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  • creating a vector with references to some of the elements of another vector

    - by memC
    hi, I have stored instances of class A in a std:vector, vec_A as vec_A.push_back(A(i)). The code is shown below. Now, I want to store references some of the instances of class A (in vec_A) in another vector or another array. For example, if the A.getNumber() returns 4, 7, 2 , I want to put a reference to that instance of A in another vector, say std:vector<A*> filtered_A or an array. Can someone sow me how to do this?? Thanks! class A { public: int getNumber(); A(int val); ~A(){}; private: int num; }; A::A(int val){ num = val; }; int A::getNumber(){ return num; }; int main(){ int i =0; int num; std::vector<A> vec_A; for ( i = 0; i < 10; i++){ vec_A.push_back(A(i)); } std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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  • How can I achieve this kind of relationship (inheritance, composition, something else)?

    - by Tim
    I would like to set up a foundation of classes for an application, two of which are person and student. A person may or may not be a student and a student is always a person. The fact that a student “is a” person led me to try inheritance, but I can't see how to make it work in the case where I have a DAO that returns an instance of person and I then want to determine if that person is a student and call student related methods for it. class Person { private $_firstName; public function isStudent() { // figure out if this person is a student return true; // (or false) } } class Student extends Person { private $_gpa; public function getGpa() { // do something to retrieve this student's gpa return 4.0; // (or whatever it is) } } class SomeDaoThatReturnsPersonInstances { public function find() { return new Person(); } } $myPerson = SomeDaoThatReturnsPersonInstances::find(); if($myPerson->isStudent()) { echo 'My person\'s GPA is: ', $myPerson->getGpa(); } This obviously doesn't work, but what is the best way to achieve this effect? Composition doesn't sond right in my mind because a person does not “have a” student. I'm not looking for a solution necessarily but maybe just a term or phrase to search for. Since I'm not really sure what to call what I'm trying to do, I haven't had much luck. Thank you!

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  • Implementing inotifycollectionchanged interface

    - by George
    Hello, I need to implement a collection with special capabilities. In addition, I want to bind this collection to a ListView, Therefore I ended up with the next code (I omitted some methods to make it shorter here in the forum): public class myCollection<T> : INotifyCollectionChanged { private Collection<T> collection = new Collection<T>(); public event NotifyCollectionChangedEventHandler CollectionChanged; public void Add(T item) { collection.Insert(collection.Count, item); OnCollectionChange(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item)); } protected virtual void OnCollectionChange(NotifyCollectionChangedEventArgs e) { if (CollectionChanged != null) CollectionChanged(this, e); } } I wanted to test it with a simple data class: public class Person { public string GivenName { get; set; } public string SurName { get; set; } } So I created an instance of myCollection class as follows: myCollection<Person> _PersonCollection = new myCollection<Person>(); public myCollection<Person> PersonCollection { get { return _PersonCollection; } } The problem is that the ListView does not update when the collection updates although I implemented the INotifyCollectionChanged interface. I know that my binding is fine (in XAML) because when I use the ObservableCollecion class instead of myCollecion class like this: ObservableCollection<Person> _PersonCollection = new ObservableCollection<Person>(); public ObservableCollection<Person> PersonCollection { get { return _PersonCollection; } } the ListView updates What is the problem?

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  • Saving Data to Relational Database (Entity Framework)

    - by sheefy
    I'm having a little bit of trouble saving data to a database. Basically, I have a main table that has associations to other tables (Example Below). Tbl_Listing ID UserID - Associated to ID in User Table CategoryID - Associated to ID in Category Table LevelID - Associated to ID in Level Table. Name Address Normally, it's easy for me to add data to the DB (using Entity Framework). However, I'm not sure how to add data to the fields with associations. The numerous ID fields just need to hold an int value that corresponds with the ID in the associated table. For example; when I try to access the column in the following manner I get a "Object reference not set to an instance of an object." error. Listing NewListing = new Listing(); NewListing.Tbl_User.ID = 1; NewListing.Tbl_Category.ID = 2; ... DBEntities.AddToListingSet(NewListing); DBEntities.SaveChanges(); I am using NewListing.Tbl_User.ID instead of NewListing.UserID because the UserID field is not available through intellisense. If I try and create an object for each related field I get a "The relationship between the two objects cannot be defined because they are attached to different ObjectContext objects." error. With this method, I am trying to add the object without the .ID shown above - example NewListing.User = UserObject. I know this should be simple as I just want to reference the ID from the associated table in the main Listing's table. Any help would be greatly appreciated. Thanks in advance, -S

