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  • Programatically clicking a HTML button by vb.net [closed]

    - by Chauhdry King
    I have to click a HTML button programatically which is on the 3rd page of the website. The button is without id. It has just name type and value. The HTML code of the button is given below <FORM NAME='form1' METHOD='post' action='/dflogin.php'> <INPUT TYPE='hidden' NAME='txtId' value='E712050-15'><INPUT TYPE='hidden' NAME='txtassId' value='1'><INPUT TYPE='hidden' NAME='txtPsw' value='HH29'><INPUT TYPE='hidden' NAME='txtLog' value='0'><h6 align='right'><INPUT TYPE='SUBMIT' NAME='btnSub' value='Next' style='background-color:#009900; color:#fff;'></h6></FORM> I am using the following code to click it Dim i As Integer Dim allButtons As HtmlElementCollection allButtons = WebBrowser1.Document.GetElementsByTagName("input") i = 0 For Each webpageelement As HtmlElement In allButtons i += 1 If i = 5 Then webpageelement.InvokeMember("click") End If Next But I am not able to click it. I am using the vb.net 2008 platform. Can anyone tell me the solution to click it?

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  • Windows Phone 7 Development &ndash; Useful Links

    - by David Turner
    Here are some excellent links for anyone developing for Windows Phone 7: J.D. Meier’s Windows Phone Developer Guidance Map – this is immense.  Also check out the Silverlight version Justin Angel’s site – some really great articles on unlocked roms, automation and Continuous Integration Windows Phone 7 Development Best Practices Wiki Jeff Blankenburg’s 31 days of Windows Phone 7 This post of Links to sample code for Windows Phone Tim Heuers blog, particularly this post of Tips and Tricks Kevin Marshall's blog, particularly the epic WP7 Development Tips Part 1 post Code Samples for Windows Phone on MSDN If you have unlocked your phone for development, then you can use the WPConnect tool to connect to the device rather than using the Zune client.  I found it useful to pin a shortcut to WPConnect in my Start Menu. The Performance Counters displayed when you debug your app on a device are useful for seeing things like frame rate and memory usage, this page on MSDN explains what the numbers mean.  Jeff Blankenburg covers this in more details on his blog I also came across this set of links to tutorials recently which looks very useful. Creating Windows Phone 7 Application and Marketplace Icons: http://expression.microsoft.com/en-us/gg317447.aspx

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  • Spring MVC vs raw servlets and template engine?

    - by Gigatron
    I've read numerous articles about the Spring MVC framework, and I still can't see the benefits of using it. It looks like writing even a simple application with it requires creating a big hodgepodge of XML files and annotations and other reams of code to conform to what the framework wants, a whole bunch of moving parts to accomplish a simple single task. Any time I look at a Spring example, I can see how I can write something with the same functionality using a simple servlet and template engine (e.g. FreeMarker, StringTemplate), in half the lines of code and little or no XML files and other artifacts. Just grab the data from the session and request, call the application domain objects if necessary, pass the results to the template engine to generate the resulting web page, done. What am I missing? Can you describe even one example of something that is actually made simpler with Spring than using a combination of raw servlets with a template engine? Or is Spring MVC just one of those overly complicated things that people use only because their boss tells them to use it?

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  • Sequence for authentication on a decoupled client?

    - by A T
    Using a sequence diagram and example code could you explain to me how authentication works when the client is completely separated from the server? I.e.: you haven't generated any of the client using a server-side template engine, rather you are communicating using REST (SOAP xor HTTP) xor RPC (XML xor JSON) with javascript on the client-side. Specifically I would like to know the sequence of: Authenticating using basic auth (user+pass) with "my" server Authenticating using OAuth2, e.g.: with Facebook, with facebook's server then whatever extra steps are needed for "my" server And how it could be implemented. (feel free to use psuedo-code [like below] or [preferably] prototyped simply using BackboneJS, AngularJS, EmberJS, BatmanJS, AgilityJS, SammyJS xor ActiveJS. if cookie.status in [Expired, Tampered, Wrong IP, Invalid, Not Found]: try auth(user,pass): if user is in my db: try authenticate(user,pass) if successful: login user # give session-cookie here? else: present user with "auth failed" msg else if user not in db: redirect to "edit-profile" page PS: I have written an example (editable) auth sequence diagram; based on facebooks' documentation.

