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• Entity framework (1): implement 1 foreign key to multiple tables

  - by Michel

  Hi, i've modeled this: i have an import table, and an import steps table import 1 .. N importsteps Now i have a table importparams, which hold key/value pairs to register all kind of info about the import or the importsteps. So i have modeled a FK in SqlServer which points to the PK of the import table and to the PK of the importsteps table (the ID's for both the import as the importsteps table are guids, so i can query the importparams with either the id from import or from importsteps and get the right importparams). Makes sense a bit? But how can i model this in the EF? I can see it's a bit hard for the EF to model this, because one realtion can point to multiple classes, but is there a way? The workaround normally is just to get all importparams where FK is the ID, but as you know the FK is not available in the EF version 1. I hope you can help me out, michel

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• Django: many-to-one fields and data integrity

  - by John

  Let's say that I have a Person who runs an inventory system. Each Person has some Cars, and each Car has a very large number of Parts (thousands, let's say). A Person, Bob, uses a Django form to create a Car. Now, Bob goes to create some Parts. It is only at the form level that Django knows that the Parts belong to some specific Car, and that the Parts.ForeignKey(Car) field should only have a specific Car as a choice. When creating a Part, you have to mess with the form's constructor or similar in order to limit the choice of Cars to only the cars owned by Bob. It does not seem proper that to enforce this ownership at the form level. It seems that other users' Cars must be inaccessible to anyone but the owner of the Car. What do you all think about this, and is there any way to enforce this?

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• F#: Define an abstract class that inherits an infterface, but does not implement it

  - by akaphenom

  I owuld like to define an abstract class that inerhits from UserControl and my own Interface IUriProvider, but doesn't implement it. The goal is to be able to define pages (for silverlight) that implement UserControl but also provide their own Uri's (and then stick them in a list / array and deal with them as a set: type IUriProvider = interface abstract member uriString: String ; abstract member Uri : unit -> System.Uri ; end type UriUserControl() as this = inherit IUriProvider with abstract member uriString: String ; inherit UserControl() Also the Uri in the definition - I would like to implement as a property getter - and am having issues with that as well. this does not compile type IUriProvider = interface abstract member uriString: String with get; end Thank you...

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• How can I model the data in a multi-language data editor in WPF with MVVM?

  - by Patrick Szalapski

  Are there any good practices to follow when designing a model/ViewModel to represent data in an app that will view/edit that data in multiple languages? Our top-level class--let's call it Course--contains several collection properties, say Books and TopicsCovered, which each might have a collection property among its data. For example, the data needs to represent course1.Books.First().Title in different languages, and course1.TopicsCovered.First().Name in different languages. We want a app that can edit any of the data for one given course in any of the available languages--as well as edit non-language-specific data, perhaps the Author of a Book (i.e. course1.Books.First().Author). We are having trouble figuring out how best to set up the model to enable binding in the XAML view. For example, do we replace (in the single-language model) each String with a collection of LanguageSpecificString instances? So to get the author in the current language: course1.Books.First().Author.Where(Function(a) a.Language = CurrentLanguage).SingleOrDefault If we do that, we cannot easily bind to any value in one given language, only to the collection of language values such as in an ItemsControl. <TextBox Text={Binding Author.???} /> <!-- no way to bind to the current language author --> Do we replace the top-level Course class with a collection of language-specific Courses? So to get the author in the current language: course1.GetLanguage(CurrentLanguage).Books.First.Author If we do that, we can only easily work with one language at a time; we might want a view to show one language and let the user edit the other. <TextBox Text={Binding Author} /> <!-- good --> <TextBlock Text={Binding ??? } /> <!-- no way to bind to the other language author --> Also, that has the disadvantage of not representing language-neutral data as such; every property (such as Author) would seem to be in multiple languages. Even non-string properties would be in multiple languages. Is there an option in between those two? Is there another way that we aren't thinking of? I realize this is somewhat vague, but it would seem to be a somewhat common problem to design for. Note: This is not a question about providing a multilingual UI, but rather about actually editing multi-language data in a flexible way.

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• Entity Framework v4 examples and tutorials of conceptual model mapping

  - by Rody van Sambeek

  In an application I'm writing I have a fairly complicated Database model. I'd like to use EF4 to map this to a whole lot nicer conceptual model. However all the tutorials I've read are with samples of 2 or 3 tables which all map 1 on 1 to the conceptual model. I'd like to learn how to correctly map the database model to a different conceptual model using VS 2010. However I can't find any good tutorials or (preferabally) instruction video's. Somebody got any tips, links or even books?

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• Why are alloc and init called separately in Objective-C?