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  • Considering moving from Java/Spring MVC to Grails

    - by MDS
    I'm currently using Java & Spring (MVC) to create a webapp, and I'm considering moving to Grails. I'd appreciate feedback/insight on the following: I have multiple application contexts in the current Java/Spring webapp that I load through the web.xml ContextLoaderListener; is it possible to have multiple application contexts in Grails? If, yes, how? This webapp extensively uses a CXF restful web service and the current Java/Spring webapp uses the bundled CXF HTTP client. Can I continue to use the (Java) CXF HTTP Client in Grails? I implemented Spring Security using a custom implementation of UserDetails and UserDetailsService, can I re-use these implementations in Grails "as is" or must I re-implement them? There is an instance where I've relied on Spring's jdbc template (rather than the available ORM) and an additional data source I defined in app context, can I re-use this in Grails? I plan on using Maven as the project management tool; are there any issues of using Maven with Grails where there is a combination of groovy and java?

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  • jquery an div tags used in a ordered list

    - by shan2on
    hello everyone, i'm not sure where my errors are lying but here is my scenario... i have an un-ordered list in html that handles my main link bar... <ul id="navlist"> <li><a href="/" id="current">home</a></li> <li><a href="#" id="search">search</a></li> <li><a href="#" id="users">login</a></li> </ul> and what i want done is to call each id and have jQuery handle each and dislpay it where specified in my css file... for now, lets just ignore my "home" link... here is a snippet of my inline jquery $(document).ready(function() { $("a").click(function () { $("div#login").slideToggle("fast"); }); }) Now, whichever div i specify, it calls that ... however it will only call one div, using either from the un-orderd list, as mentioned above in the html. My Goal is to call a search bar when search is clicked, and to call a login box when login is clicked. to my knowledge (noob), i believe use an as a class, however that is what brings me here. i believe my error is in my jquery and not my css, as stated above, either instance will be displayed when the jquery function calls either tag. any help is greatly appreciated. thanks in advance shan2on

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  • Question about singleton property

    - by Jack
    I'm reading the java tutorial for enums located here and have a question: http://java.sun.com/j2se/1.5.0/docs/guide/language/enums.html#Card The part i'm confused about is as follows: "The Card class, above, contains a static factory that returns a deck, but there is no way to get an individual card from its rank and suit. Merely exposing the constructor would destroy the singleton property (that only a single instance of each card is allowed to exist). Here is how to write a static factory that preserves the singleton property, using a nested EnumMap: " Now as I understand, changing the original private "Card" constructor to public would allow us to instantiate an unlimited number of copies of a "Card" object with a given suit+rank. The solution as proposed was to create an EnumMap which would store four Maps (one for each suit), which themselves contained 13 Card objects with the rank as their keys. And so now if you wanted to retrieve a specific Card object from the deck, you would just call the "valueOf" method. My question now is, what's the prevent you with calling the valueOf method as many times as you like? Wouldn't that lead to the same problem as making the original private constructor public? Thanks.

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  • C# Function Inheritance--Use Child Class Vars with Base Class Function

    - by Sean O'Connor
    Good day, I have a fairly simple question to experienced C# programmers. Basically, I would like to have an abstract base class that contains a function that relies on the values of child classes. I have tried code similar to the following, but the compiler complains that SomeVariable is null when SomeFunction() attempts to use it. Base class: public abstract class BaseClass { protected virtual SomeType SomeVariable; public BaseClass() { this.SomeFunction(); } protected void SomeFunction() { //DO SOMETHING WITH SomeVariable } } A child class: public class ChildClass:BaseClass { protected override SomeType SomeVariable=SomeValue; } Now I would expect that when I do: ChildClass CC=new ChildClass(); A new instance of ChildClass should be made and CC would run its inherited SomeFunction using SomeValue. However, this is not what happens. The compiler complains that SomeVariable is null in BaseClass. Is what I want to do even possible in C#? I have used other managed languages that allow me to do such things, so I certain I am just making a simple mistake here. Any help is greatly appreciated, thank you.

