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  • Good case for a Null Object Pattern? (Provide some service with a mailservice)

    - by fireeyedboy
    For a website I'm working on, I made an Media Service object that I use in the front end, as well as in the backend (CMS). This Media Service object manipulates media in a local repository (DB); it provides the ability to upload/embed video's and upload images. In other words, website visitors are able to do this in the front end, but administrators of the site are also able to do this in the backend. I'ld like this service to mail the administrators when a visitor has uploaded/embedded a new medium in the frontend, but refrain from mailing them when they upload/embed a medium themself in the backend. So I started wondering whether this is a good case for passing a null object, that mimicks the mail funcionality, to the Media Service in the backend. I thought this might come in handy when they decide the backend needs to have implemented mail functionality as well. In simplified terms I'ld like to do something like this: Frontend: $mediaService = new MediaService( new MediaRepository(), new StandardMailService() ); Backend: $mediaService = new MediaService( new MediaRepository(), new NullMailService() ); How do you feel about this? Does this make sense? Or am I setting myself up for problems down the road?

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  • Is it a good idea to use an integer column for storing US ZIP codes in a database?

    - by Yadyn
    From first glance, it would appear I have two basic choices for storing ZIP codes in a database table: Text (probably most common), i.e. char(5) or varchar(9) to support +4 extension Numeric, i.e. 32-bit integer Both would satisfy the requirements of the data, if we assume that there are no international concerns. In the past we've generally just gone the text route, but I was wondering if anyone does the opposite? Just from brief comparison it looks like the integer method has two clear advantages: It is, by means of its nature, automatically limited to numerics only (whereas without validation the text style could store letters and such which are not, to my knowledge, ever valid in a ZIP code). This doesn't mean we could/would/should forgo validating user input as normal, though! It takes less space, being 4 bytes (which should be plenty even for 9-digit ZIP codes) instead of 5 or 9 bytes. Also, it seems like it wouldn't hurt display output much. It is trivial to slap a ToString() on a numeric value, use simple string manipulation to insert a hyphen or space or whatever for the +4 extension, and use string formatting to restore leading zeroes. Is there anything that would discourage using int as a datatype for US-only ZIP codes?

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  • What do you find wrong or strange in this Perl code to simulate objects without bless?

    - by user350571
    I'm new to Perl and its blessing stuff to imitate class like functionality made me feel strange I even had to go to the bathroom. Now, please tell me: what do you don't like, find wrong or strange with this code: sub Person { my $age = shift || 15; return { printAge => sub { print "Age -> $age\n"; }, changeAge => sub { $age = shift } } } my $p = Person(); my $p2 = Person(27); $p->{printAge}->(); $p->{changeAge}->(30); $p->{printAge}->(); $p2->{printAge}->();

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  • If as assert fails, is there a bug?

    - by RichAmberale
    I've always followed the logic: if assert fails, then there is a bug. Root cause could either be: Assert itself is invalid (bug) There is a programming error (bug) (no other options) I.E. Are there any other conclusions one could come to? Are there cases where an assert would fail and there is no bug?

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  • Revisions: algorithm and data structure

    - by SODA
    Hi, I need ideas for structuring and processing data with revisions. For example, I have a database of objects (e.g. cars). Each object has a number of properties, which can be arbitrary, so there's no a set schema to describe these objects. These objects are probably saved as key-value pairs. Now I need to change property of an object. I don't want to completely rewrite it - I want to be able to go back and see history of changes to these properties, that's why I want to add new property and keep the old one (so I guess a timestamp would do the job of telling which property is the latest). At the same time I want to be able to get info about any object in a snap, with only latest versions of each of the properties. Any ideas what would be the best approach? At least please point me in the right direction. Thanks!

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  • How to calculate a measure of a total error in this clustering

    - by Vafello
    I have the following points and clustering of data S1. Can anyone tell me how to calculate the total error associated with this clustering? I know it's not a strictly programming question, but I need it for my algorithm. I think the answer should be 4/3 but I have no idea how to calculate this. Can anyone help me? x1= (2.0,1.0) x2= (2.0,2.0) x3= (1.0,2.0) S1={ x1, x2, x3 }

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  • MCV/MVP Patterns and Applications that interface with Hardware (DAQ/PLC/etc)

    - by Ryan
    I've been reading a lot about the MCV and MVP patterns for use with UI and it seems like a really nice powerful way to handle user interfaces. I am - however - having a difficult time deciding how this could integrate into a system where data in the model is created from a Data Acquisition System or Serial/Ethernet devices. There is also the added step that 70% of application interaction is performed by a PLC instead of a live user. It seems that for apps that just read/write & manipulate information from a database this works great, but how does does hardware and automation fit into these patterns? Is it as simple as another controller (for lack of a better term) that interacts with hardware that manipulates data and writes to a model? Maybe I am over thinking this or thinking too simply, so any advice would be great. I'm not quite sure where I'm going with this, so if something doesn't make sense or I was too vague leave me a comment. Thanks!

