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• IRepository with Inherited Classes

  - by Stacey

  In keeping with the Repository pattern of data input, I've a question in regards to using inherited classes. For instance, suppose I would have the class... class Employee IEmployeeRepository { Add(Employee employee); } This works fine, nothing wrong with it so far... but now let's say I continue on.. class Manager : Employee Okay, now let's assume that I never need to enter a manager different than an Employee? What's the best approach here? Would a scenario such as .. IEmployeeRepository { Add<T>(T employee) where T : Employee } Be the best approach, or do I need to abstract a different repository for each type?

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• Check if a variable is empty

  - by Thomas

  I have some user-submitted variables that I want to display in a different part of my site like this: <div class="pre_box">Term: </div> <div class="entry"><?php $key='term'; echo get_post_meta($post->ID, $key, true); ?></div> Occasionally, these variables might be empty in which case I don't want to display the label for the empty variable. In the example above I would want to hide the <div class="pre_box">Term: </div> part. Is there some simple way to check if a php variable like the one above is empty and prevent the label from being displayed?

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• jQuery .parent() does not work

  - by Misha Moroshko

  Why the following code fails with: Error: class_a_jquery_objects[0].parent is not a function ? HTML: <div> <div class='a b'></div> <div class='b c'></div> <div class='c a'></div> </div> <div id='log'></div> JS: $(function() { var class_a_jquery_objects = $(".a"); $("#log").append(class_a_jquery_objects.length + "<br />"); $("#log").append(class_a_jquery_objects[0] + "<br />"); $("#log").append(class_a_jquery_objects[0].parent() + "<br />"); });

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• Can C++ Constructors be templates?

  - by Gokul

  Hi, I have non-template class with a templatized constructor. This code compiles for me. But i remember that somewhere i have referred that constructors cannot be templates. Can someone explain whether this is a valid usage? typedef double Vector; //enum Method {A, B, C, D, E, F}; struct A {}; class Butcher { public: template <class Method> Butcher(Method); private: Vector a, b, c; }; template <> Butcher::Butcher(struct A) : a(2), b(4), c(2) { // a = 0.5, 1; // b = -1, 1, 3, 2; // c = 0, 1; } Thanks, Gokul.

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• GetValue on static field inside nested classes.

  - by Sir Gallahad

  Hi... I have the following class declared. I need to retreive the class structure and the static values without instanciate it. public MyClass() { public static string field = "Value"; public nestedClass() { public static string nestedField = "NestedValue"; } } I've successfuly used GetFields and GetNestedType to recover the class structure and GetValue(null) works fine on field, but not on nestedField. Let me sample: var fi = typeof(MyClass).GetField("field", BindingFlags.Public | BindingFlags.Static); var nt = typeof(MyClass).GetNestedType("nestedClass", BindingFlags.Public); var nfi = nt.GetField("nestedField", BindingFlags.Public | BindingFlags.Static); // All the above references are detected correctly var value = fi.GetValue(null); // until here everything works fine. value == "Value" var nestedValue = nfi.GetValue(null); // this one does not work!! Anyone knows why the last line does not work and how to work around? Thanks.

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• problem with update the counter value

  - by Edan

  Hello, I having problem to update the counter (integer value). this is the definitions of the class: public class Item_Actions { private final int MAX_ITEMS = 100; private Item myItem[]; private int counter; public Item_Actions() { myItem = new Item[MAX_ITEMS]; counter++; } //Constructor add item into the menu (Description, type & price of Item) public void addItem(Item itm) { myItem[counter] = itm; counter++; }....... Now everytime I call the addItem constructor from another class, the counter always stays on zero. What causing it and how do I save the data inside? thanks

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• Which Java library lets me initialize an object's properties from a properties file?

