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  • General ORM design question

    - by Calvin
    Suppose you have 2 classes, Person and Rabbit. A person can do a number of things to a rabbit, s/he can either feed it, buy it and become its owner, or give it away. A rabbit can have none or at most 1 owner at a time. And if it is not fed for a while, it may die. Class Person { Void Feed(Rabbit r); Void Buy(Rabbit r); Void Giveaway(Person p, Rabbit r); Rabbit[] rabbits; } Class Rabbit { Bool IsAlive(); Person pwner; } There are a couple of observations from the domain model: Person and Rabbit can have references to each other Any actions on 1 object can also change the state of the other object Even if no explicit actions are invoked, there can still be a change of state in the objects (e.g. Rabbit can be starved to death, and that causes it to be removed from the Person.rabbits array) As DDD is concerned, I think the correct approach is to synchronize all calls that may change the states in the domain model. For instance, if a Person buys a Rabbit, s/he would need to acquire a lock in Person to make a change to the rabbits array AND also another lock in Rabbit to change its owner before releasing the first one. This would prevent a race condition where 2 Persons claim to be the owner of the little Rabbit. The other approach is to let the database to handle all these synchronizations. Who makes the first call wins, but then the DB needs to have some kind of business logics to figure out if it is a valid transaction (e.g. if a Rabbit already has an owner, it cannot change its owner unless the Person gives it away). There are both pros/cons in either approach, and I’d expect the “best” solution would be somewhere in-between. How would you do it in real life? What’s your take and experience? Also, is it a valid concern that there can be another race condition the domain model has committed its change but before it is fully committed in the database? And for the 3rd observation (i.e. state change due to time factor). How will you do it?

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  • I'm new to OOP/PHP. What's the practicality of visibility and extensibility in classes?

    - by marcdev
    I'm obviously brand new to these concepts. I just don't understand why you would limit access to properties or methods. It seems that you would just write the code according to intended results. Why would you create a private method instead of simply not calling that method? Is it for iterative object creation (if I'm stating that correctly), a multiple developer situation (don't mess up other people's work), or just so you don't mess up your own work accidentally?

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  • jquery ie6 issue swaping videos through hide/show while playing.

    - by user217181
    So my code is: Click the link show the div. I'm using the jquery flash embed object. $(document).ready( function() { $('a.overview').click( function() { $('#overview').show(); // show div.contact $('#evaulting').hide(); // hide div.contact $('#his').hide(); // hide div.contact }); }); $(document).ready( function() { $('a.evaulting').click( function() { $('#evaulting').show(); // show div.contact $('#overview').hide(); // hide div.contact $('#his').hide(); // hide div.contact }); }); <div id="overview" style="display:none"> <ul> <li rel="play-norelated.swf:680:480:true:ffffff" class="flash-replaced"> <embed width="680" height="480" type="application/x-shockwave-flash" src="play-norelated.swf" pluginspage="http://www.adobe.com/go/getflashplayer" flashvars="playVideo=ent_web_480x" bgcolor="ffffff" /> <div class="alt"><h1>To Play Iron Mountain Videos - You will need to upgrade your Flash Player</h1> <p><a href="http://www.adobe.com/go/getflashplayer"><img src="http://www.adobe.com/images/shared/download_buttons/get_flash_player.gif" alt="Get Adobe Flash player" /></a></p></div> </li> </ul> </div> <div id="evaulting" style="display:none"> <ul> <li rel="play-norelated.swf:680:480:true:ffffff" class="flash-replaced"> <embed width="680" height="480" type="application/x-shockwave-flash" src="play-norelated.swf" pluginspage="http://www.adobe.com/go/getflashplayer" flashvars="playVideo=evaulting_web_480x" bgcolor="ffffff" /> <div class="alt"><h1>To Play Iron Mountain Video's - You will need to upgrade your Flash Player</h1> <p><a href="http://www.adobe.com/go/getflashplayer"><img src="http://www.adobe.com/images/shared/download_buttons/get_flash_player.gif" alt="Get Adobe Flash player" /></a></p></div> </li> </ul> </div> When I repeat this code and get the second video to load on click. It works in all browsers. The only issue I'm running into is that in IE6 the video keeps playing and in other browsers it stops the video your watching and loads the one you clicked on. I looked into using the .remove object or the .append to a div, but I can't seem to get that to work and if it does work will it play nice with IE6. Try it out and maybe solve my issues.