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  • Parsing a Multi-Index Excel File in Pandas

    - by rhaskett
    I have a time series excel file with a tri-level column MultiIndex that I would like to successfully parse if possible. There are some results on how to do this for an index on stack overflow but not the columns and the parse function has a header that does not seem to take a list of rows. The ExcelFile looks like is like the following: Column A is all the time series dates starting on A4 Column B has top_level1 (B1) mid_level1 (B2) low_level1 (B3) data (B4-B100+) Column C has null (C1) null (C2) low_level2 (C3) data (C4-C100+) Column D has null (D1) mid_level2 (D2) low_level1 (D3) data (D4-D100+) Column E has null (E1) null (E2) low_level2 (E3) data (E4-E100+) ... So there are two low_level values many mid_level values and a few top_level values but the trick is the top and mid level values are null and are assumed to be the values to the left. So, for instance all the columns above would have top_level1 as the top multi-index value. My best idea so far is to use transpose, but the it fills Unnamed: # everywhere and doesn't seem to work. In Pandas 0.13 read_csv seems to have a header parameter that can take a list, but this doesn't seem to work with parse.

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  • Error using maven profiles

    - by user3127896
    I've added two profiles to my application and that how it looks: <profiles> <profile> <id>dev</id> <properties> <db.username>root</db.username> <db.password>root</db.password> <db.connectionURL>localhost:3306</db.connectionURL> <db.driverClass>com.mysql.jdbc.Driver</db.driverClass> </properties> </profile> <profile> <id>prod</id> <properties> <db.username>prodroot</db.username> <db.password>prodpass</db.password> <db.connectionURL>localhost:3306</db.connectionURL> <db.driverClass>com.mysql.jdbc.Driver</db.driverClass> </properties> </profile> </profiles> In my jdbc.properties file i changed values like this: jdbc.driverClassName=${db.driverClass} jdbc.dialect=org.hibernate.dialect.MySQLDialect jdbc.databaseurl=jdbc:mysql://${db.connectionURL}/dbname jdbc.username=${db.username} jdbc.password=${db.password} And here's bean from spring-container.xml <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close" p:driverClassName="${jdbc.driverClassName}" p:url="${jdbc.databaseurl}" p:username="${jdbc.username}" p:password="${jdbc.password}" /> When i try to deploy my application i got following error: SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean definition with name 'dataSource' defined in ServletContext resource [/WEB-INF/spring-servlet.xml]: Could not resolve placeholder 'db.driverClass' Structure of project: Any ideas what i'm doing wrong? Thanks in advance!

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  • Python "callable" attribute (pseudo-property)

    - by mgilson
    In python, I can alter the state of an instance by directly assigning to attributes, or by making method calls which alter the state of the attributes: foo.thing = 'baz' or: foo.thing('baz') Is there a nice way to create a class which would accept both of the above forms which scales to large numbers of attributes that behave this way? (Shortly, I'll show an example of an implementation that I don't particularly like.) If you're thinking that this is a stupid API, let me know, but perhaps a more concrete example is in order. Say I have a Document class. Document could have an attribute title. However, title may want to have some state as well (font,fontsize,justification,...), but the average user might be happy enough just setting the title to a string and being done with it ... One way to accomplish this would be to: class Title(object): def __init__(self,text,font='times',size=12): self.text = text self.font = font self.size = size def __call__(self,*text,**kwargs): if(text): self.text = text[0] for k,v in kwargs.items(): setattr(self,k,v) def __str__(self): return '<title font={font}, size={size}>{text}</title>'.format(text=self.text,size=self.size,font=self.font) class Document(object): _special_attr = set(['title']) def __setattr__(self,k,v): if k in self._special_attr and hasattr(self,k): getattr(self,k)(v) else: object.__setattr__(self,k,v) def __init__(self,text="",title=""): self.title = Title(title) self.text = text def __str__(self): return str(self.title)+'<body>'+self.text+'</body>' Now I can use this as follows: doc = Document() doc.title = "Hello World" print (str(doc)) doc.title("Goodbye World",font="Helvetica") print (str(doc)) This implementation seems a little messy though (with __special_attr). Maybe that's because this is a messed up API. I'm not sure. Is there a better way to do this? Or did I leave the beaten path a little too far on this one? I realize I could use @property for this as well, but that wouldn't scale well at all if I had more than just one attribute which is to behave this way -- I'd need to write a getter and setter for each, yuck.

