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  • Resetting Objects vs. Constructing New Objects

    - by byronh
    Is it considered better practice and/or more efficient to create a 'reset' function for a particular object that clears/defaults all the necessary member variables to allow for further operations, or to simply construct a new object from outside? I've seen both methods employed a lot, but I can't decide which one is better. Of course, for classes that represent database connections, you'd have to use a reset method rather than constructing a new one resulting in needless connecting/disconnecting, but I'm talking more in terms of abstraction classes. Can anyone give me some real-world examples of when to use each method? In my particular case I'm thinking mostly in terms of ORM or the Model in MVC. For example, if I would want to retrieve a bunch of database objects for display and modify them in one operation.

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  • Is it OK to put link to SO questions in a program comments?

    - by WizardOfOdds
    In quite some codebase you can see comments stating things like: // Workaround for defect 'xxx', (See bug 1434594 on Sun's bugparade) So I've got a few questions, but they're all related. Is it OK to put link to SO questions in a program's comments: // We're now mapping from the "sorted-on column" to original indices. // // There's apparently no easy way to do this in Java, so we're // re-inventing a wheel. // // (see why here, in SO question: http://stackoverflow.com/questions/951848) Do you do it? And what are the drawbacks in doing so? (see my first comment for a terrible drawback)

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  • How do you PEP 8-name a class whose name is an acronym?

    - by Arrieta
    I try to adhere to the style guide for Python code (also known as PEP 8). Accordingly, the preferred way to name a class is using CamelCase: Almost without exception, class names use the CapWords convention. Classes for internal use have a leading underscore in addition. How can I be consistent with PEP 8 if my class name is formed by two acronyms (which in proper English should be capitalized). For instance, if my class name was 'NASA JPL', what would you name it?: class NASAJPL(): # 1 class NASA_JPL(): # 2 class NasaJpl(): # 3 I am using #1, but it looks weird; #3 looks weird too, and #2 seems to violate PEP 8. Thoughts?

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  • What is a good practice to access class attributes in class methods?

    - by Clem
    I always wonder about the best way to access a class attribute from a class method in Java. Could you quickly convince me about which one of the 3 solutions below (or a totally different one :P) is a good practice? public class Test { String a; public String getA(){ return this.a; } public setA(String a){ this.a = a; } // Using Getter public void display(){ // Solution 1 System.out.println(this.a); // Solution 2 System.out.println(getA()); // Solution 3 System.out.println(this.getA()); } // Using Setter public void myMethod(String b, String c){ // Solution 1 this.a = b + c; // Solution 2 setA(b + c); // Solution 3 this.setA(b + c); } }

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  • Migrating a simple application from Application Delegate to ViewController Class

    - by eco_bach
    Hi Frst of all wanted to send out a huge thanks for the great feedback and support. I have a simple application working, right now simply loads a sequence of images and alows the user to step thru the images by clicking a button. All of my logic is in my Application Delegate class, with the image loading, initialization of UIImage Views etc happening in my applicationDidFinishLaunching method. My next step is to migrate as much as possible all of the logic from this class to a ViewController, to take advantage of the extra functionality etc in viewcontrollers. All my images and imageViews are initialized like the following in my applicationDidFinishLaunching. img = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@image1.jpg" ofType:nil]]; imgView = [[UIImageView alloc] initWithImage:img]; How would I migrate this to a ViewController based application? Where would I put all of the logic currently in my applicationDidFinishLaunching method, or for loading of images, is it necessary to only load them here? Any feedback, tips, suggestions appreciated.

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  • replace values in a String from a Hashtable in Java

    - by Adnan
    My string looks like; String values = "I am from UK, and you are from FR"; and my hashtable; Hashtable countries = new Hashtable(); countries.put("United Kingdom", new String("UK")); countries.put("France", new String("FR")); What would be the most effective way to change the values in my string with the values from the hashtable accordingly. These are just 2 values to change, but in my case I will have 100+

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  • How to call superconstructor in a neat way

    - by sandis
    So here is my code: public MyClass (int y) { super(y,x,x); //some code } My problem is that in this case i want to generate a 'x' and sent to the super constructor. However the call to the superconstructor must be the first line in this constructor. Of course I could do something like this: int x; { x = generateX(); } But this feels ugly, and then the code will run no matter what constructor I use, which feels not so nice. Right now I am consider encapsulating my whole object in another object that only calculates x and then starts this object. Is this the best approach?

