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  • How to easily substitute a Base class

    - by JTom
    Hi, I have the following hierarchy of classes class classOne { virtual void abstractMethod() = 0; }; class classTwo : public classOne { }; class classThree : public classTwo { }; All classOne, classTwo and classThree are abstract classes, and I have another class that is defining the pure virtual methods class classNonAbstract : public classThree { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; And right now I need it differently...I need it like class classNonAbstractOne : public classOne { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; class classNonAbstractTwo : public classTwo { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; and class classNonAbstractThree : public classThree { void abstractMethod(); // Couple of new methods void doIt(); void doItToo(); }; But all the nonAbstract classes have the same new methods, with the same code...and I would like to avoid copying all the methods and it's code to every nonAbstract class. How could I accomplish that? Hopefully it's understandable...

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  • Java library class to handle scheduled execution of "callbacks"?

    - by Hanno Fietz
    My program has a component - dubbed the Scheduler - that lets other components register points in time at which they want to be called back. This should work much like the Unix cron service, i. e. you tell the Scheduler "notify me at ten minutes past every full hour". I realize there are no real callbacks in Java. Here's my approach, is there a library which already does this stuff? Feel free to suggest improvements, too. Register call to Scheduler passes: a time specification containing hour, minute, second, year month, dom, dow, where each item may be unspecified, meaning "execute it every hour / minute etc." (just like crontabs) an object containing data that will tell the calling object what to do when it is notified by the Scheduler. The Scheduler does not process this data, just stores it and passes it back upon notification. a reference to the calling object Upon startup, or after a new registration request, the Scheduler starts with a Calendar object of the current system time and checks if there are any entries in the database that match this point in time. If there are, they are executed and the process starts over. If there aren't, the time in the Calendar object is incremented by one second and the entreis are rechecked. This repeats until there is one entry or more that match(es). (Discrete Event Simulation) The Scheduler will then remember that timestamp, sleep and wake every second to check if it is already there. If it happens to wake up and the time has already passed, it starts over, likewise if the time has come and the jobs have been executed. Edit: Thanks for pointing me to Quartz. I'm looking for something much smaller, however.

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  • Unexpected space between DIV elements, no - not padding and not margins

    - by jon
    my code for the php page displaying the divs <?php session_start(); require_once("classlib/mainspace.php"); if (isset($_SESSION['username'])==FALSE) { header("location:login.php"); } $user = new User($_SESSION['username']); ?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <link rel="stylesheet" type="text/css" href="style/style.css" /> <title>SimpleTask - Home</title> </head> <body> <div id="main"> <div id="menu"> <div id="items"> <ul> <li><a href="home.php">home</a></li> <li>&bull;</li> <li><a href="projects.php">my projects</a></li> <li>&bull;</li> <li><a href="comments.php">my comments</a></li> </ul> </div> <div id="user"> <p>Welcome, <?php echo $user->GetRealName(); ?><br/><a href="editprofile.php">edit profile</a> &bull; <a href="logout.php">logout</a></p> </div> </div> <div id="content"> <h1>HOME</h1> </div> <div id="footer"> <p>footer text goes here here here here</p> </div> </div> </body> </html> and you can find my CSS here http://tasker.efficaxdevelopment.com/style/style.css and to view the live page go here http://tasker.efficaxdevelopment.com/login.php username:admin password:password

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  • Include everything, Separate with "using"

    - by Dave
    I'm developing a C++ library. It got me thinking of the ways Java and C# handle including different components of the libraries. For example, Java uses "import" to allow use of classes from other packages, while C# simply uses "using" to import entire modules. My questions is, would it be a good idea to #include everything in the library in one massive include and then just use the using directive to import specific classes and modules? Or would this just be down right crazy? EDIT: Good responses so far, here are a few mitigating factors which I feel add to this idea: 1) Internal #includes are kept as normal (short and to the point) 2) The file which includes everything is optionally supplied with the library to those who wish to use it3) You could optionally make the big include file part of the pre-compiled header

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  • How extensible should code actually be?

    - by griegs
    I've just started a new job and one of the things my new boss talked to me about was code longevity. I've always coded to make my code infinently extensible and adaptable. I figured that if someone was going to change my code in the future then it should be easy to do. But I never really had a clear idea on how far into the future that should be. So my new boss told me not to bother coding for anything more that 3 years into the future and his reasoning was that technology changes, programs expire etc. At first I was kinda taken aback and thought he was a whack job but the longer I think about it the more I'm warming to the concept. Does anyone else have an opinion on how far into the future you should code to?

