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  • C++: Create abstract class with abstract method and override the method in a subclass

    - by Martijn Courteaux
    Hi, How to create in C++ an abstract class with some abstract methods that I want to override in a subclass? How should the .h file look? Is there a .cpp, if so how should it look? In Java it would look like this: abstract class GameObject { public abstract void update(); public abstract void paint(Graphics g); } class Player extends GameObject { @Override public void update() { // ... } @Override public void paint(Graphics g) { // ... } } // In my game loop: for (int i = 0; i < objects.size(); i++) { objects.get(i).update(); } for (int i = 0; i < objects.size(); i++) { objects.get(i).paint(g); } Translating this code to C++ is enough for me.

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  • making html table columns optionally sortable

    - by jdamae
    I have an html table that is populated from a text file, formatted and semi colon separated. I would like the user to have the option of sorting alphabetically with either of the columns when clicking on the column name (header). How do I do this in php?? Or is there another way of doing this? Thanks for your help. Sample raw data/input looks like this: TYPE=abc;PART=georgetown;FILE=goog_abc.dat.2010122211.gz TYPE=xyz;PART=ucny;FILE=aol_xyz.dat.2010122209.gz Php code for table: $lines = preg_split('~\s*[\r\n]+\s*~', file_get_contents('/temp/tab.txt')); foreach($lines as $i => $line) { $pairs = explode(';', $line); foreach($pairs as $pair) { list($column, $value) = explode('=', $pair, 2); $columns[$column] = true; $rows[$i][$column] = $value; } } $columns = array_keys($columns); echo '<table><thead><tr>'; foreach($columns as $column) { echo '<th>'.$column.'</th>'; } echo '</tr></thead><tbody>'; foreach ($rows as $row) { echo '<tr>'; foreach($columns as $column){ echo '<td>'.$row[$column].'</td>'; } echo '</tr>'; } echo '</tbody></table>';

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  • Question of using static_cast on "this" pointer in a derived object to base class

    - by Johnyy
    Hi, this is an example taken from Effective C++ 3ed, it says that if the static_cast is used this way, the base part of the object is copied, and the call is invoked from that part. I wanted to understand what is happening under the hood, will anyone help? class Window { // base class public: virtual void onResize() { } // base onResize impl }; class SpecialWindow: public Window { // derived class public: virtual void onResize() { // derived onResize impl; static_cast<Window>(*this).onResize(); // cast *this to Window, // then call its onResize; // this doesn't work! // do SpecialWindow- } // specific stuff };

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  • How to override inner class methods if the inner class is defined as a property of the top class

    - by Maddy
    I have a code snippet like this class A(object): class b: def print_hello(self): print "Hello world" b = property(b) And I want to override the inner class b (please dont worry about the lowercase name) behaviour. Say, I want to add a new method or I want to change an existing method, like: class C(A): class b(A.b): def print_hello(self): print "Inner Class: Hello world" b = property(b) Now if I create C's object as c = C(), and call c.b I get TypeError: 'property' object is not callable error. How would I get pass this and call print_hello of the extended inner class? Disclaimer: I dont want to change the code for A class.

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  • Doing things with objects as if they were parents

    - by General Ackbar
    Sorry that this is probably a super noob question. But the following code give me an error saying that there are invalid arguments in my call of doStuffToLines(segments) shouldnt I be able to do this since I have my DimensionLineSegment inherits from Lines? private void doStuff() { List<DimensionLineSegment> segments = new List<DimensionLineSegment>(); doStuffToLines(segments); } private void doStuffToLines(List<Line> lines) { }

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  • Any way to allow classes implementing IEntity and downcast to have operator == comparisons?