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  • Split a string by comma, quote and full-stop.. with a few exceptions

    - by dunc
    I've got a lot of text, similar to the following paragraph, which I'd like to split into words without punctuation (', ", ,, ., newline etc).. with a few exceptions. Initially considered endemic to the Chalakudy River system in Kerala state, southern India, but now recognised to have a wider distribution in surrounding drainages including the Periyar, Manimala, and Pamba river though the Manimala data may be questionable given it seems to be the type locality of P. denisonii. In the Achankovil River basin it occurs sympatrically, and sometimes syntopically, with P. denisonii. Wild stocks may have dwindled by as much as 50% in the last 15 years or so with collection for the aquarium trade largely held responsible although habitats are also being degraded by pollution from agricultural and domestic sources, plus destructive fishing methods involving explosives or organic toxins. The text refers to P. denisonii which is a species of fish. It's an abbreviation of Genus species. I would like this reference to be one word. So, for instance, this is the kind of array I'd like to see: Array ( ... [44] given [45] it [46] seems [47] to [48] be [49] the [50] type [51] locality [52] of [53] P. denisonii [54] In [55] the ... ) The only things that distinguish these species references such as P. denisonii from a new sentence like end. New are: The P (for Puntius, as in the P. in the aforementioned example) is only ever one letter, always a capital the d (as in . denisonii) is always either a lower case letter or an apostrophe (') What regexp can I use with preg_split to give me such an array? I've tried a simple explode( " ", $array ) but it doesn't do the job at all. Thanks in advance,

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  • UIComponent in Swc

    - by mustISignUp
    In Flash, if i create a custom Movieclip, and compile it to a SWC, i can use it in .fla files (by linking to the .swc).. var mcInstance = new CustomMovieClip(); addChild(mcInstance); All the arrangement of graphics on the custom movieClip's layers is preserved. If i subclass UIComponent and compile to a swc, I can use the custom Class in my .fla file, but the new instance doesn't seem to construct the children arranged on the layers. I know that the correct way to make a custom component is to have the two frames, first to specify bounding box, second frame for assets, and that the first graphic in frame 1 is removed at runtime. But i'm not really trying to make a reusable component - i just want to use the UIComponent class (It seems to have some nice extensions to Sprite). As i really want some hand-positioned layers inside the component i figured i could have the bounding box as the first element on frame 1 (knowing that it would be removed), but any other items i put on frame 1 would be preserved - buttons, images, lines, etc. Is this possible?

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  • 2 bucks for !! java basic question

    - by Max
    How can I get a specific value from an object? I'm trying to get a value of an instance for eg. ListOfPpl newListOfPpl = new ListOfPpl(id, name, age); Object item = newListOfPpl; How can I get a value of name from an Object item?? Even if it is easy or does not interest you can anyone help me?? Edited: I was trying to build a binary tree contains the node of ListOfPpl, and need to sort it in the lexicographic. Here's my code for insertion on the node. Any clue?? public void insert(Object item){ Node current = root; Node follow = null; if(!isEmpty()){ root = new Node(item, null, null); return; }boolean left = false, right = false; while(current != null){ follow = current; left = false; right = false; //I need to compare and sort it if(item.compareTo(current.getFighter()) < 0){ current = current.getLeft(); left = true; }else { current = current.getRight(); right = true; } }if(left) follow.setLeft(new Node(item, null, null)); else follow.setRight(new Node(item, null, null)); }

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  • Javascript object properties access functions in parent constructor?

