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  • How to Populate a 'Tree' structure 'Declaratively'

    - by mackenir
    I want to define a 'node' class/struct and then declare a tree of these nodes in code in such a way that the way the code is formatted reflects the tree structure, and there's not 'too much' boiler plate in the way. Note that this isn't a question about data structures, but rather about what features of C++ I could use to arrive at a similar style of declarative code to the example below. Possibly with C++0X this would be easier as it has more capabilities in the area of constructing objects and collections, but I'm using Visual Studio 2008. Example tree node type: struct node { string name; node* children; node(const char* name, node* children); node(const char* name); }; What I want to do: Declare a tree so its structure is reflected in the source code node root = node("foo", [ node("child1"), node("child2", [ node("grand_child1"), node("grand_child2"), node("grand_child3" ]), node("child3") ]); NB: what I don't want to do: Declare a whole bunch of temporary objects/colls and construct the tree 'backwards' node grandkids[] = node[3] { node("grand_child1"), node("grand_child2"), node("grand_child3" }; node kids[] = node[3] { node("child1"), node("child2", grandkids) node("child3") }; node root = node("foo", kids);

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  • Shaping EF LINQ Query Results Using Multi-Table Includes

    - by sisdog
    I have a simple LINQ EF query below using the method syntax. I'm using my Include statement to join four tables: Event and Doc are the two main tables, EventDoc is a many-to-many link table, and DocUsage is a lookup table. My challenge is that I'd like to shape my results by only selecting specific columns from each of the four tables. But, the compiler is giving a compiler is giving me the following error: 'System.Data.Objects.DataClasses.EntityCollection does not contain a definition for "Doc' and no extension method 'Doc' accepting a first argument of type 'System.Data.Objects.DataClasses.EntityCollection' could be found. I'm sure this is something easy but I'm not figuring it out. I haven't been able to find an example of someone using the multi-table include but also shaping the projection. Thx,Mark var qry= context.Event .Include("EventDoc.Doc.DocUsage") .Select(n => new { n.EventDate, n.EventDoc.Doc.Filename, //<=COMPILER ERROR HERE n.EventDoc.Doc.DocUsage.Usage }) .ToList(); EventDoc ed; Doc d = ed.Doc; //<=NO COMPILER ERROR SO I KNOW MY MODEL'S CORRECT DocUsage du = d.DocUsage;

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  • Sharing same properties of ViewController for iPhone Stroryboard and iPad Story Board

    - by Ruhul Amin
    I'm developing a universal application. in the first view, I have the login screen for the user. In iPhone storyBoard, I have added 2 text field and one button( login check). I have added properties in ViewController.h file by dragging those objects(Ctrl key + Dragg) to .h file. I have added code for login check and it is working fine for iPhone. This is the code in ViewController.h @property (strong, nonatomic) IBOutlet UITextField *txtUserId; @property (strong, nonatomic) IBOutlet UITextField *txtUserPwd; @property (strong, nonatomic) IBOutlet UIButton *btnLogin; In the iPad storyBoard, I have added 2 text field( userid and password) and i button for login. So now, I want to bind those objects with the veriable which I declared already in ViewController.h file in case of iPhone. My questions: 1. What is the right way to bind properties for both storyboard? 2. Am I on the right direction or should I think in a different way to do it? I am new with iPhone development. Please help. Thanks. --Amin

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  • How can I refactor this to work without breaking the pattern horribly?

    - by SnOrfus
    I've got a base class object that is used for filtering. It's a template method object that looks something like this. public class Filter { public void Process(User u, GeoRegion r, int countNeeded) { List<account> selected = this.Select(u, r, countNeeded); // 1 List<account> filtered = this.Filter(selected, u, r, countNeeded); // 2 if (filtered.Count > 0) { /* do businessy stuff */ } // 3 if (filtered.Count < countNeeded) this.SendToSuccessor(u, r, countNeeded - filtered) // 4 } } Select(...), Filter(...) are protected abstract methods and implemented by the derived classes. Select(...) finds objects in the based on x criteria, Filter(...) filters those selected further. If the remaining filtered collection has more than 1 object in it, we do some business stuff with it (unimportant to the problem here). SendToSuccessor(...) is called if there weren't enough objects found after filtering (it's a composite where the next class in succession will also be derived from Filter but have different filtering criteria) All has been ok, but now I'm building another set of filters, which I was going to subclass from this. The filters I'm building however would require different params and I don't want to just implement those methods and not use the params or just add to the param list the ones I need and have them not used in the existing filters. They still perform the same logical process though. I also don't want to complicated the consumer code for this (which looks like this) Filter f = new Filter1(); Filter f2 = new Filter2(); Filter f3 = new Filter3(); f.Sucessor = f2; f2.Sucessor = f3; /* and so on adding filters as successors to previous ones */ foreach (User u in users) { foreach (GeoRegion r in regions) { f.Process(u, r, ##); } } How should I go about it?

