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• A self-creator: What pattern is this? php

  - by user151841

  I have several classes that are basically interfaces to database rows. Since the class assumes that a row already exists ( __construct expects a field value ), there is a public static function that allows creation of the row and returns an instance of the class. Here's a pseudo-code example : class fruit { public $id; public function __construct( $id ) { $this->id = $id; $sql = "SELECT * FROM Fruits WHERE id = $id"; ... $this->arrFieldValues[$field] = $row[$value]; } public function __get( $var ) { return $this->arrFieldValues[$var]; } public function __set( $var, $val ) { $sql = "UPDATE fruits SET $var = $val WHERE id = $this->id"; } public static function create( $id ) { $sql = "INSERT INTO Fruits ( fruit_name ) VALUE ( '$fruit' )"; $id = mysql_insert_id(); $fruit = & new fruit($id); return $fruit; } } $obj1 = fruit::create( "apple" ); $obj2 = & new fruit( 12 ); What is this pattern called? Edit: I changed the example to one that has more database-interface functionality. For most of the time, this kind of class would be instantiated normally, through __construct(). But sometimes when you need to create a new row first, you would call create().

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• Need free c# 4 learning resources and tutorials

  - by myax

  hi, i want to learn c# programming language.i already know c++(console only) programming.i have downloaded visual c# express 2010 .Which free resources would you recommend me to learn c# and dot net 4.0 ?

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• should a student be diversifying or mastering programming languages?

  - by Max Link

  As the question states, is it better if a student diversifies or explores when learning programming languages or should they focus only on 2-3 languages and really get to know them well? Example of what I mean by diversifying: Functional -> Scheme Procedural -> C Object Oriented -> Java Dynamic or scripting -> Python Other -> C++ I have a few breaks in between semesters sometimes (up to 3 months) and I'm thinking of either learning a new language or "master" those that I know right now. Which would benefit me in the future? I know some(about 3 months of self studying each) Java, C, and C++ already . If I'm not mistaken, where I live, the industry is heavy on Java, C++, and C#.

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• Change value of adjacent vertices and remove self loop

  - by StereoMatching

  Try to write a Karger’s algorithm with boost::graph example (first column is vertice, other are adjacent vertices): 1 2 3 2 1 3 4 3 1 2 4 4 2 3 assume I merge 2 to 1, I get the result 1 2 3 2 1 1 3 4 2 1 3 4 3 1 2 4 4 2 3 first question : How could I change the adjacent vertices("2" to "1") of vertice 1? my naive solution template<typename Vertex, typename Graph> void change_adjacent_vertices_value(Vertex input, Vertex value, Graph &g) { for (auto it = boost::adjacent_vertices(input, g); it.first != it.second; ++it.first){ if(*it.first == value){ *(it.first) = input; //error C2106: '=' : left operand must be l-value } } } Apparently, I can't set the value of the adjacent vertices to "1" by this way The result I want after "change_adjacent_vertices_value" 1 1 3 1 1 1 3 4 2 1 3 4 3 1 2 4 4 2 3 second question : How could I pop out the adjacent vertices? Assume I want to pop out the consecutive 1 from the vertice 1 The result I expected 1 1 3 1 3 4 2 1 3 4 3 1 2 4 4 2 3 any function like "pop_adjacent_vertex" could use?

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• Learning Python Basics

  - by StaticExtasy

  So I'm trying to learn python better and i've been using this website http://www.learnpython.org/ I'm on to functions right now, heres the code #Add your functions here (before the existing functions) def list_benefits(): myList = ['More organized code','More readable code','Easier code reuse','Allowing programmers to share and connect code together'] return myList def build_sentence(info): addMe = " is a benefit of functions!" for i in info: meInfo = i + addMe return meInfo def name_the_benefits_of_functions(): list_of_benefits = list_benefits() for benefit in list_of_benefits: print build_sentence(benefit) name_the_benefits_of_functions() the output being e is a benefit of functions! e is a benefit of functions! e is a benefit of functions! r is a benefit of functions! What am i missing to return the whole scentence

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• How to Make a Game like Space Invaders - Ray Wenderlich (why do my space invaders scroll off screen)

