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  • any way to simplify this with a form of dynamic class instantiation?

    - by gnychis
    I have several child classes that extend a parent class, forced to have a uniform constructor. I have a queue which keeps a list of these classes, which must extend MergeHeuristic. The code that I currently have looks like the following: Class<? extends MergeHeuristic> heuristicRequest = _heuristicQueue.pop(); MergeHeuristic heuristic = null; if(heuristicRequest == AdjacentMACs.class) heuristic = new AdjacentMACs(_parent); if(heuristicRequest == SimilarInterfaceNames.class) heuristic = new SimilarInterfaceNames(_parent); if(heuristicRequest == SameMAC.class) heuristic = new SameMAC(_parent); Is there any way to simplify that to dynamically instantiate the class, something along the lines of: heuristic = new heuristicRequest.somethingSpecial(); That would flatten that block of if statements.

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  • A Reusable Builder Class for Ruby Testing

    - by Liam McLennan
    My last post was about a class for building test data objects in C#. This post describes the same tool, but implemented in Ruby. The C# version was written first but I originally came up with the solution in my head using Ruby, and then I translated it to C#. The Ruby version was easier to write and is easier to use thanks to Ruby’s dynamic nature making generics unnecessary.  Here are my example domain classes: class Person attr_accessor :name, :age def initialize(name, age) @name = name @age = age end end class Property attr_accessor :street, :manager def initialize(street, manager) @street = street @manager = manager end end and the test class showing what the builder does: class Test_Builder < Test::Unit::TestCase def setup @build = Builder.new @build.configure({ Property => lambda { Property.new '127 Creek St', @build.a(Person) }, Person => lambda { Person.new 'Liam', 26 } }) end def test_create assert_not_nil @build end def test_can_get_a_person @person = @build.a(Person) assert_not_nil @person assert_equal 'Liam', @person.name assert_equal 26, @person.age end def test_can_get_a_modified_person @person = @build.a Person do |person| person.age = 999 end assert_not_nil @person assert_equal 'Liam', @person.name assert_equal 999, @person.age end def test_can_get_a_different_type_that_depends_on_a_type_that_has_not_been_configured_yet @my_place = @build.a(Property) assert_not_nil @my_place assert_equal '127 Creek St', @my_place.street assert_equal @build.a(Person).name, @my_place.manager.name end end Finally, the implementation of Builder: class Builder # defaults is a hash of Class => creation lambda def configure defaults @defaults = defaults end def a(klass) temp = @defaults[klass].call() yield temp if block_given? temp end end

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  • Strategies for invoking subclass methods on generic objects

    - by Brad Patton
    I've run into this issue in a number of places and have solved it a bunch of different ways but looking for other solutions or opinions on how to address. The scenario is when you have a collection of objects all based off of the same superclass but you want to perform certain actions based only on instances of some of the subclasses. One contrived example of this might be an HTML document made up of elements. You could have a superclass named HTMLELement and subclasses of Headings, Paragraphs, Images, Comments, etc. To invoke a common action across all of the objects you declare a virtual method in the superclass and specific implementations in all of the subclasses. So to render the document you could loop all of the different objects in the document and call a common Render() method on each instance. It's the case where again using the same generic objects in the collection I want to perform different actions for instances of specific subclass (or set of subclasses). For example (an remember this is just an example) when iterating over the collection, elements with external links need to be downloaded (e.g. JS, CSS, images) and some might require additional parsing (JS, CSS). What's the best way to handle those special cases. Some of the strategies I've used or seen used include: Virtual methods in the base class. So in the base class you have a virtual LoadExternalContent() method that does nothing and then override it in the specific subclasses that need to implement it. The benefit being that in the calling code there is no object testing you send the same message to each object and let most of them ignore it. Two downsides that I can think of. First it can make the base class very cluttered with methods that have nothing to do with most of the hierarchy. Second it assumes all of the work can be done in the called method and doesn't handle the case where there might be additional context specific actions in the calling code (i.e. you want to do something in the UI and not the model). Have methods on the class to uniquely identify the objects. This could include methods like ClassName() which return a string with the class name or other return values like enums or booleans (IsImage()). The benefit is that the calling code can use if or switch statements to filter objects to perform class specific actions. The downside is that for every new class you need to implement these methods and can look cluttered. Also performance could be less than some of the other options. Use language features to identify objects. This includes reflection and language operators to identify the objects. For example in C# there is the is operator that returns true if the instance matches the specified class. The benefit is no additional code to implement in your object hierarchy. The only downside seems to be the lack of using something like a switch statement and the fact that your calling code is a little more cluttered. Are there other strategies I am missing? Thoughts on best approaches?

