying to figure out how to wire up these events to the controller, so any help would be appreciated!

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  • Concept: Is mongo right for applying schemas?

    - by Jan
    I am currently in charge of checking wether it is valuable for one of our upcoming products to be developed on mongo. Without going too much into detail, I'll try to explain, what the app does. The app simply has "entities". These entities are technical stuff, like cell phones, TVs, Laptops, tablet pcs, and so forth. Of course, a cell phone has other attributes than a Tablet PCs and a Laptop has even other attributes, like RAM, CPU, display size and so on. Now I want to have something that we wanna call a scheme: We define that we need to have saved the display size, amount of ram size of flash devices, processor type, processor speed and so on for tablet pcs. For cell phone we might save display size, GSM, Edge, 3g, 4g, processor, ram, touch screen technology, bla bla bla. I think you got it :) What I want to realize is, that each "category" has a schema and when one of the system's users enters a new product (let's say the new iphone 4), the app constructs the form to be filled out with the appropriate attributes. So far it sounds nice and should not be a problem with mongo. But now the tough for which I could not find a clean solution.... An attribute modeled in mongo looks like: { _id: 1234456, name: "Attribute name", type: 0, "description" } But what to do, if i need this attribute in several languages, like: { en: {name: "Attribute name", type: 0, "description"}, de: {name: "Name des Attributs, type: 0, "Beschreibung"} } I also need to ensure that the german attribute gets updated as soon as the english gets updated, for instance when type changes from 0 to 1. Any ideas on that?

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  • Populating a Datagrid with variable number of columns and rows in Flex

    - by Rie Mino
    I am trying to figure out how to manage a Datagrid based on an XML object like this: <matrix rows="5" columns="5"> <column> <row>0.5</row> <row>0.21</row> </column> <column> <row>0.6</row> <row>0.9</row> </column> <column> <row>0.5</row> <row>0.5</row> </column> <column> <row>0.8</row> <row>0.4</row> </column> </matrix> I will need to populate the Datagrid column names based on a different XML object and use the above XML to populate each of the column's rows. I currently am able to create the Datagrid and populate its column headers but I am unsure as to how to how to add the rows for each column. The above XML will be update with new row and column elements added and deleted. This, of course, will be bound to the Datagrid to show updates. Thanks in advanced for your help.

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  • Are bad data issues that common?

    - by Water Cooler v2
    I've worked for clients that had a large number of distinct, small to mid-sized projects, each interacting with each other via properly defined interfaces to share data, but not reading and writing to the same database. Each had their own separate database, their own cache, their own file servers/system that they had dedicated access to, and so they never caused any problems. One of these clients is a mobile content vendor, so they're lucky in a way that they do not have to face the same problems that everyday business applications do. They can create all those separate compartments where their components happily live in isolation of the others. However, for many business applications, this is not possible. I've worked with a few clients, one of whose applications I am doing the production support for, where there are "bad data issues" on an hourly basis. Yeah, it's that crazy. Some data records from one of the instances (lower than production, of course) would have been run a couple of weeks ago, and caused some other user's data to get corrupted. And then, a data script will have to be written to fix this issue. And I've seen this happening so much with this client that I have to ask. I've seen this happening at a moderate rate with other clients, but this one just seems to be out of order. If you're working with business applications that share a large amount of data by reading and writing to/from the same database, are "bad data issues" that common in your environment?

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  • Linking a template class using another template class (error LNK2001)

    - by Luís Guilherme
    I implemented the "Strategy" design pattern using an Abstract template class, and two subclasses. Goes like this: template <class T> class Neighbourhood { public: virtual void alter(std::vector<T>& array, int i1, int i2) = 0; }; and template <class T> class Swap : public Neighbourhood<T> { public: virtual void alter(std::vector<T>& array, int i1, int i2); }; There's another subclass, just like this one, and alter is implemented in the cpp file. Ok, fine! Now I declare another method, in another class (including neighbourhood header file, of course), like this: void lSearch(/*parameters*/, Neighbourhood<LotSolutionInformation> nhood); It compiles fine and cleanly. When starting to link, I get the following error: 1>SolverFV.obj : error LNK2001: unresolved external symbol "public: virtual void __thiscall lsc::Neighbourhood<class LotSolutionInformation>::alter(class std::vector<class LotSolutionInformation,class std::allocator<class LotSolutionInformation> > &,int,int)" (?alter@?$Neighbourhood@VLotSolutionInformation@@@lsc@@UAEXAAV?$vector@VLotSolutionInformation@@V?$allocator@VLotSolutionInformation@@@std@@@std@@HH@Z)

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  • Clear tableView cell cache (or remove an entry)

    - by ManniAT
    Hi, I have the same question problem as described here http://stackoverflow.com/questions/2286669/iphone-how-to-purge-a-cached-uitableviewcell But my problem can't be solved with "resetting content". To be precise - I use a custom cell (own class). While running the application it is possible that I have to use a different "cell type". It's the same class - but it has (a lot of) differnt attributes. Of course I could always reset all the things at "PrepareForReuse" but that's not a good idea I guess (there are a lot things to reset). My idea - I do all these things in the constructor of the cell. And all the rows will use this "type of cell" later. When the (seldom) situation comes that I have to change the look of all rows I create a new instance of this kind of cell with different settings. And now I want to replace the queued cell with this new one. I tried it with simply calling the constructor with the same cellidentifier (in the hope it will replace the existing one) but that doesn't work. I also didn't find a "ClearReusableCells" or something like this. Is there a way to clear the cache - or to remove / replace a specific item? Manfred

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