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  • Question About Example In Robert C Martin's _Clean Code_

    - by Jonah
    This is a question about the concept of a function doing only one thing. It won't make sense without some relevant passages for context, so I'll quote them here. They appear on pgs 37-38: To say this differently, we want to be able to read the program as though it were a set of TO paragraphs, each of which is describing the current level of abstraction and referencing subsequent TO paragraphs at the next level down. To include the setups and teardowns, we include setups, then we include the test page content, and then we include the teardowns. To include the setups, we include the suite setup if this is a suite, then we include the regular setup. It turns out to be very dif?cult for programmers to learn to follow this rule and write functions that stay at a single level of abstraction. But learning this trick is also very important. It is the key to keeping functions short and making sure they do “one thing.” Making the code read like a top-down set of TO paragraphs is an effective technique for keeping the abstraction level consistent. He then gives the following example of poor code: public Money calculatePay(Employee e) throws InvalidEmployeeType { switch (e.type) { case COMMISSIONED: return calculateCommissionedPay(e); case HOURLY: return calculateHourlyPay(e); case SALARIED: return calculateSalariedPay(e); default: throw new InvalidEmployeeType(e.type); } } and explains the problems with it as follows: There are several problems with this function. First, it’s large, and when new employee types are added, it will grow. Second, it very clearly does more than one thing. Third, it violates the Single Responsibility Principle7 (SRP) because there is more than one reason for it to change. Fourth, it violates the Open Closed Principle8 (OCP) because it must change whenever new types are added. Now my questions. To begin, it's clear to me how it violates the OCP, and it's clear to me that this alone makes it poor design. However, I am trying to understand each principle, and it's not clear to me how SRP applies. Specifically, the only reason I can imagine for this method to change is the addition of new employee types. There is only one "axis of change." If details of the calculation needed to change, this would only affect the submethods like "calculateHourlyPay()" Also, while in one sense it is obviously doing 3 things, those three things are all at the same level of abstraction, and can all be put into a TO paragraph no different from the example one: TO calculate pay for an employee, we calculate commissioned pay if the employee is commissioned, hourly pay if he is hourly, etc. So aside from its violation of the OCP, this code seems to conform to Martin's other requirements of clean code, even though he's arguing it does not. Can someone please explain what I am missing? Thanks.

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  • Large Django application layout

    - by Rob Golding
    I am in a team developing a web-based university portal, which will be based on Django. We are still in the exploratory stages, and I am trying to find the best way to lay the project/development environment out. My initial idea is to develop the system as a Django "app", which contains sub-applications to separate out the different parts of the system. The reason I intended to make these "sub" applications is that they would not have any use outside the parent application whatsoever, so there would be little point in distributing them separately. We envisage that the portal will be installed in multiple locations (at different universities, for example) so the main app can be dropped into a number of Django projects to install it. We therefore have a different repository for each location's project, which is really just a settings.py file defining the installed portal applications, and a urls.py routing the urls to it. I have started to write some initial code, though, and I've come up against a problem. Some of the code that handles user authentication and profiles seems to be without a home. It doesn't conceptually belong in the portal application as it doesn't relate to the portal's functionality. It also, however, can't go in the project repository - as I would then be duplicating the code over each location's repository. If I then discovered a bug in this code, for example, I would have to manually replicate the fix over all of the location's project files. My idea for a fix is to make all the project repos a fork of a "master" location project, so that I can pull any changes from that master. I think this is messy though, and it means that I have one more repository to look after. I'm looking for a better way to achieve this project. Can anyone recommend a solution or a similar example I can take a look at? The problem seems to be that I am developing a Django project rather than just a Django application.

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  • Metaprogramming - self explanatory code - tutorials, articles, books

    - by elena
    Hello everybody, I am looking into improving my programming skils (actually I try to do my best to suck less each year, as our Jeff Atwood put it), so I was thinking into reading stuff about metaprogramming and self explanatory code. I am looking for something like an idiot's guide to this (free books for download, online resources). Also I want more than your average wiki page and also something language agnostic or preferably with Java examples. Do you know of such resources that will allow to efficiently put all of it into practice (I know experience has a lot to say in all of this but i kind of want to build experience avoiding the flow bad decisions - experience - good decisions)? EDIT: Something of the likes of this example from the Pragmatic Programmer: ...implement a mini-language to control a simple drawing package... The language consists of single-letter commands. Some commands are followed by a single number. For example, the following input would draw a rectangle: P 2 # select pen 2 D # pen down W 2 # draw west 2cm N 1 # then north 1 E 2 # then east 2 S 1 # then back south U # pen up Thank you!