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  • Null Or Empty Coalescing

    In my last blog post, I wrote about the proper way to check for empty enumerations and proposed an IsNullOrEmpty method for collections which sparked a lot of discussion. This post covers a similar issue, but from a different angle. A very long time ago, I wrote about my love for the null coalescing operator. However, over time, Ive found it to be not quite as useful as it could be when dealing with strings. For example, heres the code I might want to write: public static void DoSomething(string...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • When tracking which elements were clicked e.target.id is sometimes empty [migrated]

    - by Ivan
    I am trying to test the following JavaScript code, which is meant to keep track of the timing of user responses on a multiple choice survey: document.onclick = function(e) { var event = e || window.event; var target = e.target || e.srcElement; //time tracking var ClickTrackDate = new Date; var ClickData = ""; ClickData = target.id + "=" + ClickTrackDate.getUTCHours() + ":" + ClickTrackDate.getUTCMinutes() + ":" + ClickTrackDate.getUTCSeconds() +";"; document.getElementById("txtTest").value += ClickData; alert(target.id); // for testing } Usually target.id equals to the the id of the clicked element, as you would expect, but sometimes target.id is empty, seemingly at random, any ideas?

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  • Battery icon constantly empty when discharging Vaio VGN-FZ210CE

    - by Alex
    I have a Sony Vaio VGN-210CE laptop, and its battery does not report the drain rate properly. In 11.10 and earlier, the battery icon would update with the percentage, not the estimated time. In 12.04 and 12.10, it estimates by time, which is always some very low value because the estimated drain rate is 700W. I currently have 89% in my battery but the icon is red and empty. If there is an application I should install, or a setting I should change, please let me know. Thanks!

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  • Checking For Empty Enumerations

    While spelunking in some code recently I saw a method that looked something like this: public void Foo<T>(IEnumerable<T> items) { if(items == null || items.Count() == 0) { // Warn about emptiness } } This method accepts a generic enumeration and then proceeds to check if the enumeration is null or empty. Do you see the potential problem with this code? Ill give you a hint, its this line: items.Count() == 0 Whats the problem? Well that line right there has the potential...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Unable to empty the rubbish bin

    - by gman
    When I attempt to empty the rubbish bin the preparing window opens but nothing happens. In testing I tried to delete 1 file from the rubbish bin and received a time-out error. No files are removed from the rubbish bin after this. I have added a screen shot that includes a display of system monitor that shows high CPU usage for trash and Nautilus; not sure whether it is related. Click for a full-resolution image. Also, on a separated note, Bleachbit was also freezing on me, which may or may not be related?

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  • Empty Synchronized method in game loop

    - by Shijima
    I am studying the gameloop used in Replica Island to understand a bit about Android game development. The main loop has the below logic... GameThread.java (note the variable names in sample code dont match exact source code) while (!finished) { if (objectManager != null) { renderer.waitDrawingComplete(); //Do more gameloop stuff after drawing is complete... } } I was curious to see what waitDrawingComplete actually does, but found its just an empty syncrhonized method! I guess it does nothing, am I missing something here? GameRenderer.java line 328 public synchronized void waitDrawingComplete() { } Source code can be checked out here with SVN if you feel like having a look: https://code.google.com/p/replicaisland/source/checkout

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  • XFCE4 Empty Volume Control Applet

    - by adamt
    I just wanted to ask, what could I mess up? My situation is this: In XFCE4.10 (!) on the panel0 I put the Indicator Applet. It always showed me the volume control and network icons. When I updated to 13.10 and after cleaned some stuff, removed some orphaned package, I noticed, the volume control applet is showing mute and if I clicked on it there is an empty drowdown menu like 10x5 px.. Now it became completely useless. So my question is WHAT should I reinstall or change to get the control work?.. :/ Thanks.

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  • Desktop empty under Ubuntu 12.04

    - by Ray
    My problem is that my desktop is empty -- there are no files or directories in it. The launcher on the left and the menu at the top are both ok. But, after a recent upgrade from 12.04 to 12.10, everything in my Desktop was emptied. I do have files in my ~/Desktop directory, which is what I want displayed. In ~/.config/user-dirs.dirs, I also have XDG_DESKTOP_DIR="$HOME/Desktop/". Is there something else I should be looking for? I actually have another Ubuntu machine and I don't have the same problem there after upgrading. So, I don't think this is a bug with 12.10 but just some setting (a package, etc.) that was set in one machine but not the other. Oh, I am not sure if this is related to nautilus, but the two machines have the same nautilus-related packages installed... Any help would be appreciated!