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  • Is case after case in a switch efficient?

    - by RandomGuy
    Just a random question regarding switch case efficiency in case after case; is the following code (assume pseudo code): function bool isValid(String myString){ switch(myString){ case "stringA": case "stringB": case "stringC": return true; default: return false; } more efficient than this: function bool isValid(String myString){ switch(myString){ case "stringA": return true; case "stringB": return true; case "stringC": return true; default: return false; } Or is the performance equal? I'm not thinking in a specific language but if needed let's assume it's Java or C (for this case would be needed to use chars instead of strings).

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  • First time android game development [on hold]

    - by Dave
    My friend and i are developing a android game. This is my first time develop android game, so we don't know how to code The game is 2d game and we develop it without 3rd party engine / framework. Now we got a few questions, hope you can help us. In game play, using 'Surfaceview' only to achieve it. Is it best practice? On 'Surfaceview', a lot of difference button(Menu, pause, game object..etc) is on it, but I don't know how to code it? (actually, i have already done, but...so stupid way. Detect the user touch position (x, y) to identify where they touch[rect(x1,y1,x2,y2).contain(x,y)] Is it right? Teach me how to do if wrong. View / Surfaceview / OpenGL, which is suitable for us? (if like Tetris) Thank you for your help. Ps: My english is not good, hope you can understand what i mean.

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  • Am I copy/paste programmer ?

    - by Searock
    When ever I am stuck with a particular problem, I search for a solution in Google. And then I try to understand the code and tweak it according to my requirement. For example recently I had asked a question Reading xml document in firefox in stack overflow. Soufiane Hassou gave me a link to w3schools, where I found a example on parsing xml document, I understood how the example works, but I copied the code and tweaked it according to my requirement, since I don't like typing much. So does this make me a copy/paste programmer? How do you say if a person is a copy/paste programmer ? Thanks.

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  • How do I resolve "No JSON object could be decoded" on mythbuntu live CD?

    - by Neil
    I have been running a MythTV frontend on my laptop for some time against a MythTV backend installed in Linux Mint 12 on another computer, and everything works fine. Now, I'm trying out the Mythbuntu Live CD (12.04.1 32-bit) on the laptop, to turn it into a dedicated front end. It's connecting to the network just fine, and I can see my server. When I click on the frontend icon on the desktop, it asks me for the security code, which I've verified against mythtv-setup on the server. However, when I test that code, it shows the error message "No JSON object could be decoded". I've looked in the control center to see if there's something else I should be setting up. The message above implies to me that it can't find the server, but I can find no place in the control center to tell it where to find my myth backend, which I find a little odd. Does the live CD not work against a backend server on another machine?

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  • Is Java free/open source or it isn't?

    - by user1598390
    On November 13, 2006, Sun released much of Java as free and open source software, (FOSS), under the terms of the GNU General Public License (GPL). On May 8, 2007, Sun finished the process, making all of Java's core code available under free software/open-source distribution terms, aside from a small portion of code to which Sun did not hold the copyright. OpenJDK (Open Java Development Kit) is a free and open source implementation of the Java programming language. It is the result of an effort Sun Microsystems began in 2006. The implementation is licensed under the GNU General Public License (GNU GPL) with a linking exception. Why there are still people that say Java is not open source or free as in free speech ? Am I missing something? Is Java still privative ?

