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  • C# Different class objects in one list

    - by jeah_wicer
    I have looked around some now to find a solution to this problem. I found several ways that could solve it but to be honest I didn't realize which of the ways that would be considered the "right" C# or OOP way of solving it. My goal is not only to solve the problems but also to develop a good set of code standards and I'm fairly sure there's a standard way to handle this problem. Let's say I have 2 types of printer hardwares with their respective classes and ways of communicating: PrinterType1, PrinterType2. I would also like to be able to later on add another type if neccessary. One step up in abstraction those have much in common. It should be possible to send a string to each one of them as an example. They both have variables in common and variables unique to each class. (One for instance communicates via COM-port and has such an object, while the other one communicates via TCP and has such an object). I would however like to just implement a List of all those printers and be able to go through the list and perform things as "Send(string message)" on all Printers regardless of type. I would also like to access variables like "PrinterList[0].Name" that are the same for both objects, however I would also at some places like to access data that is specific to the object itself (For instance in the settings window of the application where the COM-port name is set for one object and the IP/port number for another). So, in short something like: In common: Name Send() Specific to PrinterType1: Port Specific to PrinterType2: IP And I wish to, for instance, do Send() on all objects regardless of type and the number of objects present. I've read about polymorphism, Generics, interfaces and such, but I would like to know how this, in my eyes basic, problem typically would be dealt with in C# (and/or OOP in general). I actually did try to make a base class, but it didn't quite seem right to me. For instance I have no use of a "string Send(string Message)" function in the base class itself. So why would I define one there that needs to be overridden in the derived classes when I would never use the function in the base class ever in the first place? I'm really thankful for any answers. People around here seem very knowledgeable and this place has provided me with many solutions earlier. Now I finally have an account to answer and vote with too. EDIT: To additionally explain, I would also like to be able to access the objects of the actual printertype. For instance the Port variable in PrinterType1 which is a SerialPort object. I would like to access it like: PrinterList[0].Port.Open() and have access to the full range of functionality of the underlaying port. At the same time I would like to call generic functions that work in the same way for the different objects (but with different implementations): foreach (printer in Printers) printer.Send(message)

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  • showDialog in Activity not displaying dialog

    - by Mohit Deshpande
    Here is my code: public class TasksList extends ListActivity { ... private static final int COLUMNS_DIALOG = 7; private static final int ORDER_DIALOG = 8; ... /** * @see android.app.Activity#onCreateDialog(int) */ @Override protected Dialog onCreateDialog(int id) { Dialog dialog; final String[] columns; Cursor c = managedQuery(Tasks.CONTENT_URI, null, null, null, null); columns = c.getColumnNames(); final String[] order = { "Ascending", "Descending" }; switch (id) { case COLUMNS_DIALOG: AlertDialog.Builder columnDialog = new AlertDialog.Builder(this); columnDialog.setSingleChoiceItems(columns, -1, new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { bundle.putString("column", columns[which]); } }); dialog = columnDialog.create(); case ORDER_DIALOG: AlertDialog.Builder orderDialog = new AlertDialog.Builder(this); orderDialog.setSingleChoiceItems(order, -1, new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { String orderS; if (order[which].equalsIgnoreCase("Ascending")) orderS = "ASC"; else orderS = "DESC"; bundle.putString("order", orderS); } }); dialog = orderDialog.create(); default: dialog = null; } return dialog; } /** * @see android.app.Activity#onOptionsItemSelected(android.view.MenuItem) */ @Override public boolean onOptionsItemSelected(MenuItem item) { switch (item.getItemId()) { case SORT_MENU: showDialog(COLUMNS_DIALOG); showDialog(ORDER_DIALOG); String orderBy = bundle.getString("column") + bundle.getString("order"); Cursor tasks = managedQuery(Tasks.CONTENT_URI, projection, null, null, orderBy); adapter = new TasksAdapter(this, tasks); getListView().setAdapter(adapter); break; case FILTER_MENU: break; } return false; } The showDialog doesn't display the dialog. I used the Debugger and it does executes these statements, but the dialog doesn't show. }

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  • Container of Generic Types in java

    - by Cyker
    I have a generic class Foo<T> and parameterized types Foo<String> and Foo<Integer>. Now I want to put different parameterized types into a single ArrayList. What is the correct way of doing this? Candidate 1: public class MMM { public static void main(String[] args) { Foo<String> fooString = new Foo<String>(); Foo<Integer> fooInteger = new Foo<Integer>(); ArrayList<Foo<?> > list = new ArrayList<Foo<?> >(); list.add(fooString); list.add(fooInteger); for (Foo<?> foo : list) { // Do something on foo. } } } class Foo<T> {} Candidate 2: public class MMM { public static void main(String[] args) { Foo<String> fooString = new Foo<String>(); Foo<Integer> fooInteger = new Foo<Integer>(); ArrayList<Foo> list = new ArrayList<Foo>(); list.add(fooString); list.add(fooInteger); for (Foo foo : list) { // Do something on foo. } } } class Foo<T> {} In a word, it is related to the difference between Foo<?> and the raw type Foo. Update: Grep What is the difference between the unbounded wildcard parameterized type and the raw type? on this link may be helpful.

