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• How do I obtain an HtmlHelper<TModel> instance for a model in ASP.NET MVC?

  - by DanM

  Let's say I have an Index view. The model I pass in is actually a collection of models, so the Html property is of type HtmlHelper<List<MyModel>>. If I want to call extension methods (e.g., Display() or DisplayFor() on the individual items in the list, however, I think I need to obtain an HtmlHelper<MyModel>. But how? I tried using the HtmlHelper<TModel> constructor, which looks like this: HtmlHelper<TModel>(ViewContext, IViewDataContainer) But I'm not having any luck with that. I don't know how to obtain the IViewDataContainer for the item, and the documentation on these things is very sparse. A lot of magic apparently happens when I do... return View(List<MyModel>); ...in my controller. How do I recreate that magic on individual items in a list/collection?

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• Using the JPA Criteria API, can you do a fetch join that results in only one join?

  - by Shaun

  Using JPA 2.0. It seems that by default (no explicit fetch), @OneToOne(fetch = FetchType.EAGER) fields are fetched in 1 + N queries, where N is the number of results containing an Entity that defines the relationship to a distinct related entity. Using the Criteria API, I might try to avoid that as follows: CriteriaBuilder builder = entityManager.getCriteriaBuilder(); CriteriaQuery<MyEntity> query = builder.createQuery(MyEntity.class); Root<MyEntity> root = query.from(MyEntity.class); Join<MyEntity, RelatedEntity> join = root.join("relatedEntity"); root.fetch("relatedEntity"); query.select(root).where(builder.equals(join.get("id"), 3)); The above should ideally be equivalent to the following: SELECT m FROM MyEntity m JOIN FETCH myEntity.relatedEntity r WHERE r.id = 3 However, the criteria query results in the root table needlessly being joined to the related entity table twice; once for the fetch, and once for the where predicate. The resulting SQL looks something like this: SELECT myentity.id, myentity.attribute, relatedentity2.id, relatedentity2.attribute FROM my_entity myentity INNER JOIN related_entity relatedentity1 ON myentity.related_id = relatedentity1.id INNER JOIN related_entity relatedentity2 ON myentity.related_id = relatedentity2.id WHERE relatedentity1.id = 3 Alas, if I only do the fetch, then I don't have an expression to use in the where clause. Am I missing something, or is this a limitation of the Criteria API? If it's the latter, is this being remedied in JPA 2.1 or are there any vendor-specific enhancements? Otherwise, it seems better to just give up compile-time type checking (I realize my example doesn't use the metamodel) and use dynamic JPQL TypedQueries.

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• Understanding c++ block of code

  - by kotoko

  I was given a c++ main and have to code it so it works. I am having some trouble understanding the code as I am a bit new to cpp. Here is the code int main(int argc, char *argv[]) { Class::setAtribute("string"); Class(Class::CONSTANT) << "starting up..."; } Some questions: How can the first line work with no variables? Is it static? The second line is really strange for me, what I can make out is a Constructor that takes in a class constante and then prints it out somehow? If someone could explain me this bit of code it would be great! Thanks in advance.

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• WPF Prism deactivate ?

  - by 2Fast4YouBR

  Hi all, I have an problem and would like to know if it is common problem or jsut with me. I am using Wpf with Prism and Unity, all with the pattern MvvM. I am loading a viewModel that has a reference to a dropdown with few items, my idea is that each time that the user click in some place to open the view that has this dropdown is that the dropdown will be shown with diferent values. The problem is that I see is that after I show the view for the first time and after the first DEACTIVATE, when I try to load it again looks like it is already in the memory (was not deactivated/disposed), so as is already in memory, it not call the constructor again of the modelView and the dropdown is shown with tha same old values. public BranchSelectionViewModel(IUnityContainer unityContainer) { this.unityContainer = unityContainer; User user = this.unityContainer.Resolve<User>(); this.branches = new ObservableCollection<Department>(user.Departments .Where(department => department.DepartmentId != user.SelectedDepartment.DepartmentId)); }

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• When (and why) is {} undefined in a JavaScript console?

