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  • Clear all class variables between instances

    - by ensnare
    This is probably a stupid question, but what's the best way to clear class variables between instances? I know I could reset each variable individually in the constructor; but is there a way to do this in bulk? Or am I doing something totally wrong that requires a different approach? Thanks for helping ... class User(): def __init__(self): #RESET ALL CLASS VARIABLES def commit(self): #Commit variables to database >>u = User() >>u.name = 'Jason' >>u.email = '[email protected]' >>u.commit() So that each time User is called the variables are fresh. Thanks.

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  • AContext.data can be nil?

    - by waza123
    In this code, as you see on Connect, AContext.Data is filled with something TmyTThreadList = class(TThreadList) id: integer; end; var unique_id:integer; procedure TfrmTestIdTCPServer.IdTCPServerConnect(AContext: TIdContext); begin CS.Enter; try inc(unique_id); finally CS.Leave; end; AContext.Data := myTThreadList.Create; list := myTThreadList(AContext.Data).LockList; try myTThreadList(AContext.Data).id := my_unique_id; list.Add(myTThreadList(AContext.Data)); finally myTThreadList(AContext.Data).UnlockList; end; end; then on disconnect, coder is checking here for Acontext.Data < nil procedure TfrmTestIdTCPServer.IdTCPServerDisconnect(AContext: TIdContext); var begin if AContext.Data <> nil then begin The question is, why he is checking for nil ? Thanks. EDIT: I'm asking this, because when I do the same, onExecute I access AContext.Data , and sometimes (when in same time is connecting many clients) AContext.Data is empty, access violation appears.

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  • OOP Design for an Economy

    - by waiwai933
    Not sure where to start, so I'm just going to plow in. Let's say I'm trying to represent an economy in OOP. A basic design I've come up with is: class Person{ int $money; // Money someone has in wallet/purse int $bank_account_id; function getAmountOfMoney() function addMoney($amountToAdd) function subtractMoney($amountToSubtract) } class BankAccount{ int $money; // Money in Bank Account int $interest_per_year; function giveInterest() function depositMoney() // Calls $person->subtractMoney() function withdrawMoney() // Calls $person->addMoney() } Are there any design flaws here?

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  • inner class within Interface

    - by harigm
    is that possible to create a inner class within an interface? If yes, why do we create like that? Anyways we are not going to create any interface objects? Do they help in any Development process?

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  • Generics with constraints hierarchy

    - by devoured elysium
    I am currently facing a very disturbing problem: interface IStateSpace<Position, Value> where Position : IPosition // <-- Problem starts here where Value : IValue // <-- and here as I don't { // know how to get away this // circular dependency! // Notice how I should be // defining generics parameters // here but I can't! Value GetStateAt(Position position); void SetStateAt(Position position, State state); } As you'll down here, both IPosition, IValue and IState depend on each other. How am I supposed to get away with this? I can't think of any other design that will circumvent this circular dependency and still describes exactly what I want to do! interface IState<StateSpace, Value> where StateSpace : IStateSpace where Value : IValue { StateSpace StateSpace { get; }; Value Value { get; set; } } interface IPosition { } interface IValue<State> where State : IState { State State { get; } } Basically I have a state space IStateSpace that has states IState inside. Their position in the state space is given by an IPosition. Each state then has one (or more) values IValue. I am simplifying the hierarchy, as it's a bit more complex than described. The idea of having this hierarchy defined with generics is to allow for different implementations of the same concepts (an IStateSpace will be implemented both as a matrix as an graph, etc). Would can I get away with this? How do you generally solve this kind of problems? Which kind of designs are used in these cases? Thanks

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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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  • My External USB drive stops after reading some data

    - by user191542
    I had the external USB 3.0 western Digital My Book essential 3TB drive. I had loto of data on it. Suddenlt when i start copying data from it then after reading 20GB or so data then i get error that system can't read from the location. I have to turn the uSB power off , disconnect it and then again connect it. so i have to trnasfer the data in small chunks like 20Gb , 30GB etc. I have n ow transferred all the data but i want to know that is hard disk gone or it can be fixed or its something windows fault not HD fault

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  • What is the equivalent of .NET events in Ruby?