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  • Recursively find files/directories within a directory

    - by enchilada
    I want to use enumeratorAtURL:includingPropertiesForKeys:options:errorHandler: to do this, as I'm coding under Snow Leopard. I know how to use this method. However, as for my purposes it's not adequate to load the contents lazily, I have the following question: How can I create an object hierarchy (of, say, the custom FileOrDirectory class with the standard children,count,isLeaf attributes) from the information I load from the enumeratorAtURL: method? I need to load this data beforehand, and show it in an outline view, for my purposes.

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  • Jython saying "No visible constructors for class"

    - by clutch
    I have a jython servlet as part of a large application running in tomcat5. I tested a few Spring Framework classes and create the objects in the Jython servlet. When I try to create objects of classes in the application I catch an Exception message "No visible constructors for class". These java classes do have a public constructor class, such as: public SchoolImpl() { } I create the object in python: from com.dc.sports.entity import SchoolImpl ... school = SchoolImpl() What am I doing wrong?

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  • How can I access x:Name from Code Behind?

    - by viky
    I have a datagrid in which I am using DataGridTemplateColumn and DataGridTextColumn. I want to access these columns at runtime so I have assigned x:Name property to them. But I was not getting that value in code behind, so I looked for DataGrid and then read objects by iterating through DataGrid.Columns. How can I read x:Name property from that object in C#? I need this to perform some specific operations with particular columns at runtime.

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  • "session" bean scope in a web application - reliable ?

    - by EugeneP
    Can you rely on this scope and be sure that every time 1) a new session starts, the Spring bean will be initialized with default values 2) while session is kept alive, the current object will store its state during session life, will never be lost or corrupted and can always be got with [webappcontext].getBean ?

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  • Call trace in Android

    - by DenMark
    I want to know how to do method tracing for Android applications. I mean, a sequence of calls on each object, not a stack trace. It's very similar to this question (Call trace in java), but on different platforms (jvm-PC vs dvm-Android). I have no control over the start arguments of dalvik, thus I cannot specify a java agent (or am I wrong here?). Is there another way to do method tracing? Thanks!

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  • Java Enum List from Class

    - by DD
    How do I go from a Class object to a list of enums generically? i.e. public static <T extends Enum> List<T> getList(Class<T> clazz) I cant find a way to get to the values() method

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  • std::list or std::multimap

    - by Tamir
    Hey, I right now have a list of a struct that I made, I sort this list everytime I add a new object, using the std::list sort method. I want to know what would be faster, using a std::multimap for this or std::list, since I'm iterating the whole list every frame (I am making a game). I would like to hear your opinion, for what should I use for this incident.

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  • Some clarification on rvalue references

    - by Dennis Zickefoose
    First: where are std::move and std::forward defined? I know what they do, but I can't find proof that any standard header is required to include them. In gcc44 sometimes std::move is available, and sometimes its not, so a definitive include directive would be useful. When implementing move semantics, the source is presumably left in an undefined state. Should this state necessarily be a valid state for the object? Obviously, you need to be able to call the object's destructor, and be able to assign to it by whatever means the class exposes. But should other operations be valid? I suppose what I'm asking is, if your class guarantees certain invariants, should you strive to enforce those invariants when the user has said they don't care about them anymore? Next: when you don't care about move semantics, are there any limitations that would cause a non-const reference to be preferred over an rvalue reference when dealing with function parameters? void function(T&); over void function(T&&); From a caller's perspective, being able to pass functions temporary values is occasionally useful, so it seems as though one should grant that option whenever it is feasible to do so. And rvalue references are themselves lvalues, so you can't inadvertently call a move-constructor instead of a copy-constructor, or something like that. I don't see a downside, but I'm sure there is one. Which brings me to my final question. You still can not bind temporaries to non-const references. But you can bind them to non-const rvalue references. And you can then pass along that reference as a non-const reference in another function. void function1(int& r) { r++; } void function2(int&& r) { function1(r); } int main() { function1(5); //bad function2(5); //good } Besides the fact that it doesn't do anything, is there anything wrong with that code? My gut says of course not, since changing rvalue references is kind of the whole point to their existence. And if the passed value is legitimately const, the compiler will catch it and yell at you. But by all appearances, this is a runaround of a mechanism that was presumably put in place for a reason, so I'd just like confirmation that I'm not doing anything foolish.