  - by JS_Riddler

  In the console of both FF and Chrome, {} is considered undefined until explicitly evaluated: {}; // undefined ({}); // ? Object Actually, it's a bit less defined than undefined -- it's apparently bad syntax: {} === undefined; // SyntaxError: Unexpected token === {}.constructor; // SyntaxError: Unexpected token . But not if it's on the other side, in which case it's fine: "[object Object]" == {}.toString(); // true Or if it's not the first expression: undefined + undefined; // NaN {} + undefined; // NaN undefined + {}; // "undefined[object Object]" What gives?

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• copy rows with special condition

  - by pooria_googooli

  I have a table with a lot of columns. For example I have a table with these columns : ID,Fname,Lname,Tel,Mob,Email,Job,Code,Company,...... ID column is auto number column. I want to copy all rows in this table to this table and change the company column value to 12 in this copied row. I don't want to write name all of the columns because I have a lot of table with a lot of columns. I tried this code but I had this error : declare @c int; declare @i int; select * into CmDet from CmDet; select @C= count(id) from CmDet; while @i < @C begin UPDATE CmDet SET company =12 WHERE company=11 set @i += 1 end error : Msg 2714, Level 16, State 6, Line 3 There is already an object named 'CmDet' in the database. I changed the code to this declare @c int declare @i int insert into CmDet select * from CmDet; select @C= count(id) from CmDet; while @i < @C begin UPDATE CmDet SET company =12 WHERE company=11 set @i += 1 end and I had this error : Msg 8101, Level 16, State 1, Line 3 An explicit value for the identity column in table 'CmDet' can only be specified when a column list is used and IDENTITY_INSERT is ON. What should I do ?

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• Strange type-related error

  - by vsb

  I wrote following program: isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] primes = filter isPrime [1 .. ] it should construct list of prime numbers. But I got this error: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:3:16: Ambiguous type variable `a' in the constraints: `Floating a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `RealFrac a' arising from a use of `isPrime' at 7/main.hs:3:16-22 `Integral a' arising from a use of `isPrime' at 7/main.hs:3:16-22 Possible cause: the monomorphism restriction applied to the following: primes :: [a] (bound at 7/main.hs:3:0) Probable fix: give these definition(s) an explicit type signature or use -XNoMonomorphismRestriction Failed, modules loaded: none. If I specify signature for isPrime function explicitly: isPrime :: Integer -> Bool isPrime x = and [x `mod` i /= 0 | i <- [2 .. truncate (sqrt x)]] I can't even compile isPrime function: [1 of 1] Compiling Main ( 7/main.hs, interpreted ) 7/main.hs:2:45: No instance for (RealFrac Integer) arising from a use of `truncate' at 7/main.hs:2:45-61 Possible fix: add an instance declaration for (RealFrac Integer) In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] In a stmt of a list comprehension: i <- [2 .. truncate (sqrt x)] 7/main.hs:2:55: No instance for (Floating Integer) arising from a use of `sqrt' at 7/main.hs:2:55-60 Possible fix: add an instance declaration for (Floating Integer) In the first argument of `truncate', namely `(sqrt x)' In the expression: truncate (sqrt x) In the expression: [2 .. truncate (sqrt x)] Failed, modules loaded: none. Can you help me understand, why am I getting these errors?

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• alternative in .Net to building Tables/TR/TD manually?

  - by egrunin

  I've got a pile of code here that looks like this: if (stateTax > 0) { tr = new TableRow(); tbl.Rows.Add(tr); td = new TableCell(); td.CssClass = "stdLabel"; td.Text = "NY State Tax"; tr.Cells.Add(td); td = new TableCell(); td.Text = string.Format("{0:C}", stateTax); td.CssClass = "justRight"; tr.Cells.Add(td); } This is a horrible hash of data and layout, but creating a special class or control every time something like this comes up seems almost as bad. What I usually do is write a helper function, which is concise but ugly: if (stateTax > 0) MakeRow(tbl, "NY State Tax", "stdLabel", string.Format("{0:C}", stateTax), "justRight"); And now I'm thinking: haven't I done this 100 times before? Isn't there a more modern way? Just to be explicit: it's a whole list of miscellaneous labels and values. They don't come from any particular data source, and the rules for when rows should be suppressed vary. This example has only two columns, but I have other places with more.