    - by Gishu
    The problem is very simple. An object needs to notify some events that might be of interest to observers. When I sat to validate a design that I cooked up now in Ruby just to validate it.. I find myself stumped as to how to implement the object events. In .Net this would be a one-liner.. .Net also does handler method signature verification,etc. e.g. // Object with events public delegate void HandlerSignature(int a); public event HandlerSignature MyEvent; public event HandlerSignature AnotherCriticalEvent; // Client MyObject.MyEvent += new HandlerSignature(MyHandlerMethod); // MyHandlerMethod has same signature as delegate Is there an EventDispatcher module or something that I am missing that I can strap on to a Ruby class ? Hoping for an answer that plays along with Ruby's principle of least surprise. An event would be the name of the event plus a queue of [observer, methodName] objects that need to be invoked when the event takes place.

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  • Learning OOP Design

    - by waiwai933
    I've read Head First Java, and I understand how OOP works. Here's my problem: I'm a PHP programmer, and while I've used OOP in PHP, I'm having trouble figuring out what should be an object and what methods to give it. For example, let's say I have a app that allows people to log in and edit a document. Why should the document be an object if there will ever only be one instance? Should I give the deleteDocument() method to the document object or the admin object? The document is the one being deleted, but the admin is the one performing the action. So my real question is, coming from a procedural background, how do I figure out what should be objects and what should have what methods?

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  • Observer pattern and violation of Single Principality Rule

    - by Devil Jin
    I have an applet which repaints itself once the text has changed Design 1: //MyApplet.java public class MyApplet extends Applet implements Listener{ private DynamicText text = null; public void init(){ text = new DynamicText("Welcome"); } public void paint(Graphics g){ g.drawString(text.getText(), 50, 30); } //implement Listener update() method public void update(){ repaint(); } } //DynamicText.java public class DynamicText implements Publisher{ // implements Publisher interface methods //notify listeners whenever text changes } Isn't this a violation of Single Responsibility Principle where my Applet not only acts as Applet but also has to do Listener job. Same way DynamicText class not only generates the dynamic text but updates the registered listeners. Design 2: //MyApplet.java public class MyApplet extends Applet{ private AppletListener appLstnr = null; public void init(){ appLstnr = new AppletListener(this); // applet stuff } } // AppletListener.java public class AppletListener implements Listener{ private Applet applet = null; public AppletListener(Applet applet){ this.applet = applet; } public void update(){ this.applet.repaint(); } } // DynamicText public class DynamicText{ private TextPublisher textPblshr = null; public DynamicText(TextPublisher txtPblshr){ this.textPblshr = txtPblshr; } // call textPblshr.notifyListeners whenever text changes } public class TextPublisher implments Publisher{ // implements publisher interface methods } Q1. Is design 1 a SPR violation? Q2. Is composition a better choice here to remove SPR violation as in design 2.

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  • Why are there so many data centres in Texas?

    - by jklp
    I've been searching for online hosting recently and have noticed a high concentration of hosting providers in Texas. Just wondering why this is? It couldn't be possibly be because of temperature (I don't think Texas is a particularly cool place to be) or maybe power is cheaper in Texas vs the rest of the States? Or maybe it's just there are laws in place which give hosting providers tax breaks? Would be very interested to find out.

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  • Having trouble animating Line in D3.js using and array of objects as data

    - by user1731245
    I can't seem to get an animated transition between line graphs when I pass in a new set of data. I am using an array of objects as data like this: [{ clicks: 40 installs: 10 time: "1349474400000" },{ clicks: 61 installs: 3 time: "1349478000000" }]; I am using this code to setup my ranges / axis's var xRange = d3.time.scale().range([0, w]), yRange = d3.scale.linear().range([h , 0]), xAxis = d3.svg.axis().scale(xRange).tickSize(-h).ticks(6).tickSubdivide(false), yAxis = d3.svg.axis().scale(yRange).ticks(5).tickSize(-w).orient("left"); var clicksLine = d3.svg.line() .interpolate("cardinal") .x(function(d){return xRange(d.time)}) .y(function(d){return yRange(d.clicks)}); var clickPath; function drawGraphs(data) { clickPath = svg.append("g") .append("path") .data([data]) .attr("class", "clicks") .attr("d", clicksLine); } function updateGraphs(data) { svg.select('path.clicks') .data([data]) .attr("d", clicksLine) .transition() .duration(500) .ease("linear") } I have tried just about everything to be able to pass in new data and see an animation between graph's. Not sure what I am missing? does it have something to do with using an array of objects instead of just a flat array of numbers as data?

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  • Can simple javascript inheritance be simplified even further?