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  • Python class representation under the hood

    - by decentralised
    OK, here is a simple Python class: class AddSomething(object): __metaclass__ = MyMetaClass x = 10 def __init__(self, a): self.a = a def add(self, a, b): return a + b We have specified a metaclass, and that means we could write something like this: class MyMetaClass(type): def __init__(cls, name, bases, cdict): # do something with the class Now, the cdict holds a representation of AddSomething: AddSomething = type('AddSomething', (object,), {'x' : 10, '__init__': __init__, 'add': add}) So my question is simple, are all Python classes represented in this second format internally? If not, how are they represented? EDIT - Python 2.7

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  • Do first-class methods exist?

    - by gdhoward
    Okay, I know first-class functions are cool, closures even better, etc. But is there any language with first-class methods? In my mind, I see a first-class method as an "object" that has both a function pointer and a pointer to a specific instance of the class/object, but the implementation doesn't matter. I just want to know if there is any language that uses them. And as a bonus, how were they implemented?

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  • How to decide to which class does a method belong

    - by Eleeist
    I have TopicBusiness.class and PostBusiness.class. I have no problem with deciding into which class methods such as addPostToDatabase() or getAllPostsFromDatabase() should go. But what about getAllPostsFromTopic(TopicEntity topic) or getNumberOfPostsInTopic(TopicEntity topic)? Should the parameter be the deciding factor? So when the method takes TopicEntity as parameter it should belong to TopicBusiness.class? I am quite puzzled by this.

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  • java class creation dynamically and make it accessible across the network different jvms i.e. serial

    - by inj.rav
    Hi. I have a requirement of creating java classes dynamically and make it accessible different jvms across the network. I tried to use reflection and javassist tool,but nothing worked. Let me explain the scenario we are using Coherence distributed cache. It has a power of doing aggregation/filtering in parallel across the cluster. For example if a class has [dynamic class] has amount variable and getAmount/setAmount methods. Then if we execute COHERENCE queries, it will start process in parallel across the cluster. I tried to create classes at run time by using javassist and reflection. I am able to access it from single JVM, but when I tried to access the same class from other jvm [through coherence cluster]. I am getting exception of class not found [as remote jvm is not having idea of this class].I can over come this by creating same class dynamically on remote jvm also and access the methods. But coherence in built methods/functions are not able to find the class. could some one help me on this matter

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  • Database class is not correctly connecting to my database.

    - by blerh
    I'm just venturing into the world of OOP so forgive me if this is a n00bish question. This is what I have on index.php: $dbObj = new Database(); $rsObj = new RS($dbObj); This is the Database class: class Database { private $dbHost; private $dbUser; private $dbPasswd; private $dbName; private $sqlCount; function __construct() { $this->dbHost = 'localhost'; $this->dbUser = 'root'; $this->dbPasswd = ''; $this->dbName = 'whatever'; $this->sqlCount = 0; } function connect() { $this->link = mysql_connect($this->db_host, $this->db_user, $this->db_passwd); if(!$this->link) $this->error(mysql_error()); $this->selection = mysql_select_db($this->db_name, $this->link); if(!$this->selection) $this->error(mysql_error()); } } I've shortened it to just the connect() method to simplify things. This is the RS class: class RS { private $username; private $password; function __construct($dbObj) { // We need to get an account from the db $dbObj->connect(); } } As you can probably see, I need to access and use the database class in my RS class. But I get this error when I load the page: Warning: mysql_connect() [function.mysql-connect]: Access denied for user 'ODBC'@'localhost' (using password: NO) in C:\xampp\htdocs\includes\database.class.php on line 22 The thing is I have NO idea where it got the idea that it needs to use ODBC as a user... I've read up on doing this stuff and from what I can gather I am doing it correctly. Could anyone lend me a hand? Thank you.