  - by André Hoffmann

  Note: I'm relatively new to Objective-C and am coming from Java and PHP. Could someone explain to me why I always have to first allocate and then initialize an instance? Couldn't this be done in the init methods like this: + (MyClass*)init { MyClass *instance = [MyClass alloc]; [instance setFoo:@"bla"]; return instance; } + (MyClass*)initWithString:(NSString*)text { MyClass *instance = [MyClass init]; [instance setFoo:text]; return instance; } ... Is this just a relict from the old C days or is there something that I'm not seeing? I know this isn't a problem as I could as well always call alloc and init, but since it's a bit tedious I'd like to at least know why I'm doing it. I'm liking the expressiveness of the language so far, but this is something that I want to fully understand in order to think the Objective-C way. Thank you!

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• Python: saving objects and using pickle. Error using pickle.dump

  - by Peterstone

  Hello I have an Error and I don´t the reason: >>> class Fruits:pass ... >>> banana = Fruits() >>> banana.color = 'yellow' >>> banana.value = 30 >>> import pickle >>> filehandler = open("Fruits.obj",'w') >>> pickle.dump(banana,filehandler) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "C:\Python31\lib\pickle.py", line 1354, in dump Pickler(file, protocol, fix_imports=fix_imports).dump(obj) TypeError: must be str, not bytes >>> I don´t know how to solve this error because I don´t understand it. Thank you so much.

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• How to gain Access to member variables of a class using void pointer but Not Object

  - by mahesh

  Hi, I am trying to access member variables of a class without using object. please let me know how to go about. class TestMem { int a; int b; public: TestMem(){} void TestMem1() { a = 10; b = 20; } }; void (TestMem::*pMem)(); int main(int argc, char* argv[]) { TestMem o1; pMem = &(TestMem::TestMem1); void *p = (void*)&pMem; // How to access a & b member variables using variable p getch(); return 0; }

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• Conditional relation

  - by Lowgain

  I've got a model like this: Stem -id -etc And then I have Stemrelation -stem_id -related_stem_id -active I can get the related stems with the following relations class Stem < ActiveRecord::Base has_many :stemrelations has_many :related_stems, :through => :stemrelations end class Stemrelation < ActiveRecord::Base belongs_to :stem belongs_to :related_stem, :class_name => "Stem", :foreign_key => "related_stem_id" end But now I'd only like to get the active relations. I tried adding this to the Stem model: has_many :active_related, :through => :stemrelations, :source => :related_stem, :conditions => {:active => true} but this gives me an error becasue it tries to check the active flag on the stem model instead of the stemrelation. What do I change here? Thanks!

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• vb.net Object Initialiser List(Of T)

  - by Tim B James

  I have been looking at some C# code: List<Employee> Employees = new List<Employee>{ new Employee{firstname="Aamir",lastname="Hasan",age=20}, new Employee{firstname="awais",lastname="Hasan",age=50}, new Employee{firstname="Bill",lastname="Hasan",age=70}, new Employee{firstname="sobia",lastname="khan",age=80}, }; Now when I convert this to vb.net Dim Employees as List(Of Employee) = New List(Of Employee)() With { New Employee() With { _ .firstname = "Aamir", _ .lastname = "Hasan", _ .age = 20 _ }, _ New Employee() With { _ .firstname = "awais", _ .lastname = "Hasan", _ .age = 50 _ }, _ New Employee() With { _ .firstname = "Bill", _ .lastname = "Hasan", _ .age = 70 _ }, _ New Employee() With { _ .firstname = "sobia", _ .lastname = "khan", _ .age = 80 _ } _ } I get the error "Name of field or property being initialized in an object initializer must start with'.'." Now I can get an array of employee using the code: Dim Employees = { New Employee() With { _ .FirstName = "Aamir", _ .LastName = "Hasan", _ .Age = 20}, _ New Employee() With { _ .FirstName = "Awais", _ .LastName = "Hasan", _ .Age = 50}, _ New Employee() With { _ .FirstName = "Bill", _ .LastName = "Hasan", _ .Age = 70 _ } _ } But I would like a List(Of Employee) as it is bugging me as to why this doesnt work in vb.net?