    - by Bob Spryn
    So I'm using this pretty standard jquery plugin pattern whereby you can grab an api after applying the jquery function to a specific instance. This API is essentially a javascript object with a bunch of methods and data. So I wanted to essentially create some private internal methods for the object only to manipulate data etc, which just doesn't need to be available as part of the API. So I tried this: // API returned with new $.TranslationUI(options, container) $.TranslationUI = function (options, container) { // private function? function monkey(){ console.log("blah blah blah"); } // extend the default settings with the options object passed this.settings = $.extend({},$.TranslationUI.defaultSettings,options); // set a reference for the container dom element this.container = container; // call the init function this.init(); }; The problem I'm running into is that init can't call that function "monkey". I'm not understanding the explanation behind why it can't. Is it because init is a prototype method?($.TranslationUI's prototype is extended with a bunch of methods including init elsewhere in the code) $.extend($.TranslationUI, { prototype: { init : function(){ // doesn't work monkey(); // editing flag this.editing = false; // init event delegates here for // languagepicker $(this.settings.languageSelector, this.container).bind("click", {self: this}, this.selectLanguage); } } }); Any explanations would be helpful. Would love other thoughts on creating private methods with this model too. These particular functions don't HAVE to be in prototype, and I don't NEED private methods protected from being used externally, but I want to know how should I have that requirement in the future.

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  • How to use the values from session variables in jsp pages that got saved using @Scope("session") in the mvc controllers

    - by droidsites
    Doing a web site using spring mvc. I added a SignupController to handle all the sign up related requests. Once user signup I am adding that to a session using @Scope("session"). Below is the SignupController code, SignupController.java @Controller @Scope("session") public class SignupController { @Autowired SignupServiceInter signUpService; private static final Logger logger = Logger.getLogger(SignupController.class); private String sessionUser; @RequestMapping("/SignupService") public ModelAndView signUp(@RequestParam("userid") String userId, @RequestParam("password") String password,@RequestParam("mailid") String emailId){ logger.debug(" userId:"+userId+"::Password::"+password+"::"); String signupResult; try { signUpService.registerUser(userId, password,emailId); sessionUser = userId; //adding the sign up user to the session return new ModelAndView("userHomePage","loginResult","Success"); //Navigate to user Home page if everything goes right } catch (UserExistsException e) { signupResult = e.toString(); return new ModelAndView("signUp","loginResult", signupResult); //Navigate to signUp page back if user does not exist } } } I am using "sessionUser" variable to store the signed up User Id. My understanding is that when I use @Scope("session") for the controller all the instance variables will added to HttpSession. So by that understanding I tried to access this "SessionUser" in userHomePage.jsp as, userHomepage.jsp Welcome to <%=session.getAttribute("sessionUser")%> But it throws null. So my question is how to use the values from session variables in jsp pages that got saved using @Scope("session") in the mvc controllers. Note: My work around is that pass that signed User Id to jsp page through ModelAndView, but it seems passing the value like these among the pages takes me back to managing state among pages using QueryStrings days.

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  • getting active records to display as a plist

    - by phil swenson
    I'm trying to get a list of active record results to display as a plist for being consumed by the iphone. I'm using the plist gem v 3.0. My model is called Post. And I want Post.all (or any array or Posts) to display correctly as a Plist. I have it working fine for one Post instance: [http://pastie.org/580902][1] that is correct, what I would expect. To get that behavior I had to do this: class Post < ActiveRecord::Base def to_plist attributes.to_plist end end However, when I do a Post.all, I can't get it to display what I want. Here is what happens: http://pastie.org/580909 I get marshalling. I want output more like this: [http://pastie.org/580914][2] I suppose I could just iterate the result set and append the plist strings. But seems ugly, I'm sure there is a more elegant way to do this. I am rusty on Ruby right now, so the elegant way isn't obvious to me. Seems like I should be able to override ActiveRecord and make result-sets that pull back more than one record take the ActiveRecord::Base to_plist and make another to_plist implementation. In rails, this would go in environment.rb, right?