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  • How to set default values to all wrong or null parameters of method?

    - by Roman
    At the moment I have this code (and I don't like it): private RenderedImage private RenderedImage getChartImage (GanttChartModel model, String title, Integer width, Integer height, String xAxisLabel, String yAxisLabel, Boolean showLegend) { if (title == null) { title = ""; } if (xAxisLabel == null) { xAxisLabel = ""; } if (yAxisLabel == null) { yAxisLabel = ""; } if (showLegend == null) { showLegend = true; } if (width == null) { width = DEFAULT_WIDTH; } if (height == null) { height = DEFAULT_HEIGHT; } ... } How can I improve it? I have some thoughts about introducing an object which will contain all these parameters as fields and then, maybe, it'll be possible to apply builder pattern. But still don't have clear vision how to implement that and I'm not sure that it's worth to be done. Any other ideas?

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  • UI View Controller crashes after interruption

    - by nosuic
    Given the multitasking of iOS I thought it wouldn't be a pain to pause and resume my app, by pressing the home button or due to a phone call, but for a particular view controller it crashes. The navigation bar is working fine i.e. when I tap "Back" it's ok, but if I try to tap controls of the displayed UI View Controller then I get EXC_BAD_ACCESS.. =/ Please find the code of my problematic View Controller below. I'm not very sure about it myself, because I used loadView to build its View, but apart from this interruption problem it works fine. StoreViewController.h #import <UIKit/UIKit.h> @protocol StoreViewDelegate <NSObject> @optional - (void)DirectionsClicked:(double)lat:(double)lon; @end @interface StoreViewController : UIViewController { double latitude; double longitude; NSString *description; NSString *imageURL; short rating; NSString *storeType; NSString *offerType; UIImageView *imageView; UILabel *descriptionLabel; id<StoreViewDelegate> storeViewDel; } @property (nonatomic) double latitude; @property (nonatomic) double longitude; @property (nonatomic) short rating; @property (nonatomic,retain) NSString *description; @property (nonatomic,retain) NSString *imageURL; @property (nonatomic,retain) NSString *storeType; @property (nonatomic,retain) NSString *offerType; @property (assign) id<StoreViewDelegate> storeViewDel; @end StoreViewController.m #import "StoreViewController.h" #import <QuartzCore/QuartzCore.h> @interface StoreViewController() -(CGSize) calcLabelSize:(NSString *)string withFont:(UIFont *)font maxSize:(CGSize)maxSize; @end @implementation StoreViewController @synthesize storeViewDel, longitude, latitude, description, imageURL, rating, offerType, storeType; - (void)mapsButtonClicked:(id)sender { } - (void)loadView { UIView *storeView = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 0.0f, 0.0f)]; // Colours UIColor *lightBlue = [[UIColor alloc] initWithRed:(189.0f / 255.0f) green:(230.0f / 255.0f) blue:(252.0f / 255.0f) alpha:1.0f]; UIColor *darkBlue = [[UIColor alloc] initWithRed:(28.0f/255.0f) green:(157.0f/255.0f) blue:(215.0f/255.0f) alpha:1.0f]; // Layout int width = self.navigationController.view.frame.size.width; int height = self.navigationController.view.frame.size.height; float firstRowHeight = 100.0f; int margin = width / 20; int imgWidth = (width - 3 * margin) / 2; // Set ImageView imageView = [[UIImageView alloc] initWithFrame:CGRectMake(margin, margin, imgWidth, imgWidth)]; CALayer *imgLayer = [imageView layer]; [imgLayer setMasksToBounds:YES]; [imgLayer setCornerRadius:10.0f]; [imgLayer setBorderWidth:4.0f]; [imgLayer setBorderColor:[lightBlue CGColor]]; // Load default image NSData *imageData = [NSData dataWithContentsOfFile:@"thumb-null.png"]; UIImage *image = [UIImage imageWithData:imageData]; [imageView setImage:image]; [storeView addSubview:imageView]; // Set Rating UIImageView *ratingView = [[UIImageView alloc] initWithFrame:CGRectMake(3 * width / 4 - 59.0f, margin, 118.0f, 36.0f)]; UIImage *ratingImage = [UIImage imageNamed:@"bb-rating-0.png"]; [ratingView setImage:ratingImage]; [ratingImage release]; [storeView addSubview:ratingView]; // Set Get Directions button UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(3 * width / 4 - 71.5f, 36.0f + 2*margin, 143.0f, 63.0f)]; [btn addTarget:self action:@selector(mapsButtonClicked:) forControlEvents:UIControlEventTouchUpInside]; UIImage *mapsImgUp = [UIImage imageNamed:@"bb-maps-up.png"]; [btn setImage:mapsImgUp forState:UIControlStateNormal]; [mapsImgUp release]; UIImage *mapsImgDown = [UIImage imageNamed:@"bb-maps-down.png"]; [btn setImage:mapsImgDown forState:UIControlStateHighlighted]; [mapsImgDown release]; [storeView addSubview:btn]; [btn release]; // Set Description Text UIScrollView *descriptionView = [[UIScrollView alloc] initWithFrame:CGRectMake(0.0f, imgWidth + 2 * margin, width, height - firstRowHeight)]; descriptionView.backgroundColor = lightBlue; CGSize s = [self calcLabelSize:description withFont:[UIFont systemFontOfSize:18.0f] maxSize:CGSizeMake(width, 9999.0f)]; descriptionLabel = [[UILabel alloc] initWithFrame:CGRectMake(margin, margin, width - 2 * margin, s.height)]; descriptionLabel.lineBreakMode = UILineBreakModeWordWrap; descriptionLabel.numberOfLines = 0; descriptionLabel.font = [UIFont systemFontOfSize:18.0f]; descriptionLabel.textColor = darkBlue; descriptionLabel.text = description; descriptionLabel.backgroundColor = lightBlue; [descriptionView addSubview:descriptionLabel]; [storeView addSubview:descriptionView]; [descriptionLabel release]; [lightBlue release]; [darkBlue release]; self.view = storeView; [storeView release]; } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc. that aren't in use. } - (void)viewDidUnload { [super viewDidUnload]; // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; } - (void)dealloc { [imageView release]; [descriptionLabel release]; [super dealloc]; } @end Any suggestions ? Thank you, F.