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  • Grails problem with nullable contraint in domain class

    - by xain
    Hi, I'm having the following problem with grails' 1.2.1 domain classes: When I set a constraint attr(nullable:true) and attr is int or bool, this condition isn't reflected in the db (postgresql 8.4). However, if attr is a String, the DB is consistent with the situation. Any hints ? Thanks

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  • meaning of import statement in java file

    - by Rozer
    Can any one clear me exactly what happend when we do import statement in java files. does it inscrease the size of file if we add more and more java classes. why we dont use classloader for the same and what are the restrictin for importing.

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  • When should I implement IDisposeable?

    - by Bobby
    What is the best practice for when to implement IDisposeable? Is the best rule of thumb to implement it if you have one managed object in the class, or does it depend if the object was created in the class or just passed in? Should I also do it for classes with no managed objects at all?

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  • C++ shared objects

    - by Klaus
    Hello, I have got four classes A, B, C and D. Class A has a member b of class B. Class B has a member c of class C. A has a member D* dpointer; This hierarchy has to be preserved (in fact this is a GUI with app, window, panel as A, B and C). Now B and C must use a method from *dpointer. Is there something more elegant than giving dpointer as a member of B and C ? Is it bad ?

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  • What will be the OOP approach? (or YOUR approach?)

    - by hsmit
    I'm having difficulties with some general OOP & Java approach. There are various ways to let classes/objects communicate with each other. To give a simple example: I need object A to perform action X. Object A needs P, Q and R to perform this action X. Will then Object A retrieve P, Q and R by itself (within action X), or must these values be parameters for action X?

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  • [Castle-DynamicProxy] What really interceptors do with my c# class?

    - by Pandiya Chendur
    I was asked to implement castle dynamic proxy in my asp.net web application and i was going through couple of articles which i got from Castle Project and Code Project about castle dynamic proxy in asp.net web application.... Both articles delt with creating interceptors but i can't get the idea why interceptors are used with classes.... Why should i intercept my class which is behaving properly?

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  • In .NET Xml Serialization, is it possible to serialize a class with an enum property with different

    - by Lasse V. Karlsen
    I have a class, containing a list property, where the list contains objects that has an enum property. When I serialize this, it looks like this: <?xml version="1.0" encoding="ibm850"?> <test> <events> <test-event type="changing" /> <test-event type="changed" /> </events> </test> Is it possible, through attributes, or similar, to get the Xml to look like this? <?xml version="1.0" encoding="ibm850"?> <test> <events> <changing /> <changed /> </events> </test> Basically, use the property value of the enum as a way to determine the tag-name? Is using a class hierarchy (ie. creating subclasses instead of using the property value) the only way? Edit: After testing, it seems even a class-hierarchy won't actually work. If there is a way to structure the classes to get the output I want, even with sub-classes, that is also an acceptable answer. Here's a sample program that will output the above Xml (remember to hit Ctrl+F5 to run in Visual Studio, otherwise the program window will close immediately): using System; using System.Collections.Generic; using System.Xml.Serialization; namespace ConsoleApplication18 { public enum TestEventTypes { [XmlEnum("changing")] Changing, [XmlEnum("changed")] Changed } [XmlType("test-event")] public class TestEvent { [XmlAttribute("type")] public TestEventTypes Type { get; set; } } [XmlType("test")] public class Test { private List<TestEvent> _Events = new List<TestEvent>(); [XmlArray("events")] public List<TestEvent> Events { get { return _Events; } } } class Program { static void Main(string[] args) { Test test = new Test(); test.Events.Add(new TestEvent { Type = TestEventTypes.Changing }); test.Events.Add(new TestEvent { Type = TestEventTypes.Changed }); XmlSerializer serializer = new XmlSerializer(typeof(Test)); XmlSerializerNamespaces ns = new XmlSerializerNamespaces(); ns.Add("", ""); serializer.Serialize(Console.Out, test, ns); } } }

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  • Calling an Overridden Method from a Parent-Class Constructor