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  • entity framework navigation property further filter without loading into memory

    - by cellik
    Hi, I've two entities with 1 to N relation in between. Let's say Books and Pages. Book has a navigation property as Pages. Book has BookId as an identifier and Page has an auto generated id and a scalar property named PageNo. LazyLoading is set to true. I've generated this using VS2010 & .net 4.0 and created a database from that. In the partial class of Book, I need a GetPage function like below public Page GetPage(int PageNumber) { //checking whether it exist etc are not included for simplicity return Pages.Where(p=>p.PageNo==PageNumber).First(); } This works. However, since Pages property in the Book is an EntityCollection it has to load all Pages of a book in memory in order to get the one page (this slows down the app when this function is hit for the first time for a given book). i.e. Framework does not merge the queries and run them at once. It loads the Pages in memory and then uses LINQ to objects to do the second part To overcome this I've changed the code as follows public Page GetPage(int PageNumber) { MyContainer container = new MyContainer(); return container.Pages.Where(p=>p.PageNo==PageNumber && p.Book.BookId==BookId).First(); } This works considerably faster however it doesn't take into account the pages that have not been serialized to the db. So, both options has its cons. Is there any trick in the framework to overcome this situation. This must be a common scenario where you don't want all of the objects of a Navigation property loaded in memory when you don't need them.

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  • String comparison in Python: is vs. ==

    - by Coquelicot
    I noticed a Python script I was writing was acting squirrelly, and traced it to an infinite loop, where the loop condition was "while line is not ''". Running through it in the debugger, it turned out that line was in fact ''. When I changed it to != rather than 'is not', it worked fine. I did some searching, and found this question, the top answer to which seemed to be just what I needed. Except the answer it gave was counter to my experience. Specifically, the answerer wrote: For all built-in Python objects (like strings, lists, dicts, functions, etc.), if x is y, then x==y is also True. I double-checked the type of the variable, and it was in fact of type str (not unicode or something). Is his answer just wrong, or is there something else afoot? Also, is it generally considered better to just use '==' by default, even when comparing int or Boolean values? I've always liked to use 'is' because I find it more aesthetically pleasing and pythonic (which is how I fell into this trap...), but I wonder if it's intended to just be reserved for when you care about finding two objects with the same id.

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  • Map Literals to Object Properties/Values

    - by vijay
    For eg, my input XML is look like this. <root> <myelemt> <input type="variable"> <variable>STARTDATE</variable> <variable>CUSTOMERNAME</variable> </input> </myelemt> </root> it is deserialized and loaded into the object MyXmlElemtObj in my code i have written like this, if(MyXmlElemtObj.input.variable.ToUpper() == "STARTDATE") ProcessObjectB(ObjectA.OrderDate); if(MyXmlElemtObj.input.variable.ToUpper() == "CUSTOMERNAME") ProcessObjectB(ObjectC.UserName); Here I am mapping those input literals to some objects value. The one thing that scares me is seeing some ** hard-coded literals** all over my code. Instead i would like to write something like ProcessObjectB(Common.GetMappedvalue(MyXmlElemtObj.input.variable)); Is there a way to isolate this mapping thing to common class, where i will predefine which literal is mapped to which values. The problem is the values are of objects created at the run time. If my question is making sense then So how do i achieve this? I think i have given all the necessary details. if anything is missing please metnion. Thx Much.