    - by George Mauer
    Basically here's the issue. All entities in my system are identified by their type and their id. new Customer() { Id = 1} == new Customer() {Id = 1}; new Customer() { Id = 1} != new Customer() {Id = 2}; new Customer() { Id = 1} != new Product() {Id = 1}; Pretty standard scenario. Since all Entities have an Id I define an interface for all entities. public interface IEntity { int Id { get; set;} } And to simplify creation of entities I make public abstract class BaseEntity<T> : where T : IEntity { int Id { get; set;} public static bool operator ==(BaseEntity<T> e1, BaseEntity<T> e2) { if (object.ReferenceEquals(null, e1)) return false; return e1.Equals(e2); } public static bool operator !=(BaseEntity<T> e1, BaseEntity<T> e2) { return !(e1 == e2); } } where Customer and Product are something like public class Customer : BaseEntity<Customer>, IEntity {} public class Product : BaseEntity<Product>, IEntity {} I think this is hunky dory. I think all I have to do is override Equals in each entity (if I'm super clever, I can even override it only once in the BaseEntity) and everything with work. So now I'm expanding my test coverage and find that its not quite so simple! First of all , when downcasting to IEntity and using == the BaseEntity< override is not used. So what's the solution? Is there something else I can do? If not, this is seriously annoying. Upadate It would seem that there is something wrong with my tests - or rather with comparing on generics. Check this out [Test] public void when_created_manually_non_generic() { // PASSES! var e1 = new Terminal() {Id = 1}; var e2 = new Terminal() {Id = 1}; Assert.IsTrue(e1 == e2); } [Test] public void when_created_manually_generic() { // FAILS! GenericCompare(new Terminal() { Id = 1 }, new Terminal() { Id = 1 }); } private void GenericCompare<T>(T e1, T e2) where T : class, IEntity { Assert.IsTrue(e1 == e2); } Whats going on here? This is not as big a problem as I was afraid, but is still quite annoying and a completely unintuitive way for the language to behave. Update Update Ah I get it, the generic implicitly downcasts to IEntity for some reason. I stand by this being unintuitive and potentially problematic for my Domain's consumers as they need to remember that anything happening within a generic method or class needs to be compared with Equals()

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  • PyQt - QLabel inheriting

    - by Ockonal
    Hello, i wanna inherit QLabel to add there click event processing. I'm trying this code: class NewLabel(QtGui.QLabel): def __init__(self, parent): QtGui.QLabel.__init__(self, parent) def clickEvent(self, event): print 'Label clicked!' But after clicking I have no line 'Label clicked!' EDIT: Okay, now I'm using not 'clickEvent' but 'mousePressEvent'. And I still have a question. How can i know what exactly label was clicked? For example, i have 2 edit box and 2 labels. Labels content are pixmaps. So there aren't any text in labels, so i can't discern difference between labels. How can i do that? EDIT2: I made this code: class NewLabel(QtGui.QLabel): def __init__(self, firstLabel): QtGui.QLabel.__init__(self, firstLabel) def mousePressEvent(self, event): print 'Clicked' #myLabel = self.sender() # None =) self.emit(QtCore.SIGNAL('clicked()'), "Label pressed") In another class: self.FirstLang = NewLabel(Form) QtCore.QObject.connect(self.FirstLang, QtCore.SIGNAL('clicked()'), self.labelPressed) Slot in the same class: def labelPressed(self): print 'in labelPressed' print self.sender() But there isn't sender object in self. What i did wrong?

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  • Cannot inherit from generic base class and specific interface using same type with generic constrain