    - by Will
    John Resig (of jQuery fame) provides a concise and elegant way to allow simple JavaScript inheritance. It was so short and sweet, in fact, that it inspired me to try and simplify it even further (see code below). I've modified his original function such that it still passes all his tests and has the potential advantage of: readability (50% less code) simplicity (you don't have to be a ninja to understand it) performance (no extra wrappers around super/base method calls) consistency with C#'s base keyword Because this seems almost too good to be true, I want to make sure my logic doesn't have any fundamental flaws/holes/bugs, or if anyone has additional suggestions to improve or refute the code (perhaps even John Resig could chime in here!). Does anyone see anything wrong with my approach (below) vs. John Resig's original approach? if (!window.Class) { window.Class = function() {}; window.Class.extend = function(members) { var prototype = new this(); for (var i in members) prototype[i] = members[i]; prototype.base = this.prototype; function object() { if (object.caller == null && this.initialize) this.initialize.apply(this, arguments); } object.constructor = object; object.prototype = prototype; object.extend = arguments.callee; return object; }; } And the tests (below) are nearly identical to the original ones except for the syntax around base/super method calls (for the reason enumerated above): var Person = Class.extend( { initialize: function(isDancing) { this.dancing = isDancing; }, dance: function() { return this.dancing; } }); var Ninja = Person.extend( { initialize: function() { this.base.initialize(false); }, dance: function() { return this.base.dance(); }, swingSword: function() { return true; } }); var p = new Person(true); alert("true? " + p.dance()); // => true var n = new Ninja(); alert("false? " + n.dance()); // => false alert("true? " + n.swingSword()); // => true alert("true? " + (p instanceof Person && p instanceof Class && n instanceof Ninja && n instanceof Person && n instanceof Class));

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  • How can I improve this design?

    - by klausbyskov
    Let's assume that our system can perform actions, and that an action requires some parameters to do its work. I have defined the following base class for all actions (simplified for your reading pleasure): public abstract class BaseBusinessAction<TActionParameters> : where TActionParameters : IActionParameters { protected BaseBusinessAction(TActionParameters actionParameters) { if (actionParameters == null) throw new ArgumentNullException("actionParameters"); this.Parameters = actionParameters; if (!ParametersAreValid()) throw new ArgumentException("Valid parameters must be supplied", "actionParameters"); } protected TActionParameters Parameters { get; private set; } protected abstract bool ParametersAreValid(); public void CommonMethod() { ... } } Only a concrete implementation of BaseBusinessAction knows how to validate that the parameters passed to it are valid, and therefore the ParametersAreValid is an abstract function. However, I want the base class constructor to enforce that the parameters passed are always valid, so I've added a call to ParametersAreValid to the constructor and I throw an exception when the function returns false. So far so good, right? Well, no. Code analysis is telling me to "not call overridable methods in constructors" which actually makes a lot of sense because when the base class's constructor is called the child class's constructor has not yet been called, and therefore the ParametersAreValid method may not have access to some critical member variable that the child class's constructor would set. So the question is this: How do I improve this design? Do I add a Func<bool, TActionParameters> parameter to the base class constructor? If I did: public class MyAction<MyParameters> { public MyAction(MyParameters actionParameters, bool something) : base(actionParameters, ValidateIt) { this.something = something; } private bool something; public static bool ValidateIt() { return something; } } This would work because ValidateIt is static, but I don't know... Is there a better way? Comments are very welcome.

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  • Interface Design Problem: Storing Result of Transactions

    - by jboyd
    Requirements: multiple sources of input (social media content) into a system multiple destinations of output (social media api's) sources and destinations WILL be added some pseudo: IContentProvider contentProvider = context.getBean("contentProvider"); List<Content> toPost = contentProvider.getContent(); for (Content c : toPost) { SocialMediaPresence smPresence = socialMediaService.getSMPresenceBySomeId(c.getDestId()); smPresence.hasTwitter(); smPresence.hasFacebook(); //just to show what this is smPresence.postContent(c); //post content could fail for some SM platforms, but shoulnd't be lost forever } So now I run out of steam, I need to know what content has been successfully posted, and if it hasn't gone too all platforms, or if another platform were added in the future that content needs to go out for it as well (therefore my content provider will need to not only know if content has gone out, but for what platforms). I'm not looking for code, although sample/pseudo is fine... I'm looking for an approach to this problem that I can implement