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  • robocode engine: how to design (write) the runtime engine -- the robot world

    - by Bob
    IBM has (had) a free learn-Java program called RoboCode, in which custom robots could be written that would then do battle in a 2D space. I would like to write the environment that supports such robots, but don't know what pattern or design to use. Each robot is a thread. Each thread is given a certain (indeterminate) amount of run-time by the JRE. A robot world engine would start by building a list of the players/robots, then enter a loop that allows each player in turn to do whatever it likes: move forward, turn left, fire toward the northwest corner, whatever. Each robot is also informed of events of interest: an enemy or several enemies are within range, it has been hit by a bullet, etc. The combination of handling threads that are also event listeners (are they also producers?) confuses me; it seems that there's more to the game engine. Even some general ideas would help. TIA.

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  • MVP on Asp.Net WebForms

    - by Nicolas Irisarri
    I'm not clear about this.... When having a gridview on the View, is the controller who has to set up the Data source, columns, etc? or I just have to expose the DataBinding stuff, fire it from the controller and let the html/codebehind on the view handle all the rendering and wiring up? To be more precise: on the view should I have private GridView _gv public _IList<Poco> Source { get {_gv.DataSource;} set {_gv.DataSource = value; _gv.DataBind();} } Or should it be (from http://stackoverflow.com/questions/153222/mvp-pattern-passive-view-and-exposing-complex-types-through-iview-asp-net-web) private GridView _datasource; public DataSource { get { return _datasource; } set { _datasource = value; _datasource.DataBind(); } } Maybe I'm having it all wrong .... Where can I find an example that is not a "Hello world" example on MVP for ASP.Net???

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  • The correct way to Fire-and-Forget an asynchronous delegate

    - by Programming Hero
    Consider me rusty on the subject of asynchronous delegates. If I want to call a method asynchronously, in a fire-and-forget style, is this an appropriate way to do it? Action action = DoSomething; action.BeginInvoke(action.EndInvoke, null); The DoSomething() method catches all exceptions and deals with them internally. Is the call to EndInvoke appropriate? Required? Is there a clearer way to achieve the same behaviour?

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  • Am I going about this the right way?