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  • .net: does anyone know a free library to download nntp messages

    - by stighy
    hi folks, i'm using ip*works for download newsgroup message and insert them into a database... ipworks is "comfortable" to use because it automatically split nntp data return into different object (or variable). So i've "author" "date" "topic" "messagge" already splitted to my use. However ipworks isn't free and it cost a lot for my use.. so i'm asking you some component or code snippet to use to download and "manage" nntp messagges. Thanks in advance and regards!

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  • binding a usercontrol to the opposite of a bool property

    - by SnOrfus
    Pretty straightforward: I'm looking to do the same as this but in winforms. Everything that google seems to pull up is wpf specific (ie. I don't want to reference presentationframework.dll) Explained if you don't want to read the link: The following is a representation of the intent of what I'd like to do, though it obviously doesn't work. CheckBox1.DataBindings.Add(new Binding("Checked", this.object, "!SomeBool"));

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  • Good Training Sources for OOP PHP, Anyone ?

    - by Codex73
    Hey Guys. I will like to see if everybody could share any good training sources on OOP on PHP language. Good Training Sources for OOP (Object Oriented Programming) PHP, anyone ? I've seen numerous tutorials, mostly superficial, some of them bad. Please share anything good either commercial or free, Video or Written.

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  • How can I create a Base64-Encoded string from an GDI+ Image in C++?

    - by Schnapple
    I asked a question recently, How can I create an Image in GDI+ from a Base64-Encoded string in C++?, which got a response that led me to the answer. Now I need to do the opposite - I have an Image in GDI+ whose image data I need to turn into a Base64-Encoded string. Due to its nature, it's not straightforward. The crux of the issue is that an Image in GDI+ can save out its data to either a file or an IStream*. I don't want to save to a file, so I need to use the resulting stream. Problem is, this is where my knowledge breaks down. This first part is what I figured out in the other question // Initialize GDI+. GdiplusStartupInput gdiplusStartupInput; ULONG_PTR gdiplusToken; GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL); // I have this decode function from elsewhere std::string decodedImage = base64_decode(Base64EncodedImage); // Allocate the space for the stream DWORD imageSize = decodedImage.length(); HGLOBAL hMem = ::GlobalAlloc(GMEM_MOVEABLE, imageSize); LPVOID pImage = ::GlobalLock(hMem); memcpy(pImage, decodedImage.c_str(), imageSize); // Create the stream IStream* pStream = NULL; ::CreateStreamOnHGlobal(hMem, FALSE, &pStream); // Create the image from the stream Image image(pStream); // Cleanup pStream->Release(); GlobalUnlock(hMem); GlobalFree(hMem); (Base64 code) And now I'm going to perform an operation on the resulting image, in this case rotating it, and now I want the Base64-equivalent string when I'm done. // Perform operation (rotate) image.RotateFlip(Gdiplus::Rotate180FlipNone); IStream* oStream = NULL; CLSID tiffClsid; GetEncoderClsid(L"image/tiff", &tiffClsid); // Function defined elsewhere image.Save(oStream, &tiffClsid); // And here's where I'm stumped. (GetEncoderClsid) So what I wind up with at the end is an IStream* object. But here's where both my knowledge and Google break down for me. IStream shouldn't be an object itself, it's an interface for other types of streams. I'd go down the road from getting string-Image in reverse, but I don't know how to determine the size of the stream, which appears to be key to that route. How can I go from an IStream* to a string (which I will then Base64-Encode)? Or is there a much better way to go from a GDI+ Image to a string?

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  • Is this a legitimate implementation of a 'remember me' function for my web app?

