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  • Trouble decoding JSON string with PHP

    - by Anthony
    I'm trying to send an array of objects from JS to PHP using JSON. I have an array of players as follows: var player; var players = new Array(); //loop for number of players player = new Object(); player.id = theID; players[i] = player; Then my AJAX call looks like this: JSONplayers = JSON.stringify(players); $.ajax({ type: "POST", url: "php/ajax_send_players.php", data: { "players" : JSONplayers } On the PHP side the decode function looks like this $players = $_REQUEST['players']; echo var_dump($players); $players = json_decode($players); echo 'players: ' .$players. '--'. $players[0] . '--'. $players[0]->id; Debugging in chrome, the JSON players var looks like this before it is sent: JSONplayers: "[{"id":"Percipient"},{"id":"4"}]" And when I vardump in PHP it looks OK, giving this: string(40) "[{\"id\":\"Percipient\"},{\"id\":\"4\"}]" But I can't access the PHP array, and the echo statement about starting with players: outputs this: players: ---- Nothing across the board...maybe it has something to do with the \'s in the array, I am new to this and might be missing something very simple. Any help would be greatly appreciated. note I've also tried json_decode($players, true) to get it as an assoc array but get similar results.

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  • Can you open a form or window in an Outlook Addin (VSTO)

    - by dontpanic
    Hi, I am new to VSTO programming. I have created a basic addin for Outlook 2007 that monitors a folder containing XML text files which it opens and then sends them as an email, then deletes them. this all works fine. I want the user to be able to configure certain settings for the way the addin/program will operate, such as the folder that it will monitor, and other things. The logical way to do this is to create a menu item in the addin (which I have also done) that opens a windows form (or XAML window) that allows them to enter the parameters. In my addin I added a new item Windows Form, which worked, and the designer opened. However, in my addin code I cannot open the form. The Show() method normally associated with form objects is not available. Is this simply something you cannot do, or am I just doing it the wrong way? I have read about Outlook form regions, but these seemed to be attached to outlook items such as a new email, task, appointment etc... there doesnt seem to be a way to create a form region that can be opened in the main window of Outlook. Ideally, I would like to go with my original method of opening a new window from a menu item, but if this isnt possible I would like to hear other solutions. Thanks, Will.

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  • Is it possible to create a python iterator over pre-defined mutable data?

    - by Wilduck
    I might be doing this wrong, if I am, let me know, but I'm curious if the following is possible: I have a class that holds a number of dictionaries, each of which pairs names to a different set of objects of a given class. For example: items = {"ball" : ItemInstance1, "sword" : ItemInstance2} people = {"Jerry" : PersonInstance1, "Bob" : PersonInstance2, "Jill" : PersonInstance3} My class would then hold the current items and people that are availible, and these would be subject to change as the state changes: Class State: def __init__(self, items, people): self.items = items self.people = people I would like to define a iter() and next() method such that it iterates through all of the values in its attributes. My first question is whether or not this is possible. If it is, will it be able to support a situation as follows: I define items and people as above then: state = State(items, people) for names, thing in state: print name + " is " + thing.color items[cheese] = ItemInstance3 for names, thing in state: print name + " weighs " + thing.weight While I feel like this would be usefull in the code I have, I don't know if it's either possible or the right approach. Everything I've read about user defined iterators has suggested that each instance of them is one use only.

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  • Getting an exception when trying to use extension method with SortedDictionary... why?

    - by Polaris878
    I'm trying to place custom objects into a sorted dictionary... I am then trying to use an extension method (Max()) on this sorted dictionary. However, I'm getting the exception: "At least one object must implement IComparable". I don't understand why I'm getting that, as my custom object obviously implements IComparable. Here is my code: public class MyDate : IComparable<MyDate> { int IComparable<MyDate>.CompareTo(MyDate obj) { if (obj != null) { if (this.Value.Ticks < obj.Value.Ticks) { return 1; } else if (this.Value.Ticks == obj.Value.Ticks) { return 0; } else { return -1; } } } public MyDate(DateTime date) { this.Value = date; } public DateTime Value; } class Program { static void Main(string[] args) { SortedDictionary<MyDate, int> sd = new SortedDictionary<MyDate,int>(); sd.Add(new MyDate(new DateTime(1)), 1); sd.Add(new MyDate(new DateTime(2)), 2); Console.WriteLine(sd.Max().Value); // Throws exception!! } } What on earth am I doing wrong???