    - by simendsjo
    Sorry about the strange title. I really have no idea how to express it any better... I get an error on the following snippet. I use the class Dummy everywhere. Doesn't the compiler understand the constraint I've added on DummyImplBase? Is this a compiler bug as it works if I use Dummy directly instead of setting it as a constraint? Error 1 'ConsoleApplication53.DummyImplBase' does not implement interface member 'ConsoleApplication53.IRequired.RequiredMethod()'. 'ConsoleApplication53.RequiredBase.RequiredMethod()' cannot implement 'ConsoleApplication53.IRequired.RequiredMethod()' because it does not have the matching return type of 'ConsoleApplication53.Dummy'. C:\Documents and Settings\simen\My Documents\Visual Studio 2008\Projects\ConsoleApplication53\ConsoleApplication53\Program.cs 37 27 ConsoleApplication53 public class Dummy { } public interface IRequired<T> { T RequiredMethod(); } public interface IDummyRequired : IRequired<Dummy> { void OtherMethod(); } public class RequiredBase<T> : IRequired<T> { public T RequiredMethod() { return default(T); } } public abstract class DummyImplBase<T> : RequiredBase<T>, IDummyRequired where T: Dummy { public void OtherMethod() { } }

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  • Running single test class or group with Surefire and TestNG

    - by Slartibartfast
    I want to run single test class from command line using Maven and TestNG Things that doesn't work: mvn -Dtest=ClassName test I have defined groups in pom.xml, and this class isn't in one of those groups. So it got excluded on those grounds. mvn -Dgroups=skipped-group test mvn -Dsurefire.groups=skipped-group test when config is <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-surefire-plugin</artifactId> <version>2.7.1</version> <configuration> <groups>functest</groups> </configuration> </plugin> Parameters work fine in there are no groups defined in pom.xml. Similarly, when surefire is configured with <configuration> <includes> <include>**/*UnitTest.java</include> </includes> </configuration> I can add another test with -Dtest parameter, but cannot add group. In any combination, I can narrow down tests to be executed with groups, but not expand them. What's wrong with my configuration? Is there a way to run a single test or group outside of those defined in pom.xml? Tried on Ubuntu 10.04 with Maven 2.2.1, TestNG 5.14.6 and Surefire 2.7.1

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  • Scala: Mixing traits with private fields

    - by Vilius Normantas
    It's not much of a question, it's rather my excitement that it's possible at all! I wrote this little example just to prove the opposite - I expected either a compiler error or one of the values (111 or 222, I wasn't sure). scala> trait T1 { private val v = 111; def getValueT1 = v } scala> trait T2 { private val v = 222; def getValueT2 = v } scala> class T12 extends T1 with T2 scala> val t = new T12 scala> t.getValueT1 res9: Int = 111 scala> t.getValueT2 res10: Int = 222 Why doesn't the v get overridden? Off course this works only as long as vs are private, but still.

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  • asp.net Can I force every page to inherit from a base page? Also should some of this logic be in my master page?

    - by Bex
    Hi! I have a web app that has a base page. Each page needs to inherit from this base page as it contains properties they all need as well as dealing with the login rights. My base page has some properties, eg: IsRole1, IsRole2, currentUserID, Role1Allowed, Role2Allowed. On the init of each page I set the properties "Role1Allowed" and "Role2Allowed" Private Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init Role1Allowed = True Role2Allowed= False End Sub The basepage then decides if the user needs redirecting. 'Sample code so not exactly what is going to be, bug gives the idea Protected Overridable Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) If Role1Allowed And Not Role1 Then 'Redirect somewhere End If End Sub The page then must override this pageload if they need anything else in it, but making sure they call the base pageload first. Protected Overrides Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load MyBase.Page_Load(sender, e) If Not IsPostBack Then BindGrid() End If End Sub The other properties (IsRole1, IsRole, currentUserID) are also accessible by the page so it can be decided if certain things need doing based on the user. (I hope this makes sense) Ok so I have 2 questions Should this functionality be in the base page or should it somehow be in the master, and if so how would I get access to all the properties if it was? As there are multiple people working on this project and creating pages some are forgetting to inherit from this basepage, or call the base pageload when overriding it. Is there any way to force them to do this? Thanks for any help. bex

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  • Display: table-cell problems in chrome