  - by Kjetil Ødegaard

  Is there a Java library that lets you "deserialize" a properties file directly into an object instance? Example: say you have a file called init.properties: username=fisk password=frosk and a Java class with some properties: class Connection { private String username; private String password; public void setUsername(String username) { this.username = username; } public void setPassword(String password) { this.password = password; } } I want to do this: Connection c = MagicConfigurator.configure("init.properties", new Connection()) and have MagicConfigurator apply all the values from the properties file to the Connection instance. Is there a library with a class like this?

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• Can this be done with multiple inhertance?

  - by Milo

  Here is what I would like to do. Say I have Class Widget. I then create Button from Widget. I then create ModifiedWidget which re-implements certain functions of Widget. I then want Button to use ModifiedWidget rather than plain Widget. Is this possible to do some how? Thanks class Button : public Widget; class SuperButton : public Button, public ModifiedWidget; I'm just not sure if that would do what I want it to though.

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• Forbid public Add and Delete for a List<T>

  - by aaginor

  Hi folks, in my C#-project, I have a class which contains a List public class MyClass { public MyClass parent; public List<MyClass> children; ... } I want to prevent the user of the class from Adding (and Deleting) an Element to the children-List, but he shall still be able to parse its elements. I want to handle the Adding and Deleting within MyClass, providing an AddChild(MyClass item) and DeleteChild(MyClass item) to ensure that, when an item is added to the child list, the parent of that item will be set properly. Any idea how to do this besides implementing my own IList? Thanks in advance, Frank

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• mx.core::BitmapAsset could not be found

  - by asksuperuser

  I tried the code EmbedAssets.as below found in sample here: http://www.senocular.com/flash/tutorials/as3withmxmlc/ I got this error when building with mxmlc.exe and testing the ouput EmbedAssets.swf in Flash Player 9: VerifyError: Error #1014: mx.core::BitmapAsset could not be found package { import flash.display.Sprite; public class EmbedAssets extends Sprite { [Embed(source="images/trophy.png")] private var TrophyImage:Class; [Embed(source="swfs/satdish.swf")] private var SatelliteAnimation:Class; public function EmbedAssets() { addChild(new SatelliteAnimation()); addChild(new TrophyImage()); } } } satdish.swf is not corrupted so I don't understand why this error message.

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• Hibernate - why use many-to-one to represent a one-to-one?

  - by aberrant80

  I've seen people use many-to-one mappings to represent one-to-one relationships. I've also read this in a book by Gavin King and on articles. For example, if a customer can have exactly one shipping address, and a shipping address can belong to only one customer, the mapping is given as: <class name="Customer" table="CUSTOMERS"> ... <many-to-one name="shippingAddress" class="Address" column="SHIPPING_ADDRESS_ID" cascade="save-update" unique="true"/> ... </class> The book reasons as (quoting it): "You don't care what's on the target side of the association, so you can treat it like a to-one association without the many part." My question is, why use many-to-one and not one-to-one? What is it about a one-to-one that makes it a less desirable option to many-to-one? Thanks.

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• C++ operator overloading doubt

  - by avd

  I have a code base, in which for Matrix class, these two definitions are there for () operator: template <class T> T& Matrix<T>::operator() (unsigned row, unsigned col) { ...... } template <class T> T Matrix<T>::operator() (unsigned row, unsigned col) const { ...... } One thing I understand is that the second one does not return the reference but what does const mean in the second declaration. Also which function is called when I do say mat(i,j)

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• Copying pointers in C++

  - by tunnuz

  Hello, I have a class A containing two pointers to objects of another class B. I want to initialize one pointer or the other depending on which one is passed to init(), which also takes other parameters. My situation is thus the following: class A { public: A(); init(int parameter, int otherParameter, B* toBeInitialized); protected: B* myB; B* myOtherB; }; Now my point is that I want to call init() as: init(640, 480, this->myB); or init(640, 480, this->myOtherB); Now, my init is implemented as: void init( int parameter, int otherParameter, B* toBeInitialized ) { toBeInitialized = someConstructorFunction(parameter, otherParameter); } The problem is that the two pointers are not initialized, I suspect that toBeInitialized is overwritten, but the original parameter is not modified. I am doing something wrong? Should I use references to pointers? Thank you Tommaso