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  • Recursive Iterators

    - by soandos
    I am having some trouble making an iterator that can traverse the following type of data structure. I have a class called Expression, which has one data member, a List<object>. This list can have any number of children, and some of those children might be other Expression objects. I want to traverse this structure, and print out every non-list object (but I do want to print out the elements of the list of course), but before entering a list, I want to return "begin nest" and after I just exited a list, I want to return "end nest". I was able to do this if I ignored the class wherever possible, and just had List<object> objects with List<object> items if I wanted a subExpression, but I would rather do away with this, and instead have an Expressions as the sublists (it would make it easier to do operations on the object. I am aware that I could use extension methods on the List<object> but it would not be appropriate (who wants an Evaluate method on their list that takes no arguments?). The code that I used to generate the origonal iterator (that works) is: public IEnumerator GetEnumerator(){ return theIterator(expr).GetEnumerator(); } private IEnumerable theIterator(object root) { if ((root is List<object>)){ yield return " begin nest "; foreach (var item in (List<object>)root){ foreach (var item2 in theIterator(item)){ yield return item2; } } yield return " end nest "; } else yield return root; } A type swap of List<object> for expression did not work, and lead to a stackOverflow error. How should the iterator be implemented? Update: Here is the swapped code: public IEnumerator GetEnumerator() { return this.GetEnumerator(); } private IEnumerable theIterator(object root) { if ((root is Expression)) { yield return " begin nest "; foreach (var item in (Expression)root) { foreach (var item2 in theIterator(item)) yield return item2; } yield return " end nest "; } else yield return root; }

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  • initialise a var in scala

    - by user unknown
    I have a class where I like to initialize my var by reading a configfile, which produces intermediate objects/vals, which I would like to group and hide in a method. Here is the bare minimum of the problem - I call the ctor with a param i, in reality a File to parse, and the init-method generates the String s, in reality more complicated than here, with a lot of intermediate objects being created: class Foo (val i: Int) { var s : String; def init () { s = "" + i } init () } This will produce the error: class Foo needs to be abstract, since variable s is not defined. In this example it is easy to solve by setting the String to "": var s = "";, but in reality the object is more complex than String, without an apropriate Null-implementation. I know, I can use an Option, which works for more complicated things than String too: var s : Option [String] = None def init () { s = Some ("" + i) } or I can dispense with my methodcall. Using an Option will force me to write Some over and over again, without much benefit, since there is no need for a None else than to initialize it that way I thought I could. Is there another way to achieve my goal?

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  • Changing type of object in a conditional

    - by David Doria
    I'm having a bit of trouble with dynamic_casting. I need to determine at runtime the type of an object. Here is a demo: include include class PersonClass { public: std::string Name; virtual void test(){}; //it is annoying that this has to be here... }; class LawyerClass : public PersonClass { public: void GoToCourt(){}; }; class DoctorClass : public PersonClass { public: void GoToSurgery(){}; }; int main(int argc, char *argv[]) { PersonClass* person = new PersonClass; if(true) { person = dynamic_cast(person); } else { person = dynamic_cast(person); } person-GoToCourt(); return 0; } I would like to do the above. The only legal way I found to do it is to define all of the objects before hand: PersonClass* person = new PersonClass; LawyerClass* lawyer; DoctorClass* doctor; if(true) { lawyer = dynamic_cast(person); } else { doctor = dynamic_cast(person); } if(true) { lawyer-GoToCourt(); } The main problem with this (besides having to define a bunch of objects that won't be use) is that I have to change the name of the 'person' variable. Is there a better way? (I am not allowed to change any of the classes (Person, Lawyer, or Doctor) because they are part of a library that people who will use my code have and won't want to change). Thanks, Dave

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  • Recreating a workflow instance with the same instance id

    - by Miron Brezuleanu
    We have some objects that have an associated workflow instance. The objects are identified with a GUID, which is also the GUID of the workflow instance associated with the object. We need to restart (see NOTE 3 for the meaning of 'restart') the workflow instance if the workflow definition changed (there is no state in the workflow itself and it is written to support restarting in this manner). The restarting is performed by calling Terminate on the WorkflowInstance, then recreating the instance with the same GUID. The weird part is that this works every other attempt (odd attempts - the workflow is stopped, but for some reason doesn't restart, even attempt - the already terminated workflow is recreated and started successfully). While I admit that using 'second hand' GUIDs is a sign of extraordinary cheapness (and something we plan to change), I'm wondering why this isn't working. Any ideas? NOTES: The terminated workflow instance is passivated (waiting for a notification) at the time of the termination. The Terminate call successfully deletes the data persisted in the database for that instance. We're using 'restarting' with a meaning that's less common in the context of WF - not restarting a passivated instance, but force the workflow to start again from the beginning of its definition. Thanks!

