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• Hot to get generic type from object type

  - by Murat

  My Classes are; class BaseClass { } class DerivedClass1 : BaseClass { } class GenericClass<T> { } class DerivedClass2 : BaseClass { GenericClass<DerivedClass1> subItem; } I want to access all fields of DerivedClass2 class. I use System.Reflection and FieldInfo.GetValue() method; Bu I cant get subItem field. FieldInfo.GetValue() method return type is "object". And I cant cast to GenericClass<DerivedClass1> or I cant get DerivedClass1 type. I try this with BaseClass BaseClass instance = FieldInfo.Getvalue(this) as GenericClass<BaseClass>; but instance is null. How to get instance with type or how to get only type?

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• Bad method names and what it says about code structure.

  - by maxfridbe

  (Apologies in advance if this is a re-post but I didn't find similar posts) What bad method name patterns have you seen in code and what did it tell you about the code. For instance, I keep seeing: public void preform___X___IfNecessary(...); I believe that this is bad because the operation X has an inversion of conditions. Note that this is a public method because classes methods might legitimately require private helpers like this

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• OO Objective-C design with XML parsing

  - by brainfsck

  Hi, I need to parse an XML record that represents a QuizQuestion. The "type" attribute tells the type of question. I then need to create an appropriate subclass of QuizQuestion based on the question type. The following code works ([auto]release statements omitted for clarity): QuizQuestion *question = [[QuizQuestion alloc] initWithXMLString:xml]; if( [ [question type] isEqualToString:@"multipleChoiceQuestion"] ) { [myQuestions addObject:[[MultipleChoiceQuizQuestion alloc] initWithXMLString:xml]; } //QuizQuestion.m -(id)initWithXMLString:(NSString*)xml { self.type = ...// parse "type" attribute from xml // parse the rest of the xml } //MultipleChoiceQuizQuestion.m -(id)initWithXMLString:(NSString*)xml { if( self= [super initWithXMLString:xml] ) { // multiple-choice stuff } } Of course, this means that the XML is parsed twice: once to find out the type of QuizQuestion, and once when the appropriate QuizQuestion is initialized. To prevent parsing the XML twice, I tried the following approach: // MultipleChoiceQuizQuestion.m -(id)initWithQuizRecord:(QuizQuestion*)record { self=record; // record has already parsed the "type" and other parameters // multiple-choice stuff } However, this fails due to the "self=record" assignment; whenever the MultipleChoiceQuizQuestion tries to call an instance-method, it tries to call the method on the QuizQuestion class instead. Can someone tell me the correct approach for parsing XML into the appropriate subclass when the parent class needs to be initialized to know which subclass is appropriate?

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• NHibernate MVVM Session Best Practice

  - by LnDCobra

  What is the best place to store the NHibernate session if we only need one? In the main windows view model? In the app? In the DataAccess Class?

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• how to get individual(s) for given class/individual with given object property using SPARQL

  - by udayalkonline

  hi, I have simple ontology called "campus.owl".There is a class called"Lecturer" and which has two sub classes ,RegularLecturer and VisitingLecturer.There is a another class called "Student" which is a sibling class of Lecturer class. I have created individuals for all the classes. Student class is joind with Lecture class with "has" object property. problem I want to get some Lecturer/VisitingLecturer individuals for given student individual. Could you please help me to get this result! Thanks in advance! PREFIX rdfs: http://www.w3.org/2000/01/rdf-schema# PREFIX rdf: http://www.w3.org/1999/02/22-rdf-syntax-ns# PREFIX my: http://www.semanticweb.org/ontologies/2010/5/Ontology1275975684120.owl# SELECT ?lec WHERE { ?lec..........??? } any idea..?? Thank in advance!

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• How do I dynamically name objects in Java?

  - by hatboysam

  Let's say I needed to make a series of String[] objects. I know that if i wanted to make a string array called "test" to hold 3 Strings I could do String[] test = new String[3]; But let's say I needed to make a series of these arrays and I wanted them to be named, 1,2, 3, 4, 5... etc. For however many I needed and I didn't know how many I'd need. How do I achieve a similar effect to this: for (int k=0; k=5; k++){ String[] k = new String[3]; } Which would created 5 string arrays named 1 through 5. Basically I want to be able to create array objects with a name detemined by some other function. Why can't I seem to do this? Am I just being stupid?