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  • SQL SERVER – Fix: Error: Compatibility Level Drop Down is Empty

    - by Pinal Dave
    I currently have SQL Server 2012 and SQL Server 2014 both installed on the same machine. My job requires me to travel a lot and I like to travel light. Hence, I have only one computer with all the software installed in it. I can install Virtual Machines but as I was able to install SQL Server 2012 and SQL Server 2014 side by side, I just went ahead with that option. Now one day when I opened up my SQL Server 2014 and went to the properties of the my database, I realized that the dropdown box for Compatibility level is empty. I just can’t select anything there or see what is the current Compatibility level of the database. This was the first time for me so I was bit confused and I tried to search online. Upon searching online I realize that if I was not the first, there are very few questions on this subject on various forums as well as there is no convincing answer to this problem online. That means, I was pretty much first one to face this error. See the image of the situation I was facing. Now I decided to resolve this issue as soon as I can. I spent a few minutes here and there and realize my mistake. I had connected to SQL Server 2014 instance from SQL Server 2012 Management Studio. Hence, I was not able to see any compatibility related settings. Once I connected to SQL Server 2014 instance with SQL Server 2014 Management Studio – this issue was resolved. Well, simple things sometimes keep us very busy. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Unity on Ubuntu 11.10 - The Dash Home button brings up the panel, but is empty

    - by David M. Coe
    The dash home button brings up a panel that is greyed out, but it is totally empty. It seems to be the very same issue as this: Dash home button brings up blank window which is unanswered. /usr/lib/nux/unity_support_test -p returns OpenGL vendor string: X.Org R300 Project OpenGL renderer string: Gallium 0.4 on ATI RV370 OpenGL version string: 2.1 Mesa 7.11 Not software rendered: yes Not blacklisted: yes GLX fbconfig: yes GLX texture from pixmap: yes GL npot or rect textures: yes GL vertex program: yes GL fragment program: yes GL vertex buffer object: yes GL framebuffer object: yes GL version is 1.4+: yes Unity 3D supported: yes I've tried a unity --reset but that doesn't seem to work. Unity seems to reset, but I get the following warning over and over: cs space validation failed unity What should I do next to try and fix this? Edit: Attempted fixes: I've refomatted, did not work. I've done apt-get remove unity then apt-get update then apt-get install unity, did not work. I've switched to Unity 2d and this seems to work. How can I get regualar Unity working or atleast find the error?

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  • Objective C: Include class and call method

    - by Nic Hubbard
    I have built a class which has a few methods in it, once of which returns an array, lets call this class A. I have a second class, class B, which I would like to use to call the method from class A. But, now how do I call that method from class A and store what is returned in a var in class B? Do I have to initiate the class? I have made sure to include the .h file from class A into class B. Thanks for helping a newbie.

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  • How to add a method to an existing class in PHP?

    - by sombe
    I'm using WordPress as a CMS, and I want to extend one of its classes without having to inherit from another class; i.e. I simply want to "add" more methods to that class: class A { function do_a() { echo 'a'; } } then: function insert_this_function_into_class_A() { echo 'b'; } (some way of inserting the latter into A class) and: A::insert_this_function_into_class_A(); # b Is this even possible in tenacious PHP?

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  • Does java have a class that represents a timer?

    - by Eric
    I'd like a timer class that allows me to call: .start()   .getElapsedTime()   .stop()   .reset() Does Java have such a class, or do I need to use my own (which I've already written). From a best-practice point of view, I should use the Java class libraries classes if they exist, but I'm not sure whether this one does. Can anyone give me a link to the javadoc for this class, if it exists?

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  • how to make object public to all function in a class?

    - by thesocialhacker
    I've created a class that calls an object in the "__construct" how can i make this object available through out the class. class SocialMedia { function __construct() { $object = "whatever"; } } how can I access $object in the other funtions (which are static) from with in the class. I've tried to use "$this-object" but I get an error "$this when not in object context" when I try to call it from my other static functions.

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  • How to create a PeopleCode Application Package/Application Class using PeopleTools Tables