  - by Erv Noel

  I'm following this tutorial(http://www.raywenderlich.com/51068/how-to-make-a-game-like-space-invaders-with-sprite-kit-tutorial-part-1) and I've run into a problem right after the part where I add [self determineInvaderMovementDirection]; to my GameScene.m file (specifically to my moveInvadersForUpdate method) The tutorial states that the space invaders should be moving accordingly after adding this piece of code but when I run they move to the left and they do not come back. I'm not sure what I am doing wrong as I have followed this tutorial very carefully. Any help or clarification would be greatly appreciated. Thanks in advance ! Here is the full GameScene.m #import "GameScene.h" #import <CoreMotion/CoreMotion.h> #pragma mark - Custom Type Definitions /* The type definition and constant definitions 1,2,3 take care of the following tasks: 1.Define the possible types of invader enemies. This can be used in switch statements later when things like displaying different sprites images for each enemy type. The typedef makes InvaderType a formal Obj-C type that is type checked for method arguments and variables.This is so that the wrong method argument is not used or assigned to the wrong variable. 2. Define the size of the invaders and that they'll be laid out in a grid of rows and columns on the screen. 3. Define a name that will be used to identify invaders when searching for them. */ //1 typedef enum InvaderType { InvaderTypeA, InvaderTypeB, InvaderTypeC } InvaderType; /* Invaders move in a fixed pattern: right, right, down, left, down, right right. InvaderMovementDirection tracks the invaders' progress through this pattern */ typedef enum InvaderMovementDirection { InvaderMovementDirectionRight, InvaderMovementDirectionLeft, InvaderMovementDirectionDownThenRight, InvaderMovementDirectionDownThenLeft, InvaderMovementDirectionNone } InvaderMovementDirection; //2 #define kInvaderSize CGSizeMake(24,16) #define kInvaderGridSpacing CGSizeMake(12,12) #define kInvaderRowCount 6 #define kInvaderColCount 6 //3 #define kInvaderName @"invader" #define kShipSize CGSizeMake(30, 16) //stores the size of the ship #define kShipName @"ship" // stores the name of the ship stored on the sprite node #define kScoreHudName @"scoreHud" #define kHealthHudName @"healthHud" /* this class extension allows you to add “private” properties to GameScene class, without revealing the properties to other classes or code. You still get the benefit of using Objective-C properties, but your GameScene state is stored internally and can’t be modified by other external classes. As well, it doesn’t clutter the namespace of datatypes that your other classes see. This class extension is used in the method didMoveToView */ #pragma mark - Private GameScene Properties @interface GameScene () @property BOOL contentCreated; @property InvaderMovementDirection invaderMovementDirection; @property NSTimeInterval timeOfLastMove; @property NSTimeInterval timePerMove; @end @implementation GameScene #pragma mark Object Lifecycle Management #pragma mark - Scene Setup and Content Creation /*This method simply invokes createContent using the BOOL property contentCreated to make sure you don’t create your scene’s content more than once. This property is defined in an Objective-C Class Extension found near the top of the file()*/ - (void)didMoveToView:(SKView *)view { if (!self.contentCreated) { [self createContent]; self.contentCreated = YES; } } - (void)createContent { //1 - Invaders begin by moving to the right self.invaderMovementDirection = InvaderMovementDirectionRight; //2 - Invaders take 1 sec for each move. Each step left, right or down // takes 1 second. self.timePerMove = 1.0; //3 - Invaders haven't moved yet, so set the time to zero self.timeOfLastMove = 0.0; [self setupInvaders]; [self setupShip]; [self setupHud]; } /* Creates an invade sprite of a given type 1. Use the invadeType parameterr to determine color of the invader 2. Call spriteNodeWithColor:size: of SKSpriteNode to alloc and init a sprite that renders as a rect of the given color invaderColor with size kInvaderSize */ -(SKNode*)makeInvaderOfType:(InvaderType)invaderType { //1 SKColor* invaderColor; switch (invaderType) { case InvaderTypeA: invaderColor = [SKColor redColor]; break; case InvaderTypeB: invaderColor = [SKColor greenColor]; break; case InvaderTypeC: invaderColor = [SKColor blueColor]; break; } //2 SKSpriteNode* invader = [SKSpriteNode spriteNodeWithColor:invaderColor size:kInvaderSize]; invader.name = kInvaderName; return invader; } -(void)setupInvaders { //1 - loop over the rows CGPoint baseOrigin = CGPointMake(kInvaderSize.width / 2, 180); for (NSUInteger row = 0; row < kInvaderRowCount; ++row) { //2 - Choose a single InvaderType for all invaders // in this row based on the row number InvaderType invaderType; if (row % 3 == 0) invaderType = InvaderTypeA; else if (row % 3 == 1) invaderType = InvaderTypeB; else invaderType = InvaderTypeC; //3 - Does some math to figure out where the first invader // in the row should be positioned CGPoint invaderPosition = CGPointMake(baseOrigin.x, row * (kInvaderGridSpacing.height + kInvaderSize.height) + baseOrigin.y); //4 - Loop over the columns for (NSUInteger col = 0; col < kInvaderColCount; ++col) { //5 - Create an invader for the current row and column and add it // to the scene SKNode* invader = [self makeInvaderOfType:invaderType]; invader.position = invaderPosition; [self addChild:invader]; //6 - update the invaderPosition so that it's correct for the //next invader invaderPosition.x += kInvaderSize.width + kInvaderGridSpacing.width; } } } -(void)setupShip { //1 - creates ship using makeShip. makeShip can easily be used later // to create another ship (ex. to set up more lives) SKNode* ship = [self makeShip]; //2 - Places the ship on the screen. In SpriteKit the origin is at the lower //left corner of the screen. The anchorPoint is based on a unit square with (0, 0) at the lower left of the sprite's area and (1, 1) at its top right. Since SKSpriteNode has a default anchorPoint of (0.5, 0.5), i.e., its center, the ship's position is the position of its center. Positioning the ship at kShipSize.height/2.0f means that half of the ship's height will protrude below its position and half above. If you check the math, you'll