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  • The same property and procedure in different Classes. How they can be accessed ?

    - by lyborko
    Hi, I created several new objects TMyMemo = class (TMemo) private FYahoo = Integer; procedure SetYahoo(Value:integer) public procedure Google(A,B:integer; S:string); published property Yahoo:integer read FYahoo write SetYahoo; end; TMyPaintbox = class (TPaintbox) private FYahoo = Integer; procedure SetYahoo(Value:integer) public procedure Google(A,B:integer; S:string); published property Yahoo:integer read FYahoo write SetYahoo; end; TMyButton = class (TButton) private FYahoo = Integer; procedure SetYahoo(Value:integer) public procedure Google(A,B:integer; S:string); published property Yahoo:integer read FYahoo write SetYahoo; end; . . . These Controls are placed on Form1. Is there a way, how can I change the same property (Yahoo) and run the procedure (Google), which is declared in different objects (inheritance is not possible) ? procedure Form1.Button1Click(Sender:TObject); var i:integer; begin for i:=0 to Form1.ControlCount-1 do begin Controls[i].Google(4,5, 'Web'); // this should be changed somehow Controls[i].Yahoo:=6; // this should be changed somehow end; end; end; Thanks

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  • Implementing Unowned relationship Google App Engine

    - by nwallman
    My question is more of a best practices question on how to implement unowned relationships with Google App Engine. I am using JDO to do my persistence and like recommended in the google docs I'm persisting my list of unowned relationships like so: @PersistenceCapable(identityType = IdentityType.APPLICATION) public class User implements Serializable, UserDetails { ... @Persistent private List<Key> groups; ... } Now I came across my predicament when I went to query that list of objects using they Key object. So when I get my list of group keys in order to actually return a list of Group objects I have to do a look up on that key to get the object. My question is what is the recommended way of doing a unowned look up on a model object? Should I have an instance of the PersistanceManagerFactory on my Model object so I can do a lookup? Should I have an instance of my GroupDAO object on my Model object so I can do a look up? Should I have a Utility to do this type of lookup? I'm new to this so I just want to know which is the best way to do this. Thanks.

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  • django multiprocess problem

    - by iKiR
    I have django application, running under lighttpd via fastcgi. FCGI running script looks like: python manage.py runfcgi socket=<path>/main.socket method=prefork \ pidfile=<path>/server.pid \ minspare=5 maxspare=10 maxchildren=10 maxrequests=500 \ I use SQLite. So I have 10 proccess, which all work with the same DB. Next I have 2 views: def view1(request) ... obj = MyModel.objects.get_or_create(id=1) obj.param1 = <some value> obj.save () def view2(request) ... obj = MyModel.objects.get_or_create(id=1) obj.param2 = <some value> obj.save () And If this views are executed in two different threads sometimes I get MyModel instance in DB with id=1 and updated either param1 or param2 (BUT not both) - it depends on which process was the first. (of course in real life id changes, but sometimes 2 processes execute these two views with same id) The question is: What should I do to get instance with updated param1 and param2? I need something for merging changes in different processes. One decision is create interprocess lock object but in this case I will get sequence executing views and they will not be able to be executed simultaneously, so I ask help

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  • Compare Properties automatically

    - by juergen d
    I want to get the names of all properties that changed for matching objects. I have these (simplified) classes: public enum PersonType { Student, Professor, Employee } class Person { public string Name { get; set; } public PersonType Type { get; set; } } class Student : Person { public string MatriculationNumber { get; set; } } class Subject { public string Name { get; set; } public int WeeklyHours { get; set; } } class Professor : Person { public List<Subject> Subjects { get; set; } } Now I want to get the objects where the Property values differ: List<Person> oldPersonList = ... List<Person> newPersonList = ... List<Difference> = GetDifferences(oldPersonList, newPersonList); public List<Difference> GetDifferences(List<Person> oldP, List<Person> newP) { //how to check the properties without casting and checking //for each type and individual property?? //can this be done with Reflection even in Lists?? } In the end I would like to have a list of Differences like this: class Difference { public List<string> ChangedProperties { get; set; } public Person NewPerson { get; set; } public Person OldPerson { get; set; } } The ChangedProperties should contain the name of the changed properties.