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• Creating Pages with unique PageMaps

  - by Michael Krauklis

  I have a wicket Application that has long lived Pages. I would like each instance of this Page to be created with a unique PageMap for reasons I won't get into here, but when I try to specify a PageMap on the constructor of my Page I end up getting OOM and StackOverflow errors. Here is the code: public <CTOR>() { super(Session.get().newPageMap("" + System.currentTimeMillis())); ... I'm using a custom BookmarkablePageLink (custom in that it does not pass on the current PageMap name to the new Page) to effectively abandon the old Page/PageMap and create a new one with a new PageMap. The errors seem to be coming from page serialization after only two or three pages have been created. Can anyone find issue with this approach?

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• Empty Datagrid problem in VB6

  - by Hybrid SyntaX

  Hello Recently, i encountered a problem; when I bind a recordset to datagrid ,and run the application the datagrid is not populated even though recordset has data I use the following code Option Explicit Dim conn As New ADODB.Connection Dim cmd As New ADODB.Command Dim recordset As New ADODB.recordset Private Sub InitializeConnection() Dim str As String str = _ "Provider=Microsoft.Jet.OLEDB.4.0;" & _ "Data Source=" + App.Path + "\phonebook.mdb;" & _ "Persist Security Info=False" conn.CursorLocation = adUseClient conn.ConnectionString = str conn.Open (conn.ConnectionString) End Sub Private Sub AbandonConnection() If conn.State <> 0 Then conn.Close End If End Sub Private Sub Persons_Read() Dim qry_all As String ' qry_all = "select * from person,web,phone Where web.personid = person.id And phone.personid = person.id" qry_all = "SELECT * FROM person" Call InitializeConnection cmd.CommandText = qry_all cmd.CommandType = adCmdText Set cmd.ActiveConnection = conn If conn.State = 1 Then Set recordset = cmd.Execute() End If Call BindDatagrid Call AbandonConnection End Sub Private Function Person_Add() End Function Private Function Person_Delete() End Function Private Function Person_Update() End Function Private Sub BindDatagrid() Set dg_Persons.DataSource = recordset dg_Persons.Refresh End Sub Private Sub cmd_Add_Click() Person_Add End Sub Private Sub cmd_Delete_Click() Person_Delete End Sub Private Sub cmd_Update_Click() Person_Update End Sub Private Sub Form_Load() Call Persons_Read End Sub Private Sub mnu_About_Click() frm_About.Show End Sub Thanks in advance

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• F# function calling syntax confusion

  - by Daniel

  I have a piece of code: links |> Seq.map (fun x -> x.GetAttributeValue ("href", "no url")) Which I wanted to rewrite to: links |> Seq.map (fun x -> (x.GetAttributeValue "href" "no url")) But the F# compiler doesn't seem to like that. I was under the impression that these two function calls were interchangeable: f (a, b) (f a b) The error that I get is: The member or object constructor 'GetAttributeValue' taking 2 arguments are not accessible from this code location. All accessible versions of method 'GetAttributeValue' take 2 arguments. Which seems amusing, as it seems to indicate that it needs what I'm giving it. What am I missing here?

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• What is the definition of a Service object ?

  - by Maskime

  I've been working a lot with PHP. But recently i was sent on a work wich use Java. In PHP i used to do a lot of Singleton object but this pattern has not the same signification in Java that it has in PHP. So i wanted to go for an utility class (a class with static method) but my chief doesn't like this kind of classes and ask me to go for services object. So my guess was that a service object is just a class with a constructor that implement some public methods... Am i right ?