see that the ship's bottom aligns exactly with the bottom of the scene. ship.position = CGPointMake(self.size.width / 2.0f, kShipSize.height/2.0f); [self addChild:ship]; } -(SKNode*)makeShip { SKNode* ship = [SKSpriteNode spriteNodeWithColor:[SKColor greenColor] size:kShipSize]; ship.name = kShipName; return ship; } -(void)setupHud { //Sets the score label font to Courier SKLabelNode* scoreLabel = [SKLabelNode labelNodeWithFontNamed:@"Courier"]; //1 - Give the score label a name so it becomes easy to find later when // the score needs to be updated. scoreLabel.name = kScoreHudName; scoreLabel.fontSize = 15; //2 - Color the score label green scoreLabel.fontColor = [SKColor greenColor]; scoreLabel.text = [NSString stringWithFormat:@"Score: %04u", 0]; //3 - Positions the score label near the top left corner of the screen scoreLabel.position = CGPointMake(20 + scoreLabel.frame.size.width/2, self.size.height - (20 + scoreLabel.frame.size.height/2)); [self addChild:scoreLabel]; //Applies the font of the health label SKLabelNode* healthLabel = [SKLabelNode labelNodeWithFontNamed:@"Courier"]; //4 - Give the health label a name so it can be referenced later when it needs // to be updated to display the health healthLabel.name = kHealthHudName; healthLabel.fontSize = 15; //5 - Colors the health label red healthLabel.fontColor = [SKColor redColor]; healthLabel.text = [NSString stringWithFormat:@"Health: %.1f%%", 100.0f]; //6 - Positions the health Label on the upper right hand side of the screen healthLabel.position = CGPointMake(self.size.width - healthLabel.frame.size.width/2 - 20, self.size.height - (20 + healthLabel.frame.size.height/2)); [self addChild:healthLabel]; } #pragma mark - Scene Update - (void)update:(NSTimeInterval)currentTime { //Makes the invaders move [self moveInvadersForUpdate:currentTime]; } #pragma mark - Scene Update Helpers //This method will get invoked by update -(void)moveInvadersForUpdate:(NSTimeInterval)currentTime { //1 - if it's not yet time to move, exit the method. moveInvadersForUpdate: // is invoked 60 times per second, but you don't want the invaders to move // that often since the movement would be too fast to see if (currentTime - self.timeOfLastMove < self.timePerMove) return; //2 - Recall that the scene holds all the invaders as child nodes; which were // added to the scene using addChild: in setupInvaders identifying each invader // by its name property. Invoking enumerateChildNodesWithName:usingBlock only loops over the invaders because they're named kInvaderType; which makes the loop skip the ship and the HUD. The guts og the block moves the invaders 10 pixels either right, left or down depending on the value of invaderMovementDirection [self enumerateChildNodesWithName:kInvaderName usingBlock:^(SKNode *node, BOOL *stop) { switch (self.invaderMovementDirection) { case InvaderMovementDirectionRight: node.position = CGPointMake(node.position.x - 10, node.position.y); break; case InvaderMovementDirectionLeft: node.position = CGPointMake(node.position.x - 10, node.position.y); break; case InvaderMovementDirectionDownThenLeft: case InvaderMovementDirectionDownThenRight: node.position = CGPointMake(node.position.x, node.position.y - 10); break; InvaderMovementDirectionNone: default: break; } }]; //3 - Record that you just moved the invaders, so that the next time this method is invoked (1/60th of a second from when it starts), the invaders won't move again until the set time period of one second has elapsed. self.timeOfLastMove = currentTime; //Makes it so that the invader movement direction changes only when the invaders are actually moving. Invaders only move when the check on self.timeOfLastMove passes (when conditional expression is true) [self determineInvaderMovementDirection]; } #pragma mark - Invader Movement Helpers -(void)determineInvaderMovementDirection { //1 - Since local vars accessed by block are default const(means they cannot be changed), this snippet of code qualifies proposedMovementDirection with __block so that you can modify it in //2 __block InvaderMovementDirection proposedMovementDirection = self.invaderMovementDirection; //2 - Loops over the invaders in the scene and refers to the block with the invader as an argument [self enumerateChildNodesWithName:kInvaderName usingBlock:^(SKNode *node, BOOL *stop) { switch (self.invaderMovementDirection) { case InvaderMovementDirectionRight: //3 - If the invader's right edge is within 1pt of the right edge of the scene, it's about to move offscreen. Sets proposedMovementDirection so that the invaders move down then left. You compare the invader's frame(the frame that contains its content in the scene's coordinate system) with the scene width. Since the scene has an anchorPoint of (0,0) by default and is scaled to fill it's parent view, this comparison ensures you're testing against the view's edges. if (CGRectGetMaxX(node.frame) >= node.scene.size.width - 1.0f) { proposedMovementDirection = InvaderMovementDirectionDownThenLeft; *stop = YES; } break; case InvaderMovementDirectionLeft: //4 - If the invader's left edge is within 1 pt of the left edge of the scene, it's about to move offscreen. Sets the proposedMovementDirection so invaders move down then right if (CGRectGetMinX(node.frame) <= 1.0f) { proposedMovementDirection = InvaderMovementDirectionDownThenRight; *stop = YES; } break; case InvaderMovementDirectionDownThenLeft: //5 - If invaders are moving down then left, they already moved down at this point, so they should now move left. proposedMovementDirection = InvaderMovementDirectionLeft; *stop = YES; break; case InvaderMovementDirectionDownThenRight: //6 - if the invaders are moving down then right, they already moved down so they should now move right. proposedMovementDirection = InvaderMovementDirectionRight; *stop = YES; break; default: break; } }]; //7 - if the proposed invader movement direction is different than the current invader movement direction, update the current direction to the proposed direction if (proposedMovementDirection != self.invaderMovementDirection) { self.invaderMovementDirection = proposedMovementDirection; } } #pragma mark - Bullet Helpers #pragma mark - User Tap Helpers #pragma mark - HUD Helpers #pragma mark - Physics Contact Helpers #pragma mark - Game End Helpers @end