    - by Vaibhav Bajpai
    I tried calling an overridden method from a constructor of a parent class and noticed different behavior across languages. C++ - echoes A.foo() class A{ public: A(){foo();} virtual void foo(){cout<<"A.foo()";} }; class B : public A{ public: B(){} void foo(){cout<<"B.foo()";} }; int main(){ B *b = new B(); } Java - echoes B.foo() class A{ public A(){foo();} public void foo(){System.out.println("A.foo()");} } class B extends A{ public void foo(){System.out.println("B.foo()");} } class Demo{ public static void main(String args[]){ B b = new B(); } } C# - echoes B.foo() class A{ public A(){foo();} public virtual void foo(){Console.WriteLine("A.foo()");} } class B : A{ public override void foo(){Console.WriteLine("B.foo()");} } class MainClass { public static void Main (string[] args) { B b = new B(); } } I realize that in C++ objects are created from top-most parent going down the hierarchy, so when the constructor calls the overridden method, B does not even exist, so it calls the A' version of the method. However, I am not sure why I am getting different behavior in Java and C#.

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  • Implementing prototypes OR instantiating class objects

    - by intuited
    I'm wondering how to implement prototypal inheritance in Python. It seems like the way to do this would be to either use a metaclass to cause instantiations to actually be classes, rather than objects, or use some magical powers to transform an existing object into a class. The second method would seem to be more flexible, in that it could be applied to existing objects of varied types, while the first would likely be more convenient for typical use cases. Insights on the practicality of these two approaches, as well as alternative suggestions, are hereby requested.

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  • JQuery/AJAX: Loading external DIVs using dynamic content

    - by ticallian
    I need to create a page that will load divs from an external page using Jquery and AJAX. I have come across a few good tutorials, but they are all based on static content, my links and content are generated by PHP. The main tutorial I am basing my code on is from: http://yensdesign.com/2008/12/how-to-load-content-via-ajax-in-jquery/ The exact function i need is as follows: Main page contains a permanent div listing some links containing a parameter. Upon click, link passes parameter to external page. External page filters recordset against parameter and populates div with results. The new div contains a new set of links with new parameters. The external div is loaded underneath the main pages first div. Process can then be repeated creating a chain of divs under each other. The last div in the chain will then direct to a new page collating all the previously used querystrings. I can handle all of the PHP work with populating the divs on the main and external pages. It's the JQuery and AJAX part i'm struggling with. $(document).ready(function(){ var sections = $('a[id^=link_]'); // Link that passes parameter to external page var content = $('div[id^=content_]'); // Where external div is loaded to sections.click(function(){ //load selected section switch(this.id){ case "div01": content.load("external.php?param=1 #section_div01"); break; case "div02": content.load("external.php?param=2 #section_div02"); break; } }); The problem I am having is getting JQuery to pass the dynamically generated parameters to the external page and then retrieve the new div. I can currently only do this with static links (As above).

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  • Do I Need To Reference Indirect DLLs

    - by ChloeRadshaw
    Suppose I have DLLA which is a standalone library that contains classes I use I have DLLB that references DLLA I now have DLLC that references DLLB - Why is it that DLLC also needs a reference to DLLA? Can I not have VS2005 build a dll which contains all the assemblies it needs embedded inside it?

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  • Dispose, when is it called?

    - by Snake
    Consider the following code: namespace DisposeTest { using System; class Program { static void Main(string[] args) { Console.WriteLine("Calling Test"); Test(); Console.WriteLine("Call to Test done"); } static void Test() { DisposeImplementation di = new DisposeImplementation(); } } internal class DisposeImplementation : IDisposable { ~DisposeImplementation() { Console.WriteLine("~ in DisposeImplementation instance called"); } public void Dispose() { Console.WriteLine("Dispose in DisposeImplementation instance called"); } } } The Dispose just never get's called, even if I put a wait loop after the Test(); invocation. So that quite sucks. I want to write a class that is straightforward and very easy to use, to make sure that every possible resource is cleaned up. I don't want to put that responsibilty to the user of my class. Possible solution: use using, or call Dispose myself(basicly the same). Can I force the user to use a using? Or can I force the dispose to be called? Calling GC.Collect(); after Test(); doesn't work either. Putting di to null doesn't invoke Dispose either. The Deconstructor DOES work, so the object get's deconstructed when it exits Test()

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  • out of memory error , my app's fault?

    - by arnold
    hello all, i have a aplication on the android market , in wich exceptions and errors are catched and sent to me by acra. But i receive quite a lot out of memory errors.. In different kind of classes...some my app, some general java.. Does this always mean there is a problem in my app, or can it also be the phone ran out of memory due to a other process? Will users also get a fc dialog ? thnks

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