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  • What's the standard behaviour for an out parameter when a TryXxxx method returns false?

    - by Matt Lacey
    Assuming a method with the following signature bool TryXxxx(object something, out int toReturn) What is it acceptable for toReturn to be if TryXxxx returns false? In that it's infered that toReturn should never be used if TryXxxx fails does it matter? If toReturn was a nulable type, then it would make sense to return null. But int isn't nullable and I don't want to have to force it to be. If toReturn is always a certain value if TryXxxx fails we risk having the position where 2 values could be considered to indicate the same thing. I can see this leading to potential possible confusion if the 'default' value was returned as a valid response (when TryXxxx returns true). From an implementation point if view it looks like having toReturn be a[ny] value is easiest, but is there anything more important to consider?

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  • Communication between layers in an application

    - by Petar Minchev
    Hi guys! Let's assume we have the following method in the business layer. What's the best practice to tell the UI layer that something went wrong and give also the error message? Should the method return an empty String when it was OK, otherwise the error message, or should it throw another exception in the catch code wrapping the caught exception? If we choose the second variant then the UI should have another try,catch which is too much try,catch maybe. Here is a pseudocode for the first variant. public String updateSomething() { try { //Begin transaction here dataLayer.do1(); dataLayer.do2(); dataLayer.doN(); } catch(Exception exc) { //Rollback transaction code here return exc.message; } return ""; } Is this a good practice or should I throw another exception in the catch(then the method will be void)?

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  • How to use a 3rd party control inside the viewmodel?