    - by user246114
    Hi, I'm trying to add a "remember me" feature to my web app to let a user stay logged in between browser restarts. I think I got the bulk of it. I'm using google app engine for the backend which lets me use java servlets. Here is some pseudo-code to demo: public class MyServlet { public void handleRequest() { if (getThreadLocalRequest().getSession().getAttribute("user") != null) { // User already has session running for them. } else { // No session, but check if they chose 'remember me' during // their initial login, if so we can have them 'auto log in' // now. Cookie[] cookies = getThreadLocalRequest().getCookies(); if (cookies.find("rememberMePlz").exists()) { // The value of this cookie is the cookie id, which is a // unique string that is in no way based upon the user's // name/email/id, and is hard to randomly generate. String cookieid = cookies.find("rememberMePlz").value(); // Get the user object associated with this cookie id from // the data store, would probably be a two-step process like: // // select * from cookies where cookieid = 'cookieid'; // select * from users where userid = 'userid fetched from above select'; User user = DataStore.getUserByCookieId(cookieid); if (user != null) { // Start session for them. getThreadLocalRequest().getSession() .setAttribute("user", user); } else { // Either couldn't find a matching cookie with the // supplied id, or maybe we expired the cookie on // our side or blocked it. } } } } } // On first login, if user wanted us to remember them, we'd generate // an instance of this object for them in the data store. We send the // cookieid value down to the client and they persist it on their side // in the "rememberMePlz" cookie. public class CookieLong { private String mCookieId; private String mUserId; private long mExpirationDate; } Alright, this all makes sense. The only frightening thing is what happens if someone finds out the value of the cookie? A malicious individual could set that cookie in their browser and access my site, and essentially be logged in as the user associated with it! On the same note, I guess this is why the cookie ids must be difficult to randomly generate, because a malicious user doesn't have to steal someone's cookie - they could just randomly assign cookie values and start logging in as whichever user happens to be associated with that cookie, if any, right? Scary stuff, I feel like I should at least include the username in the client cookie such that when it presents itself to the server, I won't auto-login unless the username+cookieid match in the DataStore. Any comments would be great, I'm new to this and trying to figure out a best practice. I'm not writing a site which contains any sensitive personal information, but I'd like to minimize any potential for abuse all the same, Thanks

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  • ASP.NET Repeater and DataBinder.Eval

    - by Fernando
    I've got a <asp:Repeater> in my webpage, which is bound to a programatically created dataset. The purpose of this repeater is to create an index from A-Z, which, when clicked, refreshes the information on the page. The repeater has a link button like so: <asp:LinkButton ID="indexLetter" Text='<%#DataBinder.Eval(Container.DataItem,"letter")%>' runat="server" CssClass='<%#DataBinder.Eval(Container.DataItem, "cssclass")%>' Enabled='<%#DataBinder.Eval(Container.DataItem,"enabled")%>'></asp:LinkButton> The dataset is created the following way: protected DataSet getIndex(String index) { DataSet ds = new DataSet(); ds.Tables.Add("index"); ds.Tables["index"].Columns.Add("letter"); ds.Tables["index"].Columns.Add("cssclass"); ds.Tables["index"].Columns.Add("enabled"); char alphaStart = Char.Parse("A"); char alphaEnd = Char.Parse("Z"); for (char i = alphaStart; i <= alphaEnd; i++) { String cssclass="", enabled="true"; if (index == i.ToString()) { cssclass = "selected"; enabled = "false"; } ds.Tables["index"].Rows.Add(new Object[3] {i.ToString(),cssclass,enabled }); } return ds; } However, when I run the page, a "Specified cast is not valid exception" is thrown in Text='<%#DataBinder.Eval(Container.DataItem,"letter")'. I have no idea why, I have tried manually casting to String with (String), I've tried a ToString() method, I've tried everything. Also, if in the debugger I add a watch for DataBinder.Eval(Container.DataItem,"letter"), the value it returns is "A", which according to me, should be fine for the Text Property. EDIT: Here is the exception: System.InvalidCastException was unhandled by user code Message="Specified cast is not valid." Source="App_Web_cmu9mtyc" StackTrace: at ASP.savecondition_aspx._DataBinding_control7(Object sender, EventArgs e) in e:\Documents and Settings\Fernando\My Documents\Visual Studio 2008\Projects\mediTrack\mediTrack\saveCondition.aspx:line 45 at System.Web.UI.Control.OnDataBinding(EventArgs e) at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) at System.Web.UI.Control.DataBind() at System.Web.UI.Control.DataBindChildren() InnerException: Any advice will be greatly appreciated, thank you EDIT 2: Fixed! The problem was not in the Text or CSS tags, but in the Enabled tag, I had to cast it to a Boolean value. The problem was that the exception was signaled at the Text tag, I don't know why

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  • Accessing CSR extension stack in M2Crypto

    - by Charles Duffy
    Howdy! I have a certificate signing request with an extension stack added. When building a certificate based on this request, I would like to be able to access that stack to use in creating the final certificate. However, while M2Crypto.X509.X509 has a number of helpers for accessing extensions (get_ext, get_ext_at and the like), M2Crypto.X509.Request appears to provide only a member for adding extensions, but no way to inspect the extensions already associated with a given object. Am I missing something here?