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  • Advantages and disadvantages of building a single page web application

    - by ryanzec
    I'm nearing the end of a prototyping/proof of concept phase for a side project I'm working on, and trying to decide on some larger scale application design decisions. The app is a project management system tailored more towards the agile development process. One of the decisions I need to make is whether or not to go with a traditional multi-page application or a single page application. Currently my prototype is a traditional multi-page setup, however I have been looking at backbone.js to clean up and apply some structure to my Javascript (jQuery) code. It seems like while backbone.js can be used in multi-page applications, it shines more with single page applications. I am trying to come up with a list of advantages and disadvantages of using a single page application design approach. So far I have: Advantages All data has to be available via some sort of API - this is a big advantage for my use case as I want to have an API to my application anyway. Right now about 60-70% of my calls to get/update data are done through a REST API. Doing a single page application will allow me to better test my REST API since the application itself will use it. It also means that as the application grows, the API itself will grow since that is what the application uses; no need to maintain the API as an add-on to the application. More responsive application - since all data loaded after the initial page is kept to a minimum and transmitted in a compact format (like JSON), data requests should generally be faster, and the server will do slightly less processing. Disadvantages Duplication of code - for example, model code. I am going to have to create models both on the server side (PHP in this case) and the client side in Javascript. Business logic in Javascript - I can't give any concrete examples on why this would be bad but it just doesn't feel right to me having business logic in Javascript that anyone can read. Javascript memory leaks - since the page never reloads, Javascript memory leaks can happen, and I would not even know where to begin to debug them. There are also other things that are kind of double edged swords. For example, with single page applications, the data processed for each request can be a lot less since the application will be asking for the minimum data it needs for the particular request, however it also means that there could be a lot more small request to the server. I'm not sure if that is a good or bad thing. What are some of the advantages and disadvantages of single page web applications that I should keep in mind when deciding which way I should go for my project?

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  • How can I unit test a class which requires a web service call?

    - by Chris Cooper
    I'm trying to test a class which calls some Hadoop web services. The code is pretty much of the form: method() { ...use Jersey client to create WebResource... ...make request... ...do something with response... } e.g. there is a create directory method, a create folder method etc. Given that the code is dealing with an external web service that I don't have control over, how can I unit test this? I could try and mock the web service client/responses but that breaks the guideline I've seen a lot recently: "Don't mock objects you don't own". I could set up a dummy web service implementation - would that still constitute a "unit test" or would it then be an integration test? Is it just not possible to unit test at this low a level - how would a TDD practitioner go about this?

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  • Oracle University Partner Enablement Update (19th March)

    - by swalker
    Java SE 7 Certification News The following exam has recently gone into Production: Exam Title and Code Certification Track Upgrade to Java SE 7 Programmer (1Z0-805) Oracle Certified Professional, Java SE 7 Programmer Full preparation details are available on the exam page, including prerequisites for this certification, exam topics and pricing. Exams can be taken at an Oracle Test Center near you or at any Pearson VUE Testing Center. The following exam has recently become available for beta testing: Exam Code and Title Certification Track Java SE 7 Programmer II (1Z1-804) Oracle Certified Professional, Java SE 7 Programmer Full preparation details are available on the exam page, including prerequisites for this certification, exam topics and pricing. A beta exam offers you two distinct advantages: you will be one of the first to get certified you pay a lower price. Beta exams can be taken at any Pearson VUE Testing Center. Stay Connected to Oracle University: LinkedIn OracleMix Twitter Facebook

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  • What is the correct way to handle debug output in Java?

    - by Federico Zancan
    As my current Java projects grow bigger and bigger, I feel a likewise growing need to insert debug output in several points of my code. To enable or disable this feature appropriately, depending on the opening or closure of the test sessions, I usually put a private static final boolean DEBUG = false at the beginning of the classes my tests are inspecting, and trivially use it this way (for example): public MyClass { private static final boolean DEBUG = false; ... some code ... public void myMethod(String s) { if (DEBUG) { System.out.println(s); } } } and the like. But that doesn't bliss me out, because of course it works but there could be too many classes in which to set DEBUG to true, if you are not staring at just a couple of them. Conversely, I (like - I think - many others) wouldn't love to put the whole application in debug mode, as the amount of text being output could be overwhelming. So, is there a correct way to architecturally handle such situation or the most correct way is to use the DEBUG class member?

