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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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  • 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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  • Need to set mailx variable to specify the From address

    - by user256817
    Running Oracle Linux 5.8 (which is just re-branded RedHat EL 5.8) I must change the From address. But we have scripts that use mailx which cannot be re-written to use any extra flags, so I'd like to use internal variables instead, which I see on the linux.die.net manpage on mailx is an alternative to the -r flag: -r address Sets the From address. Overrides any from variable specified in environment or startup files. Tilde escapes are disabled. The -r address options are passed to the mail transfer agent unless SMTP is used. This option exists for compatibility only; it is recommended to set the from variable directly instead. (Source: http://linux.die.net/man/1/mailx) How can we use these mailx variables? I tried adding this to /root/.mailrc, no go: set [email protected] I also added that to /etc/mail.rc with no gold. So I am turning to you, SuperUsers...

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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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  • Puppet templates and undefined/nil variables

    - by larsks
    I often want to include default values in Puppet templates. I was hoping that given a class like this: class myclass ($a_variable=undef) { file { '/tmp/myfile': content => template('myclass/myfile.erb'), } } I could make a template like this: a_variable = <%= a_variable || "a default value" %> Unfortunately, undef in Puppet doesn't translate to a Ruby nil value in the context of the template, so this doesn't actually work. What is the canonical way of handling default values in Puppet templates? I can set the default value to an empty string and then use the empty? test... a variable = <%= a_variable.empty? ? "a default value" : a_variable %> ...but that seems a little clunky.

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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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  • Setting Environment Variable for nginx and Rails consumption

    - by kolrie
    Apache's module mod_env offers a handy way of setting environment variables in configuration files, like: <VirtualHost *:80> ServerName xyz.com DocumentRoot /var/www/rails_app/public PassengerAppRoot /var/www/rails_app SetEnv MY_VARIABLE contents </VirtualHost> http://httpd.apache.org/docs/2.0/mod/mod_env.html#setenv However, in nginx I couldn't find anything that serves the same purpose. What's the alternative here? I thought of setting environment variables in .profile files (I am using Ubuntu 10.04), but that wouldn't have the same "per vHost" isolation I have with Apache, right? What are the alternatives here?

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  • Do ALL your variables need to be declared private? [closed]

    - by skizeey
    Possible Duplicate: Why do we need private variables? I know that it's best practice to stay safe, and that we should always prevent others from directly accessing a class' properties. I hear this all the time from university professors, and I also see this all the time in a lot of source code released on the App Hub. In fact, professors say that they will actually take marks off for every variable that gets declared public. Now, this leaves me always declaring variables as private. No matter what. Even if each of these variables were to have both a getter and a setter. But here's the problem: it's tedious work. I tend to quickly lose interest in a project every time I need to have a variable in a class that could have simply been declared public instead of private with a getter and a setter. So my question is, do I really need to declare all my variables private? Or could I declare some variables public whenever they require both a getter and a setter?

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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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  • Do ALL your variables need to be declared private?

    - by shovonr
    I know that it's best practice to stay safe, and that we should always prevent others from directly accessing a class' properties. I hear this all the time from university professors, and I also see this all the time in a lot of source code released on the App Hub. In fact, professors say that they will actually take marks off for every variable that gets declared public. Now, this leaves me always declaring variables as private. No matter what. Even if each of these variables were to have both a getter and a setter. But here's the problem: it's tedious work. I tend to quickly loose interest in a project every time I need to have a variable in a class that could have simply been declared public instead of private with a getter and a setter. So my question is, do I really need to declare all my variables private? Or could I declare some variables public whenever they require both a getter and a setter?

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  • Where should you store variables for a search program in java?

    - by Bored915
    I'm wondering which is a more effective storage method in java. Would be better to save variables that will not change in a class or a resource? They're going to be variables that contain a set amount so that later a search program will go through the list of variables so as to recognize possible options. Also if there is a more efficient method of storing them please say so or if i doesn't matter where i store them.

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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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