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• Magento - save quote_address on cart addAction using observer

  - by Byron

  I am writing a custom Magento module that gives rate quotes (based on an external API) on the product page. After I get the response on the product page, it adds some of the info from the response into the product view's form. The goal is to save the address (as well as some other things, but those can be in the session for now). The address needs to be saved to the quote, so that the checkout (onestepcheckout, free version) will automatically fill those values in (city, state, zip, country, shipping method [of which there are 3]) and load the rate quote via ajax (which it's already doing). I have gone about this by using an Observer, and watching for the cart events. I fill in the address and save it. When I end up on the cart page or checkout page ~4/5 times the data is lost, and the sql table shows that the quote_address is getting save with no address info, even though there is an explicit save. The observer method's I've used are: checkout_cart_update_item_complete checkout_cart_product_add_after The code saving is: (I've tried this with the address, quote and cart all not calling save() with the same results, as well as not calling setQuote() $quote->getShippingAddress() ->setCountryId($params['estimate_to_country']) ->setCity($params['estimate_to_city']) ->setPostcode($params['estimate_to_zip_code']) ->setRegionId($params['estimate_to_state_code']) ->setRegion($params['estimate_to_state']) ->setCollectShippingRates(true) ->setShippingMethod($params['carrier_method']) ->setQuote($quote) ->save(); $quote->getBillingAddress() ->setCountryId($params['estimate_to_country']) ->setCity($params['estimate_to_city']) ->setPostcode($params['estimate_to_zip_code']) ->setRegionId($params['estimate_to_state_code']) ->setRegion($params['estimate_to_state']) ->setCollectShippingRates(true) ->setShippingMethod($params['carrier_method']) ->setQuote($quote) ->save(); $quote->save(); $cart->save(); I imagine there's a good chance this is not the best place to save this info, but I am not quite sure. I was wondering if there is a good place to do this without overriding a whole controller to save the address on the add to cart action. Thanks so much, let me know if I need to clarify

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• can't create partial objects with accepts_nested_attributes_for

  - by Isaac Cambron

  I'm trying to build a form that allows users to update some records. They can't update every field, though, so I'm going to do some explicit processing (in the controller for now) to update the model vis-a-vis the form. Here's how I'm trying to do it: Family model: class Family < ActiveRecord::Base has_many :people, dependent: :destroy accepts_nested_attributes_for :people, allow_destroy: true, reject_if: ->(p){p[:name].blank?} end In the controller def check edited_family = Family.new(params[:family]) #compare to the one we have in the db #update each person as needed/allowed #save it end Form: = form_for current_family, url: check_rsvp_path, method: :post do |f| = f.fields_for :people do |person_fields| - if person_fields.object.user_editable = person_fields.text_field :name, class: "person-label" - else %p.person-label= person_fields.object.name The problem is, I guess, that Family.new(params[:family]) tries to pull the people out of the database, and I get this: ActiveRecord::RecordNotFound in RsvpsController#check Couldn't find Person with ID=7 for Family with ID= That's, I guess, because I'm not adding a field for family id to the nested form, which I suppose I could do, but I don't actually need it to load anything from the database for this anyway, so I'd rather not. I could also hack around this by just digging through the params hash myself for the data I need, but that doesn't feel a slick. It seems nicest to just create an object out of the params hash and then work with it. Is there a better way? How can I just create the nested object?

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• PHP inheriting/extending a particular instance of an Object

  - by delta9

  Is there any way to force PHP to extend an existing/particular (and for that matter, already instantiated) instance of an object? This imaginary code should explain what I am wondering: class Base { public $var; function __construct($var){ $this->var = $name; } } class Extender extends Base { function __construct($parent) { parent = $parent; } } $base = new Base('yay!'); $extender = new Extender($base); echo 'Extended base var value: '.$extender->var.'<br/>'; Output (would be): Extended base var value: yay! To be clear, I am wanting to instantiate an object that extends a PARTICULAR INSTANCE of another object, one that has already been instantiated. I am aware that I can pass a reference to an object to another object (via it's constructor function) and then add it as a property of the receiving object, I'm wondering if there is a real way to do this?