    - by Sander
    I have a 3rd party control which among other things performs loading of some data. I want my viewmodel to keep track of this load operation and adjust its own state accordingly. If it were up to me, I'd do the data loading far away from the view, but it is not. So, I seem to be in the situation where my viewmodel depends on my view. How do I best handle this? I feel rather dirty making the view publish events to the viewmodel but I don't see any other reasonable way to get this info into the viewmodel. A similar situation might crop up with standard controls, too - imagine if your viewmodel depends on the events coming from a MediaElement - how do you properly model this? Do you put the MediaElement into the viewmodel? That doesn't sound right. If publishing the events to the viewmodel is indeed the most reasonable way, is there some common pattern used for this? How do you do it?

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  • JavaScript-library-based Project Organization

    - by Laith J
    Hello, I'm very new to the JavaScript library world. I have used JS by itself before to create a mini social network but this is the first time I use a JS library and I really don't know how to go about this. I'm planning to use Google Closure and I'm really not sure how I should go about organizing the code. Should I put everything in one file since it's a web app and should have one screen? Should I separate the code to many chunks and put them in different files? Or should I put different dialogs (like settings) in a separate page and thus a separate file? Like all programmers I'm a perfectionist so please help me out with this one, thanks.

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  • Handling input from a keyboard wedge

    - by JDibble
    Following on from the question asked by Mykroft Best way to handle input from a keyboard “wedge” http://stackoverflow.com/questions/42437/best-way-to-handle-input-from-a-keyboard-wedge. I need to write a class that intercepts key strokes, if the input is determined to be from the keyboard wedge (as described in the above post) the data will be directed to POS classes to handle, otherwise they keystrokes must be passed on to be handled in windows in the normal manner. This raises two questions How can I intercept key strokes when not in a WinForm. How can I pass on the keypresses to windows. Thanks JDibble

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  • Program structure in long running data processing python script

    - by fmark
    For my current job I am writing some long-running (think hours to days) scripts that do CPU intensive data-processing. The program flow is very simple - it proceeds into the main loop, completes the main loop, saves output and terminates: The basic structure of my programs tends to be like so: <import statements> <constant declarations> <misc function declarations> def main(): for blah in blahs(): <lots of local variables> <lots of tightly coupled computation> for something in somethings(): <lots more local variables> <lots more computation> <etc., etc.> <save results> if __name__ == "__main__": main() This gets unmanageable quickly, so I want to refactor it into something more manageable. I want to make this more maintainable, without sacrificing execution speed. Each chuck of code relies on a large number of variables however, so refactoring parts of the computation out to functions would make parameters list grow out of hand very quickly. Should I put this sort of code into a python class, and change the local variables into class variables? It doesn't make a great deal of sense tp me conceptually to turn the program into a class, as the class would never be reused, and only one instance would ever be created per instance. What is the best practice structure for this kind of program? I am using python but the question is relatively language-agnostic, assuming a modern object-oriented language features.

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  • Cannot save model due to bad transaction? Django

    - by Kenneth Love
    Trying to save a model in Django admin and I keep getting the error: Transaction managed block ended with pending COMMIT/ROLLBACK I tried restarting both the Django (1.2) and PostgreSQL (8.4) processes but nothing changed. I added "autocommit": True to my database settings but that didn't change anything either. Everything that Google has turned up has either not been answered or the answer involved not having records in the users table, which I definitely have. The model does not have a custom save method and there are no pre/post save signals tied to it. Any ideas or anything else I can provide to make answering this easier?

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  • How to make a jQuery plugin (the right way)?