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  • Practical refactoring

    - by ahb
    I've read about refactoring and probably did it before I even knew about it, however I don't really know much about it is actually done and what it practically means. What, from your view, is refactoring? How and when do you do it?

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  • Does C# allow method overloading, PHP style (__call)?

    - by mr.b
    In PHP, there is a special method named __call($calledMethodName, $arguments), which allows class to catch calls to non-existing methods, and do something about it. Since most of classic languages are strongly typed, compiler won't allow calling a method that does not exist, I'm clear with that part. What I want to accomplish (and I figured this is how I would do it in PHP, but C# is something else) is to proxy calls to a class methods and log each of these calls. Right now, I have code similar to this: class ProxyClass { static logger; public AnotherClass inner { get; private set; } public ProxyClass() { inner = new AnotherClass(); } } class AnotherClass { public void A() {} public void B() {} public void C() {} // ... } // meanwhile, in happyCodeLandia... ProxyClass pc = new ProxyClass(); pc.inner.A(); pc.inner.B(); // ... So, how can I proxy calls to an object instance in extensible way? Extensible, meaning that I don't have to modify ProxyClass whenever AnotherClass changes. In my case, AnotherClass can have any number of methods, so it wouldn't be appropriate to overload or wrap all methods to add logging. I am aware that this might not be the best approach for this kind of problem, so if anyone has idea what approach to use, shoot. Thanks!

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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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  • Buy or build tool for Data Reporting ?

    - by Manoj
    We have been asked to provide a data reporting solution. The followng are the requirements: i. The client has a lot of data which is generated everyday as an outcome of the tests they run. These tests are run at several sites and they get automatically backed up into a central server. ii. They already have perl scripts which post process them and generates excel based reports. iii. They need a web based interface for comparing those reports and they need to mark and track issues which might be present in those data. I am confused if we should build our own tool for this or we should go for already exiting tool(any suggestions?). Can you please provide supportive arguments for the decision that you would suggest?

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  • Database Table Schema and Aggregate Roots

    - by bretddog
    Hi, Applicaiton is single user, 1-tier(1 pc), database SqlCE. DataService layer will be (I think) : Repository returning domain objects and quering database with LinqToSql (dbml). There are obviously a lot more columns, this is simplified view. http://img573.imageshack.us/img573/3612/ss20110115171817w.png This is my first attempt of creating a 2 tables database. I think the table schema makes sense, but I need some reassurance or critics. Because the table relations looks quite scary to be honest. I'm hoping you could; Look at the table schema and respond if there are clear signs of troubles or errors that you spot right away.. And if you have time, Look at Program Summary/Questions, and see if the table layout makes makes sense to those points. Please be brutal, I will try to defend :) Program summary: a) A set of categories, each having a set of strategies (1:m) b) Each day a number of items will be produced. And each strategy MAY reference it. (So there can be 50 items, and a strategy may reference 23 of them) c) An item can be referenced by more than one strategy. So I think it's an m:m relation. d) Status values will be logged at fixed time-fractions through the day, for: - .... each Strategy.....each StrategyItem....each item e) An action on an item may be executed by a strategy that reference it. - This is logged as ItemAction (Could have called it StrategyItemAction) User Requsts b) - e) described the main activity mode of the program. To work with only today's DayLog , for each category. 2nd priority activity is retrieval of history, which typically will be From all categories, from day x to day y; Get all StrategyDailyLog. Questions First, does the overall layout look sound? I'm worried to see that there are so many relationships in all directions, connecting everything. Is this normal, or does it look like trouble? StrategyItem is made to represent an m:m relationship. Is it correct as I noted 1:m / 1:1 (marked red) ? StrategyItemTimeLog and ItemTimeLog; Logs values that both need to be retrieved together, when retreiving a StrategyItem. Reason I separated is that the first one is strategy-specific, and several strategies can reference same item. So I thought not to duplicate those values that are not dependent no strategy, but only on the item. Hence I also dragged out the LogTime, as it seems to be the only parameter to unite the logs. But this all looks quite disturbing with those 3 tables. Does it make sense at all? Or you have suggestion? Pink circles shows my vague attempt of Aggregate Root Paths. I've been thinking in terms of "what entity is responsible for delete". Though I'm unsure about the actual root. I think it's Category. Does it make sense related to User Requests described above?