    - by Andreea Vaduva
    This article describes how - in PeopleCode (Release PeopleTools 8.50) - to enable a grid without enabling each static column, using a dynamic Application Class. The goal is to disable the following grid with three columns “Effort Date”, ”Effort Amount” and “Charge Back” , when the Check Box “Finished with task” is selected , without referencing each static column; this PeopleCode could be used dynamically with any grid. If the check box “Finished with task” is cleared, the content of the grid columns is editable (and the buttons “+” and “-“ are available): So, you create an Application Package “CLASS_EXTENSIONS” that contains an Application Class “EWK_ROWSET”. This Application Class is defined with Class extends “ Rowset” and you add two news properties “Enabled” and “Visible”: After creating this Application Class, you use it in two PeopleCode Events : Rowinit and FieldChange : This code is very ‘simple’, you write only one command : ” &ERS2.Enabled = False” → and the entire grid is “Enabled”… and you can use this code with any Grid! So, the complete PeopleCode to create the Application Package is (with explanation in [….]) : ******Package CLASS_EXTENSIONS : [Name of the Package: CLASS_EXTENSIONS] --Beginning of the declaration part------------------------------------------------------------------------------ class EWK_ROWSET extends Rowset; [Definition Class EWK_ROWSET as a subclass of Class Rowset] method EWK_ROWSET(&RS As Rowset); [Constructor is the Method with the same name of the Class] property boolean Visible get set; property boolean Enabled get set; [Definition of the property “Enabled” in read/write] private [Before the word “private”, all the declarations are publics] method SetDisplay(&DisplaySW As boolean, &PropName As string, &ChildSW As boolean); instance boolean &EnSW; instance boolean &VisSW; instance Rowset &NextChildRS; instance Row &NextRow; instance Record &NextRec; instance Field &NextFld; instance integer &RowCnt, &RecCnt, &FldCnt, &ChildRSCnt; instance integer &i, &j, &k; instance CLASS_EXTENSIONS:EWK_ROWSET &ERSChild; [For recursion] Constant &VisibleProperty = "VISIBLE"; Constant &EnabledProperty = "ENABLED"; end-class; --End of the declaration part------------------------------------------------------------------------------ method EWK_ROWSET [The Constructor] /+ &RS as Rowset +/ %Super = &RS; end-method; get Enabled /+ Returns Boolean +/; Return &EnSW; end-get; set Enabled /+ &NewValue as Boolean +/; &EnSW = &NewValue; %This.InsertEnabled=&EnSW; %This.DeleteEnabled=&EnSW; %This.SetDisplay(&EnSW, &EnabledProperty, False); [This method is called when you set this property] end-set; get Visible /+ Returns Boolean +/; Return &VisSW; end-get; set Visible /+ &NewValue as Boolean +/; &VisSW = &NewValue; %This.SetDisplay(&VisSW, &VisibleProperty, False); end-set; method SetDisplay [The most important PeopleCode Method] /+ &DisplaySW as Boolean, +/ /+ &PropName as String, +/ /+ &ChildSW as Boolean +/ [Not used in our example] &RowCnt = %This.ActiveRowCount; &NextRow = %This.GetRow(1); [To know the structure of a line ] &RecCnt = &NextRow.RecordCount; For &i = 1 To &RowCnt [Loop for each Line] &NextRow = %This.GetRow(&i); For &j = 1 To &RecCnt [Loop for each Record] &NextRec = &NextRow.GetRecord(&j); &FldCnt = &NextRec.FieldCount; For &k = 1 To &FldCnt [Loop for each Field/Record] &NextFld = &NextRec.GetField(&k); Evaluate Upper(&PropName) When = &VisibleProperty &NextFld.Visible = &DisplaySW; Break; When = &EnabledProperty; &NextFld.Enabled = &DisplaySW; [Enable each Field/Record] Break; When-Other Error "Invalid display property; Must be either VISIBLE or ENABLED" End-Evaluate; End-For; End-For; If &ChildSW = True Then [If recursion] &ChildRSCnt = &NextRow.ChildCount; For &j = 1 To &ChildRSCnt [Loop for each Rowset child] &NextChildRS = &NextRow.GetRowset(&j); &ERSChild = create CLASS_EXTENSIONS:EWK_ROWSET(&NextChildRS); &ERSChild.SetDisplay(&DisplaySW, &PropName, &ChildSW); [For each Rowset child, call Method SetDisplay with the same parameters used with the Rowset parent] End-For; End-If; End-For; end-method; ******End of the Package CLASS_EXTENSIONS:[Name of the Package: CLASS_EXTENSIONS] About the Author: Pascal Thaler joined Oracle University in 2005 where he is a Senior Instructor. His area of expertise is Oracle Peoplesoft Technology and he delivers the following courses: For Developers: PeopleTools Overview, PeopleTools I &II, Batch Application Engine, Language Oriented Object PeopleCode, Administration Security For Administrators : Server Administration & Installation, Database Upgrade & Data Management Tools For Interface Users: Integration Broker (Web Service)

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