    - by Psytronic
    Hey Guys, I'm starting a WPF project, and just finished the base of the UI, it seems very convoluted though, so I'm not sure if I've gone around laying it out in the right way. I don't want to get to start developing the back-end and realise that I've done the front wrong, and make life harder for myself. Coming from a background of <DIV's and CSS to style this is a lot different, and really want to get it right from the start. Essentially it's a one week calendar (7 days, Mon-Sunday, defaulting to the current week.) Which will eventually link up to a DB and if I have an appointment for something on this day it will show it in the relevant day. I've opted for a Grid rather than ListView because of the way it will work I will not be binding the results to a collection or anything along those lines. Rather I will be filling out a Combo box within the canvas for each day (yet to be placed in the code) for each event and on selection it will show me further details. XAML: <Window x:Class="WOW_Widget.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:Extensions="clr-namespace:WOW_Widget" DataContext="{Binding RelativeSource={RelativeSource Self}}" Title="Window1" Height="239" Width="831" <Window.Resources <LinearGradientBrush x:Key="NormalBrush" StartPoint="0,0" EndPoint="0,1" <GradientBrush.GradientStops <GradientStopCollection <GradientStop Offset="1.0" Color="White"/ <GradientStop Offset="0.0" Color="LightSlateGray"/ </GradientStopCollection </GradientBrush.GradientStops </LinearGradientBrush <LinearGradientBrush x:Key="grdDayHeader" StartPoint="0,0" EndPoint="0,1" <GradientBrush.GradientStops <GradientStopCollection <GradientStop Offset="0.0" Color="Peru" / <GradientStop Offset="1.0" Color="White" / </GradientStopCollection </GradientBrush.GradientStops </LinearGradientBrush <LinearGradientBrush x:Key="grdToday" StartPoint="0,0" EndPoint="0,1" <GradientBrush.GradientStops <GradientStopCollection <GradientStop Offset="0.0" Color="LimeGreen"/ <GradientStop Offset="1.0" Color="DarkGreen" / </GradientStopCollection </GradientBrush.GradientStops </LinearGradientBrush <Style TargetType="{x:Type GridViewColumnHeader}" <Setter Property="Background" Value="Khaki" / </Style <Style x:Key="DayHeader" TargetType="{x:Type Label}" <Setter Property="Background" Value="{StaticResource grdDayHeader}" / <Setter Property="Width" Value="111" / <Setter Property="Height" Value="25" / <Setter Property="HorizontalContentAlignment" Value="Center" / </Style <Style x:Key="DayField" <Setter Property="Canvas.Width" Value="111" / <Setter Property="Canvas.Height" Value="60" / <Setter Property="Canvas.Background" Value="White" / </Style <Style x:Key="Today" <Setter Property="Canvas.Background" Value="{StaticResource grdToday}" / </Style <Style x:Key="CalendarColSpacer" <Setter Property="Canvas.Width" Value="1" / <Setter Property="Canvas.Background" Value="Black" / </Style <Style x:Key="CalendarRowSpacer" <Setter Property="Canvas.Height" Value="1" / <Setter Property="Canvas.Background" Value="Black" / </Style </Window.Resources <Grid Background="{StaticResource NormalBrush}" <Border BorderBrush="Black" BorderThickness="1" Width="785" Height="86" Margin="12,12,12,104" <Canvas Height="86" Width="785" VerticalAlignment="Top" <Grid <Grid.ColumnDefinitions <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / <ColumnDefinition / </Grid.ColumnDefinitions <Grid.RowDefinitions <RowDefinition / <RowDefinition / <RowDefinition / </Grid.RowDefinitions <Label Grid.Column="0" Grid.Row="0" Content="Monday" Style="{StaticResource DayHeader}" / <Canvas Grid.Column="1" Grid.RowSpan="3" Grid.Row="0" Style="{StaticResource CalendarColSpacer}" / <Label Grid.Column="2" Grid.Row="0" Content="Tuesday" Style="{StaticResource DayHeader}" / <Canvas Grid.Column="3" Grid.RowSpan="3" Grid.Row="0" Style="{StaticResource CalendarColSpacer}" / <Label Grid.Column="4" Grid.Row="0" Content="Wednesday" Style="{StaticResource DayHeader}" / <Canvas Grid.Column="5" Grid.RowSpan="3" Grid.Row="0" Style="{StaticResource CalendarColSpacer}" / <Label Grid.Column="6" Grid.Row="0" Content="Thursday" Style="{StaticResource DayHeader}" / <Canvas Grid.Column="7" Grid.RowSpan="3" Grid.Row="0" Style="{StaticResource CalendarColSpacer}" / <Label Grid.Column="8" Grid.Row="0" Content="Friday" Style="{StaticResource DayHeader}" / <Canvas Grid.Column="9" Grid.RowSpan="3" Grid.Row="0" Style="{StaticResource CalendarColSpacer}" / <Label Grid.Column="10" Grid.Row="0" Content="Saturday" Style="{StaticResource DayHeader}" / <Canvas Grid.Column="11" Grid.RowSpan="3" Grid.Row="0" Style="{StaticResource CalendarColSpacer}" / <Label Grid.Column="12" Grid.Row="0" Content="Sunday" Style="{StaticResource DayHeader}" / <Canvas Grid.Column="0" Grid.ColumnSpan="13" Grid.Row="1" Style="{StaticResource CalendarRowSpacer}" / <Canvas Grid.Column="0" Grid.Row="2" Margin="0" Style="{StaticResource DayField}" <Label Name="lblMondayDate" / </Canvas <Canvas Grid.Column="2" Grid.Row="2" Margin="0" Style="{StaticResource DayField}" <Label Name="lblTuesdayDate" / </Canvas <Canvas Grid.Column="4" Grid.Row="2" Margin="0" Style="{StaticResource DayField}" <Label Name="lblWednesdayDate" / </Canvas <Canvas Grid.Column="6" Grid.Row="2" Margin="0" Style="{StaticResource DayField}" <Label Name="lblThursdayDate" / </Canvas <Canvas Grid.Column="8" Grid.Row="2" Margin="0" Style="{StaticResource DayField}" <Label Name="lblFridayDate" / </Canvas <Canvas Grid.Column="10" Grid.Row="2" Margin="0" Style="{StaticResource DayField}" <Label Name="lblSaturdayDate" / </Canvas <Canvas Grid.Column="12" Grid.Row="2" Margin="0" Style="{StaticResource DayField}" <Label Name="lblSundayDate" / </Canvas </Grid </Canvas </Border <Canvas Height="86" HorizontalAlignment="Right" Margin="0,0,12,12" Name="canvas1" VerticalAlignment="Bottom" Width="198"</Canvas </Grid </Window CS: public partial class Window1 : Window { private DateTime today = new DateTime(); private Label[] Dates = new Label[7]; public Window1() { DateTime start = today = DateTime.Now; int day = (int)today.DayOfWeek; while (day != 1) { start = start.Subtract(new TimeSpan(1, 0, 0, 0)); day--; } InitializeComponent(); Dates[0] = lblMondayDate; Dates[1] = lblTuesdayDate; Dates[2] = lblWednesdayDate; Dates[3] = lblThursdayDate; Dates[4] = lblFridayDate; Dates[5] = lblSaturdayDate; Dates[6] = lblSundayDate; FillWeek(start); } private void FillWeek(DateTime start) { for (int d = 0; d < Dates.Length; d++) { TimeSpan td = new TimeSpan(d, 0, 0, 0); DateTime _day = start.Add(td); if (_day.Date == today.Date) { Canvas dayCanvas = (Canvas)Dates[d].Parent; dayCanvas.Style = (Style)this.Resources["Today"]; } Dates[d].Content = (int)start.Add(td).Day; } } } Thanks for any tips you guys can give Psytronic