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• Custom Gesture in cocos2d

  - by Lewis

  I've found a little tutorial that would be useful for my game: http://blog.mellenthin.de/archives/2012/02/13/an-one-finger-rotation-gesture-recognizer/ But I can't work out how to convert that gesture to work with cocos2d, I have found examples of pre made gestures in cocos2d, but no custom ones, is it possible? EDIT STILL HAVING PROBLEMS WITH THIS: I've added the code from Sentinel below (from SO), the Gesture and RotateGesture have both been added to my solution and are compiling. Although In the rotation class now I only see selectors, how do I set those up? As the custom gesture found in that project above looks like: header file for custom gesture: #import <Foundation/Foundation.h> #import <UIKit/UIGestureRecognizerSubclass.h> @protocol OneFingerRotationGestureRecognizerDelegate <NSObject> @optional - (void) rotation: (CGFloat) angle; - (void) finalAngle: (CGFloat) angle; @end @interface OneFingerRotationGestureRecognizer : UIGestureRecognizer { CGPoint midPoint; CGFloat innerRadius; CGFloat outerRadius; CGFloat cumulatedAngle; id <OneFingerRotationGestureRecognizerDelegate> target; } - (id) initWithMidPoint: (CGPoint) midPoint innerRadius: (CGFloat) innerRadius outerRadius: (CGFloat) outerRadius target: (id) target; - (void)reset; - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event; - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event; - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event; - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event; @end .m for custom gesture file: #include <math.h> #import "OneFingerRotationGestureRecognizer.h" @implementation OneFingerRotationGestureRecognizer // private helper functions CGFloat distanceBetweenPoints(CGPoint point1, CGPoint point2); CGFloat angleBetweenLinesInDegrees(CGPoint beginLineA, CGPoint endLineA, CGPoint beginLineB, CGPoint endLineB); - (id) initWithMidPoint: (CGPoint) _midPoint innerRadius: (CGFloat) _innerRadius outerRadius: (CGFloat) _outerRadius target: (id <OneFingerRotationGestureRecognizerDelegate>) _target { if ((self = [super initWithTarget: _target action: nil])) { midPoint = _midPoint; innerRadius = _innerRadius; outerRadius = _outerRadius; target = _target; } return self; } /** Calculates the distance between point1 and point 2. */ CGFloat distanceBetweenPoints(CGPoint point1, CGPoint point2) { CGFloat dx = point1.x - point2.x; CGFloat dy = point1.y - point2.y; return sqrt(dx*dx + dy*dy); } CGFloat angleBetweenLinesInDegrees(CGPoint beginLineA, CGPoint endLineA, CGPoint beginLineB, CGPoint endLineB) { CGFloat a = endLineA.x - beginLineA.x; CGFloat b = endLineA.y - beginLineA.y; CGFloat c = endLineB.x - beginLineB.x; CGFloat d = endLineB.y - beginLineB.y; CGFloat atanA = atan2(a, b); CGFloat atanB = atan2(c, d); // convert radiants to degrees return (atanA - atanB) * 180 / M_PI; } #pragma mark - UIGestureRecognizer implementation - (void)reset { [super reset]; cumulatedAngle = 0; } - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesBegan:touches withEvent:event]; if ([touches count] != 1) { self.state = UIGestureRecognizerStateFailed; return; } } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesMoved:touches withEvent:event]; if (self.state == UIGestureRecognizerStateFailed) return; CGPoint nowPoint = [[touches anyObject] locationInView: self.view]; CGPoint prevPoint = [[touches anyObject] previousLocationInView: self.view]; // make sure the new point is within the area CGFloat distance = distanceBetweenPoints(midPoint, nowPoint); if ( innerRadius <= distance && distance <= outerRadius) { // calculate rotation angle between two points CGFloat angle = angleBetweenLinesInDegrees(midPoint, prevPoint, midPoint, nowPoint); // fix value, if the 12 o'clock position is between prevPoint and nowPoint if (angle > 180) { angle -= 360; } else if (angle < -180) { angle += 360; } // sum up single steps cumulatedAngle += angle; // call delegate if ([target respondsToSelector: @selector(rotation:)]) { [target rotation:angle]; } } else { // finger moved outside the area self.state = UIGestureRecognizerStateFailed; } } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesEnded:touches withEvent:event]; if (self.state == UIGestureRecognizerStatePossible) { self.state = UIGestureRecognizerStateRecognized; if ([target respondsToSelector: @selector(finalAngle:)]) { [target finalAngle:cumulatedAngle]; } } else { self.state = UIGestureRecognizerStateFailed; } cumulatedAngle = 0; } - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesCancelled:touches withEvent:event]; self.state = UIGestureRecognizerStateFailed; cumulatedAngle = 0; } @end Then its initialised like this: // calculate center and radius of the control CGPoint midPoint = CGPointMake(image.frame.origin.x + image.frame.size.width / 2, image.frame.origin.y + image.frame.size.height / 2); CGFloat outRadius = image.frame.size.width / 2; // outRadius / 3 is arbitrary, just choose something >> 0 to avoid strange // effects when touching the control near of it's center gestureRecognizer = [[OneFingerRotationGestureRecognizer alloc] initWithMidPoint: midPoint innerRadius: outRadius / 3 outerRadius: outRadius target: self]; [self.view addGestureRecognizer: gestureRecognizer]; The selector below is also in the same file where the initialisation of the gestureRecogonizer: - (void) rotation: (CGFloat) angle { // calculate rotation angle imageAngle += angle; if (imageAngle > 360) imageAngle -= 360; else if (imageAngle < -360) imageAngle += 360; // rotate image and update text field image.transform = CGAffineTransformMakeRotation(imageAngle * M_PI / 180); [self updateTextDisplay]; } I can't seem to get this working in the RotateGesture class can anyone help me please I've been stuck on this for days now. SECOND EDIT: Here is the users code from SO that was suggested to me: Here is projec on GitHub: SFGestureRecognizers It uses builded in iOS UIGestureRecognizer, and don't needs to be integrated into cocos2d sources. Using it, You can make any gestures, just like you could, if you whould work with UIGestureRecognizer. For example: I made a base class Gesture, and subclassed it for any new gesture: //Gesture.h @interface Gesture : NSObject <UIGestureRecognizerDelegate> { UIGestureRecognizer *gestureRecognizer; id delegate; SEL preSolveSelector; SEL possibleSelector; SEL beganSelector; SEL changedSelector; SEL endedSelector; SEL cancelledSelector; SEL failedSelector; BOOL preSolveAvailable; CCNode *owner; } - (id)init; - (void)addGestureRecognizerToNode:(CCNode*)node; - (void)removeGestureRecognizerFromNode:(CCNode*)node; -(void)recognizer:(UIGestureRecognizer*)recognizer; @end //Gesture.m #import "Gesture.h" @implementation Gesture - (id)init { if (!(self = [super init])) return self; preSolveAvailable = YES; return self; } - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer { return YES; } - (BOOL)gestureRecognizer:(UIGestureRecognizer *)recognizer shouldReceiveTouch:(UITouch *)touch { //! For swipe gesture recognizer we want it to be executed only if it occurs on the main layer, not any of the subnodes ( main layer is higher in hierarchy than children so it will be receiving touch by default ) if ([recognizer class] == [UISwipeGestureRecognizer class]) { CGPoint pt = [touch locationInView:touch.view]; pt = [[CCDirector sharedDirector] convertToGL:pt]; for (CCNode *child in owner.children) { if ([child isNodeInTreeTouched:pt]) { return NO; } } } return YES; } - (void)addGestureRecognizerToNode:(CCNode*)node { [node addGestureRecognizer:gestureRecognizer]; owner = node; } - (void)removeGestureRecognizerFromNode:(CCNode*)node { [node removeGestureRecognizer:gestureRecognizer]; } #pragma mark - Private methods -(void)recognizer:(UIGestureRecognizer*)recognizer { CCNode *node = recognizer.node; if (preSolveSelector && preSolveAvailable) { preSolveAvailable = NO; [delegate performSelector:preSolveSelector withObject:recognizer withObject:node]; } UIGestureRecognizerState state = [recognizer state]; if (state == UIGestureRecognizerStatePossible && possibleSelector) { [delegate performSelector:possibleSelector withObject:recognizer withObject:node]; } else if (state == UIGestureRecognizerStateBegan && beganSelector) [delegate performSelector:beganSelector withObject:recognizer withObject:node]; else if (state == UIGestureRecognizerStateChanged && changedSelector) [delegate performSelector:changedSelector withObject:recognizer withObject:node]; else if (state == UIGestureRecognizerStateEnded && endedSelector) { preSolveAvailable = YES; [delegate performSelector:endedSelector withObject:recognizer withObject:node]; } else if (state == UIGestureRecognizerStateCancelled && cancelledSelector) { preSolveAvailable = YES; [delegate performSelector:cancelledSelector withObject:recognizer withObject:node]; } else if (state == UIGestureRecognizerStateFailed && failedSelector) { preSolveAvailable = YES; [delegate performSelector:failedSelector withObject:recognizer withObject:node]; } } @end Subclass example: //RotateGesture.h #import "Gesture.h" @interface RotateGesture : Gesture - (id)initWithTarget:(id)target preSolveSelector:(SEL)preSolve possibleSelector:(SEL)possible beganSelector:(SEL)began changedSelector:(SEL)changed endedSelector:(SEL)ended cancelledSelector:(SEL)cancelled failedSelector:(SEL)failed; @end //RotateGesture.m #import "RotateGesture.h" @implementation RotateGesture - (id)initWithTarget:(id)target preSolveSelector:(SEL)preSolve possibleSelector:(SEL)possible beganSelector:(SEL)began changedSelector:(SEL)changed endedSelector:(SEL)ended cancelledSelector:(SEL)cancelled failedSelector:(SEL)failed { if (!(self = [super init])) return self; preSolveSelector = preSolve; delegate = target; possibleSelector = possible; beganSelector = began; changedSelector = changed; endedSelector = ended; cancelledSelector = cancelled; failedSelector = failed; gestureRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(recognizer:)]; gestureRecognizer.delegate = self; return self; } @end Use example: - (void)addRotateGesture { RotateGesture *rotateRecognizer = [[RotateGesture alloc] initWithTarget:self preSolveSelector:@selector(rotateGesturePreSolveWithRecognizer:node:) possibleSelector:nil beganSelector:@selector(rotateGestureStateBeganWithRecognizer:node:) changedSelector:@selector(rotateGestureStateChangedWithRecognizer:node:) endedSelector:@selector(rotateGestureStateEndedWithRecognizer:node:) cancelledSelector:@selector(rotateGestureStateCancelledWithRecognizer:node:) failedSelector:@selector(rotateGestureStateFailedWithRecognizer:node:)]; [rotateRecognizer addGestureRecognizerToNode:movableAreaSprite]; } I dont understand how to implement the custom gesture code at the start of this post into the rotateGesture class which is a subclass of the gesture class written by the SO user. Any ideas please? When I get 6 more rep I'll add a bounty to this.