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  • Few Basic Questions in Overriding

    - by Dahlia
    I have few problems with my basic and would be thankful if someone can clear this. What does it mean when I say base *b = new derived; Why would one go for this? We very well separately can create objects for class base and class derived and then call the functions accordingly. I know that this base *b = new derived; is called as Object Slicing but why and when would one go for this? I know why it is not advisable to convert the base class object to derived class object (because base class is not aware of the derived class members and methods). I even read in other StackOverflow threads that if this is gonna be the case then we have to change/re-visit our design. I understand all that, however, I am just curious, Is there any way to do this? class base { public: void f(){cout << "In Base";} }; class derived:public base { public: void f(){cout << "In Derived";} }; int _tmain(int argc, _TCHAR* argv[]) { base b1, b2; derived d1, d2; b2 = d1; d2 = reinterpret_cast<derived*>(b1); //gives error C2440 b1.f(); // Prints In Base d1.f(); // Prints In Derived b2.f(); // Prints In Base d1.base::f(); //Prints In Base d2.f(); getch(); return 0; } In case of my above example, is there any way I could call the base class f() using derived class object? I used d1.base()::f() I just want to know if there any way without using scope resolution operator? Thanks a lot for your time in helping me out!

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  • Android NDK import-module / code reuse

    - by Graeme
    Morning! I've created a small NDK project which allows dynamic serialisation of objects between Java and C++ through JNI. The logic works like this: Bean - JavaCInterface.Java - JavaCInterface.cpp - JavaCInterface.java - Bean The problem is I want to use this functionality in other projects. I separated out the test code from the project and created a "Tester" project. The tester project sends a Java object through to C++ which then echo's it back to the Java layer. I thought linking would be pretty simple - ("Simple" in terms of NDK/JNI is usually a day of frustration) I added the JNIBridge project as a source project and including the following lines to Android.mk: NDK_MODULE_PATH=.../JNIBridge/jni/" JNIBridge/jni/JavaCInterface/Android.mk: ... include $(BUILD_STATIC_LIBRARY) JNITester/jni/Android.mk: ... include $(BUILD_SHARED_LIBRARY) $(call import-module, JavaCInterface) This all works fine. The C++ files which rely on headers from JavaCInterface module work fine. Also the Java classes can happily use interfaces from JNIBridge project. All the linking is happy. Unfortunately JavaCInterface.java which contains the native method calls cannot see the JNI method located in the static library. (Logically they are in the same project but both are imported into the project where you wish to use them through the above mechanism). My current solutions are are follows. I'm hoping someone can suggest something that will preserve the modular nature of what I'm trying to achieve: My current solution would be to include the JavaCInterface cpp files in the calling project like so: LOCAL_SRC_FILES := FunctionTable.cpp $(PATH_TO_SHARED_PROJECT)/JavaCInterface.cpp But I'd rather not do this as it would lead to me needing to update each depending project if I changed the JavaCInterface architecture. I could create a new set of JNI method signatures in each local project which then link to the imported modules. Again, this binds the implementations too tightly.

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  • Saving tree-structures in Databases

    - by Nina Null
    Hello everyone. I use Hibernate/Spring and a MySQL Database for my data management. Currently I display a tree-structure in a JTable. A tree can have several branches, in turn a branch can have several branches (up to nine levels) again, or having leaves. Lately I have performanceproblemes, as soon as I want to create new branches on deeper levels. At this time a branch has a foreign key to its parent. The domainobject has access to its parent by calling getParent(), which returns the parent-branch. The deeper the level, the longer it takes to create a new branch. Microbenchmark results for creating a new branch are like: Level 1: 32 ms. Level 3: 80 ms. Level 9: 232 ms. Obviously the level (which means the number of parents) is responsible for this. So I wanted to ask, if there are any appendages to work around this kind of problem. I don’t understand why Hibernate needs to know about the whole object tree (all parents until the root) while creating a new branch. But as far as I know this can be the only reason for the delay while creating a new branch, because a branch doesn’t have any other relations to any other objects. I would be very thankful for any workarounds or suggestions. greets, jambusa

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  • NSCollectionView: Can the same object not be in the array more than once or is this a bug?