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  • Table with a lot of attributes

    - by Robert
    Hi, I'm planing to build some database project. One of the tables have a lot of attributes. My question is: What is better, to divide the the class into 2 separate tables or put all of them into one table. below is an example create table User { id, name, surname,... show_name, show_photos, ...) or create table User { id, name, surname,... ) create table UserPrivacy {usr_id, show_name, show_photos, ...) The performance i suppose is similar due to i can use index.

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  • Tables as relations in ER diagrams

    - by Richard Mar.
    Assume I have the following tables (**bold** - primary key, *italics* - foreign key): patient(**patient_id**, name) disease(**disease_id**, name) patient_disease(**p_d_id**, *patient_id*, *disease,_id* ) I want to draw the ER diagram for this. My idea is to make two entities, one for patient and one for disease, then make a n-to-n relation between them, with p_d_id as its attribute. Is that how it's supposed to be?

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  • Fowler Analysis Patterns lately?

    - by Berryl
    As much as I've always loved this one is how much I always wished there were more meaty examples of how to apply some of the concepts available. Is anyone aware of anything out there worth looking at that attempts to that? Cheers, Berryl

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  • Database model for saving random boolean expressions

    - by zarko.susnjar
    I have expressions like this: (cat OR cats OR kitten OR kitty) AND (dog OR dogs) NOT (pigeon OR firefly) Anyone having idea how to make tables to save those? Before I got request for usage of brackets, I limited usage of operators to avoid ambiguous situations. So only ANDs and NOTs or only ORs and saved those in this manner: operators id | name 1 | AND 2 | OR 3 | NOT keywords id | keyword 1 | cat 2 | dog 3 | firefly expressions id | operator | keywordId 1 | 0 | 1 1 | 1 | 2 1 | 3 | 3 which was: cat AND dog NOT firefly But now, I'm really puzzled...

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  • Uses of the Apache commons-proxy library?

    - by Adrian
    I'm looking at the Apache commons-proxy library to implement some Proxy patterns in my current project. The Javadocs are all very well, but I'd really like to see some tutorials or just a project that uses the library so I can get more of a feel for it. Alas, searching for such things just tends to net you a lot of pages about setting up HTTP proxies using Apache. So I'm hoping that people here can help me.

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  • What should layers in dotnet application ? Pleas guide me

    - by haansi
    Hi, I am using layered architecture in dotnet (mostly I work on web projects). I am confuse what layers should I use ? I have small idea that there should be the following layers. user interface customer types (custom entities) business logic layer data access layer My purpose is sure quality of work and maximum re-usability of code. some one suggested to add common types layer in it. Please guide me what should be layers ? and in each layer what part should go ? thanks for your precious time and advice. haansi

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  • Disposing underlying object from finalizer in an immutable object

    - by Juan Luis Soldi
    I'm trying to wrap around Awesomium and make it look to the rest of my code as close as possible to NET's WebBrowser since this is for an existing application that already uses the WebBrowser. In this library, there is a class called JSObject which represents a javascript object. You can get one of this, for instance, by calling the ExecuteJavascriptWithResult method of the WebView class. If you'd call it like myWebView.ExecuteJavascriptWithResult("document", string.Empty).ToObject(), then you'd get a JSObject that represents the document. I'm writing an immutable class (it's only field is a readonly JSObject object) called JSObjectWrap that wraps around JSObject which I want to use as base class for other classes that would emulate .NET classes such as HtmlElement and HtmlDocument. Now, these classes don't implement Dispose, but JSObject does. What I first thought was to call the underlying JSObject's Dispose method in my JSObjectWrap's finalizer (instead of having JSObjectWrap implement Dispose) so that the rest of my code can stay the way it is (instead of having to add using's everywhere and make sure every JSObjectWrap is being properly disposed). But I just realized if more than two JSObjectWrap's have the same underlying JSObject and one of them gets finalized this will mess up the other JSObjectWrap. So now I'm thinking maybe I should keep a static Dictionary of JSObjects and keep count of how many of each of them are being referenced by a JSObjectWrap but this sounds messy and I think could cause major performance issues. Since this sounds to me like a common pattern I wonder if anyone else has a better idea.