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• Dynamic binding in C++

  - by chmike

  I'm implementing a CORBA like server. Each class has remotely callable methods and a dispatch method with two possible input, a string identifying the method or an integer which would be the index of the method in a table. A mapping of the string to the corresponding integer would be implemented by a map. The caller would send the string on the first call and get back the integer with the response so that it simply has to send the integer on subsequent calls. It is just a small optimization. The integer may be assigned dynamically on demand by the server object. The server class may be derived from another class with overridden virtual methods. What could be a simple and general way to define the method binding and the dispatch method ?

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• Inheritance: possible to change base reference to something else?

  - by fred

  For example I have two classes, Base and Derived as shown below: class Base { public string Name { get; set; } public Base() { } } class Derived : Base { public Derived(Base b) { base = b; // doesn't compile, but is there any way to do something similar? } } So that they behave like this: Base b = new Base(); b.Name = "Bob"; Derived d = new Derived(b); d.Name = "John"; // b.Name is now "John" also Is this possible? I guess one way would be to keep the Base b reference in Derived and override Derived.Name to point to b.Name? Is there an easier way though, for example if I have like 50 properties to override? class Derived : Base { Base b; public override string Name { get { return b.Name; } set { b.Name = value; } } public Derived(Base b) { this.b = b; } }

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• App Engine: how would you... snapshotting entities

  - by Andrew B.

  Let's say you have two kinds, Message and Contact, related by a db.ListProperty of keys on Message. A user creates a message, adds some contacts as recipients, and emails the message. Later, the user deletes one of the contact entities that was a recipient of the message. Our application should delete the appropriate Contact entity, but we want to preserve the original recipient list for the message that was sent for the user's records. In essence, we want a snapshot of the message entity at the time it was sent. If we naively delete the contact entity, though, we lose snapshot integrity; if not, we are left with an invalid key. How would you handle this situation, either in controller logic or model changes? class User(db.Model): email = db.EmailProperty(required=True) class Contact(db.Model): email = db.EmailProperty(required=True) user = db.ReferenceProperty(User, collection_name='contacts') class Message(db.Model): recipients = db.ListProperty(db.Key) # contacts sender = db.ReferenceProperty(User, collection_name='messages') body = db.TextProperty() is_emailed = db.BooleanProperty(default=False)

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• Hold border and Resize two or more DIV simultaneously in the same container

  - by Manu

  Code : <div id="widget1"> <div class="part blue">this is the part</div> <div class="part white">of the genial</div> <div class="part red">and good widget</div> </div> Let's say that div#widget1 is 99px width and div.part are 33px by default. How can I easily resize div.blue by increasing its width and deacreasing width of other div.part proportionnaly ? http://jqueryui.com/demos/resizable/#synchronous-resize : give an example which show element increase in the same time. Thanks,

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• Calculate average in each group

  - by Gokul

  I am using the following class class Country { int CountryID {get; set;} List<City> city {get; set;} } class City { int CountryID {get; set; } string city {get; set;} int sqkm {get; set;} } Here's is some sample data for Country and City Country US UK Canada City CityC CityF CityA CityB CityG CityD CityE I am populating using List<Country> countries = new List<Country> { new Country() { CountryID = "US", city = new List<City> { new City() {CountryID = "US", City ="CityF", sqkm = 2803 }, and so on Question 1: I want to use LINQ to find avg sq. km of land per country Eg: Canada - 2459 UK - 3243 US - 3564

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• How Do I Select a `td` Element in a Row That Has a Checkbox That is Checked?

  - by Russ Bradberry

  I have a table that looks somethings like this: <table> <tr class="row even"> <td><input type="checkbox" /></td> <td class="name">foo</td> <td class="metric">22</td> </tr> ...etc What I want to do is get an array of all td.metric only in rows that have the checkbox checked. This didn't work out as expected: var ticks = $.map($("tr td input:checked td.metric"), function(v,i){ return ... });

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• Can I join 2+ styles together into a superstyle?