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  • OpenLDAP and user role based accedss controll (RBAC)

    - by Jason
    Hello, my company uses an openldap server which stores corporate user information ((username,passwd and some other information like email are stored in ldap).. Till now they only use it for authentication but now we'd like to use for authentication also, this means that we'll create roles (as ldap attributes in a new schema) and assign those roles in the users. My actual question is if there is a best-practice to follow for using openldap for authentication on many applications (most written in php). I understand how to make roles and assign them to users for just one application, but what about the others (each application of course has its own roles). Should I just create an ou=appName,ou=roles,dc=mycompany for each application, put the roles as attributes there and just add each role as an attribute of the user object ? is there any other recommendations ? thanks

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  • spring roo vs appfuse generate service /dao layer

    - by cometta
    I am looking for feedback from experienced users on spring roo and appfuse. Which do you think does a better job reverse engineering database tables and generating a service layer, dao layer, and jpa entities? If I am not mistaken, spring roo currently cannot reverse engineer a database.

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  • code review: Is it subjective or objective(quantifiable) ?

    - by Ram
    I am putting together some guidelines for code reviews. We do not have one formal process yet, and trying to formalize it. And our team is geographically distributed We are using TFS for source control (used it for tasks/bug tracking/project management as well, but migrated that to JIRA) with VS2008 for development. What are the things you look for when doing a code review ? These are the things I came up with Enforce FXCop rules (we are a Microsoft shop) Check for performance (any tools ?) and security (thinking about using OWASP- code crawler) and thread safety Adhere to naming conventions The code should cover edge cases and boundaries conditions Should handle exceptions correctly (do not swallow exceptions) Check if the functionality is duplicated elsewhere method body should be small(20-30 lines) , and methods should do one thing and one thing only (no side effects/ avoid temporal coupling -) Do not pass/return nulls in methods Avoid dead code Document public and protected methods/properties/variables What other things do you generally look for ? I am trying to see if we can quantify the review process (it would produce identical output when reviewed by different persons) Example: Saying "the method body should be no longer than 20-30 lines of code" as opposed to saying "the method body should be small" Or is code review very subjective ( and would differ from one reviewer to another ) ? The objective is to have a marking system (say -1 point for each FXCop rule violation,-2 points for not following naming conventions,2 point for refactoring etc) so that developers would be more careful when they check in their code.This way, we can identify developers who are consistently writing good/bad code.The goal is to have the reviewer spend about 30 minutes max, to do a review (I know this is subjective, considering the fact that the changeset/revision might include multiple files/huge changes to the existing architecture etc , but you get the general idea, the reviewer should not spend days reviewing someone's code) What other objective/quantifiable system do you follow to identify good/bad code written by developers? Book reference: Clean Code: A handbook of agile software craftmanship by Robert Martin