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• Problems with real-valued input deep belief networks (of RBMs)

  - by Junier

  I am trying to recreate the results reported in Reducing the dimensionality of data with neural networks of autoencoding the olivetti face dataset with an adapted version of the MNIST digits matlab code, but am having some difficulty. It seems that no matter how much tweaking I do on the number of epochs, rates, or momentum the stacked RBMs are entering the fine-tuning stage with a large amount of error and consequently fail to improve much at the fine-tuning stage. I am also experiencing a similar problem on another real-valued dataset. For the first layer I am using a RBM with a smaller learning rate (as described in the paper) and with negdata = poshidstates*vishid' + repmat(visbiases,numcases,1); I'm fairly confident I am following the instructions found in the supporting material but I cannot achieve the correct errors. Is there something I am missing? See the code I'm using for real-valued visible unit RBMs below, and for the whole deep training. The rest of the code can be found here. rbmvislinear.m: epsilonw = 0.001; % Learning rate for weights epsilonvb = 0.001; % Learning rate for biases of visible units epsilonhb = 0.001; % Learning rate for biases of hidden units weightcost = 0.0002; initialmomentum = 0.5; finalmomentum = 0.9; [numcases numdims numbatches]=size(batchdata); if restart ==1, restart=0; epoch=1; % Initializing symmetric weights and biases. vishid = 0.1*randn(numdims, numhid); hidbiases = zeros(1,numhid); visbiases = zeros(1,numdims); poshidprobs = zeros(numcases,numhid); neghidprobs = zeros(numcases,numhid); posprods = zeros(numdims,numhid); negprods = zeros(numdims,numhid); vishidinc = zeros(numdims,numhid); hidbiasinc = zeros(1,numhid); visbiasinc = zeros(1,numdims); sigmainc = zeros(1,numhid); batchposhidprobs=zeros(numcases,numhid,numbatches); end for epoch = epoch:maxepoch, fprintf(1,'epoch %d\r',epoch); errsum=0; for batch = 1:numbatches, if (mod(batch,100)==0) fprintf(1,' %d ',batch); end %%%%%%%%% START POSITIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% data = batchdata(:,:,batch); poshidprobs = 1./(1 + exp(-data*vishid - repmat(hidbiases,numcases,1))); batchposhidprobs(:,:,batch)=poshidprobs; posprods = data' * poshidprobs; poshidact = sum(poshidprobs); posvisact = sum(data); %%%%%%%%% END OF POSITIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% poshidstates = poshidprobs > rand(numcases,numhid); %%%%%%%%% START NEGATIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% negdata = poshidstates*vishid' + repmat(visbiases,numcases,1);% + randn(numcases,numdims) if not using mean neghidprobs = 1./(1 + exp(-negdata*vishid - repmat(hidbiases,numcases,1))); negprods = negdata'*neghidprobs; neghidact = sum(neghidprobs); negvisact = sum(negdata); %%%%%%%%% END OF NEGATIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% err= sum(sum( (data-negdata).^2 )); errsum = err + errsum; if epoch>5, momentum=finalmomentum; else momentum=initialmomentum; end; %%%%%%%%% UPDATE WEIGHTS AND BIASES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% vishidinc = momentum*vishidinc + ... epsilonw*( (posprods-negprods)/numcases - weightcost*vishid); visbiasinc = momentum*visbiasinc + (epsilonvb/numcases)*(posvisact-negvisact); hidbiasinc = momentum*hidbiasinc + (epsilonhb/numcases)*(poshidact-neghidact); vishid = vishid + vishidinc; visbiases = visbiases + visbiasinc; hidbiases = hidbiases + hidbiasinc; %%%%%%%%%%%%%%%% END OF UPDATES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% end fprintf(1, '\nepoch %4i error %f \n', epoch, errsum); end dofacedeepauto.m: clear all close all maxepoch=200; %In the Science paper we use maxepoch=50, but it works just fine. numhid=2000; numpen=1000; numpen2=500; numopen=30; fprintf(1,'Pretraining a deep autoencoder. \n'); fprintf(1,'The Science paper used 50 epochs. This uses %3i \n', maxepoch); load fdata %makeFaceData; [numcases numdims numbatches]=size(batchdata); fprintf(1,'Pretraining Layer 1 with RBM: %d-%d \n',numdims,numhid); restart=1; rbmvislinear; hidrecbiases=hidbiases; save mnistvh vishid hidrecbiases visbiases; maxepoch=50; fprintf(1,'\nPretraining Layer 2 with RBM: %d-%d \n',numhid,numpen); batchdata=batchposhidprobs; numhid=numpen; restart=1; rbm; hidpen=vishid; penrecbiases=hidbiases; hidgenbiases=visbiases; save mnisthp hidpen penrecbiases hidgenbiases; fprintf(1,'\nPretraining Layer 3 with RBM: %d-%d \n',numpen,numpen2); batchdata=batchposhidprobs; numhid=numpen2; restart=1; rbm; hidpen2=vishid; penrecbiases2=hidbiases; hidgenbiases2=visbiases; save mnisthp2 hidpen2 penrecbiases2 hidgenbiases2; fprintf(1,'\nPretraining Layer 4 with RBM: %d-%d \n',numpen2,numopen); batchdata=batchposhidprobs; numhid=numopen; restart=1; rbmhidlinear; hidtop=vishid; toprecbiases=hidbiases; topgenbiases=visbiases; save mnistpo hidtop toprecbiases topgenbiases; backpropface; Thanks for your time

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• Problems with real-valued deep belief networks (of RBMs)

  - by Junier

  I am trying to recreate the results reported in Reducing the dimensionality of data with neural networks of autoencoding the olivetti face dataset with an adapted version of the MNIST digits matlab code, but am having some difficulty. It seems that no matter how much tweaking I do on the number of epochs, rates, or momentum the stacked RBMs are entering the fine-tuning stage with a large amount of error and consequently fail to improve much at the fine-tuning stage. I am also experiencing a similar problem on another real-valued dataset. For the first layer I am using a RBM with a smaller learning rate (as described in the paper) and with negdata = poshidstates*vishid' + repmat(visbiases,numcases,1); I'm fairly confident I am following the instructions found in the supporting material but I cannot achieve the correct errors. Is there something I am missing? See the code I'm using for real-valued visible unit RBMs below, and for the whole deep training. The rest of the code can be found here. rbmvislinear.m: epsilonw = 0.001; % Learning rate for weights epsilonvb = 0.001; % Learning rate for biases of visible units epsilonhb = 0.001; % Learning rate for biases of hidden units weightcost = 0.0002; initialmomentum = 0.5; finalmomentum = 0.9; [numcases numdims numbatches]=size(batchdata); if restart ==1, restart=0; epoch=1; % Initializing symmetric weights and biases. vishid = 0.1*randn(numdims, numhid); hidbiases = zeros(1,numhid); visbiases = zeros(1,numdims); poshidprobs = zeros(numcases,numhid); neghidprobs = zeros(numcases,numhid); posprods = zeros(numdims,numhid); negprods = zeros(numdims,numhid); vishidinc = zeros(numdims,numhid); hidbiasinc = zeros(1,numhid); visbiasinc = zeros(1,numdims); sigmainc = zeros(1,numhid); batchposhidprobs=zeros(numcases,numhid,numbatches); end for epoch = epoch:maxepoch, fprintf(1,'epoch %d\r',epoch); errsum=0; for batch = 1:numbatches, if (mod(batch,100)==0) fprintf(1,' %d ',batch); end %%%%%%%%% START POSITIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% data = batchdata(:,:,batch); poshidprobs = 1./(1 + exp(-data*vishid - repmat(hidbiases,numcases,1))); batchposhidprobs(:,:,batch)=poshidprobs; posprods = data' * poshidprobs; poshidact = sum(poshidprobs); posvisact = sum(data); %%%%%%%%% END OF POSITIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% poshidstates = poshidprobs > rand(numcases,numhid); %%%%%%%%% START NEGATIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% negdata = poshidstates*vishid' + repmat(visbiases,numcases,1);% + randn(numcases,numdims) if not using mean neghidprobs = 1./(1 + exp(-negdata*vishid - repmat(hidbiases,numcases,1))); negprods = negdata'*neghidprobs; neghidact = sum(neghidprobs); negvisact = sum(negdata); %%%%%%%%% END OF NEGATIVE PHASE %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% err= sum(sum( (data-negdata).^2 )); errsum = err + errsum; if epoch>5, momentum=finalmomentum; else momentum=initialmomentum; end; %%%%%%%%% UPDATE WEIGHTS AND BIASES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% vishidinc = momentum*vishidinc + ... epsilonw*( (posprods-negprods)/numcases - weightcost*vishid); visbiasinc = momentum*visbiasinc + (epsilonvb/numcases)*(posvisact-negvisact); hidbiasinc = momentum*hidbiasinc + (epsilonhb/numcases)*(poshidact-neghidact); vishid = vishid + vishidinc; visbiases = visbiases + visbiasinc; hidbiases = hidbiases + hidbiasinc; %%%%%%%%%%%%%%%% END OF UPDATES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% end fprintf(1, '\nepoch %4i error %f \n', epoch, errsum); end dofacedeepauto.m: clear all close all maxepoch=200; %In the Science paper we use maxepoch=50, but it works just fine. numhid=2000; numpen=1000; numpen2=500; numopen=30; fprintf(1,'Pretraining a deep autoencoder. \n'); fprintf(1,'The Science paper used 50 epochs. This uses %3i \n', maxepoch); load fdata %makeFaceData; [numcases numdims numbatches]=size(batchdata); fprintf(1,'Pretraining Layer 1 with RBM: %d-%d \n',numdims,numhid); restart=1; rbmvislinear; hidrecbiases=hidbiases; save mnistvh vishid hidrecbiases visbiases; maxepoch=50; fprintf(1,'\nPretraining Layer 2 with RBM: %d-%d \n',numhid,numpen); batchdata=batchposhidprobs; numhid=numpen; restart=1; rbm; hidpen=vishid; penrecbiases=hidbiases; hidgenbiases=visbiases; save mnisthp hidpen penrecbiases hidgenbiases; fprintf(1,'\nPretraining Layer 3 with RBM: %d-%d \n',numpen,numpen2); batchdata=batchposhidprobs; numhid=numpen2; restart=1; rbm; hidpen2=vishid; penrecbiases2=hidbiases; hidgenbiases2=visbiases; save mnisthp2 hidpen2 penrecbiases2 hidgenbiases2; fprintf(1,'\nPretraining Layer 4 with RBM: %d-%d \n',numpen2,numopen); batchdata=batchposhidprobs; numhid=numopen; restart=1; rbmhidlinear; hidtop=vishid; toprecbiases=hidbiases; topgenbiases=visbiases; save mnistpo hidtop toprecbiases topgenbiases; backpropface; Thanks for your time