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  • Auto-generated values for columns in database

    - by Jamal
    Is it a good practice to initialize columns that we can know their values in database, for example identity columns of type unique identifier can have a default value (NEWID()), or columns that shows the record create date can have a default value (GETDATE()). Should I go through all my tables and do this whereever I am sure that I won't need to assign the value manually and the Auto-generated value is correct. I am also thinking about using linq-to-sql classes and setting the "Auto Generated Value" property of these columns to true. Maybe this is what everybody already knows or maybe I am asking a question about a fundamental issue, if so please tell me.

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  • DI with disposable objects

    - by sunnychaganty
    Suppose my repository class looks like this: class myRepository : IDisposable{ private DataContext _context; public myRepository(DataContext context){ _context = context; } public void Dispose(){ // to do: implement dispose of DataContext } } now, I am using Unity to control the lifetime of my repository & the data context & configured the lifetimes as: DataContext - singleton myRepository - create a new instance each time Does this mean that I should not be implementing the IDisposable on the repository to clean up the DataContext? Any guidance on such items?

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  • Online graphing and data visualization frameworks

    - by Marques
    I have been looking around at web applications and websites with rich graphs, charts, and data visualization and for the most part have been able to determine which frameworks or tools websites are using. However I was looking over 'resumup.com' and couldn't determine what they are using. Does anyone know off hand or can you tell? It doesn't seem like any javascript framework i've seen unless its custom...is it some sort of flash or flex framework? Any help would be greatly appreciated. Thanks, Marques

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  • purchasing source code from third party vendor

    - by Richard Friend
    Hi Our company uses some third party vendors to write some of our external facing web sites, however with one vendor we keep experiencing over inflated charges for simple changes and it has been decided to bring the product in-house. I have been tasked to provide a list of deliverables/checkpoints that would form a part of the agreement. what is the minimum you would expect if you are purchasing the source code of a product that you have paid for the development of, should we expect code for any custom libraries they may be using that were written not for us etc.. This is all written in .net so i am well aware we could just get the code via reflector, however i dont think my boss would go for this ;-)

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  • Need a good way to store data in a DB from a table on a webpage that can have N columns.

    - by Abe Miessler
    Users need to be able to add a specific type of column to an otherwise static table on my web page and then save the information they enter in there to the database. I've been told that in reality they will almost never go over 5 columns but I would rather support N. The columns will all be of the same datatype. My first thought was to have an XML column with the values from all added columns in there but I was curious if anyone else had come up with a better solution. Suggestions?

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  • C# Event Handlers Using an Enum

    - by Jimbo
    I have a StatusChanged event that is raised by my object when its status changes - however, the application needs to carry out additional actions based on what the new status is. e.g If the new status is Disconnected, then it must update the status bar text and send an email notification. So, I wanted to create an Enum with the possible statuses (Connected, Disconnected, ReceivingData, SendingData etc.) and have that sent with the EventArgs parameter of the event when it is raised (see below) Define the object: class ModemComm { public event CommanderEventHandler ModemCommEvent; public delegate void CommanderEventHandler(object source, ModemCommEventArgs e); public void Connect() { ModemCommEvent(this, new ModemCommEventArgs ModemCommEventArgs.eModemCommEvent.Connected)); } } Define the new EventArgs parameter: public class ModemCommEventArgs : EventArgs{ public enum eModemCommEvent { Idle, Connected, Disconnected, SendingData, ReceivingData } public eModemCommEvent eventType { get; set; } public string eventMessage { get; set; } public ModemCommEventArgs(eModemCommEvent eventType, string eventMessage) { this.eventMessage = eventMessage; this.eventType = eventType; } } I then create a handler for the event in the application: ModemComm comm = new ModemComm(); comm.ModemCommEvent += OnModemCommEvent; and private void OnModemCommEvent(object source, ModemCommEventArgs e) { } The problem is, I get a 'Object reference not set to an instance of an object' error when the object attempts to raise the event. Hoping someone can explain in n00b terms why and how to fix it :)

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