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  • Noftification between J2EE components.

    - by Pratik
    Hi There! I have a design problem . My application has multiple J2EE components ,In simple terms one acts as a service provider(Non UI) and others are consumers(UI webapp) . The consumer gets the configuration data from the service provider(this basically reads the data from DB) during the start up and stores it in the Cache. The cache gets refreshed after periodic time to reflect any changes done at the database. The Problem Apart from the cache refresh ,I also want to notify the consumers when someone changes the DB . that configuration has been changed please reload it. What notification mechanism's can I use to achieve this. Thanks! Pratik

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  • singleton vs factory?

    - by fayer
    i've got 3 Log classes that all implements iLog interface: DatabaseLog FileLog ScreenLog there can only be one instance of them. initially i though of using single pattern for each class but then i thought why not use a factory for instantiation instead, cause then i wont have to create single pattern for each one of them and for all future Log classes. and maybe someone would want them as multiple objects in the future. so my questions is: should i use factory or singleton pattern here?

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  • General advice and guidelines on how to properly override object.GetHashCode()

    - by Svish
    According to MSDN, a hash function must have the following properties: If two objects compare as equal, the GetHashCode method for each object must return the same value. However, if two objects do not compare as equal, the GetHashCode methods for the two object do not have to return different values. The GetHashCode method for an object must consistently return the same hash code as long as there is no modification to the object state that determines the return value of the object's Equals method. Note that this is true only for the current execution of an application, and that a different hash code can be returned if the application is run again. For the best performance, a hash function must generate a random distribution for all input. I keep finding myself in the following scenario: I have created a class, implemented IEquatable<T> and overridden object.Equals(object). MSDN states that: Types that override Equals must also override GetHashCode ; otherwise, Hashtable might not work correctly. And then it usually stops up a bit for me. Because, how do you properly override object.GetHashCode()? Never really know where to start, and it seems to be a lot of pitfalls. Here at StackOverflow, there are quite a few questions related to GetHashCode overriding, but most of them seems to be on quite particular cases and specific issues. So, therefore I would like to get a good compilation here. An overview with general advice and guidelines. What to do, what not to do, common pitfalls, where to start, etc. I would like it to be especially directed at C#, but I would think it will work kind of the same way for other .NET languages as well(?). I think maybe the best way is to create one answer per topic with a quick and short answer first (close to one-liner if at all possible), then maybe some more information and end with related questions, discussions, blog posts, etc., if there are any. I can then create one post as the accepted answer (to get it on top) with just a "table of contents". Try to keep it short and concise. And don't just link to other questions and blog posts. Try to take the essence of them and then rather link to source (especially since the source could disappear. Also, please try to edit and improve answers instead of created lots of very similar ones. I am not a very good technical writer, but I will at least try to format answers so they look alike, create the table of contents, etc. I will also try to search up some of the related questions here at SO that answers parts of these and maybe pull out the essence of the ones I can manage. But since I am not very stable on this topic, I will try to stay away for the most part :p

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  • Catching OutOfMemoryError

    - by dotsid
    Documentation for java.lang.Error says: An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch But as java.lang.Error is subclass of java.lang.Throwable I can catch this type of throwable. I understand why this is not good idea to catch this sort of exceptions. As far as I understand, if we decide to caught it, the catch handler should not allocate any memory by itself. Otherwise OutOfMemoryError will be thrown again. So, my question is: is there any real word scenarios when catching java.lang.OutOfMemoryError may be a good idea? if we catching java.lang.OutOfMemoryError how can we sure that catch handler doesn't allocate any memory by itself (any tools or best practicies)? Thanks a lot.