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• Cannot format first column in WxPython's ListCtrl

  - by Matt Clarke

  If I set the format of the first column in a ListCtrl to align centre (or align right) nothing happens. It works for the other columns. This only happens on Windows - I have tested it on Linux and it works fine. Does anyone know if there is a work-round or other solution? Here is an example based on code found at http://zetcode.com/wxpython/ import wx import sys packages = [('jessica alba', 'pomona', '1981'), ('sigourney weaver', 'new york', '1949'), ('angelina jolie', 'los angeles', '1975'), ('natalie portman', 'jerusalem', '1981'), ('rachel weiss', 'london', '1971'), ('scarlett johansson', 'new york', '1984' )] class Actresses(wx.Frame): def __init__(self, parent, id, title): wx.Frame.__init__(self, parent, id, title, size=(380, 230)) hbox = wx.BoxSizer(wx.HORIZONTAL) panel = wx.Panel(self, -1) self.list = wx.ListCtrl(panel, -1, style=wx.LC_REPORT) self.list.InsertColumn(0, 'name', wx.LIST_FORMAT_CENTRE,width=140) self.list.InsertColumn(1, 'place', wx.LIST_FORMAT_CENTRE,width=130) self.list.InsertColumn(2, 'year', wx.LIST_FORMAT_CENTRE, 90) for i in packages: index = self.list.InsertStringItem(sys.maxint, i[0]) self.list.SetStringItem(index, 1, i[1]) self.list.SetStringItem(index, 2, i[2]) hbox.Add(self.list, 1, wx.EXPAND) panel.SetSizer(hbox) self.Centre() self.Show(True) app = wx.App() Actresses(None, -1, 'actresses') app.MainLoop()

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• Create a Python User() class that both creates new users and modifies existing users

  - by ensnare

  I'm trying to figure out the best way to create a class that can modify and create new users all in one. This is what I'm thinking: class User(object): def __init__(self,user_id): if user_id == -1 self.new_user = True else: self.new_user = False #fetch all records from db about user_id self._populateUser() def commit(self): if self.new_user: #Do INSERTs else: #Do UPDATEs def delete(self): if self.new_user == False: return False #Delete user code here def _populate(self): #Query self.user_id from database and #set all instance variables, e.g. #self.name = row['name'] def getFullName(self): return self.name #Create a new user >>u = User() >>u.name = 'Jason Martinez' >>u.password = 'linebreak' >>u.commit() >>print u.getFullName() >>Jason Martinez #Update existing user >>u = User(43) >>u.name = 'New Name Here' >>u.commit() >>print u.getFullName() >>New Name Here Is this a logical and clean way to do this? Is there a better way? Thanks.

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• IMB_ibImageFromMemory: unknown fileformat?

  - by Antoni4040

  Here's my add-on: import bpy import os import sys import subprocess import threading class ExportToGIMP(bpy.types.Operator): bl_idname = "uv.exporttogimp" bl_label = "Export to GIMP" def execute(self, context): self.filepath = os.path.join(os.path.dirname(bpy.data.filepath), "Layout") bpy.ops.uv.export_layout(filepath=self.filepath, check_existing=True, export_all=False, modified=False, mode='PNG', size=(1024, 1024), opacity=0.25, tessellated=False) self.files = os.path.dirname(bpy.data.filepath) cmd = " (python-fu-bgsync RUN-NONINTERACTIVE)" subprocess.Popen(['gimp', '-b', cmd]) self.update() return {'FINISHED'}; def update(self): self.thread = threading.Timer(3.0, self.update).start() self.filepath2 = "/home/antoni4040/????afa/Layout1.png" bpy.ops.image.open(filepath=self.filepath2, filter_blender=False, filter_image=True, filter_movie=False, filter_python=False, filter_font=False, filter_sound=False, filter_text=False, filter_btx=False, filter_collada=False, filter_folder=True, filemode=9, relative_path=False) tex = bpy.data.textures.new(name = self.filepath2, type = "IMAGE") def exporttogimp_menu(self, context): self.layout.operator(ExportToGIMP.bl_idname, text="Export To GIMP") bpy.utils.register_class(ExportToGIMP) bpy.types.IMAGE_MT_uvs.append(exporttogimp_menu) But I can't load an image, because I get this: Reached EOF while decoding PNG IMB_ibImageFromMemory: unknown fileformat (/home/antoni4040/????afa/Layout1.png) What is that?

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• Python Decorators and inheritance

  - by wheaties

  Help a guy out. Can't seem to get a decorator to work with inheritance. Broke it down to the simplest little example in my scratch workspace. Still can't seem to get it working. class bar(object): def __init__(self): self.val = 4 def setVal(self,x): self.val = x def decor(self, func): def increment(self, x): return func( self, x ) + self.val return increment class foo(bar): def __init__(self): bar.__init__(self) @decor def add(self, x): return x Oops, name "decor" is not defined. Okay, how about @bar.decor? TypeError: unbound method "decor" must be called with a bar instance as first argument (got function instance instead) Ok, how about @self.decor? Name "self" is not defined. Ok, how about @foo.decor?! Name "foo" is not defined. AaaaAAaAaaaarrrrgggg... What am I doing wrong?

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• Is this the correct way to reloadData on a UITableView?

  - by Sheehan Alam

  I am trying to append objects to my data source and then reload the table. Is this the correct way of approaching it? self.items is my datasource //Copy current items self.itemsCopy = [self.items mutableCopy];//[[NSMutableArray alloc] initWithArray:self.items copyItems:NO]; NSLog(@"Copy Size before append: %d",[itemsCopy count]); //Get new items int lastMsgID = [self getLastMessageID]; [self.coreData getMoreMessages:self.title lastID:lastMsgID]; //This will update self.items with 30 objects //Append new items [itemsCopy addObjectsFromArray:self.items]; //Empty items and copy itemsCopy [self.items removeAllObjects]; self.items = [self.itemsCopy mutableCopy]; NSLog(@"Actual Size after append: %d",[self.items count]); //Reload data [tableView reloadData];

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• TypeError: object not callable when making instance

  - by TSM

  I've searched around other threads with similar questions, but I'm not finding the answer. Basically, I have a class: import Android_Class class Android_Revision(object): def __init__(self): # dict for storing the classes in this revision # (format {name : classObject}): self.Classes = {} self.WorkingClass = Android_Class() self.RevisionNumber = '' def __call__(self): print "Called" def make_Class(self, name): newClass = Android_Class(name) self.Classes.update({name : newClass}) self.WorkingClass = newClass def set_Class(self, name): if not(self.Classes.has_key(name)): newClass = Android_Class(name) self.Classes.update({name : newClass}) self.WorkingClass = self.Classes.get(name) I'm trying to make an instance of this class: Revision = Android_Revision() and that's when I'm getting the error. I'm confused because I have another situation where I'm doing almost the exact same thing, and it's working fine. I can't figure out what differences between the two would lead to this error. Thanks.