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  • C#, weird optimization

    - by Snake
    Hi, I'm trying to read my compiled C# code. this is my code: using(OleDbCommand insertCommand = new OleDbCommand("...", connection)) { // do super stuff } But! We all know that a using gets translated to this: { OleDbCommand insertCommand = new OleDbCommand("...", connection) try { //do super stuff } finally { if(insertCommand != null) ((IDisposable)insertCommand).Dispose(); } } (since OleDbCommand is a reference type). But when I decompile my assembly (compiled with .NET 2.0) I get this in Resharper: try { insertCommand = new OleDbCommand("", connection); Label_0017: try { //do super stuff } finally { Label_0111: if ((insertCommand == null) != null) { goto Label_0122; } insertCommand.Dispose(); Label_0122:; } I'm talking about this line: if ((insertCommand == null) != null). True is not null, it never is, nor is false. So how is my object disposed properly? WTF? Thanks! -Kristof

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  • Coding without Grock. Is it wrong?

    - by OldCurmudgeon
    Should a professional programmer allow themselves to write code without completely understanding the requirements? In my 30+ years as a programmer I must have written many thousands of lines of code without completely understanding what is required of me at the time. In most cases the results were rubbish that should have been discarded. Every other industry that employs professionals has systems to root out such behavior. Ours does not. Is this right?

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  • When is it better to use a method versus a property for a class definition?

    - by ccomet
    Partially related to an earlier question of mine, I have a system in which I have to store complex data as a string. Instead of parsing these strings as all kinds of separate objects, I just created one class that contains all of those objects, and it has some parser logic that will encode all properties into strings, or decode a string to get those objects. That's all fine and good. This question is not about the parser itself, but about where I should house the logic for the parser. Is it a better choice to put it as a property, or as a method? In the case of a property, say public string DataAsString, the get accessor would house the logic to encode all of the data into a string, while the set accessor would decode the input value and set all of the data in the class instance. It seems convenient because the input/output is indeed a string. In the case of a method, one method would be Encode(), which returns the encoded string. Then, either the constructor itself would house the logic for the decoding a string and require the string argument, or I write a Decode(string str) method which is called separately. In either case, it would be using a method instead of a property. So, is there a functional difference between these paths, in terms of the actual running of the code? Or are they basically equivalent and it then boils down to a choice of personal preference or which one looks better? And in that kind of question... which would look cleaner anyway?

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  • Why is it bad to use boolean flags in databases? And what should be used instead?

    - by David Chanin
    I've been reading through some of guides on database optimization and best practices and a lot of them suggest not using boolean flags at all in the DB schema (ex http://forge.mysql.com/wiki/Top10SQLPerformanceTips). However, they never provide any reason as to why this is bad. Is it a peformance issue? is it hard to index or query properly? Furthermore, if boolean flags are bad, what should you use to store boolean values in a database? Is it better to store boolean flags as an integer and use a bitmask? This seems like it would be less readable.

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  • Using DTOs and BOs

    - by ryanzec
    One area of question for me about DTOs/BOs is about when to pass/return the DTOs and when to pass/return the BOs. My gut reaction tells me to always map NHibernate to the DTOs, not BOs, and always pass/return the DTOs. Then whenever I needed to perform business logic, I would convert my DTO into a BO. The way I would do this is that my BO would have a have a constructor that takes a parameter that is the type of my interface (that defines the required fields/properties) that both my DTO and BO implement as the only argument. Then I would be able to create my BO by passing it the DTO in the constructor (since both with implement the same interface, they both with have the same properties) and then be able to perform my business logic with that BO. I would then also have a way to convert a BO to a DTO. However, I have also seen where people seem to only work with BOs and only work with DTOs in the background where to the user, it looks like there are no DTOs. What benefits/downfalls are there with this architecture vs always using BO's? Should I always being passing/returning either DTOs or BOs or mix and match (seems like mixing and matching could get confusing)?

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  • Android ignoring my setWidth() and setHeight()

    - by popoffka
    So, why does this code: package org.popoffka.apicross; import android.app.Activity; import android.os.Bundle; import android.widget.Button; public class Game extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Button testButton = new Button(this); testButton.setBackgroundResource(R.drawable.cell); testButton.setWidth(20); testButton.setHeight(20); setContentView(testButton); } } ...produce this thing: http://i42.tinypic.com/2hgdzme.png even though there's a setWidth(20) and setHeight(20) in the code? (R.drawable.cell is actually a 20x20 PNG image containing a white cell with a silver border)

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  • Two different tables or just one with bool column?