    - by Sean
    I may be doing this all wrong, but I thought I was on the right track until I hit this little snag. Basically I was putting together a toy using NSCollectionView and trying to understand how to hook that all up using IB. I have a button which will add a couple of strings to the NSArrayController: The first time I press this button, my strings appear in the collection view as expected: The second time I press the button, the views scroll down and room is made - but the items don't appear to get added. I just see blank space: The button is implemented as follows (controller is a pointer to the NSArrayController I added in IB): - (IBAction)addStuff:(id)control { [controller addObjects:[NSArray arrayWithObjects:@"String 1",@"String 2",@"String 3",nil]]; } I'm not sure what I'm doing wrong. Rather than try to explain all the connections/binds/etc, if you need more info, I'd be grateful if you could just take a quick look at the toy project itself. UPDATE: After more experimentation as suggested by James Williams, it seems the problem stems from having multiple objects with the same memory address in the array. This confuses either NSArrayController or NSCollectionView (not sure which). Changing my addStuff: to this resulted in the behavior I originally expected: [controller addObjects:[NSArray arrayWithObjects:[NSMutableString stringWithString:@"String 1"],[NSMutableString stringWithString:@"String 2"],[NSMutableString stringWithString:@"String 3"],nil]]; So the question now, I guess, is if this is a bug I should report to Apple or if this is intended/documented behavior and I just missed it?

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  • Render multiple Form instances

    - by vorpyg
    I have a simple application where users are supposed to bet on outcome of a match. A match consists of two teams, a result and a stake. Matches with teams are created in the Django admin, and participants are to fill in result and stake. The form must be generated dynamically, based on the matches in the database. My idea is to have one (Django) Form instance for each match and pass these instances to the template. It works fine when I do it from django shell, but the instances aren't rendered when I load my view. The form looks like this: class SuggestionForm(forms.Form): def __init__(self, *args, **kwargs): try: match = kwargs.pop('match') except KeyError: pass super(SuggestionForm, self).__init__(*args, **kwargs) label = match self.fields['result'] = forms.ChoiceField(label=label, required=True, choices=CHOICES, widget=forms.RadioSelect()) self.fields['stake'] = forms.IntegerField(label='', required=True, max_value=50, min_value=10, initial=10) My (preliminary) view looks like this: def suggestion_form(request): matches = Match.objects.all() form_collection = {} for match in matches: f = SuggestionForm(request.POST or None, match=match) form_collection['match_%s' % match.id] = f return render_to_response('app/suggestion_form.html', { 'forms': form_collection, }, context_instance = RequestContext(request) ) My initial thought was that I could pass the form_collection to the template and the loop throught the collection like this, but id does not work: {% for form in forms %} {% for field in form %} {{ field }} {% endfor %} {% endfor %} (The output is actually the dict keys with added spaces in between each letter - I've no idea why…) It works if I only pass one Form instance to the template and only runs the inner loop. Suggestions are greatly appreciated.

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  • How to detect .NET WPF memory leak or GC long run?

    - by Néstor Sánchez A.
    I have the next very strange situation and problem: .NET 4.0 application for diagram editing (WPF). Runs ok in my PC: 8GM RAM, 3.0GHz, i7 quad-core. While creating objects (mostly diagram nodes and connectors, plus all the undo/redo information) the TaskManager show, as expected, some memory usage "jumps" (up and down). These mem-usage "jumps" also remains executing AFTER user interaction ended. Maybe this is the GC cleaning/regorganizing memory? To see what is going on, I've used the Ants mem profiler, but somewhat it prevents those "jumps" to happen after user interaction. PROBLEM: It Freezes/Hangs after seconds or minutes of usage in some slow/weak laptos/netbooks of my beta testers (under 2GHz of speed and under 2GB of RAM). I was thinking of a memory leak, but... EDIT: Also, there is the case that the memory usage grows and grows until collapse (only in slow machines). In a Windows XP Mode machine (VM in Win 7) with only 512MB of RAM Assigned it works fine without mem-usage "jumps" after user interaction (no GC cleaning?!). So, I really have a big trouble because I cannot reproduce the error, only see these strange behaviour (mem jumps), and the tool supposed to show me what is happening is hiding the problem (like the "observer's paradox"). Any ideas on what's happening and how to solve it?