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  • Repository Pattern Standardization of methods

    - by Nix
    All I am trying to find out the correct definition of the repository pattern. My original understanding was this (extremely dubmed down) Separate your Business Objects from your Data Objects Standardize access methods in data access layer. I have really seen 2 different implementations. Implementation 1 : public Interface IRepository<T>{ List<T> GetAll(); void Create(T p); void Update(T p); } public interface IProductRepository: IRepository<Product> { //Extension methods if needed List<Product> GetProductsByCustomerID(); } Implementation 2 : public interface IProductRepository { List<Product> GetAllProducts(); void CreateProduct(Product p); void UpdateProduct(Product p); List<Product> GetProductsByCustomerID(); } Notice the first is generic Get/Update/GetAll, etc, the second is more of what I would define "DAO" like. Both share an extraction from your data entities. Which I like, but i can do the same with a simple DAO. However the second piece standardize access operations I see value in, if you implement this enterprise wide people would easily know the set of access methods for your repository. Am I wrong to assume that the standardization of access to data is an integral piece of this pattern ? Rhino has a good article on implementation 1, and of course MS has a vague definition and an example of implementation 2 is here.

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  • How to manage feeds with subclassed object in Django 1.2?

    - by Matteo
    Hi, I'm trying to generate a feed rss from a model like this one, selecting all the Entry objects: from django.db import models from django.contrib.sites.models import Site from django.contrib.auth.models import User from imagekit.models import ImageModel import datetime class Entry(ImageModel): date_pub = models.DateTimeField(default=datetime.datetime.now) author = models.ForeignKey(User) via = models.URLField(blank=True) comments_allowed = models.BooleanField(default=True) icon = models.ImageField(upload_to='icon/',blank=True) class IKOptions: spec_module = 'journal.icon_specs' cache_dir = 'icon/resized' image_field = 'icon' class Post(Entry): title = models.CharField(max_length=200) description = models.TextField() slug = models.SlugField(unique=True) def __unicode__(self): return self.title class Photo(Entry): alt = models.CharField(max_length=200) description = models.TextField(blank=True) original = models.ImageField(upload_to='photo/') class IKOptions: spec_module = 'journal.photo_specs' cache_dir = 'photo/resized' image_field = 'original' def __unicode__(self): return self.alt class Quote(Entry): blockquote = models.TextField() cite = models.TextField(blank=True) def __unicode__(self): return self.blockquote When I use the render_to_response in my views I simply call: def get_journal_entries(request): entries = Entry.objects.all().order_by('-date_pub') return render_to_response('journal/entries.html', {'entries':entries}) And then I use a conditional template to render the right snippets of html: {% extends "base.html" %} {% block main %} <hr> {% for entry in entries %} {% if entry.post %}[...]{% endif %}[...] But I cannot do the same with the Feed Framework in django 1.2... Any suggestion, please?

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  • In Java, is there a performance gain in using interfaces for complex models?

    - by Gnoupi
    The title is hardly understandable, but I'm not sure how to summarize that another way. Any edit to clarify is welcome. I have been told, and recommended to use interfaces to improve performances, even in a case which doesn't especially call for the regular "interface" role. In this case, the objects are big models (in a MVC meaning), with many methods and fields. The "good use" that has been recommended to me is to create an interface, with its unique implementation. There won't be any other class implementing this interface, for sure. I have been told that this is better to do so, because it "exposes less" (or something close) to the other classes which will use methods from this class, as these objects are referring to the object from its interface (all public methods from the implementation being reproduced in the interface). This seems quite strange to me, as it seems like a C++ use to me (with header files). There I see the point, but in Java? Is there really a point in making an interface for such unique implementation? I would really appreciate some clarifications on the topic, so I could justify not following such kind of behavior, and the hassle it creates from duplicating all declarations. Edit: Plenty of valid points in most answers, I'm wondering if I won't switch this question for a community wiki, so we can regroup these points in more structured answers.