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• adding a js method

  - by Sorin Buturugeanu

  Hi! I have a js function that is named getID which is basically return document.getElementById(id) I want to make another function, getTag that would return getElementsByTagName. The part that I can't seem to manage is that I want to be able to call them like this: getID('myid').getTag('input') = so this would return all the input elements inside the element with the id myid Thanks! ps: getTag would also have to work if it's called by it's own, but then it would just return document.getElementsByTagName

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• When Drag a object from one div to another , format gets changed

  - by Anuj

  When a object is dragged and dropped from one div to another, the format in li gets changes to text only. I want it in the same format i.e 'li' after droping it. $(function() { $( "#catalog ul" ).sortable({ zIndex: 10000, revert: true }); $( "#catalog" ).accordion(); $( "#catalog ul" ).draggable({ appendTo: "body", helper: "clone", zIndex: 10000 }); $( "#dialogIteration ol" ).droppable({ activeClass: "ui-state-default", hoverClass: "ui-state-hover", drop: function( event, ui ) { $( this ).find( ".placeholder" ).remove(); $( "<li></li>" ).text( ui.draggable.text() ).appendTo( this ); } }).sortable({ items: "li:not(.placeholder)", sort: function() { // gets added unintentionally by droppable interacting with sortable // using connectWithSortable fixes this, but doesn't allow you to customize active/hoverClass options $( this ).removeClass( "ui-state-default" ); } }); $( "ul, li" ).disableSelection(); $("#dialogIteration").dialog(); }); Demo: http://jsfiddle.net/coolanuj/7683X/7/

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• What are pointers to class members used for?

  - by srikfreak

  I have read about pointers to class members, but I have never seen them being used in any practical applications. Can someone explain what are the use cases of such pointers? Is it really necessary to have such pointers? Eg. class abc { public: int a; abc(int val) { a = val; } }; int main { int abc::*data; abc obj(5); data = &abc::a; cout << "Value of a is " << obj.*data << endl; return 0; } In the above eg. why is the value of 'a' accessed in this manner? What is the advantage of using pointers to class members?

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• Is there a name for a language feature that allows assignment/creation?

  - by Alex Mcp

  This is a bit hard for me to articulate, but in PHP you can say something like: $myArray['someindex'] = "my string"; and if there is no index named that, it will create/assign the value, and if there IS an index, it will overwrite the existing value. Compare this to Javascript where today I had to do checks like so: if (!myObject[key]) myObject[key] = "value"; I know this may be a bit of a picky point, but is there a name for the ability of PHP (and many other languages) to do these checks on their own as opposed to the more verbose (read: PITA) method of Javascript?

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• Fatal error: Call to a member function item() on a non-object

  - by Andree

  Hi there! I have a weird problem. I have a PHP class with the following method: public function __construct() { parent::__construct(); $this->CI =& get_instance(); $this->log(method_exists($this->CI->config, 'item')); // Outputs TRUE $firephp_enabled = $this->CI->config->item('firephp_enabled'); // Error point $this->setEnabled($firephp_enabled); } $this->CI->config has a method item, and it has been verified using method_exists(). But when I call $this->CI->config->item(), I got the following error: Fatal error: Call to a member function item() on a non-object Can anyone tell me what might be the problem here? Thanks, Andree.

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• SOA design principles with regards to database relationships

  - by Eitan

  If I were to extricate my current membership provider from my solution, i.e. as a dll and expose it as a web service with it's own db, how would I model the relationships with regards to SOA design. For example I have a table: USER id, name, lastname, username, password, role. and table PRODUCT id, name, price, createdate, userid the foreign key being userid to table user. How would I model the relationship and/or query the db. If I wanted to get all products that were uploaded today for example, before I would query: SELECT u.name, u.lastname, u.username, p.* FROM PRODUCT p INNER JOIN USER u ON p.userid = u.id WHERE createdate = '05/05/2010' Now that I don't have the table within the database how would I perform this query? Thanks.

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• how to avoid returning mocks from a mocked object list

  - by koen

  I'm trying out mock/responsibility driven design. I seem to have problems to avoid returning mocks from mocks in the case of finder objects. An example could be an object that checks whether the bills from last month are paid. It needs a service that retrieves a list of bills for that. So I need to mock that service that retrieves the bills. At the same time I need that mock to return mocked Bills (since I don't want my test to rely on the correctness bill implementation). Is my design flawed? Is there a better way to test this? Or is this the way it will need to be when using finder objects (the finding of the bills in this case)?

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• rails: has_many :through validation?

  - by ramonrails

  Rails 2.1.0 (Cannot upgrade for now due to several constraints) I am trying to achieve this. Any hints? A project has many users through join model A user has many projects through join model Admin class inherits User class. It also has some Admin specific stuff. Admin like inheritance for Supervisor and Operator Project has one Admin, One supervisor and many operators. Now I want to 1. submit data for project, admin, supervisor and operator in a single project form 2. validate all and show errors on the project form. Project has_many :projects_users ; has_many :users, :through => :projects_users User has_many :projects_users ; has_many :projects, :through => :projects_users ProjectsUser = :id integer, :user_id :integer, :project_id :integer, :user_type :string ProjectUser belongs_to :project, belongs_to :user Admin < User # User has 'type:string' column for STI Supervisor < User Operator < User Is the approach correct? Any and all suggestions are welcome.