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  • Removing entry from table

    - by Bnhjhvbq7
    Can't remove an entry from table. here's my code dropItem = dropList[ math.random( #dropList ) ] dropSomething[brick.index] = crackSheet:grabSprite(dropItem, true) dropSomething[brick.index].x = brick.x dropSomething[brick.index].y = brick.y dropSomething[brick.index].name = dropItem dropSomething[brick.index].type = "dropppedItems" collision function bounce(event) local item = event.other if item.type == "dropppedItems" then if item.name == "bomb" then Lives = Lives - 1 LivesNum.text = tostring(Lives) end item:removeSelf(); end end What I've tried: item:removeSelf(); - removes the whole table item = nil - seams to do nothing, the object continue to move and i still see the image

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  • Java: Finding objects in collections.

    - by Jake
    This problem occurs over and over. I have some complicated object, such as a Cat, which has many properties, such as age, favorite cat food, and so forth. A bunch of Cats are stored in a Java Collection, and I need to find all the Cats that are aged 3, or those whose favorite cat food is Whiskas. Surely, I can write a custom method that finds those Cats with a specific property, but this gets cumbersome with many properties; is there some generic way of doing this?

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  • Gradual memory leak in loop over contents of QTMovie

    - by Benji XVI
    I have a simple foundation tool that exports every frame of a movie as a .tiff file. Here is the relevant code: NSString* movieLoc = [NSString stringWithCString:argv[1]]; QTMovie *sourceMovie = [QTMovie movieWithFile:movieLoc error:nil]; int i=0; while (QTTimeCompare([sourceMovie currentTime], [sourceMovie duration]) != NSOrderedSame) { // save image of movie to disk NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSData *currentImageData = [[sourceMovie currentFrameImage] TIFFRepresentation]; [currentImageData writeToFile:filePath atomically:NO]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } [pool drain]; return 0; As you can see, in order to prevent very large memory buildups with the various transparently-autoreleased variables in the loop, we create, and flush, an autoreleasepool with every run through the loop. However, over the course of stepping through a movie, the amount of memory used by the program still gradually increases. Instruments is not detecting any memory leaks per se, but the object trace shows certain General Data blocks to be increasing in size. [Edited out reference to slowdown as it doesn't seem to be as much of a problem as I thought.] Edit: let's knock out some parts of the code inside the loop & see what we find out... Test 1 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } Here we simply loop over the whole movie, creating the filename and logging it. Memory characteristics: remains at 15MB usage for the duration. Test 2 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; [sourceMovie stepForward]; [arp release]; } Here we add back in the creation of the NSImage from the current frame. Memory characteristics: gradually increasing memory usage. RSIZE is at 60MB by frame 200; 75MB by f300. Test 3 while (banana) { NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSImage *image = [sourceMovie currentFrameImage]; NSData *imageData = [image TIFFRepresentation]; [sourceMovie stepForward]; [arp release]; } We've added back in the creation of an NSData object from the NSImage. Memory characteristics: Memory usage is again increasing: 62MB at f200; 75MB at f300. In other words, largely identical. It looks like a memory leak in the underlying system QTMovie uses to do currentFrameImage, to me.

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  • java program to get the current date without timestamp

    - by Lakshman
    I need a java program to get the current date without timestamp Date d = new Date(); gives me date and timestamp But i need only date, without timestamp. I use this date to compare with another date object that does not have timestamp. on printing System.out.println("Current Date : " + d) of d it should print May 11 2010 - 00:00:00 .

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  • SQL Images in different tables

    - by Adonis L
    I am storing images in a SQL database , right now I have images being stored in separate tables depending on the object the images belong to, is there any reason ( performance etc..) why I should keep it this way and not store all images in the same table?

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