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  • How should we setup up complex situations for tests?

    - by ShaneC
    I'm currently working on what I would call integration tests. I want to verify that if a WCF service is called it will do what I expect. Let's take a very simple scenario. Assume we have a contract object that we can put on hold or take off hold. Now writing the put on hold test is quite simple. You create a contract instance and execute the code that puts it on code. The question I have comes when we want to test the taking off hold service call. The problem is that putting a contract on hold can be actually quite complicated leading to various objects all be modified. So usually I would use the Builder pattern and do something like this.. var onHoldContract = new ContractBuilder().PutOnHold().Build(); The problem I have with this is now I have to pretty much replicate a large part of my put on hold service. Now when I change what putting something on hold means I have two places I have to modify. The other option that immediately jumps out at me is to just use the put on hold service as part of my test setup but now I'm coupling my test to the success of another piece of code which is something I don't like to do since it can lead to failures in one spot breaking unrelated tests elsewhere (if put on hold failed for example). Any other options I'm missing out here? or opinions on which method is preferable and why?

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  • -(void)dealloc - How ? Objective - C

    - by sagar
    Please Note that - this is not similar than this question. OK. To understand my question, First of all please see both of these destructors. - (void)dealloc { [Marketdetails release]; Marketdetails=nil; [parsedarray release]; parsedarray=nil; [Marketid release]; Marketid=nil; [marketname release]; marketname=nil; [super dealloc]; } - (void)dealloc { [super dealloc]; [Marketdetails release]; Marketdetails=nil; [parsedarray release]; parsedarray=nil; [Marketid release]; Marketid=nil; [marketname release]; marketname=nil; } See, Both destructors have different code. In First Destructor first current class objects are released & then [super dealloc] is called. In second Desctructor first [super dealloc] is called. My question is as follows. Where should we write [super dealloc] ? first or last ? or it doesn't matter ?

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  • Null reference exceptions in .net

    - by Carlo
    Hello, we're having this big problem with our application. It's a rather large application with several modules, and thousands and thousands lines of code. A lot of parts of the application are designed to exist only with a reference to another object, for example a Person object can never exists without a House object, so if you at any point in the app say: bool check = App.Person.House == null; check should always be false (by design), so, to keep using that example, while creating modules, testing, debugging, App.Person.House is never null, but once we shipped the application to our client, they started getting a bunch of NullReferenceException with the objects that by design, should never have a null reference. They tell us the bug, we try to reproduce it here, but 90% of the times we can't, because here it works fine. The app is being developed with C# and WPF, and by design, it only runs on Windows XP SP 3, and the .net framework v3.5, so we KNOW the user has the same operative system, service pack, and .net framework version as we do here, but they still get this weird NullReferenceExceptions that we can't reproduce. So, I'm just wondering if anyone has seen this before and how you fixed it, we have the app running here at least 8 hours a day in 5 different computers, and we never see those exceptions, this only happens to the client for some reason. ANY thought, any clue, any solution that could get us closer to fixing this problem will be greatly appreciated. Thanks!

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  • C# / IronPython Interop with shared C# Class Library