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• What is a Windows scripting language that: does not rely on .NET and offers the most OOP support and

  - by jJack

  What is a Windows scripting language that: does not rely on .NET and offers the most OOP support and has simplest deployment? It doesn't necessarily need to be a scripting language; It can be in the form of a compiled executable, however it needs to be self contained--only ONE file, no DLL's and it cannot be declared to "include" other files. I cannot rely on the user having any .NET installed and it needs to be able to run on Windows 7 64 bit. By "most OOP support", I basically mean anything that has better OOP support than VBScript. A little context: Everything I have done thus far is in VBScript and writes a bunch of data into an .html file, which in the end is to be viewed by Internet Explorer. It also zips up a bunch of directories and files. It heavily relies on accessing the registry, file-system, and WMI (I can probably do without accessing WMI though, as long as I have good registry access). I can bring myself to code in any language so long as it meets me ridonkulous requirements stated above. I look forward to some good answers from those more experienced than I.

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• How to access stdClass variables stdClass Object([max(id)])=>64)

  - by Theopile

  I need the very last valid entry in a database table which would be the row with the greatest primary key. So using mysqli, my query is "SELECT MAX(id) FROM table LIMIT 1". This query returns the correct number(using print_r()) but I cannot figure out how to access it. Here is the main code. Note that the $this-link refers to class with a mysqli connection. $q="select max(id) from stones limit 1"; $qed=$this->link->query($q) or die(mysqli_error()); if($qed){ $row=$qed->fetch_object(); print_r($row); echo $lastid=$row;//here is the problem } The valid line print_r($row) echos out "stdClass Object ( [max(id)] = 68 )"

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• Grabbing random object from ArrayList is not random.

  - by Isai

  I am creating a method where if you pass in a parameter of type Random, then it will return a random object. Here is basically what I am trying to do: public T choose(Random r) { int randomInt = r.nextInt(randomList.size()); // randomList is just a instance variable return randomList.get(randomInt); } The random list has this the following strings:[2, 2, 2, 1, 1, 1, 1, c, c, c, a, a, a, a] Then I made a driver with the following code for (int i = 0; i < 10; i++) { System.out.print(rndList.choose(rnd)); // rnd is initialized as a static Random variable } However my outputs are not coming out random. I used the debugger and found out that my choose method generates an integer that is relatively low, so it will always print out either 2's or 1's but never c's or a's. I can't figure out why this is happening and help would be greatly appreciated.

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• c#: what is the point in having a purely public property

  - by Craig Johnston

  What is the point in having a property inside a class that simply get and sets a member variable? What practical difference would be there to just making the variable public?

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• How to access the subject of a compose mail item in Outlook

  - by vwfreak034

  In Outlook, I can set the subject for a new message (when composing a new mail message), but I want to prepend text. So I need to get the subject first, and then set it. Outlook.Application application = Globals.ThisAddIn.Application; Outlook.Inspector inspector = application.ActiveInspector(); Outlook.MailItem myMailItem = (Outlook.MailItem)inspector.CurrentItem; if (myMailItem != null && !string.IsNullOrEmpty(myMailItem.Subject)) { myMailItem.Subject = "Following up on your order"; } This code works on replies, but not for new messages, because in that case, myMailItem is null.

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• Python: Recursively access dict via attributes as well as index access?

  - by Luke Stanley

  I'd like to be able to do something like this: from dotDict import dotdictify life = {'bigBang': {'stars': {'planets': [] } } } dotdictify(life) #this would be the regular way: life['bigBang']['stars']['planets'] = {'earth': {'singleCellLife': {} }} #But how can we make this work? life.bigBang.stars.planets.earth = {'singleCellLife': {} } #Also creating new child objects if none exist, using the following syntax life.bigBang.stars.planets.earth.multiCellLife = {'reptiles':{},'mammals':{}} My motivations are to improve the succinctness of the code, and if possible use similar syntax to Javascript for accessing JSON objects for efficient cross platform development.(I also use Py2JS and similar.)

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• To Wrap or Not to Wrap: Wrapping Data Access in a Service Facade

  - by PureCognition

  For a while now, my team and I have been wrapping our data access layer in a web service facade (using WCF) and calling it from the business logic layer. Meanwhile, we could simply use the repository pattern where the business logic layer consumes the data access layer locally through an interface, and at any point in time, we can switch things out for it to hit a service instead (if necessary). The question is: When is it a good time to wrap the data access layer in a service facade and when isn't it? Right now, it seems like the main advantage is that other applications can consume the service, but if they are internal applications written in .NET then they can just consume the .NET assembly instead. Are there other advantages of having the DAL be wrapped in a service that I am unaware of?

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