    - by Aidas
    We have two tables: OriginalDocument and ProcessedDocument. In the first one we put an original, not processed document. After it's validated and processed (converted to our xml format and parsed), it's put into Document table. Processed document can be valid or invalid. Which makes more sense: have two different tables for valid and invalid documents or just have one with 'Valid' column? Some of the columns (~5-7) are irrelevant for invalid document. Storing both invalid and valid documents would also make Document table filled with 'NULL' columns (if document is invalid, information like document number, receiver can be unknown). What else should we consider and weigh, when making this decision?

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  • How to maintain an ordered table with Core Data (or SQL) with insertions/deletions?

    - by Jean-Denis Muys
    This question is in the context of Core Data, but if I am not mistaken, it applies equally well to a more general SQL case. I want to maintain an ordered table using Core Data, with the possibility for the user to: reorder rows insert new lines anywhere delete any existing line What's the best data model to do that? I can see two ways: 1) Model it as an array: I add an int position property to my entity 2) Model it as a linked list: I add two one-to-one relations, next and previous from my entity to itself 1) makes it easy to sort, but painful to insert or delete as you then have to update the position of all objects that come after 2) makes it easy to insert or delete, but very difficult to sort. In fact, I don't think I know how to express a Sort Descriptor (SQL ORDER BY clause) for that case. Now I can imagine a variation on 1): 3) add an int ordering property to the entity, but instead of having it count one-by-one, have it count 100 by 100 (for example). Then inserting is as simple as finding any number between the ordering of the previous and next existing objects. The expensive renumbering only has to occur when the 100 holes have been filled. Making that property a float rather than an int makes it even better: it's almost always possible to find a new float midway between two floats. Am I on the right track with solution 3), or is there something smarter?

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  • Many-To-Many dimensional model

    - by Mevdiven
    Folks, I have a dimension table called DIM_FILE which holds information of the files we received from customers. Each file has detail records which constitutes my FACT table, CUST_DETAIL. In the main process, file is gone through several stages and each stage tags a status to it. Long in a short, I have many-to-many relationship. Any ideas around star schema dimensional modeling. A customer record only belong to a single file and a file can have multiple statuses. FACT ---- CustID FileID AmountDue DIM_FILE -------- FileID FileName DateReceived FILE_STATUS ----------- FileID StatusDateTime StatusCode

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  • Class hierarchy problem (with generic's variance!)

    - by devoured elysium
    The problem: class StatesChain : IState, IHasStateList { private TasksChain tasks = new TasksChain(); ... public IList<IState> States { get { return _taskChain.Tasks; } } IList<ITask> IHasTasksCollection.Tasks { get { return _taskChain.Tasks; } <-- ERROR! You can't do this in C#! I want to return an IList<ITask> from an IList<IStates>. } } Assuming the IList returned will be read-only, I know that what I'm trying to achieve is safe (or is it not?). Is there any way I can accomplish what I'm trying? I wouldn't want to try to implement myself the TasksChain algorithm (again!), as it would be error prone and would lead to code duplication. Maybe I could just define an abstract Chain and then implement both TasksChain and StatesChain from there? Or maybe implementing a Chain<T> class? How would you approach this situation? The Details: I have defined an ITask interface: public interface ITask { bool Run(); ITask FailureTask { get; } } and a IState interface that inherits from ITask: public interface IState : ITask { IState FailureState { get; } } I have also defined an IHasTasksList interface: interface IHasTasksList { List<Tasks> Tasks { get; } } and an IHasStatesList: interface IHasTasksList { List<Tasks> States { get; } } Now, I have defined a TasksChain, that is a class that has some code logic that will manipulate a chain of tasks (beware that TasksChain is itself a kind of ITask!): class TasksChain : ITask, IHasTasksList { IList<ITask> tasks = new List<ITask>(); ... public List<ITask> Tasks { get { return _tasks; } } ... } I am implementing a State the following way: public class State : IState { private readonly TaskChain _taskChain = new TaskChain(); public State(Precondition precondition, Execution execution) { _taskChain.Tasks.Add(precondition); _taskChain.Tasks.Add(execution); } public bool Run() { return _taskChain.Run(); } public IState FailureState { get { return (IState)_taskChain.Tasks[0].FailureTask; } } ITask ITask.FailureTask { get { return FailureState; } } } which, as you can see, makes use of explicit interface implementations to "hide" FailureTask and instead show FailureState property. The problem comes from the fact that I also want to define a StatesChain, that inherits both from IState and IHasStateList (and that also imples ITask and IHasTaskList, implemented as explicit interfaces) and I want it to also hide IHasTaskList's Tasks and only show IHasStateList's States. (What is contained in "The problem" section should really be after this, but I thought puting it first would be way more reader friendly). (pff..long text) Thanks!

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