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• How to manage security of these self hosted web apis, to ensure that the request coming for accessing data is authenticated?

  - by Husrat Mehmood

  Let's pretend I am going to work on an enterprise application. Say I have 11 modules in the application and I would have to develop Dashboards for every role in the organization for whom I are going to develop application. We Decided to use Asp.Net Web Api and return json data from our apis. We are going to include 11 Self hosted web apis projects in our application (one self hosted web api) for every module. All 11 modules are connected to one Sql server 2012 Database. Then once api is ready we would have to create Business Dashboards (Based upon roles in Organization). So Now my web api client is Asp.Net Mvc application.Asp.Net mvc will consume those web apis. Here is the part for whom all explanation is done. How should I manage Security of all 11 self hosted web apis? How should I only authenticated request is coming? If I authenticate user by login and password and then redirect user to appropriate Dashboard designed for the role that user have and load data by consuming web apis. How should I ensure that the request coming for accessing data is authenticated?

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• Why is UITableView not reloading (even on the main thread)?

  - by radesix

  I have two programs that basically do the same thing. They read an XML feed and parse the elements. The design of both programs is to use an asynchronous NSURLConnection to get the data then to spawn a new thread to handle the parsing. As batches of 5 items are parsed it calls back to the main thread to reload the UITableView. My issue is it works fine in one program, but not the other. I know that the parsing is actually occuring on the background thread and I know that [tableView reloadData] is executing on the main thread; however, it doesn't reload the table until all parsing is complete. I'm stumped. As far as I can tell... both programs are structured exactly the same way. Here is some code from the app that isn't working correctly. - (void)startConnectionWithURL:(NSString *)feedURL feedList:(NSMutableArray *)list { self.feedList = list; // Use NSURLConnection to asynchronously download the data. This means the main thread will not be blocked - the // application will remain responsive to the user. // // IMPORTANT! The main thread of the application should never be blocked! Also, avoid synchronous network access on any thread. // NSURLRequest *feedURLRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:feedURL]]; self.bloggerFeedConnection = [[[NSURLConnection alloc] initWithRequest:feedURLRequest delegate:self] autorelease]; // Test the validity of the connection object. The most likely reason for the connection object to be nil is a malformed // URL, which is a programmatic error easily detected during development. If the URL is more dynamic, then you should // implement a more flexible validation technique, and be able to both recover from errors and communicate problems // to the user in an unobtrusive manner. NSAssert(self.bloggerFeedConnection != nil, @"Failure to create URL connection."); // Start the status bar network activity indicator. We'll turn it off when the connection finishes or experiences an error. [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; } - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { self.bloggerData = [NSMutableData data]; } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { [bloggerData appendData:data]; } - (void)connectionDidFinishLoading:(NSURLConnection *)connection { self.bloggerFeedConnection = nil; [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; // Spawn a thread to fetch the link data so that the UI is not blocked while the application parses the XML data. // // IMPORTANT! - Don't access UIKit objects on secondary threads. // [NSThread detachNewThreadSelector:@selector(parseFeedData:) toTarget:self withObject:bloggerData]; // farkData will be retained by the thread until parseFarkData: has finished executing, so we no longer need // a reference to it in the main thread. self.bloggerData = nil; } If you read this from the top down you can see when the NSURLConnection is finished I detach a new thread and call parseFeedData. - (void)parseFeedData:(NSData *)data { // You must create a autorelease pool for all secondary threads. NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; self.currentParseBatch = [NSMutableArray array]; self.currentParsedCharacterData = [NSMutableString string]; self.feedList = [NSMutableArray array]; // // It's also possible to have NSXMLParser download the data, by passing it a URL, but this is not desirable // because it gives less control over the network, particularly in responding to connection errors. // NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data]; [parser setDelegate:self]; [parser parse]; // depending on the total number of links parsed, the last batch might not have been a "full" batch, and thus // not been part of the regular batch transfer. So, we check the count of the array and, if necessary, send it to the main thread. if ([self.currentParseBatch count] > 0) { [self performSelectorOnMainThread:@selector(addLinksToList:) withObject:self.currentParseBatch waitUntilDone:NO]; } self.currentParseBatch = nil; self.currentParsedCharacterData = nil; [parser release]; [pool release]; } In the did end element delegate I check to see that 5 items have been parsed before calling the main thread to perform the update. - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { if ([elementName isEqualToString:kItemElementName]) { [self.currentParseBatch addObject:self.currentItem]; parsedItemsCounter++; if (parsedItemsCounter % kSizeOfItemBatch == 0) { [self performSelectorOnMainThread:@selector(addLinksToList:) withObject:self.currentParseBatch waitUntilDone:NO]; self.currentParseBatch = [NSMutableArray array]; } } // Stop accumulating parsed character data. We won't start again until specific elements begin. accumulatingParsedCharacterData = NO; } - (void)addLinksToList:(NSMutableArray *)links { [self.feedList addObjectsFromArray:links]; // The table needs to be reloaded to reflect the new content of the list. if (self.viewDelegate != nil && [self.viewDelegate respondsToSelector:@selector(parser:didParseBatch:)]) { [self.viewDelegate parser:self didParseBatch:links]; } } Finally, the UIViewController delegate: - (void)parser:(XMLFeedParser *)parser didParseBatch:(NSMutableArray *)parsedBatch { NSLog(@"parser:didParseBatch:"); [self.selectedBlogger.feedList addObjectsFromArray:parsedBatch]; [self.tableView reloadData]; } If I write to the log when my view controller delegate fires to reload the table and when cellForRowAtIndexPath fires as it's rebuilding the table then the log looks something like this: parser:didParseBatch: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: parser:didParseBatch: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: parser:didParseBatch: parser:didParseBatch: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath Clearly, the tableView is not reloading when I tell it to every time. The log from the app that works correctly looks like this: parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath parser:didParseBatch: tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath tableView:cellForRowAtIndexPath

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• Any good, easy to learn from books or tutorials for learning assembly? [on hold]

  - by pythonian29033

  I've been a developer since 2009 and I've learnt a lot of languages since, but I've always wanted to understand and be able to code in the lowest level language so I can directly (or at least very close to directly) speak to machines through my code. There was a point in time when someone showed me how to do an if statement in assembly, but out of all the books that I got, I could never really understand where/how to start learning to code in assembler. any help please? I'm obsessed with learning this! PS: if you have any software suggestions, I use ubuntu and am looking to convert to backtrack soon, so it would be preferred if you could give me something that'll be easily installed on debian linux, otherwise don't sweat it, give me the name of the windows software and I'll find an equivalent myself

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• How to self Motivate technically to put my ideas into execution or just getting a job at MNC like google or microsoft..