    - by Adam Haile
    I'm trying to use IronPython as an intermediary between a C# GUI and some C# libraries, so that it can be scripted post compile time. I have a Class library DLL that is used by both the GUI and the python and is something along the lines of this: namespace MyLib { public class MyClass { public string Name { get; set; } public MyClass(string name) { this.Name = name; } } } The IronPython code is as follows: import clr clr.AddReferenceToFile(r"MyLib.dll") from MyLib import MyClass ReturnObject = MyClass("Test") Then, in C# I would call it as follows: ScriptEngine engine = Python.CreateEngine(); ScriptScope scope = null; scope = engine.CreateScope(); ScriptSource source = engine.CreateScriptSourceFromFile("Script.py"); source.Execute(scope); MyClass mc = scope.GetVariable<MyClass>("ReturnObject ") When I call this last bit of code, source.Execute(scope) runs returns successfully, but when I try the GetVariable call, it throw the following exception Microsoft.Scripting.ArgumentTypeException: expected MyClass , got MyClass So, you can see that the class names are exactly the same, but for some reason it thinks they are different. The DLL is in a different directory than the .py file (I just didn't bother to write out all the path setup stuff), could it be that there is an issue with the interpreter for IronPython seeing these objects as difference because it's somehow seeing them as being in a different context or scope?

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  • NetBeans Platform - how to refresh the property sheet view of a node?

    - by I82Much
    Hi all, I am using the PropertySheetView component to visualize and edit the properties of a node. This view should always reflect the most recent properties of the object; if there is a change to the object in another process, I want to somehow refresh the view and see the updated properties. The best way I was able to do this is something like the following (making use of EventBus library to publish and subscribe to changes in objects): public DomainObjectWrapperNode(DomainObject obj) { super (Children.LEAF, Lookups.singleton(obj)); EventBus.subscribe(DomainObject.class, this); } public void onEvent(DomainObject event) { // Do a check to determine if the updated object is the one wrapped by this node; // if so fire a property sets change firePropertySetsChange(null, this.getPropertySets()); } This works, but my place in the scrollpane is lost when the sheet refreshes; it resets the view to the top of the list and I have to scroll back down to where I was before the refresh action. So my question is, is there a better way to refresh the property sheet view of a node, specifically so my place in the property list is not lost upon refresh?

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  • Sweave can't see a vector if run from a function ?

    - by PaulHurleyuk
    I have a function that sets a vector to a string, copies a Sweave document with a new name and then runs that Sweave. Inside the Sweave document I want to use the vector I set in the function, but it doesn't seem to see it. (Edit: I changed this function to use tempdir(() as suggested by Dirk) I created a sweave file test_sweave.rnw; % \documentclass[a4paper]{article} \usepackage[OT1]{fontenc} \usepackage{Sweave} \begin{document} \title{Test Sweave Document} \author{gb02413} \maketitle <<>>= ls() Sys.time() print(paste("The chosen study was ",chstud,sep="")) @ \end{document} and I have this function; onOK <- function(){ chstud<-"test" message(paste("Chosen Study is ",chstud,sep="")) newfile<-paste(chstud,"_report",sep="") mypath<-paste(tempdir(),"\\",sep="") setwd(mypath) message(paste("Copying test_sweave.Rnw to ",paste(mypath,newfile,".Rnw",sep=""),sep="")) file.copy("c:\\local\\test_sweave.Rnw", paste(mypath,newfile,".Rnw",sep=""), overwrite=TRUE) Sweave(paste(mypath,newfile,".Rnw",sep="")) require(tools) texi2dvi(file = paste(mypath,newfile,".tex",sep=""), pdf = TRUE) } If I run the code from the function directly, the resulting file has this output for ls(); > ls() [1] "chstud" "mypath" "newfile" "onOK" However If I call onOK() I get this output; > ls() [1] "onOK" and the print(...chstud...)) function generates an error. I suspect this is an environment problem, but I assumed because the call to Sweave occurs within the onOK function, it would be in the same enviroment, and would see all the objects created within the function. How can I get the Sweave process to see the chstud vector ? Thanks Paul.

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  • PHP Exceptions in Classes

    - by mike condiff
    I'm writing a web application (PHP) for my friend and have decided to use my limited OOP training from Java. My question is what is the best way to note in my class/application that specific critical things failed without actually breaking my page. Currently my problem is I have an Object "SummerCamper" which takes a camper_id as it's argument to load all of the necessary data into the object from the database. Say someone specifies a camper_id in the querystring that does not exist, I pass it to my objects constructor and the load fails. Currently I don't see a way for me to just return false from the constructor. I have read I could possibly do this with Exceptions, throwing an exception if no records are found in the database or if some sort of validation fails on input of the camper_id from the application etc. However, I have not really found a great way to alert my program that the Object Load has failed. I tried returning false from within the CATCH but the Object still persists in my php page. I do understand I could put a variable $is_valid = false if the load fails and then check the Object using a get method but I think there may be better ways. What is the best way of achieving the essential termination of an object if a load fails? Should I load data into the object from outside the constructor? Is there some osrt of design pattern that I should look into? Any help would be appreciated.