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• Cannot understand the behaviour of dotnet compiler while instantiating a class thru interface(C#)

  - by Newbie

  I have a class that impelemnts an interface. The interface is public interface IRiskFactory { void StartService(); void StopService(); } The class that implements the interface is public class RiskFactoryService : IRiskFactory { } Now I have a console application and one window service. From the console application if I write the following code static void Main(string[] args) { IRiskFactory objIRiskFactory = new RiskFactoryService(); objIRiskFactory.StartService(); Console.ReadLine(); objIRiskFactory.StopService(); } It is working fine. However, when I mwrite the same piece of code in Window service public partial class RiskFactoryService : ServiceBase { IRiskFactory objIRiskFactory = null; public RiskFactoryService() { InitializeComponent(); objIRiskFactory = new RiskFactoryService(); <- ERROR } /// <summary> /// Starts the service /// </summary> /// <param name="args"></param> protected override void OnStart(string[] args) { objIRiskFactory.StartService(); } /// <summary> /// Stops the service /// </summary> protected override void OnStop() { objIRiskFactory.StopService(); } } It throws error: Cannot implicitly convert type 'RiskFactoryService' to 'IRiskFactory'. An explicit conversion exists (are you missing a cast?) When I type casted to the interface type, it started working objIRiskFactory = (IRiskFactory)new RiskFactoryService(); My question is why so? Thanks.(C#)

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• Do fields need to be explicitly final to have a "proper" immutable object?

  - by Yishai

  You often read about immutable objects requiring final fields to be immutable in Java. Is this in fact the case, or is it simply enough to have no public mutability and not actually mutate the state? For example, if you have an immutable object built by the builder pattern, you could do it by having the builder assign the individual fields as it builds, or having the builder hold the fields itself and ultimately return the immutable object by passing the values to its (private) constructor. Having the fields final has the obvious advantage of preventing implementation errors (such as allowing code to retain a reference to the builder and "building" the object multiple times while in fact mutating an existing object), but having the Builder store its data inside the object as it is built would seem to be DRYer. So the question is: Assuming the Builder does not leak the Object early and stops itself from modifying the object once built (say by setting its reference to the object as null) is there actually anything gained (such as improved thread safety) in the "immutability" of the object if the object's fields were made final instead?

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• C++ enforce conditions on inherited classes

  - by user231536

  I would like to define an abstract base class X and enforce the following: a) every concrete class Y that inherits from X define a constructor Y(int x) b) it should be possible to test whether two Y objects are equal. For a, one not very good solution is to put a pure virtual fromInt method in X which concrete class will have to define. But I cannot enforce construction. For b), I cannot seem to use a pure virtual method in X bool operator == (const X& other) const =0; because in overridden classes this remains undefined. It is not enough to define bool operator == (const Y& other) const { //stuff} because the types don't match. How do I solve these problems?

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• Java swing doesn't show changes to source

  - by out_sider

  I'm using Java Swing graphical editor with netbeans to make my project...but using it brings some limitations like I can't add to a jpanel an image,using java swing options. So i'll need to code it, implementing a new jPanel. My problem is that the code generated by the java swing graphical editor can't be edited so instead of adding the new JPanel code in the initComponents() section I'm doing it after this function is called in the constructor of my main JPanel. But any code I add is not recognized by the "Designer" which means that after making my coded objects I can't use them in the "Designer" and everything must be coded, which is a pain considering how much easier is previewing and moving elements in the "Designer" tool. How can I code what I want but steel appear in the "DEsigner"? Thx in advance

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• Why does coffeescript generate classes like this?

  - by ryeguy

  Given the following coffeescript code: class Animal constructor: (@name) -> speak: (things) -> "My name is #{@name} and I like #{things}" This is generated: var Animal = (function() { function Animal(name) { this.name = name; } Animal.prototype.speak = function(things) { return "My name is " + this.name + " and I like " + things; }; return Animal; })(); But why isn't this more idiomatic code generated? var Animal = function Animal(name) { this.name = name; }; Animal.prototype.speak = function(things) { return "My name is " + this.name + " and I like " + things; }; I know that coffeescript wraps a lot of stuff in anonymous functions to control scope leak, but what could leak here?