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  • What is better: CSS hacks or browser detection?

    - by Darryl Hein
    Commonly when I look around the Internet, I find that people are generally using CSS hacks to make their website look the same in all browsers. Personally, I have found this to be quite time consuming to find all of these hacks and test them; each change you make you have to test in 4+ browsers to make sure it didn't break anything else. About a year ago, I looked around the Internet for what other major sites are using (Yahoo, Google, BBC, etc) and found that most of them are doing some form of browser detection (JS, HTML if statements, server based). I have started doing this as well. On almost all of the sites I have worked on recently, I use jQuery, so I use the built in browser detection. Is there a reason you use or don't use either of these?

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  • Assert a good practice or not ?

    - by rkenshin
    Is it a good practice to use Assert for function parameters to enforce their validity. I was going through the source code of Spring Framework and I noticed that they use Assert.notNull a lot. Here's an example public static ParsedSql parseSqlStatement(String sql) { Assert.notNull(sql, "SQL must not be null");} Here's Another one public NamedParameterJdbcTemplate(DataSource dataSource) { Assert.notNull(dataSource, "The [dataSource] argument cannot be null."); this .classicJdbcTemplate = new JdbcTemplate(dataSource); } public NamedParameterJdbcTemplate(JdbcOperations classicJdbcTemplate) { Assert.notNull(classicJdbcTemplate, "JdbcTemplate must not be null"); this .classicJdbcTemplate = classicJdbcTemplate; } Thank you

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  • Cast then check or check then cast?

    - by jamesrom
    Which method is regarded as best practice? Cast first? public string Describe(ICola cola) { var coke = cola as CocaCola; if (coke != null) { string result; // some unique coca-cola only code here. return result; } var pepsi = cola as Pepsi; if (pepsi != null) { string result; // some unique pepsi only code here. return result; } } Or should I check first, cast later? public string Describe(ICola cola) { if (cola is CocaCola) { coke = (CocaCola) cola; string result; // some unique coca-cola only code here. return result; } if (cola is Pepsi) { pepsi = (Pepsi) cola; string result; // some unique pepsi only code here. return result; } } Can you see any other way to do this?

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  • Organising asp.net website development process

    - by ZX12R
    Is there a standard practice to organize the process of developing a simple website. there is no use implementing MVC as there is no data base involved. It will be very useful in organizing the project and separating the aspx files and master page content(this can be very useful in implementing simple cms techniques) user controls scripts styles images is there any industry standard or best practice for this.? thanks in advance :) Update: yes the way i have listed is convenient. but it would be great if i could separate server codes and files like master,aspx.. and the actual page content. One more reason for not using MVC: I usually outsource the SEO process. Now an MVC application can be greek/latin for my SEO expert. :)

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  • Repository pattern with lazying loading using POCO

    - by Simon G
    Hi, I'm in the process of starting a new project and creating the business objects and data access etc. I'm just using plain old clr objects rather than any orms. I've created two class libraries: 1) Business Objects - holds all my business objects, all this objects are light weight with only properties and business rules. 2) Repository - this is for all my data access. The majority of my objects will have child list in and my question is what is the best way to lazy load these values as I don't want to bring back unnecessary information if I dont need to. I've thought about when using the "get" on the child property to check if its "null" and if it is call my repository to get the child information. This has two problems from what I can see: 1) The object "knows" how to get itself I would rather no data access logic be held in the object. 2) This required both classes to reference each other which in visual studio throws a circular dependency error. Does anyone have any suggestions on how to overcome this issue or any recommendations on my projects layout and where it can be improved? Thanks

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  • Why is IoC / DI not common in Python?

    - by tux21b
    In Java IoC / DI is a very common practice which is extensively used in web applications, nearly all available frameworks and Java EE. On the other hand, there are also lots of big Python web applications, but beside of Zope (which I've heard should be really horrible to code) IoC doesn't seem to be very common in the Python world. (Please name some examples if you think that I'm wrong). There are of course several clones of popular Java IoC frameworks available for Python, springpython for example. But none of them seems to get used practically. At least, I've never stumpled upon a Django or sqlalchemy+<insert your favorite wsgi toolkit here> based web application which uses something like that. In my opinion IoC has reasonable advantages and would make it easy to replace the django-default-user-model for example, but extensive usage of interface classes and IoC in Python looks a bit odd and not »pythonic«. But maybe someone has a better explanation, why IoC isn't widely used in Python.