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  • Why is JavaMail Transport.send() a static method?

    - by skiphoppy
    I'm revising code I did not write that uses JavaMail, and having a little trouble understanding why the JavaMail API is designed the way it is. I have the feeling that if I understood, I could be doing a better job. We call: transport = session.getTransport("smtp"); transport.connect(hostName, port, user, password); So why is Eclipse warning me that this: transport.send(message, message.getAllRecipients()); is a call to a static method? Why am I getting a Transport object and providing settings that are specific to it if I can't use that object to send the message? How does the Transport class even know what server and other settings to use to send the message? It's working fine, which is hard to believe. What if I had instantiated Transport objects for two different servers; how would it know which one to use? In the course of writing this question, I've discovered that I should really be calling: transport.sendMessage(message, message.getAllRecipients()); So what is the purpose of the static Transport.send() method? Is this just poor design, or is there a reason it is this way?

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  • Bubble sort dropped images based on their names

    - by user2259784
    I have written a simple bubble sort function that sort an array of Image objects based on image names. For some reason my function is not swapping the elements of array when needed ( basically new assignment is not working) Here is my code : listOfFiles = event.dataTransfer.files; sortImages(listOfFiles); function sortImages(listOfFiles) { var re = /[0-9]/; var temp; for( var index=0; index < listOfFiles.length ; index++) { for ( var index2=0; index2 < listOfFiles.length-1 ; index2++) { var one = parseFloat(re.exec(listOfFiles[index2].name )); var two = parseFloat(re.exec(listOfFiles[index2+1].name)); console.log(one + " : " + two); if (one > two) { console.log(listOfFiles[index2+1]); console.log(listOfFiles[index2]); //following three lines don't work temp = listOfFiles[index2+1]; listOfFiles[index2+1] = listOfFiles[index2]; listOfFiles[index2] = temp; console.log(listOfFiles[index2+1]); console.log(listOfFiles[index2]); } } } }

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  • Ninject: Shared DI/IoC container

    - by joblot
    Hi I want to share the container across various layers in my application. I started creating a static class which initialises the container and register types in the container. public class GeneralDIModule : NinjectModule { public override void Load() { Bind().To().InSingletonScope(); } } public abstract class IoC { private static IKernel _container; public static void Initialize() { _container = new StandardKernel(new GeneralDIModule(), new ViewModelDIModule()); } public static T Get<T>() { return _container.Get<T>(); } } I noticed there is a Resolve method as well. What is the difference between Resolve and Get? In my unit tests I don’t always want every registered type in my container. Is there a way of initializing an empty container and then register types I need. I’ll be mocking types as well in unit test so I’ll have to register them as well. There is an Inject method, but it says lifecycle of instance is not managed? Could someone please set me in right way? How can I register, unregister objects and reset the container. Thanks

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  • Group / User based security. Table / SQL question

    - by Brett
    Hi, I'm setting up a group / user based security system. I have 4 tables as follows: user groups group_user_mappings acl where acl is the mapping between an item_id and either a group or a user. The way I've done the acl table, I have 3 columns of note (actually 4th one as an auto-id, but that is irrelevant) col 1 item_id (item to access) col 3 user_id (user that is allowed to access) col 3 group_id (group that is allowed to access) So for example item1, peter, , item2, , group1 item3, jane, , so either the acl will give access to a user or a group. Any one line in the ACL table with either have an item - user mapping, or an item group. If I want to have a query that returns all objects a user has access to, I think I need to have a SQL query with a UNION, because I need 2 separate queries that join like.. item - acl - group - user AND item - acl - user This I guess will work OK. Is this how its normally done? Am I doing this the right way? Seems a little messy. I was thinking I could get around it by creating a single user group for each person, so I only ever deal with groups in my SQL, but this seems a little messy as well..