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• What's the standard way to organize the contents of Java packages -- specifically the location of in

  - by RenderIn

  I suppose this could go for many OO languages. I'm building my domain objects and am not sure where the best place is for the interfaces & abstract classes. If I have a pets package with various implementations of the APet abstract class: should it live side-by-side with them or in the parent package? How about interfaces? It seems like they almost have to live above the implementations in the parent package, since there could potentially be other subpackages which implement it, while there seems to be a stronger correlation between one abstract class and a subpackage. e.g. com.foo com.foo.IConsumer (interface) com.foo.APet (abstract) com.foo.pets.Dog extends APet implements IConsumer OR com.foo com.foo.IConsumer (interface) com.foo.pets.APet (abstract) com.foo.pets.Dog extends APet implements IConsumer or something else?

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• Class hierarchy problem (with generic's variance!)

  - by devoured elysium

  The problem: class StatesChain : IState, IHasStateList { private TasksChain tasks = new TasksChain(); ... public IList<IState> States { get { return _taskChain.Tasks; } } IList<ITask> IHasTasksCollection.Tasks { get { return _taskChain.Tasks; } <-- ERROR! You can't do this in C#! I want to return an IList<ITask> from an IList<IStates>. } } Assuming the IList returned will be read-only, I know that what I'm trying to achieve is safe (or is it not?). Is there any way I can accomplish what I'm trying? I wouldn't want to try to implement myself the TasksChain algorithm (again!), as it would be error prone and would lead to code duplication. Maybe I could just define an abstract Chain and then implement both TasksChain and StatesChain from there? Or maybe implementing a Chain<T> class? How would you approach this situation? The Details: I have defined an ITask interface: public interface ITask { bool Run(); ITask FailureTask { get; } } and a IState interface that inherits from ITask: public interface IState : ITask { IState FailureState { get; } } I have also defined an IHasTasksList interface: interface IHasTasksList { List<Tasks> Tasks { get; } } and an IHasStatesList: interface IHasTasksList { List<Tasks> States { get; } } Now, I have defined a TasksChain, that is a class that has some code logic that will manipulate a chain of tasks (beware that TasksChain is itself a kind of ITask!): class TasksChain : ITask, IHasTasksList { IList<ITask> tasks = new List<ITask>(); ... public List<ITask> Tasks { get { return _tasks; } } ... } I am implementing a State the following way: public class State : IState { private readonly TaskChain _taskChain = new TaskChain(); public State(Precondition precondition, Execution execution) { _taskChain.Tasks.Add(precondition); _taskChain.Tasks.Add(execution); } public bool Run() { return _taskChain.Run(); } public IState FailureState { get { return (IState)_taskChain.Tasks[0].FailureTask; } } ITask ITask.FailureTask { get { return FailureState; } } } which, as you can see, makes use of explicit interface implementations to "hide" FailureTask and instead show FailureState property. The problem comes from the fact that I also want to define a StatesChain, that inherits both from IState and IHasStateList (and that also imples ITask and IHasTaskList, implemented as explicit interfaces) and I want it to also hide IHasTaskList's Tasks and only show IHasStateList's States. (What is contained in "The problem" section should really be after this, but I thought puting it first would be way more reader friendly). (pff..long text) Thanks!

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• How do I bind a Listview SelectedItem to a Textbox using the TwoWay mode?

  - by Nick U

  I am very new to WPF and testing some things that I would like to include in an application that I will be working on. I have a 2 row ListView (bound to a textbox) with the names Scott Guthrie and Jon Skeet in it. I am trying to select "Scott Guthrie" in the ListView and have it populate the TextBox. I want to be able to edit the text and tab off and have the ListView updated. Edit:I removed the code since that really didn't add anything to the question.

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• How to document object-oriented MATLAB code?

  - by jjkparker

  I'm writing a sizable application using object-oriented MATLAB, and this has gotten me thinking about how to document the code. If this was C, I would use Doxygen. For Java, I'd use JavaDoc. Both have mostly agreed-upon standards for how class and method documentation should look and what it should contain. But what about MATLAB code? The most I've seen in TMW's own classes is a short sentence or two at the top of the class, and I can't find any topics devoted to documenting sizable MATLAB applications. So how do you document your MATLAB classes? Any particular style issues or additional tools?

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• Factor Clojure code setting many different fields in a Java object

  - by chris

  How do I factor code setting many different fields in a Java object? I would like to factor (set! (. employee name) "Chris") (set! (. employee age) 100) (set! (. employee salary) 5000) to (doseq [field '((name "Chris") (age 100) (salary 5000))] (set! (. employee (first field)) (second field))) However this won't work because the period is a macro, and tries to evaluate (first field) literally. By the way, I understand that setting fields is not good practice. I need to inter-operate with legacy code.

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• Function Object in Java .