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  • Attribute Address getting displayed instead of Attribute Value

    - by Manish
    I am try to create the following. I want to have one drop down menu. Depending on the option selected in the first drop down menu, options in second drop down menu will be displayed. The options in 2nd drop down menu is supposed by dynamic, i.e., options change with the change of values in first menu. Here, instead of getting the drop down menus, I am getting the following Choose your Option1: Choose your Option2: Note: I strictly don't want to use javascript. home_form.py class HomeForm(forms.Form): def __init__(self, *args, **kwargs): var_filter_con = kwargs.pop('filter_con', None) super(HomeForm, self).__init__(*args, **kwargs) if var_filter_con == '***': var_empty_label = None else: var_empty_label = ' ' self.option2 = forms.ModelChoiceField(queryset = db_option2.objects.filter(option1_id = var_filter_con).order_by("name"), empty_label = var_empty_label, widget = forms.Select(attrs={"onChange":'this.form.submit();'}) ) self.option1 = forms.ModelChoiceField(queryset = db_option1.objects.all().order_by("name"), empty_label=None, widget=forms.Select(attrs={"onChange":'this.form.submit();'}) ) view.py def option_view(request): if request.method == 'POST': form = HomeForm(request.POST) if form.is_valid(): cd = form.cleaned_data if cd.has_key('option1'): f = HomeForm(filter_con = cd.get('option1')) return render_to_response('homepage.html', {'home_form':f,}, context_instance=RequestContext(request)) return render_to_response('invalid_data.html', {'form':form,}, context_instance=RequestContext(request)) else: f = HomeForm(filter_con = '***') return render_to_response('homepage.html', {'home_form':f,}, context_instance=RequestContext(request)) homepage.html <!DOCTYPE HTML> <head> <title>Nivaaran</title> </head> <body> <form method="post" name = 'choose_opt' action=""> {% csrf_token %} Choose your Option1: {{ home_form.option1 }} <br/> Choose your Option2: {{ home_form.option2 }} </form> </body>

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  • Sending information between JavaScript and Web Services using AJAX

    - by COB-CSU-AM
    Alright so I'm using Microsoft's Web Services and AJAX to get information from a SQL database for use with java script on the client side. And I'm wondering what the best method is. Before I started working on the project, the web services were setup to return a C# List filled with some objects. Those objects variables (ints, strings, etc.) contain the data I want to use. Of course, java script can't do much with this, to the best of my knowledge. I then modified the web service to return a 2D Array, but java script got confused, and to the best of my knowledge can't handle 2D array's returned from C#. I then tried to use a regular array, but then a found the length property of an array in JS doesn't carry over, so I couldn't preform a for loop through all the items, because there wasn't anyway of knowing how many elements there were. The only other thing I can thing of is returning a string with special char's to separate the data, but this seems way too convoluted. Any suggestions? Thanks in advance!

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  • Memory usage does not drop -- no leaks though

    - by climbon
    I have UINavigationController controlling several views. One of the views is composed of 20 scrollable pages. Each page is a constructed on the fly from UIViews by adding buttons, labels, UIImageViews etc. When this UIView is popped off the stack, the memory usage remains the same. Hence it keeps rising if I keep pushing/popping that view. In my dealloc, I am traversing through all 20 pages and finding each type of object which got added via addSubview and then do a release on it but instruments says my memory usage never goes down! I am trying to use 'retainCount' to see what is up with objects I am releasing but I am perhaps not getting true picture via retainCount. For some elements retainCount shows 2 so I try to release that object twice but then app crashes. If I release it once it works but memory usage never go down :( Q1: Do I need to traverse find each element and then do a release on that element ? Why can't I release a parent object and all objects contained by it would get released automatically ? Q2: Is retainCount a reliable indicator ?

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  • Stable/repeatable random sort (MySQL, Rails)

    - by Matt Rogish
    I'd like to paginate through a randomly sorted list of ActiveRecord models (rows from MySQL database). However, this randomization needs to persist on a per-session basis, so that other people that visit the website also receive a random, paginate-able list of records. Let's say there are enough entities (tens of thousands) that storing the randomly sorted ID values in either the session or a cookie is too large, so I must temporarily persist it in some other way (MySQL, file, etc.). Initially I thought I could create a function based on the session ID and the page ID (returning the object IDs for that page) however since the object ID values in MySQL are not sequential (there are gaps), that seemed to fall apart as I was poking at it. The nice thing is that it would require no/minimal storage but the downsides are that it is likely pretty complex to implement and probably CPU intensive. My feeling is I should create an intersection table, something like: random_sorts( sort_id, created_at, user_id NULL if guest) random_sort_items( sort_id, item_id, position ) And then simply store the 'sort_id' in the session. Then, I can paginate the random_sorts WHERE sort_id = n ORDER BY position LIMIT... as usual. Of course, I'd have to put some sort of a reaper in there to remove them after some period of inactivity (based on random_sorts.created_at). Unfortunately, I'd have to invalidate the sort as new objects were created (and/or old objects being removed, although deletion is very rare). And, as load increases the size/performance of this table (even properly indexed) drops. It seems like this ought to be a solved problem but I can't find any rails plugins that do this... Any ideas? Thanks!!