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  • Best exception handling practices or recommendations?

    - by user828584
    I think the two main problems with my programs are my code structure/organization and my error handling. I'm reading Code Complete 2, but I need something to read for working with potential problems. For example, on a website, if something can only happen if the user tampers with data via javascript, do you write for that? Also, when do you not catch errors? When you write a class that expects a string and an int as input, and they aren't a string and int, do you check for that, or do you let it bubble up to the calling method that passed incorrect parameters? I know this is a broad topic that can't be answered in a single answer here, so what I'm looking for is a book or resource that's commonly accepted as teaching proper exception handling practice.

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  • Are there deprecated practices for multithread and multiprocessor programming that I should no longer use?

    - by DeveloperDon
    In the early days of FORTRAN and BASIC, essentially all programs were written with GOTO statements. The result was spaghetti code and the solution was structured programming. Similarly, pointers can have difficult to control characteristics in our programs. C++ started with plenty of pointers, but use of references are recommended. Libraries like STL can reduce some of our dependency. There are also idioms to create smart pointers that have better characteristics, and some version of C++ permit references and managed code. Programming practices like inheritance and polymorphism use a lot of pointers behind the scenes (just as for, while, do structured programming generates code filled with branch instructions). Languages like Java eliminate pointers and use garbage collection to manage dynamically allocated data instead of depending on programmers to match all their new and delete statements. In my reading, I have seen examples of multi-process and multi-thread programming that don't seem to use semaphores. Do they use the same thing with different names or do they have new ways of structuring protection of resources from concurrent use? For example, a specific example of a system for multithread programming with multicore processors is OpenMP. It represents a critical region as follows, without the use of semaphores, which seem not to be included in the environment. th_id = omp_get_thread_num(); #pragma omp critical { cout << "Hello World from thread " << th_id << '\n'; } This example is an excerpt from: http://en.wikipedia.org/wiki/OpenMP Alternatively, similar protection of threads from each other using semaphores with functions wait() and signal() might look like this: wait(sem); th_id = get_thread_num(); cout << "Hello World from thread " << th_id << '\n'; signal(sem); In this example, things are pretty simple, and just a simple review is enough to show the wait() and signal() calls are matched and even with a lot of concurrency, thread safety is provided. But other algorithms are more complicated and use multiple semaphores (both binary and counting) spread across multiple functions with complex conditions that can be called by many threads. The consequences of creating deadlock or failing to make things thread safe can be hard to manage. Do these systems like OpenMP eliminate the problems with semaphores? Do they move the problem somewhere else? How do I transform my favorite semaphore using algorithm to not use semaphores anymore?

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  • Identify memory leak in Java app