    - by macek
    I know there are jQuery cookie plugins out there, but I wanted to write one for the sake of better learning the jQuery plugin pattern. I like the separation of "work" in small, manageable functions, but I feel like I'm passing name, value, and options arguments around too much. Is there a way this can be refactored? I'm looking for snippets of code to help illustrate examples provided with in answers. Any help is appreciated. Thanks :) example usage $.cookie('foo', 'bar', {expires:7}); $.cookie('foo'); //=> bar $.cookie('foo', null); $.cookie('foo'); //=> undefined Edit: I did a little bit of work on this. You can view the revision history to see where this has come from. It still feels like more refactoring can be done to optimize the flow a bit. Any ideas? the plugin (function($){ $.cookie = function(name, value, options) { if (typeof value == 'undefined') { return get(name); } else { options = $.extend({}, $.cookie.defaults, options || {}); return (value != null) ? set(name, value, options) : unset(name, options); } }; $.cookie.defaults = { expires: null, path: '/', domain: null, secure: false }; var set = function(name, value, options){ console.log(options); return document.cookie = options_string(name, value, options); }; var get = function(name){ var cookies = {}; $.map(document.cookie.split(';'), function(pair){ var c = $.trim(pair).split('='); cookies[c[0]] = c[1]; }); return decodeURIComponent(cookies[name]); }; var unset = function(name, options){ value = ''; options.expires = -1; set(name, value, options); }; var options_string = function(name, value, options){ var pairs = [param.name(name, value)]; $.each(options, function(k,v){ pairs.push(param[k](v)); }); return $.map(pairs, function(p){ return p === null ? null : p; }).join(';'); }; var param = { name: function(name, value){ return name + "=" + encodeURIComponent(value); }, expires: function(value){ // no expiry if(value === null){ return null; } // number of days else if(typeof value == "number"){ d = new Date(); d.setTime(d.getTime() + (value * 24 * 60 * 60 * 1000)); } // date object else if(typeof value == "object" && value instanceof "Date") { d = value; } return "expires=" + d.toUTCString(); }, path: function(value){ return "path="+value; }, domain: function(value){ return value === null ? null : "domain=" + value; }, secure: function(bool){ return bool ? "secure" : null; } }; })(jQuery);

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  • how to merge ecommerce transaction data between two databases

    - by yamspog
    We currently run an ecommerce solution for a leisure and travel company. Everytime we have a release, we must bring the ecommerce site down as we update database schema and the data access code. We are using a custom built ORM where each data entity is responsible for their own CRUD operations. This is accomplished by dynamically generating the SQL based on attributes in the data entity. For example, the data entity for an address would be... [tableName="address"] public class address : dataEntity { [column="address1"] public string address1; [column="city"] public string city; } So, if we add a new column to the database, we must update the schema of the database and also update the data entity. As you can expect, the business people are not too happy about this outage as it puts a crimp in their cash-flow. The operations people are not happy as they have to deal with a high-pressure time when database and applications are upgraded. The programmers are upset as they are constantly getting in trouble for the legacy system that they inherited. Do any of you smart people out there have some suggestions?

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  • Constructor Overload Problem in C++ Inheritance

    - by metdos
    Here my code snippet: class Request { public: Request(void); ……….. } Request::Request(void) { qDebug()<<"Request: "<<"Hello World"; } class LoginRequest :public Request { public: LoginRequest(void); LoginRequest(QDomDocument); …………… } LoginRequest::LoginRequest(void) { qDebug()<<"LoginRequest: "<<"Hello World"; requestType=LOGIN; requestId=-1; } LoginRequest::LoginRequest(QDomDocument doc){ qDebug()<<"LoginRequest: "<<"Hello World with QDomDocument"; LoginRequest::LoginRequest(); xmlDoc_=doc; } When call constructor of Overrided LoginRequest LoginRequest *test=new LoginRequest(doc); I came up with this result: Request: Hello World LoginRequest: Hello World with QDomDocument Request: Hello World LoginRequest: Hello World Obviously both constructor of LoginRequest called REquest constructor. Is there any way to cape with this situation? I can construct another function that does the job I want to do and have both constructors call that function. But I wonder is there any solution?

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

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

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  • Why is there so much poorly indented code out there?

    - by dsimcha
    The more I browse the code to open source projects in languages that aren't Python, the more I realize that it seems a lot of programmers don't believe in proper indentation. (I won't mention any projects specifically to avoid having anyone take this question too personally.) Usually code is indented, but in a way just different enough from the standard style that it drives me crazy, especially in old/crufty code. I've noticed that when I write in C-like languages, I tend to indent correctly as religiously as when I'm writing in Python, with the exception of debugging code that I actually want to stick out like a sore thumb. Given how easy it is with a modern IDE to fix incorrect indentation, what are some rationales for not religiously keeping indentation in sync with braces?

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  • How to not over-use jQuery?

    - by Fedyashev Nikita
    Typical jQuery over-use: $('button').click(function() { alert('Button clicked: ' + $(this).attr('id')); }); Which can be simplified to: $('button').click(function() { alert('Button clicked: ' + this.id); }); Which is way faster. Can you give me any more examples of similar jQuery over-use?

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