  - by Tony

  I wanna implement a javascript like method in java , is this possible ? Say , I have a Person class : public class Person { private String name ; private int age ; // constructor ,accessors are omitted } And a list with Person objects: Person p1 = new Person("Jenny",20); Person p2 = new Person("Kate",22); List<Person> pList = Arrays.asList(new Person[] {p1,p2}); I wanna implement a method like this: modList(pList,new Operation (Person p) { incrementAge(Person p) { p.setAge(p.getAge() + 1)}; }); modList receives two params , one is a list , the other is the "Function object", it loops the list ,and apply this function to every element in the list. In functional programming language,this is easy , I don't know how java do this? Maybe could be done through dynamic proxy, does that have a performance trade off?

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• dynamic behavior of factory class

  - by manu1001

  I have a factory class that serves out a bunch of properties. Now, the properties might come either from a database or from a properties file. This is what I've come up with. public class Factory { private static final INSTANCE = new Factory(source); private Factory(DbSource source) { // read from db, save properties } private Factory(FileSource source) { // read from file, save properties } // getInstance() and getProperties() here } What's a clean way of switching between these behaviors based on the environment. I want to avoid having to recompile the class each time.

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• JSTL param implicit object

  - by srinannapa

  Hi , i'm using struts 2 and jstl. facing problem with param implicit object. Here is the test code : <% request.setAttribute ("error", "Failed"); %> <%= request.getAttribute("error") %> ----------> Prints "Failed" <c:out value="${param.error}"></c:out> ---------> Prints nothing?? Why param.error is not producing the result.

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• Order SimpleXMLElement by element

  - by ron

  Hi everyone I need to order a SimpleXMLElement by a node called padre like this. $xml = new SimpleXMLElement('sitemap.xml',null,true); sort($xml, "padre" ); foreach($xml as $url ) { echo "loc}' title='".rescue_name($url-loc)."'".rescue_name($url-loc)." {$url-padre}"; } I don't know why is not working please let me know what is my error. Thanks in advance

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• Are there any specific workflows or design patterns that are commonly used to create large functional programming applications?

  - by Andrew

  I have been exploring Clojure for a while now, although I haven't used it on any nontrivial projects. Basically, I have just been getting comfortable with the syntax and some of the idioms. Coming from an OOP background, with Clojure being the first functional language that I have looked very much into, I'm naturally not as comfortable with the functional way of doing things. That said, are there any specific workflows or design patterns that are common with creating large functional applications? I'd really like to start using functional programming "for real", but I'm afraid that with my current lack of expertise, it would result in an epic fail. The "Gang of Four" is such a standard for OO programmers, but is there anything similar that is more directed at the functional paradigm? Most of the resources that I have found have great programming nuggets, but they don't step back to give a broader, more architectural look.

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• Fatal error: Function name must be a string in.. PHP error

  - by Jonesy

  Hi I have a class called User and a method called insertUser(). function insertUser($first_name, $last_name, $user_name, $password, $email_address, $group_house_id) { $first_name = mysql_real_escape_string($first_name); $last_name = mysql_real_escape_string($last_name); $user_name = mysql_real_escape_string($user_name); $password = mysql_real_escape_string($password); $email_address = mysql_real_escape_string($email_address); $query = "INSERT INTO Users (FirstName,LastName,UserName,Password,EmailAddress, GroupHouseID) VALUES ('$first_name','$last_name','$user_name','$password','$email_address','$group_house_id')"; $mysql_query($query); } And I call it like this: $newUser = new User(); $newUser->insertUser($first_name, $last_name, $user_name, $email, $password, $group_house_id); When I run the code I get this error: Fatal error: Function name must be a string in /Library/WebServer/Documents/ORIOnline/includes/class_lib.php on line 33 Anyone know what I am doing wronly? Also, this is my first attempt at OO PHP. Cheers, Jonesy

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• add method to reflection-object and named-scopes

  - by toy

  I Like to add a method to my has_many relation in the way that it is applyed on the relation object. I got an Order wich :has_many line_items I like to write things like order.line_items.calculate_total # returns the sum of line_items this I could do with: :has_many line_items do def calculate_total ... end end but this would not be applyed to named_scopes like payalbes_only: order.line_items.payables_only.calculate_total here calculate total would receive all line_items of order and not the scoped ones from payables_only-scope. My log tells me that the paybles_only scope is even not applied to the sql.

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• When do instance variables get initialized and values assigned?