    - by F21
    I have 3 divs that I would like to display as table cells: <div class="field"> <div class="row"> <label for="name">Subdomain</label> <input type="text" id="name" name="name"> <div class="subdomain-base ">test</div> </div> </div> This is the CSS that I am using: body{ font-size: 13px; } .field { width:450px; display: table; } .row { display: table-row; width: 100%; } .row > * { display: table-cell; border: 1px solid red; } label { width: 125px; height: 18px; } input { max-width: none; min-width: 0; overflow: auto; height: 18px; width: 100%; } .subdomain-base { height: 18px; width: 1px; } .subdomain-base { color: blue; font-size: 13px; } It works perfectly in Firefox 24: However, it has a height problem in Chrome 30 (latest): I have been trying all sorts of things to fix the problem with Chrome, but it seems like nothing works. Why is chrome getting that extra height? Jsfiddle: http://jsfiddle.net/ahLMH/

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  • How to manage a single-selection (exclusive) list?

    - by Andy
    I've got a detail view that consists of a table view with a few rows of data. I can fill the rows just fine, and moving back and forth from the parent view to the subview works too. This detail view should allow the user to select a single value, placing a checkmark accessory in the cell and then returning to the parent view (where the selected value becomes the cell.textLabel.text property of the cell from which the detail view was called). This all works as of right now. However, when the user taps the cell in the parent view to go back to the detail view (to change their selection), my checkmark has disappeared and I cannot for the life of me figure out how to make it stay. Here's my cellForRowAtIndexPath: method: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease]; } NSString *labelText = [[phones objectAtIndex:indexPath.row] valueForKey:@"phoneNumberLabel"]; cell.textLabel.text = labelText; NSString *currentLabel = [ruleBuilder.tableView cellForRowAtIndexPath:selectedIndexPath].textLabel.text; if (labelText == currentLabel) { cell.accessoryType = UITableViewCellAccessoryCheckmark; } NSString *detailText = [[phones objectAtIndex:indexPath.row] valueForKey:@"phoneNumber"]; cell.detailTextLabel.text = detailText; return cell; } I've checked out Apple's sample code for exclusive-list management in Table View Programming Guide, but the snippet seems incomplete, and I can't find the related code in Apple's sample code. This doesn't seem like it ought to be that hard to do.

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  • how to achieve this single line css format....

    - by metal-gear-solid
    I tried many formats but this is best to find classes and IDs easily without using "Find". but it is good if width of editor is wide. I use this tool to format my css in single line http://www.newmediacampaigns.com/files/posts/css-formatting/clean.php #wrapper {width:800px; margin:0 auto;} #header {height:100px; position:relative;} #feature .post {width:490px; float:left;} #feature .link {width:195px; display:inline; margin:0 10px 0 0;float:right;border-bottom:1px solid red} #footer {clear:both; font-size:93%; float:none;} I need like this. see selector #feature .link i need if any selector has more than 3 properties then it should go at next line like in this example.because i work in cms where width of textbox where i write cssis not much wide. Is there any tool/software can format CSS like this. or after getting single line format can we this formatting for big lines. in automated way #wrapper {width:800px; margin:0 auto;} #header {height:100px; position:relative;} #feature .post {width:490px; float:left;} #feature .link {width:195px; display:inline; margin:0 10px 0 0; float:right;bottom:1px solid red} #footer {clear:both; font-size:93%; float:none;}

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  • Issue scrolling table view with content inset

    - by Rog
    Hi all, I am experiencing a weird scrolling issue and I was hoping someone could give me a hand in trying to identify why this is happening. I have included the part of my code that I think is relevant to the question but am happy to update this post with whatever else is needed. I have implemented a pull to refresh view in the tableview's content inset area. The refresh fires an Async NSURLConnection that pulls data from a webserver, parses the relevant information and refreshes the table as required. This is where the refresh process kicks off: - (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{ if (scrollView.contentOffset.y <= - 65.0f && !self.reloading) { self.reloading = YES; [self reloadTableViewDataSource]; [refreshHeaderView setState:EGOOPullRefreshLoading]; [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.2]; self.tableView.contentInset = UIEdgeInsetsMake(60.0f, 0.0f, 0.0f, 0.0f); [UIView commitAnimations]; } } Problem is if I start to scroll whilst the content inset is "visible" (i.e. during reload) I get this weird behaviour where my table sections do not scroll all the way to the top - see screenshot for a clear visual of what I am trying to describe here. I have included a couple of screenshots below that clearly identify what is happening at the moment. Has anyone experienced this before? Any ideas on what I should be looking at to try and fix it? Many thanks in advance, Rog And this is the result if I start scrolling the table. The orange bit at the top of the image is the actual navigation bar, where I would expect the table section (date 1 December 2010) to be.