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• TDD, Unit Test and architectural changes

  - by Leandro

  I'm writing an RPC middleware in C++. I have a class named RPCClientProxy that contains a socket client inside: class RPCClientProxy { ... private: Socket* pSocket; ... } The constructor: RPCClientProxy::RPCClientProxy(host, port) { pSocket = new Socket(host, port); } As you can see, I don't need to tell the user that I have a socket inside. Although, to make unit tests for my proxies it would be necessary to create mocks for sockets and pass them to the proxies, and to do so I must use a setter or pass a factory to the sockets in the proxies's constructors. My question: According to TDD, is it acceptable to do it ONLY because the tests? As you can see, these changes would change the way the library is used by a programmer.

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• Class basic operators

  - by swan

  Hi, Is it necessary to have a copy constructor, destructor and operator= in a class that have only static data member, no pointer class myClass{ int dm; public: myClass(){ dm = 1; } ~myClass(){ } // Is this line usefull ? myClass(const myClass& myObj){ // and that operator? this->dm = myObj.dm; } myClass& operator=(const myClass& myObj){ // and that one? if(this != &myObj){ this->dm = myObj.dm; } return *this; } }; I read that the compiler build one for us, so it is better to not have one (when we add a data member we have to update the operators)

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• Silently binding a variable instance to a class in C++?

  - by gct

  So I've got a plugin-based system I'm writing. Users can create a child class of a Plugin class and then it will be loaded at runtime and integrated with the rest of the system. When a Plugin is run from the system, it's run in the context of a group of plugins, which I call a Session. My problem is that inside the user plugins, two streaming classes called pf_ostream and pf_istream can be used to read/write data to the system. I'd like to bind the plugin instance's session variable to pf_ostream and pf_istream somehow so that when the user instantiates those classes, it's already bound to the session for them (basically I don't want them to see the session internals) I could just do this with a macro, wrapping a call to the constructor like: #define MAKE_OSTREAM = pf_ostream_int(this->session) But I thought there might be a better way. I looked at using a nested class inside Plugin wrapping pf_ostream but it appears nested classes don't get access to the enclosing classes variables in a closure sort of way. Does anyone know of a neat way to do this?

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• Tie destruction of an object (sealed) to destruction of an unmanaged buffer

  - by testtestSO

  I'll explain my situation first: I'm interested of using the Bitmap constructor that takes scan0, stride and format, because I'm decoding tiled images and I'd like to choose my own stride so I can decode the tiles without caring about the bounds in the decoder part. Anyway, the problem is that the documentation says: The caller is responsible for allocating and freeing the block of memory specified by the scan0 parameter. However, the memory should not be released until the related Bitmap is released. I can't release the buffer easily, because the Bitmap is then passed to another class that will eventually destroy it and I don't have control over it. Is there some way (hacky, I know) to tell the GC to also release my buffer when the Bitmap is destroyed? (Also, any alternative solution is welcome).

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• Disallow taking pointer/reference to const to a temporary object in C++ (no C++0X)

  - by KRao

  Hi, I am faced with the following issue. Consider the following class: //Will be similar to bost::reference_wrapper template<class T> class Ref { public: explicit Ref(T& t) : m_ptr(&t) {} private: T* m_ptr; }; and this function returning a double double fun() {return 1.0;} If we now have double x = 1.0; const double xc = 1.0; Ref<double> ref1(x); //OK Ref<const double> refc1(cx); //OK good so far, however: //Ref<double> ref2( fun() ); //Fails as I want it to Ref<const double> refc2( fun() ); //Works but I would like it not to Is there a way to modify Ref (the way you prefer) but not the function fun, so that the last line returns a compile-time error? Please notice you can modify the constructor signature (as long as I am able to initialise the Ref as intended). Thank you in advance for your help!

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