  - by Demla Pawan

  I mean, How to self Motivate to get a job at google or create another google in future. ,as there is no mentor who can guide me on this topic, so asked it here: I'm a Graduate in BE IT,but with less grades,with interest in learning new programming languages, but not yet done anything great like developed some system or anything. And I'm left with 2 more years to prove my worth to someone. So,is their a quick guide to start learning a language and then just go on implementing your ideas and it gets appreciated or I get a good Job ant Big MNC's. By the way, I just build one website for my one client and running my wordpress blog. And I had tried my hands on basic of C++,Java,JS,JSP,PHP,Ubuntu,web designing in past.

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• Fastest Method to Learn Web Design for a Developer

  - by hekevintran

  I am a Web developer and in my projects I have noticed that my weakest point is not being good at the front-end design. Relying on other designers can be annoying if they are not able to produce as quickly as I want. My perspective on HTML/CSS is that it is basically a big hack that amazingly works. There are too many CSS and browser specific bugs/quirks to learn and remember them all without spending extreme amounts of time trying to untangle everything. Is there a fast track route to getting CSS into my brain? I have looked at some CSS books, but to me they really read as long lists of how to render things correctly in IE6 and how to make corners rounded. (Seriously why does it require so many tricks to make a sharp corner round? On any platform but the Web this would be called a major oversight.) Does there exist something that does the analogous to CSS that jQuery does for JavaScript? Using jQuery you don't need to know JavaScript well to make things that work. I am not interested in learning why IE6 does things in weird ways because I don't care about supporting it at all. I am more interested in a method of learning how to use CSS to do what I want without spending hours and hours reading obscure blogs.

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• Which java web technology to learn to develop Rich Internet Applications ?

  - by Cshah

  Hi, I have developed web applications using JSF (myfaces components). But in these days of responsive UI, JSF doesnt fare well. I m hearing a lot about AJAX, GWT, etc. So i wanted your opinion on which web technology/framework should i learn inorder to develop web applications for enterprise products. Some of the web technologies that i m hearing are: ICE Faces (With AJAX Bridge support) GWT extJS and extGWT JavaFX Apache Wicket Jquery AJAX Open laszlo Which of the above or the combination of the above would help me ? Some of the parameters on which you can rate these web technologies are: Ease of learning Maintainability of web application code Community support IDE support - Eclipse or NetBeans Off the shelf component availability (like textbox,table grids, option menus) License - Does it cost for commercial use ? User Experience - responsive UI. Shouldnt be sluggish A similar question on SO does answer my question partially. Would want more info though. EDIT: Answers collated: Based on the answers : AJAX would be the best thing to start for learning fundamentals, then learn JQUERY. Any component based frame work that can complement ajax,jquery ? Edit 2: If i had to design a web application like StackOverFlow (in java platform) which would be the best choice to learn and adopt? Wicket + Jquery, WiQuery GWT Some XYZ Faces technology(RichFaces/ICEFaces) + AJAX. Comments appreciated from some one who has worked with them and can rate them in the above mentioned parameters.

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• Why do programmers have to learn for their whole lives and aren't you afraid of that?

  - by serg555

  Programming technologies are evolving so fast that programmers constantly have to learn more and more to catch up whether you want it or not. Often it is not just learning more in the same direction but starting from a scratch. Lets say you were a topnotch programmer in 1999 who quit for 10 years and went to a job interview in 2009 (funny even to imagine) - how much of your knowledge is still needed? And if we take a carpenter, engineer, doctor or even mathematician - they all are still good specialists after 10 years. So why programming is so not stable? Is it because it is just relatively new or because something important is still missing after 50 years and we can't find it to settle in that direction? Do you think after some time situation will change? Learning something new all the time is exciting and all, but it is starting to worry me that as I become older it will be harder and harder. After all "you can't teach an old dog new tricks" and I'm afraid that at the end I just end up behind college students and become one of those "cobol dinosaurs", only it will be probably "java dinosaurs" by that time.

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• Just 2 free months 2 learn or improve my skills

  - by microspino

  On the 30 of June I will leave my every day work to start as freelance developer. I'd like to set a period of 2 months apart to improve my dev skills. At work I code in C# and during my spare time I enjoyed building Ruby on Rails web applications and creating some Arduino prototypes. I'm something more than junior but I don't feel really a senior developer because I never had a big corporate project built and designed by me with help of other juniors (although I don't think this is really a good definiton of a "senior", It helps describing my feelings). Using a scale from 0 (ignorant) to 10 (proficient like a "samurai") the list below describes my skills that I would like to improve with just 2 months. I've already bought some nice and updated books on all the subjects hereunder: The order doesn't matter C = 1 C# & .Net = 6 Arduino & Processing = 2 Ruby = 5 Rails = 5 HTML/XHTML/CSS = 9 Javascript = 6 Objective-C/iPhone dev = 2 Python = 4 Django = 4 Desing Patterns = 3 Algorythms = 3 Git = 5 I haven't included SQL or Databases in general nor Networking because I spent 10 years working in the past with them and I feel pretty solid for now. As an aside, I've made up some interest in Redis, Node.js, HTML5 reading about them on the web. After two months, since I have to pay my bills, I could go searching for some new job. If learning and developing were really good maybe I could also invest on something I gave birth during them. Can You give me some piece of advice on which you think It's better to improve or develop a learning project on (something like a "summer of code" thing)? The all point Is to see my weeknesses and work on them.

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• How difficult is it for an old-school programmer to pick up an FPGA kit and make something useful wi

  - by JUST MY correct OPINION

  I'm an old, old, old coder. (How old? I've used paper tape in anger.) I've programmed in a lot of languages and under a lot of paradigms (spaghetti, structured, object-oriented, functional and a smattering of logical). I'm getting bored. FPGAs look interesting to me. I have the crazy notion of resurrecting some of the ancient hardware I worked on in the days using FPGAs. I know this can be done because I've seen PDP-10 and PDP-11 implementations in FPGAs. I'd like to do the same for a few machines that are perhaps not as popular as those two, however. While I am an old, old coder, what I am not is an electronics or computer systems engineer. I'll be learning from scratch if I go down this path. My question, therefore, is two-fold: How difficult will it be for this old dinosaur to pick up and learn FPGAs to the point that interesting (not necessarily practical -- more from a hobbyist perspective) projects can be made? What should I start with learning-wise to go down this path? I know where to get FPGA kits, but I haven't found anything like "FPGAs for Complete Dinosaurs" yet anywhere out there.

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• What's the correct terminology for something that isn't quite classification nor regression?

  - by TC

  Let's say that I have a problem that is basicly classification. That is, given some input and a number of possible output classes, find the correct class for the given input. Neural networks and decision trees are some of the algorithms that may be used to solve such problems. These algorithms typically only emit a single result however: the resulting classification. Now what if I weren't only interested in one classification, but in the posterior probabilities that the input belongs to each of the classes. I.E., instead of the answer "This input belongs in class A", I want the answer "This input belongs to class A with 80%, class B with 15% and class C with 5%". My question is not on how to obtain these posterior probabilities, but rather on the correct terminology to describe the process of finding them. You could call it regression, since we are now trying to estimate a number of real valued numbers, but I am not quite sure if that's right. I feel it's not exactly classification either, it's something in between the two. Is there a word that describes the process of finding the class conditional posterior probabilities that some input belongs in each of the possible output classes? P.S. I'm not exactly sure if this question is enough of a programming question, but since it's about machine learning and machine learning generally involves a decent amount of programming, let's give it a shot.

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