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  • European wireless data

    - by drewk
    I am on my way to Europe for 20 days with the wife and teenage kids. Among us, we have 3 iPhones, 1 Blackberry, 2 iPad 3G and 2 Macbook Pro laptops. Each has Skype. I am very concerned about AT&T data charges, and I am looking for a sensible alternative. For example, the AT&T data plans for the phones and iPads are $200 EACH for 200 MB per device. That is $1,200 and does not even cover the laptops. Ouch!!! I am thinking about a prepaid data plan from a European cell system of some sort combined with a GSM data modem and a Cradlepoint router, such as the CTR500. So, questions: 1) Anyone know of a GSM data source in Europe where I can buy a GSM Modem compatible with the CTR500 at a reasonable prepaid rate? 2) Experience with the CTR500?

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  • How can I copy Data from one sheet to another Sheet in Excel 07 Through Macro

    - by Mwaseem Alvi
    Hello, I am using MS Office 2007. Please let me know that how can I copy whole data from sheet one to sheet two. I want to copy the whole data from row 5 to onward in sheet two. The whole scenrio is given below in detail. Sheet one: Copy the data from column B and Row 3 Sheet Two: Paste the Copied Data in Column B and Row 3 Sheet One: Copy the whole data from Column B to Column G and Row 5 to onward Sheet Two: Paste whole copied data in sheet two from last filled row to onward Data dont overwrite on any row or column. Every data will be add in sheet two from sheet one when macro will be run. Thanks

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  • How to apply Single Responsibility Principle to a service class

    - by Shekhar
    Hello Suppose we are designing a UserServiceImpl class which does CRUD(Create, Read, Update, and Delete) operations. In my view Create, Read, Update, and Delete are four reasons for a class to change. Does this class violates Single Responsibility Principle? If it violates, then should we have four classes like CreateUserServiceImpl, ReadUserServiceImpl, UpdateUserServiceImpl, and DeleteUserServiceImpl. Isn't it an overkill to have lots of classes? Thanks Shekhar

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  • Best practices for handling math calculations in a flash project?

    - by VideoDnd
    I'm building a Flash project where it needs to handle some math, like an acceleration formula. My director has recommended a design pattern where I include the calculations directly in the flash object, but that doesn't seem like it's very good OOP. What's the best practice for calculations in Flash? Should it be a separate object, so I can keep the "non-Flash" parts together and out of the way? What are people's experiences with including it inline vs. keeping it separate?

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  • How do I access data within this multidimensional array?

    - by dmanexe
    I have this array: $items_pool = Array ( [0] => Array ( [id] => 1 [quantity] => 1 ) [1] => Array ( [id] => 2 [quantity] => 1 ) [2] => Array ( [id] => 72 [quantity] => 6 ) [3] => Array ( [id] => 4 [quantity] => 1 ) [4] => Array ( [id] => 5 [quantity] => 1 ) [5] => Array ( [id] => 7 [quantity] => 1 ) [6] => Array ( [id] => 8 [quantity] => 1 ) [7] => Array ( [id] => 9 [quantity] => 1 ) [8] => Array ( [id] => 19 [quantity] => 1 ) [9] => Array ( [id] => 20 [quantity] => 1 ) [10] => Array ( [id] => 22 [quantity] => 1 ) [11] => Array ( [id] => 29 [quantity] => 0 ) ) I'm trying to loop through this array and perform a conditional based on $items_pool[][id]'s value. I want to then report back TRUE or NULL/FALSE, so I'm just testing the presence of to be specific.

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  • How to have a policy class implement a virtual function?

    - by dehmann
    I'm trying to design a policy-based class, where a certain interface is implemented by the policy itself, so the class derives from the policy, which itself is a template (I got this kind of thinking from Alexandrescu's book): #include <iostream> #include <vector> class TestInterface { public: virtual void test() = 0; }; class TestImpl1 { public: void test() {std::cerr << "Impl1" << std::endl;} }; template<class TestPolicy> class Foo : public TestInterface, TestPolicy { }; Then, in the main() function, I call test() on (potentially) various different objects that all implement the same interface: int main() { std::vector<TestInterface*> foos; foos.push_back(new Foo<TestImpl1>()); foos[0]->test(); delete foos[0]; return 0; } It doesn't compile, though, because the following virtual functions are pure within ‘Foo<TestImpl1>’: virtual void TestInterface::test() I thought TestInterface::test() is implemented because we derive from TestImpl1?

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