  - by AKh

  When doees the instance variable get initialized? Is it after the constructor block is done or before it? Consider this example: public abstract class Parent { public Parent(){ System.out.println("Parent Constructor"); init(); } public void init(){ System.out.println("parent Init()"); } } public class Child extends Parent { private Integer attribute1; private Integer attribute2 = null; public Child(){ super(); System.out.println("Child Constructor"); } public void init(){ System.out.println("Child init()"); super.init(); attribute1 = new Integer(100); attribute2 = new Integer(200); } public void print(){ System.out.println("attribute 1 : " +attribute1); System.out.println("attribute 2 : " +attribute2); } } public class Tester { public static void main(String[] args) { Parent c = new Child(); ((Child)c).print(); } } OUTPUT: Parent Constructor Child init() parent Init() Child Constructor attribute 1 : 100 attribute 2 : null When the memory for the atribute 1 & 2 are allocated in the heap ? Curious to know why is attribute 2 is NULL ? Are there any design flaws?

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• What is a flexible, hybrid python collection object?

  - by Naveen

  As a way to get used to python, I am trying to translate some of my code to python from Autohotkey_L. I am immediately running into tons of choices for collection objects. Can you help me figure out a built in type or a 3rd party contributed type that has as much as possible, the functionality of the AutoHotkey_L object type and its methods. AutoHotkey_L Objects have features of a python dict, list, and a class instance. I understand that there are tradeoffs for space and speed, but I am just interested in functionality rather than optimization issues.

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• Class Methods Inheritence

  - by Roman A. Taycher

  I was told that static methods in java didn't have Inheritance but when I try the following test package test1; public class Main { /** * @param args the command line arguments */ public static void main(String[] args) { TB.ttt(); TB.ttt2(); } } package test1; public class TA { static public Boolean ttt() { System.out.println("TestInheritenceA"); return true; } static public String test ="ClassA"; } package test1; public class TB extends TA{ static public void ttt2(){ System.out.println(test); } } it printed : TestInheritenceA ClassA so do java static methods (and fields have) inheritance (if you try to call a class method does it go down the inheritance chai looking for class methods). Was this ever not the case,are there any inheritance OO languages that are messed up like that for class methods?

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• Why won't Ubuntu copy large files to FAT32 flash Drives?

  - by yurividal

  Since I installed 11.10 I am unable to copy large files (say 1gb or more) to ANY usb drive that is formated as FAT. The file starts copying, but soon an error appears, saying "Unable to Copy" . "Error splicing file: Input/output error". I am able to do it via terminal, using the cp command. I use Gnome3, but the same error has happened in Unity as well. Apparently it works if I format the USB drive as NTFS or EXT3, EXT4. But, for many appliances, FAT is necessary. The problem is also not with the USB port, because it works under Windows. It did not happen before, when I had 10.04 installed.

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• Which Large File System Format to use for USB Flash drive compatible with Ubuntu/Mac/Windows?

  - by wajiw

  I've had this problem for a long time and can't find a solution. I switch between the 3 OSes all the time and use a 1TB USB Drive to do so. I can't seem to find a format that is compatible across all systems that handles large files (at least 8-9 GB). Does anyone have a solution for this? Recently I've tried exFat but that messes up the filesystem when trying to read on windows after adding files from Ubuntu (using the fuse driver). The OSes currently I'm using are Windows Vista/7, Mac OS X (10.6.5) and Ubuntu 10.10

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• Java synchronized method lock on object, or method?

  - by wuntee

  If I have 2 synchronized methods in the same class, but each accessing different variables, can 2 threads access those 2 methods at the same time? Does the lock occur on the object, or does it get as specific as the variables inside the synchronized method? Example: class x{ private int a; private int b; public synchronized void addA(){ a++; } public synchronized void addB(){ b++; } } Can 2 threads access the same instance of class x performing x.addA() and x.addB() at the same time?

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• Accessing a Class Member from a First-Class Function

  - by dbyrne

  I have a case class which takes a list of functions: case class A(q:Double, r:Double, s:Double, l:List[(Double)=>Double]) I have over 20 functions defined. Some of these functions have their own parameters, and some of them also use the q, r, and s values from the case class. Two examples are: def f1(w:Double) = (d:Double) => math.sin(d) * w def f2(w:Double, q:Double) = (d:Double) => d * q * w The problem is that I then need to reference q, r, and s twice when instantiating the case class: A(0.5, 1.0, 2.0, List(f1(3.0), f2(4.0, 0.5))) //0.5 is referenced twice I would like to be able to instantiate the class like this: A(0.5, 1.0, 2.0, List(f1(3.0), f2(4.0))) //f2 already knows about q! What is the best technique to accomplish this? Can I define my functions in a trait that the case class extends? EDIT: The real world application has 7 members, not 3. Only a small number of the functions need access to the members. Most of the functions don't care about them.

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