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  • How to setup the c++ rule of three in a virtual base class

    - by Minion91
    I am trying to create a pure virtual base class (or simulated pure virtual) my goal: User can't create instances of BaseClass. Derived classes have to implement default constructor, copy constructor, copy assignment operator and destructor. My attempt: class Base { public: virtual ~Base() {}; /* some pure virtual functions */ private: Base() = default; Base(const Base& base) = default; Base& operator=(const Base& base) = default; } This gives some errors complaining that (for one) the copy constructor is private. But i don't want this mimicked constructor to be called. Can anyone give me the correct construction to do this if this is at all possible?

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  • Unable to Call Instantiate in Class Member Function

    - by onguarde
    The following javascript is attached to a gameObject. var instance : GameObject; class eg_class { function eg_func(){ var thePrefab : GameObject; instance = Instantiate(thePrefab); } } Error, Unknown identifier: 'instance'. Unknown identifier: 'Instantiate'. Questions, 1) Why is it that "instance" cannot be accessed within a class? Isn't it supposed to be a public variable? 2) "Instantiate" function works in Start()/Update() root functions. Is there a way to make it work from within member functions? Thanks in advance!

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  • How do we know to favour composition over generalisation is always the right choice?

    - by Carnotaurus
    Whether an object physically exists or not, we can choose to model it in different ways. We could arbitarily use generalisation or composition in many cases. However, the GoF principle of "favour composition over generalisation [sic]" guides us to use composition. So, when we model, for example, a line then we create a class that contains two members PointA and PointB of the type Point (composition) instead of extending Point (generalisation). This is just a simplified example of how we can arbitarily choose composition or inheritance to model, despite that objects are usually much more complex. How do we know that this is the right choice? It matters at least because there could be a ton of refactoring to do if it is wrong?

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  • Google I/O 2012 - A Master Class in Map Styling

    Google I/O 2012 - A Master Class in Map Styling Scott Shawcroft, Jonah Jones Custom Styled Maps allow developers to customize the look and feel of the underlying Google Maps tiles. This makes it really easy to make a great looking map. You can tailor your map to your message, to your color scheme, or to help emphasize your data. In this class, master maps designers will help you build beautiful, elegant styles that make your maps work for you. For all I/O 2012 sessions, go to developers.google.com From: GoogleDevelopers Views: 23 0 ratings Time: 38:21 More in Science & Technology

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  • initial Class design: access modifiers and no-arg constructors

    - by yas
    Context: Student working through Class design in personal/side project for Summer. I've never written anything implemented by others or had to maintain code. Trying to maximize encapsulation and imagining what would make code easy to maintain. Concept: Tight/Loose Class design where Tight and Loose refer to access modifiers and constructors. Tight: initially, everything, including setters, is private and a no-arg constructor is not provided (only a full constructor). Loose: not Tight Exceptions: the obvious like toString Reasoning: If code, at the very beginning, is tight, then it should be guaranteed that changes, with respect to access/creation, should never damage existing implementations. The loosening of code happens incrementally and must be thought through, justified, and safe (validated). Benefit: Existing implementing code should not break if changes are made later. Cost: Takes more time to create. Since this is my own thinking, I hope to get feedback as to whether I should push to work this way. Good idea or bad idea?

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  • Deep Cloning C++ class that inherits CCNode in Cocos2dx

    - by A Devanney
    I stuck with something in Cocos2dx ... I'm trying to deep clone one of my classes that inherits CCNode. Basically i have.... GameItem* pTemp = new GameItem(*_actualItem); // loops through all the blocks in gameitem and updates their position pTemp->moveDown(); // if in boundary or collision etc... if (_gameBoard->isValidMove(pTemp)) { _actualItem = pTemp; // display the position CCLog("pos (1) --- (X : %d,Y : %d)", _actualItem->getGridX(),_actualItem->getGridY()); } Then doesn't work, because the gameitem inherits CCNode and has the collection of another class that also inherits CCNode. its just creating a shallow copy and when you look at children of the gameitem node in the copy, just point to the original? class GameItem : public CCNode { // maps to the actual grid position of the shape CCPoint* _rawPosition; // tracks the current grid position int _gridX, _gridY; // tracks the change if the item has moved CCPoint _offset; public: //constructors GameItem& operator=(const GameItem& item); GameItem(Shape shape); ... } then in the implementation.... GameItem& GameItem::operator=(const GameItem& item) { _gridX = item.getGridX(); _gridY = item.getGridY(); _offset = item.getOffSet(); _rawPosition = item.getRawPosition(); // how do i copy the node? return *this; } // shape contains an array of position for the game character GameItem::GameItem(Shape shape) { _rawPosition = shape.getShapePositions(); //loop through all blocks in position for (int i = 0; i < 7; i++) { // get the position of the first block in the shape and add to the position of the first block int x = (int) (getRawPosition()[i].x + getGridX()); int y = (int) (getRawPosition()[i].y + getGridY()); //instantiate a block with the position and type Block* block = Block::blockWithFile(x,y,(i+1), shape); // add the block to the this node this->addChild(block); } } And for clarity here is the block class class Block : public CCNode{ private: // using composition over inheritance CCSprite* _sprite; // tracks the current grid position int _gridX, _gridY; // used to store actual image number int _blockNo; public: Block(void); Block(int gridX, int gridY, int blockNo); Block& operator=(const Block& block); // static constructor for the creation of a block static Block* blockWithFile(int gridX, int gridY,int blockNo, Shape shape); ... } The blocks implementation..... Block& Block::operator=(const Block& block) { _sprite = new CCSprite(*block._sprite); _gridX = block._gridX; _gridY = block._gridY; _blockNo = block._blockNo; //again how to clone CCNode? return *this; } Block* Block::blockWithFile(int gridX, int gridY,int blockNo, Shape shape) { Block* block = new Block(); if (block && block->initBlockWithFile(gridX, gridY,blockNo, shape)) { block->autorelease(); return block; } CC_SAFE_DELETE(block); return NULL; } bool Block::initBlockWithFile(int gridX, int gridY,int blockNo, Shape shape) { setGridX(gridX); setGridY(gridY); setBlockNo(blockNo); const char* characterImg = helperFunctions::Format(shape.getFileName(),blockNo); // add to the spritesheet CCTexture2D* gameArtTexture = CCTextureCache::sharedTextureCache()->addImage("Character.pvr.ccz"); CCSpriteBatchNode::createWithTexture(gameArtTexture); // block settings _sprite = CCSprite::createWithSpriteFrameName(characterImg); // set the position of the block and add it to the layer this->setPosition(CONVERTGRIDTOACTUALPOS_X_Y(gridX,gridY)); this->addChild(_sprite); return true; } Any ideas are welcome at this point!! thanks