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  • Using enums or a set of classes when I know I have a finite set of different options?

    - by devoured elysium
    Let's say I have defined the following class: public abstract class Event { public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } What would you prefer between this: public class AsleepEvent : Event { public AsleepEvent(DateTime time) : base(time) { } } public class AwakeEvent : Event { public AwakeEvent(DateTime time) : base(time) { } } and this: public enum StateEventType { NowAwake, NowAsleep } public class StateEvent : Event { protected StateEventType stateType; public MealEvent(DateTime time, StateEventType stateType) : base(time) { stateType = stateType; } } and why? I am generally more inclined to the first option, but I can't explain why. Is it totally the same or are any advantages in using one instead of the other? Maybe with the first method its easier to add more "states", altough in this case I am 100% sure I will only want two states: now awake, and now asleep (they signal the moments when one awakes and one falls asleep).

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  • How to determine which inheriting class is using an abstract class's methods.

    - by Kin
    In my console application have an abstract Factory class "Listener" which contains code for listening and accepting connections, and spawning client classes. This class is inherited by two more classes (WorldListener, and MasterListener) that contain more protocol specific overrides and functions. I also have a helper class (ConsoleWrapper) which encapsulates and extends System.Console, containing methods for writing to console info on what is happening to instances of the WorldListener and MasterListener. I need a way to determine in the abstract ListenerClass which Inheriting class is calling its methods. Any help with this problem would be greatly appreciated! I am stumped :X Simplified example of what I am trying to do. abstract class Listener { public void DoSomething() { if(inheriting class == WorldListener) ConsoleWrapper.WorldWrite("Did something!"); if(inheriting class == MasterListener) ConsoleWrapper.MasterWrite("Did something!"); } } public static ConsoleWrapper { public void WorldWrite(string input) { System.Console.WriteLine("[World] {0}", input); } } public class WorldListener : Listener { public void DoSomethingSpecific() { ConsoleWrapper.WorldWrite("I did something specific!"); } } public void Main() { new WorldListener(); new MasterListener(); } Expected output [World] Did something! [World] I did something specific! [Master] Did something! [World] I did something specific!

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  • Session is null when inherit from System.Web.UI.Page

    - by Andreas K.
    I want to extend the System.Web.UI.Page-class with some extra stuff. In the ctor I need the value of a session-variable. The problem is that the Session-object is null... public class ExtendedPage : System.Web.UI.Page { protected foo; public ExtendedPage() { this.foo = (int)HttpContext.Current.Session["foo"]; // NullReferenceException } } If I move the part with the session-object into the Load-Event everything works fine... public class ExtendedPage : System.Web.UI.Page { protected foo; public ExtendedPage() { this.Load += new EventHandler(ExtendedPage_Load); } void ExtendedPage_Load(object sender, EventArgs e) { this.foo = (int)HttpContext.Current.Session["foo"]; } } Why is the Session-object null in the first case??

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  • In Java, is it possible for a super constructor invocation actually invoke a constructor in the calling class?