  - by Kurru

  Hi I was looking to join 2 styles together to make a super style for easy use and customisation of my page. Is it possible to define something like this? (if so how) .bold { font-weight: bold;} .color1 {color: white;} .boldColor {.bold; .color1;} where .boldColor is effectively .boldColor {font-weight:bold; color:white;} I want this so that I can have styles thoughout the page and be able to easily change the colors in many places in 1 place. I'm currently using <p class="bold color"> but some of my class defs are becoming long so I'd like to be able to use <p class="boldColor"> Thanks

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• Should we avoid to use Object as the input parameter/ output value of a method?

  - by developer.cyrus

  Take Java syntax as an example, though the question itself is language independent. If the following snippet takes an object MyAbstractEmailTemplate as input argument in the method setTemplate, the class MyGateway will then become tightly-coupled with the object MyAbstractEmailTemplate, which lessens the re-usability of the class MyGateway. A compromise is to use dependency-injection to ease the instantiation of MyAbstractEmailTemplate. This might solve the coupling problem to some extent, but the interface is still rigid, hardly providing enough ?exibility to other developers/ applications. So if we only use primitive data type (or even plain XML in web service) as the input/ output of a method, it seems the coupling problem no longer exists. So what do you think? public class MyGateway { protected MyAbstractEmailTemplate template; publoc void setTemplate(MyAbstractEmailTemplate template) { this.template = template; } }

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• How are value types implemented in .NET

  - by Michael

  Been looking around the net and can't find any articles about how value types are actually implemented. For instance, an Int32 is a struct and it's direct parent is System.ValueType and that's ultimate parent is System.Object. Object is a class - I imagine ValueType is a class? What's the class hierarchy? What part does the CLR have to play? At what stage and how does the CLR know to allocate value types to the stack? (FYI, I am aware that value types are stored where they are declared).

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• Dynamic validation in jquery

  - by mansoor

  $(document).ready(function(){ $('a[rel=addhint]').click(function(){ var html='<div><label>Hint</label>'; html+='<span class="input"><input type="text" size="30" class="text" name="hint"/><a href="#" rel="delhint">delete</a></span><br class="clear" /></div>'; $('div#hintTextContainer').append(html); bindDelHintAll(); return false; }); I want when a new text area include vadition of required field and max length will also apply on it.

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• Sharing base object with inheritance

  - by max

  I have class Base. I'd like to extend its functionality in a class Derived. I was planning to write: class Derived(Base): def __init__(self, base_arg1, base_arg2, derived_arg1, derived_arg2): super().__init__(base_arg1, base_arg2) # ... def derived_method1(self): # ... Sometimes I already have a Base instance, and I want to create a Derived instance based on it, i.e., a Derived instance that shares the Base object (doesn't re-create it from scratch). I thought I could write a static method to do that: b = Base(arg1, arg2) # very large object, expensive to create or copy d = Derived.from_base(b, derived_arg1, derived_arg2) # reuses existing b object but it seems impossible. Either I'm missing a way to make this work, or (more likely) I'm missing a very big reason why it can't be allowed to work. Can someone explain which one it is? [Of course, if I used composition rather than inheritance, this would all be easy to do. But I was hoping to avoid the delegation of all the Base methods to Derived through __getattr__.]

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• manage date fields when are int in the db

  - by Luca Romagnoli

  Hi in my db there is a field "date_start" type integer. This is the part of form for this field <div class="editor-label"> <%: Html.LabelFor(model => model.date_start) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.date_start, new { @class = "calendar" })%> <%: Html.ValidationMessageFor(model => model.date_start) %> </div> In the form i want that the field's format is date type. and memorize it in int type after calling a my function for the convertion. How can i manage it? thanks

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