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  • Setting an instanced class property overwrites the property in all instances.

    - by Peter Moore
    I have two instances of a class. Setting a property in the first instance will set it for the second instance too. Why? It shouldn't. The property is not a "prototype property". Check the code below, what happens to Peter Griffin? Two objects are created and given the name "Peter Griffin" and "Roger Moore" but the alert boxes will say "Peter Moore" and "Roger Moore". What happened to Peter Griffin? var BaseClass = function(){ this.name = ""; this.data = {}; this.data.lastname = ""; } var ExtendedClass = function(){ this.setName = function(fname, lname){ this.name = fname; this.data.lastname = lname; } this.hello = function(){ alert("Full name: " + this.name + " " + this.data.lastname); } } ExtendedClass.prototype = new BaseClass(); pilot = new ExtendedClass(); driver = new ExtendedClass(); pilot.setName("Peter", "Griffin"); driver.setName("Roger", "Moore"); pilot.hello(); // Full name: Peter Moore driver.hello(); // Full name: Roger Moore

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  • Compile error on inheritance of generic inner class extending with bounds

    - by Arne Burmeister
    I have a problem when compiling a generic class with an inner class. The class extends a generic class, the inner class also. Here the interface implemented: public interface IndexIterator<Element> extends Iterator<Element> { ... } The generic super class: public abstract class CompoundCollection<Element, Part extends Collection<Element>> implements Collection<Element> { ... protected class CompoundIterator<Iter extends Iterator<Element>> extends ImmutableIterator<Element> { ... } } The generic subclass with the compiler error: public class CompoundList<Element> extends CompoundCollection<Element, List<Element>> implements List<Element> { ... private class CompoundIndexIterator extends CompoundIterator<IndexIterator<Element>> implements IndexIterator<Element> { ... } } The error is: type parameter diergo.collect.IndexIterator<Element> is not within its bound extends CompoundIterator<IndexIterator<Element>> ^ What is wrong? The code compiles with eclipse, but bot with java 5 compiler (I use ant with java 5 on a mac and eclipse 3.5). No, I cannot convert it to a static inner class.

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  • jQuery - IF then Remove class on .hover

    - by danit
    I have the following jQuery function: $(function(){ if ($(".menu li").hasClass("active")) { $(".active").css("margin-top", "6px"); } }); This is applied to a CSS/jQuery menu, which expands and contracts when each menu item is hovered over. The onClick event adds a margin-top of 6px to give the impressions of a button depress. I'm then using PHP to detect which page the user is visiting to add an .active class to the relevant menu item. The question, the .active class should remain in place until the user hovers over a different menu item. At which point the .active class should be removed from this element - As the .active class is reused on the .hover events. Here is the basic HTML Markup: <ul id="menu"> <li> <div class="inner"> <div class="button"><img src="images/insightbutton.png" /></div> <div class="description">&nbsp;</div> </div> </li> <li> <div class="inner"> <div class="button"><img src="images/insightbutton.png" /></div> <div class="description">&nbsp;</div> </div> </li> </ul> How can I keep the .active class applied to the active menu item, but remove it when .inner is hovered over?

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  • pointer-to-pointer of derived class in multiple inheritance

    - by Abdul jalil
    i have 3 classes A,B and C. C is derived from A and B. i get pointer to pointer of class C and cast to A** , and B ** , the variable that hold the the B** has the address of A** in my example B ** BdoublePtr hold the address of A** .i am using the following code #include "conio.h" #include "stdio.h" #include "string.h" class A{ public: A() { strA=new char[30]; strcpy(strA,"class A"); } char *strA; }; class B { public: B() { strB=new char[30]; strcpy(strB,"class B"); } char *strB; }; class C :public A, public B { public: C() { strC=new char[30]; strcpy(strC,"class C"); } char *strC; }; int main(void) { C* ptrC=new C(); A * Aptr=(A*)ptrC; printf("\n class A value : %s",Aptr-strA); B * Bptr=(B*)ptrC; printf("\n class B value :%s",Bptr-strB); printf("\n\nnow with double pointer "); A ** AdoublePtr=(A **)&ptrC; Aptr=AdoublePtr; printf("\n class A value : %s",Aptr-strA); B * BdoublePtr=(B **)&ptrC; Bptr=*BdoublePtr; printf("\n class B value : %s",Bptr-strB); getch(); return 0; }

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