    - by John Assymptoth
    Super constructor invocation definition: [Primary.] [NonWildTypeArguments] super ( ArgumentListopt ) ; A super constructor call can be prefixed by an Primary expression. Example (taken from JLS): class Outer { class Inner{ } } class ChildOfInner extends Outer.Inner { ChildOfInner() { (new Outer()).super(); // (new Outer()) is the Primary } } Does a Primary expression exist that makes the call to super() the invocation of a constructor of the calling class? Or Java prevents that?

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  • Python:How to override inner class methods if the inner class is defined as a property of the top cl

    - by Maddy
    I have a code snippet like this class A(object): class b: def print_hello(self): print "Hello world" b = property(b) And I want to override the inner class 'b'(please dont worry about the lowercase name) behaviour. Say, I want to add a new method or I want to change an existing method, like: class C(A): class b(A.b): def print_hello(self): print "Inner Class: Hello world" b = property(b) Now if I create C's object as c = C(), and call c.b I get TypeError: 'property' object is not callable error. How would I get pass this and call print_hello of the extended inner class? Disclaimer: I dont want to change the code for A class.

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  • Best way to insert items from a Derived class's constructor into a Base class's private std::vector?

    - by Will
    I have these classes: class Base { ... private: std::vector<X> v; }; class Derived { Derived(X*, int n); } where the constructor of Derived is passed an array of item Xs, which I need to insert into my vector v in the Base class. (X is a smart pointer) Currently I see two ways to do this: 1) Create a function in Base: InsertItem(X*) that will insert an item into the vector. 2) Create a vector in Derived that contains the full list, then get it into Base by moving the entire vector. I dont see any advantages to #2, but was wondering if #1 was a good solution, or if there are better ways to do this. Thanks!

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  • Cant overload python socket.send

    - by ralu
    Code from socket import socket class PolySocket(socket): def __init__(self,*p): print "PolySocket init" socket.__init__(self,*p) def sendall(self,*p): print "PolySocket sendall" return socket.sendall(self,*p) def send(self,*p): print "PolySocket send" return socket.send(self,*p) def connect(self,*p): print "connecting..." socket.connect(self,*p) print "connected" HOST="stackoverflow.com" PORT=80 readbuffer="" s=PolySocket() s.connect((HOST, PORT)) s.send("a") s.sendall("a") Output: PolySocket init connecting... connected PolySocket sendall As we can see, send method is not overloaded.

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  • Using a class within another class in asp.net

    - by Phil
    In my site I have class A which selects the required page module (blog,content,gallery etc). I also have class B which provides sqlclient database objects and sql statements. If I use class B in a web form via "Imports Class B". I am able to access the contents. I now would like to use class B within class A but am struggling to find the correct syntax for importing it. Please can someone give me a basic example. We are coming from a classic asp background, and used to simply use includes. We are using VB Thanks.

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  • Make TBODY scrollable in Webkit browsers

    - by Andrew
    I'm aware of this question, but none of the answers work in Safari, Chrome, etc. The accepted strategy (as demonstrated here) is to set the tbody height and overflow properties like so: <table> <thead> <tr><th>This is the header and doesn't scroll</th></tr> </thead> <tbody style="height:100px; overflow:auto;"> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> <tr><td>content that scrolls</td></tr> </tbody> </table> Unfortunately, this does not work in any webkit browsers. There is a bug report about it that doesn't seem to be a high priority (reported June 05). So my question is: are there alternate strategies that do actually work? I've tried the two-table approach, but it's impossible to guarantee that the header will line up with the content. Do I just have to wait for Webkit to fix it?

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  • Should I use a metaclass, class decorator, or override the __new__ method?

    - by 007brendan
    Here is my problem. I want the following class to have a bunch of property attributes. I could either write them all out like foo and bar, or based on some other examples I've seen, it looks like I could use a class decorator, a metaclass, or override the __new__ method to set the properties automagically. I'm just not sure what the "right" way to do it would be. class Test(object): def calculate_attr(self, attr): # do calculaty stuff return attr @property def foo(self): return self.calculate_attr('foo') @property def bar(self): return self.calculate_attr('bar')

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