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  • Template access of symbol in unnamed namespace

    - by Fred Larson
    We are upgrading our XL C/C++ compiler from V8.0 to V10.1 and found some code that is now giving us an error, even though it compiled under V8.0. Here's a minimal example: test.h: #include <iostream> #include <string> template <class T> void f() { std::cout << TEST << std::endl; } test.cpp: #include <string> #include "test.h" namespace { std::string TEST = "test"; } int main() { f<int>(); return 0; } Under V10.1, we get the following error: "test.h", line 7.16: 1540-0274 (S) The name lookup for "TEST" did not find a declaration. "test.cpp", line 6.15: 1540-1303 (I) "std::string TEST" is not visible. "test.h", line 5.6: 1540-0700 (I) The previous message was produced while processing "f<int>()". "test.cpp", line 11.3: 1540-0700 (I) The previous message was produced while processing "main()". We found a similar difference between g++ 3.3.2 and 4.3.2. I also found in g++, if I move the #include "test.h" to be after the unnamed namespace declaration, the compile error goes away. So here's my question: what does the Standard say about this? When a template is instantiated, is that instance considered to be declared at the point where the template itself was declared, or is the standard not that clear on this point? I did some looking though the n2461.pdf draft, but didn't really come up with anything definitive.

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  • Is `super` local variable?

    - by Michael
    // A : Parent @implementation A -(id) init { // change self here then return it } @end A A *a = [[A alloc] init]; a. Just wondering, if self is a local variable or global? If it's local then what is the point of self = [super init] in init? I can successfully define some local variable and use like this, why would I need to assign it to self. -(id) init { id tmp = [super init]; if(tmp != nil) { //do stuff } return tmp; } b. If [super init] returns some other object instance and I have to overwrite self then I will not be able to access A's methods any more, since it will be completely new object? Am I right? c. super and self pointing to the same memory and the major difference between them is method lookup order. Am I right? sorry, don't have Mac to try, learning theory as for now...

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  • How to change the Array Element names in XmlSerialization?

    - by MSDN Geek
    Hi Guys, Consider the following code: [Serializable] public class Human { public string Name { get; set; } } Then, using (MemoryStream ms = new MemoryStream()) { Human[] mans = new Human[] { new Human() { Name = "Moim" } }; XmlSerializer xs = new XmlSerializer(typeof(Human[])); xs.Serialize(ms, mans); string s = System.Text.ASCIIEncoding.ASCII.GetString(ms.ToArray()); } At this point, the variable s will hold a value like, <?xml version="1.0"?> <ArrayOfHuman xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Human> <Name>Moim</Name> </Human> </ArrayOfHuman> Now all I need to do is, changing the xml array root element 'ArrayOfHuman' to something like 'MyFavoriteArrayRootName'. I have seen the IXmlSerializable interface but, that skips the root element name. Anybody has got any idea how to achieve this? All comments will be greatly appreciated. Best regards.

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  • What is the common way to program action listeners?

    - by Roman
    I just started to learn how to use action listeners. To my understanding it works in the following way: There are some classes which contains "addActionListener" method by default (for example classes for buttons). Using this method we add an action listener to an object. For example: listenedObject.addActionListener(listeningObject). When an action with the "listenedObject" is performed, the "actionPerformed" method of the "listeningObject" will be called. So, it means that when we program a class for the listeningObject, we need to put there "actionPerformed" method. What is not clear to me, should we create a new class for every object that we want to listen. It does not seem to me as an elegant solution. On the other hand, if we have one action listener class for all (or at least many) object, than we have a problem since a instance of this class will not know which object is calling the "actionPerformed" method (and we need to know that since actions performed by the actionPerformed differs depending on who is called for this method). In my opinion, for every listened object we need to create are "personal" action listener and we can do it by setting a specific value to the corresponding field of the action listener. But I am not sure that it is a standard way to go? How do usually people do it?