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  • Looping through covariates in regression using R

    - by Kyle Peyton
    I'm trying to run 96 regressions and save the results as 96 different objects. To complicate things, I want the subscript on one of the covariates in the model to also change 96 times. I've almost solved the problem but I've unfortunately hit a wall. The code so far is, for(i in 1:96){ assign(paste("z.out", i,sep=""), lm(rMonExp_EGM~ TE_i+ Month2+Month3+Month4+Month5+Month6+Month7+Month8+Month9+ Month10+Month11+Month12+Yrs_minus_2004 + as.factor(LGA),data=Pokies)) } This works on the object creation side (e.g. I have z.out1 - z.out96) but I can't seem to get the subscript on the covariate to change as well. I have 96 variables called TE_1, TE_2 ... TE_96 in the dataset. As such, the subscript on TE_, the "i" needs to change to correspond to each of the objects I create. That is, z.out1 should hold the results from this model: z.out1 <- lm(rMonExp_EGM~ TE_1 + Month2+Month3+Month4+Month5+Month6+Month7+Month8+Month9+ Month10+Month11+Month12+Yrs_minus_2004 + as.factor(LGA),data=Pokies) And z.out96 should be: z.out96 <- lm(rMonExp_EGM~ TE_96+ Month2+Month3+Month4+Month5+Month6+Month7+Month8+Month9+ Month10+Month11+Month12+Yrs_minus_2004 + as.factor(LGA),data=Pokies) Hopefully this makes sense. I'm grateful for any tips/advice. cheers, kyle

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  • Qt: QStackedWidget solution

    - by Martin
    I'm building a Qt application that have about 30 different views (QWidgets). My idea is to use a QStackedWidget to make it easy to switch between the different views in the application. I have two different solutions of how to implement this and use as little memory as possible when the user navigates through the application. Solution 1: Everytime I need to show a view I check if it is already in the stack. (The user might open the same view many times, maybe a view showing an item from a database). If the view is in the stack already it doesn't need to be created again and I can just show the view. The good thing with this solution is that I reuse the views (widgets) so they only need to be created once. This is good as the UI and other stuff should look the same everytime the user show a view, so why not reuse it? The problem with this solution is that every view has childrens. Maybe an object, a QList with objects or other things. A good thing with Qt is that you can use the parent-children mechanism so that the children will be deleted when the parent is deleted. As I never delete the parent (view) I need to handle this myself as the children might need to be deleted from different times when the view is shown. (Maybe the view show a list with objects and the list should be updated from a database each time the view is shown.) Solution 2: Everytime I need to show a QWidget I create a new one and show it. When it is not shown anymore, I delete it from memory. This is a quite easy solution. And as I delete the views when they are not shown both the view and it's children should be deleted from memory so it shouldn't increase memory, am I right? Which one of the solutions do you recommend?

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  • How would I include open source library in my iPhone application?

    - by greypoint
    I have found an existing open source library that I would like to include in my iPhone project (the unrar source code found here: http://www.rarlab.com/rar_add.htm ). I have compiled this source as a linked library on my Mac with "make lib" which creates the libunrar.so file just fine. These are the makefile settings for that target: lib: WHAT=RARDLL lib: $(OBJECTS) $(LIB_OBJ) @rm -f libunrar.so $(LINK) -shared -o libunrar.so $(LDFLAGS) $(OBJECTS) $(LIB_OBJ) Obviously I can't use this on iPhone but I imagine I should be able to compile with different options to make a static library that I can use. Do I: Compile it on the Mac with different make options then drag the resulting library (some kind of .a ?) into my xcode project? or Drag all of the source code into my xcode project and create special targets of some kind to create it? or Something else entirely different? I've been working on solving my unrar problem for a couple of weeks now and I believe using this library will give me the best results but I just don't know the final steps to make use of it. Thanks for all advice.

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