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  • Notification between J2EE components.

    - by Pratik
    Hi There! I have a design problem . My application has multiple J2EE components ,In simple terms one acts as a service provider(Non UI) and others are consumers(UI webapp) . The consumer gets the configuration data from the service provider(this basically reads the data from DB) during the start up and stores it in the Cache. The cache gets refreshed after periodic time to reflect any changes done at the database. The Problem Apart from the cache refresh ,I also want to notify the consumers when someone changes the DB . that configuration has been changed please reload it. What notification mechanism's can I use to achieve this. Thanks! Pratik

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  • Etiquette for refactoring other people's sourcecode?

    - by Prutswonder
    Our team of software developers consists of a bunch of experienced programmers with a variety of programming styles and preferences. We do not have standards for everything, just the bare necessities to prevent total chaos. Recently, I bumped into some refactoring done by a colleague. My code looked somewhat like this: public Person CreateNewPerson(string firstName, string lastName) { var person = new Person() { FirstName = firstName, LastName = lastName }; return person; } Which was refactored to this: public Person CreateNewPerson (string firstName, string lastName) { Person person = new Person (); person.FirstName = firstName; person.LastName = lastName; return person; } Just because my colleague needed to update some other method in one of the classes I wrote, he also "refactored" the method above. For the record, he's one of those developers that despises syntactic sugar and uses a different bracket placement/identation scheme than the rest of us. My question is: What is the (C#) programmer's etiquette for refactoring other people's sourcecode (both semantic and syntactic)?

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  • Fix common library functions, or abandon then?

    - by Ian Boyd
    Imagine i have a function with a bug in it: Boolean MakeLocation(String City, String State) { //Given "Springfield", "MO" //return "Springfield, MO" return City+", "+State; } So the call: MakeLocation("Springfield", "MO"); would return "Springfield, MO" Now there's a slight problem, what if the user called: MakeLocation("Springfield, MO", "OH"); The called it wrong, obviously. But the function would return "Springfield, MO, OH". The system was functioning like this for many years, until i noticed the function being used wrong, and i corrected it. And i also updated the original function to catch such an obvious mistake - in case it's happening elsewhere: Boolean MakeLocation(String City, String State) { //Given "Springfield", "MO" //return "Springfield, MO" if (City.Contains, ",") throw new EMakeLocationException("City name contains a comma. You probably didn't mean that"); return City+", "+State; } And testing showed the problem fixed. Except we missed an edge case, and the customer found it. So now the moral dillema. Do you ever add new sanity checks, safety checks, assertions to exising code? Or do you call the old function abandoned, and have a new one: Boolean MakeLocation(String City, String State) { //Given "Springfield", "MO" //return "Springfield, MO" return City+", "+State; } Boolean MakeLocation2(String City, String State) { //Given "Springfield", "MO" //return "Springfield, MO" if (City.Contains, ",") throw new EMakeLocationException("City name contains a comma. You probably didn't mean that"); return City+", "+State; } The same can apply for anything: Question FetchQuestion(Int id) { if (id == 0) throw new EFetchQuestionException("No question ID specified"); ... } Do you risk breaking existing code, at the expense of existing code being wrong?

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  • Best Practise for Writing a POS System

    - by Gary
    Hi, I'm putting together a basic POS system in C# that needs to print to a receipt printer and open a cash drawer. Do I have to use the Microsoft Point of Service SDK? I've been playing around with printing to my Samsung printer using the Windows driver that came with it, and it seems to work great. I assume though that other printers may not come with Windows drivers and then I would be stuck? Or would I be able to simply use the Generic/Text Driver to print to any printer that supports it? For the cash drawer I would need to send codes directly to the COM port which is fine with me, if it saves me the hassle of helping clients setup OPOS drivers on there systems. Am I going down the wrong path here? Thanks, Gary

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