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  • Design: How to declare a specialized memory handler class

    - by Michael Dorgan
    On an embedded type system, I have created a Small Object Allocator that piggy backs on top of a standard memory allocation system. This allocator is a Boost::simple_segregated_storage< class and it does exactly what I need - O(1) alloc/dealloc time on small objects at the cost of a touch of internal fragmentation. My question is how best to declare it. Right now, it's scope static declared in our mem code module, which is probably fine, but it feels a bit exposed there and is also now linked to that module forever. Normally, I declare it as a monostate or a singleton, but this uses the dynamic memory allocator (where this is located.) Furthermore, our dynamic memory allocator is being initialized and used before static object initialization occurs on our system (as again, the memory manager is pretty much the most fundamental component of an engine.) To get around this catch 22, I added an extra 'if the small memory allocator exists' to see if the small object allocator exists yet. That if that now must be run on every small object allocation. In the scheme of things, this is nearly negligable, but it still bothers me. So the question is, is there a better way to declare this portion of the memory manager that helps decouple it from the memory module and perhaps not costing that extra isinitialized() if statement? If this method uses dynamic memory, please explain how to get around lack of initialization of the small object portion of the manager.

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  • JVM GC demote object to eden space?

    - by Kevin
    I'm guessing this isn't possible...but here goes. My understanding is that eden space is cheaper to collect than old gen space, especially when you start getting into very large heaps. Large heaps tend to come up with long running applications (server apps) and server apps a lot of the time want to use some kind of caches. Caches with some kind of eviction (LRU) tend to defeat some assumptions that GC makes (temporary objects die quickly). So cache evictions end up filling up old gen faster than you'd like and you end up with a more costly old gen collection. Now, it seems like this sort of thing could be avoided if java provided a way to mark a reference as about to die (delete keyword)? The difference between this and c++ is that the use is optional. And calling delete does not actually delete the object, but rather is a hint to the GC that it should demote the object back to Eden space (where it will be more easily collected). I'm guessing this feature doesn't exist, but, why not (is there a reason it's a bad idea)?

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  • C++ interpreter conceptual problem

    - by Jan Wilkins
    I've built an interpreter in C++ for a language created by me. One main problem in the design was that I had two different types in the language: number and string. So I have to pass around a struct like: class myInterpreterValue { myInterpreterType type; int intValue; string strValue; } Objects of this class are passed around million times a second during e.g.: a countdown loop in my language. Profiling pointed out: 85% of the performance is eaten by the allocation function of the string template. This is pretty clear to me: My interpreter has bad design and doesn't use pointers enough. Yet, I don't have an option: I can't use pointers in most cases as I just have to make copies. How to do something against this? Is a class like this a better idea? vector<string> strTable; vector<int> intTable; class myInterpreterValue { myInterpreterType type; int locationInTable; } So the class only knows what type it represents and the position in the table This however again has disadvantages: I'd have to add temporary values to the string/int vector table and then remove them again, this would eat a lot of performance again. Help, how do interpreters of languages like Python or Ruby do that? They somehow need a struct that represents a value in the language like something that can either be int or string.

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  • NHibernate mapping with two special cases

    - by brainimus
    I am using NHibernate to map a class to a database table. The Part table has an ID column (primary key) and a ParentPart column (along with a few others). class Part { public virtual long ID{ get; set; } public virtual Part ParentPart { get; set; } } The ParentPart is normally another valid part in the part table but I have two special cases. I have a case where the ParentPart column can be 0 (zero) and another case where it can be -1. Neither of these cases currently represent another valid Part object. I was thinking I could make 2 subclasses of Part (ZeroPart and NegativeOnePart) that would never persist. I want the zero and -1 values to be entered in the column but not persist the entire ZeroPart or NegativeOnePart objects. I am unsure how to map this (I'm using hbm files) or if this even the correct approach. How can I map this so that normal valid parts are persisted but I can also handle the special cases? As an aside: My current hbm file has the Part.ID's unsaved value as zero but I think I can just change this in the mapping to something different and default it in the class.

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