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  • Generic delegate instances

    - by Luc C
    I wonder if C# (or the underlying .NET framework) supports some kind of "generic delegate instances": that is a delegate instance that still has an unresolved type parameter, to be resolved at the time the delegate is invoked (not at the time the delegate is created). I suspect this isn't possible, but I'm asking it anyway... Here is an example of what I'd like to do, with some "???" inserted in places where the C# syntax seems to be unavailable for what I want. (Obviously this code doesn't compile) class Foo { public T Factory<T>(string name) { // implementation omitted } } class Test { public void TestMethod() { Foo foo = new Foo(); ??? magic = foo.Factory; // No type argument given here yet to Factory! // What would the '???' be here (other than 'var' :) )? string aString = magic<string>("name 1"); // type provided on call int anInt = magic<int>("name 2"); // another type provided on another call // Note the underlying calls work perfectly fine, these work, but i'd like to expose // the generic method as a delegate. string aString2 = foo.Factory<string>("name 1"); int anInt2 = foo.Factory<int>("name 2"); } } Is there a way to actually do something like this in C#? If not, is that a limitation in the language, or is it in the .NET framework?

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  • Is inheritance bad nowadays?

    - by mafutrct
    Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

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  • (Java) Get value of string loaded into dynamic-type object?

    - by Michael
    I'm very new to Java (~10 days), so my code is probably pretty bad, but here's what I've got: ArgsDataHolder argsData = new ArgsDataHolder(); // a class that holds two // ArrayList's where each element // representing key/value args Class thisArgClass; String thisArgString; Object thisArg; for(int i=2; i< argsString.length; i++) { thisToken = argsString[i]; thisArgClassString = getClassStringFromToken(thisToken).toLowerCase(); System.out.println("thisArgClassString: " + thisArgClassString); thisArgClass = getClassFromClassString(thisArgClassString); // find closing tag; concatenate middle Integer j = new Integer(i+1); thisArgString = getArgValue(argsString, j, "</" + thisArgClassString + ">"); thisArg = thisArgClass.newInstance(); thisArg = thisArgClass.valueOf(thisArgString); argsData.append(thisArg, thisArgClass); } The user basically has to input a set of key/value arguments into the command prompt in this format: <class>value</class>, e.g. <int>62</int>. Using this example, thisArgClass would be equal to Integer.class, thisArgString would be a string that read "62", and thisArg would be an instance of Integer that is equal to 62. I tried thisArg.valueOf(thisArgString), but I guess valueOf(<String>) is only a method of certain subclasses of Object. For whatever reason, I can't seem to be able to cast thisArg to thisArgClass (like so: thisArg = (thisArgClass)thisArgClass.newInstance();, at which point valueOf(<String>) should become accessible. There's got to be a nice, clean way of doing this, but it is beyond my abilities at this point. How can I get the value of the string loaded into a dynamically-typed object (Integer, Long, Float, Double, String, Character, Boolean, etc.)? Or am I just overthinking this, and Java will do the conversion for me? :confused:

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  • destructor being called by subclass

    - by zero
    I'm currently learning more about php objects and constructors/destructors, but i've noticed in my code that the parent class's destructor is being called twice, I thought it was because i was extending the first class to my second class and that the second class was calling it, but this is what the php docs say about that: Like constructors, parent destructors will not be called implicitly by the engine. In order to run a parent destructor, one would have to explicitly call parent::__destruct() in the destructor body. so if it is not being called by the subclass then is it because by extended the first class that i've made a reference to the parent class making it call itself twice or I'm I way off base here? the code: <?php class test{ public $test1 = "this is a test of a pulic property"; private $test2 = "this is a test of a private property"; protected $test3 = "this is a test of a protected property"; const hello = 900000; function __construct($h){ //echo 'this is the constructor test '.$h; } function x($x2){ echo ' this is fn x'.$x2; } function y(){ print "this is fn y"; } } $obj = new test("this is an \"arg\" sent to instance of test"); class hey extends test{ function hey(){ $this->x('<br>from the host with the most'); echo ' <br>from hey class'.$this->test3; } } $obj2 = new hey(); echo $obj2::hello; ?>

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