    - by Vincent Ma
    One important advantage of java is programer don't care memory management and GC handle it well. Maybe this is one reason why java is more popular. As Java programer you real dont care it? After you meet Out of memory you will realize it it’s not true. Java GC and memory is big topic you can get some information in here Today just let me show how to identify memory leak quickly. Let quickly review demo java code, it’s one kind of memory leak in our code, using static collection and always add some object. import java.util.ArrayList;import java.util.List; public class MemoryTest { public static void main(String[] args) { new Thread(new MemoryLeak(), "MemoryLeak").start(); }} class MemoryLeak implements Runnable { public static List<Integer> leakList = new ArrayList<Integer>(); public void run() { int num =0; while(true) { try { Thread.sleep(1); } catch (InterruptedException e) { } num++; Integer i = new Integer(num); leakList.add(i); } }} run it with java -verbose:gc -XX:+PrintGCDetails -Xmx60m -XX:MaxPermSize=160m MemoryTest after about some minuts you will get Exception in thread "MemoryLeak" java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOf(Arrays.java:2760) at java.util.Arrays.copyOf(Arrays.java:2734) at java.util.ArrayList.ensureCapacity(ArrayList.java:167) at java.util.ArrayList.add(ArrayList.java:351) at MemoryLeak.run(MemoryTest.java:25) at java.lang.Thread.run(Thread.java:619)Heap def new generation total 18432K, used 3703K [0x045e0000, 0x059e0000, 0x059e0000) eden space 16384K, 22% used [0x045e0000, 0x0497dde0, 0x055e0000) from space 2048K, 0% used [0x055e0000, 0x055e0000, 0x057e0000) to space 2048K, 0% used [0x057e0000, 0x057e0000, 0x059e0000) tenured generation total 40960K, used 40959K [0x059e0000, 0x081e0000, 0x081e0000) the space 40960K, 99% used [0x059e0000, 0x081dfff8, 0x081e0000, 0x081e0000) compacting perm gen total 12288K, used 2083K [0x081e0000, 0x08de0000, 0x10de0000) the space 12288K, 16% used [0x081e0000, 0x083e8c50, 0x083e8e00, 0x08de0000)No shared spaces configured. OK let us quickly identify it using JProfile Download JProfile in here  Run JProfile and attach MemoryTest get largest size of  Objects in Memory View in here is Integer then select Integer and go to Heap Walker. get GC Graph for this object  Then you get detail code raise this issue quickly now.  That is enjoy it.

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  • Microsoft StyleCop is now Open Source

    - by Scott Dorman
    I have previously talked about Microsoft StyleCop. For those that might not know about it, StyleCop is a source analysis tool (different from the static analysis that FxCop performs) that analyzes the source code directly. As a result, it focuses on more design (or style) issues such as layout, readability and documentation. In an interesting move (and one that I am happy to see), Microsoft has decided to make StyleCop an open source project (under the MS-PL license) available on CodePlex. (The project site isn’t up  yet, but should be in the next few weeks.) This will give the development community the opportunity to help contribute to the project, expanding support to other languages (currently it only supports C#), adding features, and fixing bugs. Shortly after the CodePlex site is up, StyleCop 4.4 will be released which includes support for C# 4.0 as well as a large number of bug fixes and other improvements. Technorati Tags: Code Style and Standard,StyleCop

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  • MOSS 2007 &ndash; WCM Blank WebPart Page Zone ID&rsquo;s

    - by Jeff Julian
    Here is the list of Zone ID’s for the Blank WebPart Page (BlankWebPartPage.aspx") that is part of the Publishing Portal with MOSS 2007: TitleBar Header TopLeftRow TopRightRow CenterLeftColumn CenterColumn CenterRightColumn Footer RightColumn I was in need of these and wasn’t able to find them with a simple search on Google so I wanted to share them with you. To get a list of WebPartZone objects for a page that a webpart lives on can be done with the following code:  foreach (WebPartZone zone in this.WebPartManager.Zones) {          this.Controls.Add(new LiteralControl(zone.ID + "<br />")); } Use this code in a webpart that inherits from Microsoft.SharePoint.WebPartPages.WebPart. This is a simple way to do the equivalent of a Response.Write while having the output in the webpart zone your part resides in.  It also saves you from attaching to the process and debugging with the watch or quick watch. Technorati Tags: MOSS,WebParts,BlankWebPartPage.aspx,Zones

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  • Software Licenses: No Distribution and Private Selling Using Dual Licenses

    - by user102945
    Hi I recently wrote a couple of WordPress Themes in PHP and was wondering what license i should put on it. I don't mind users reusing my code but i don't want them to be able to sell and redistribute my themes as i want to retain that right. I heard somewhere that an all rights reserved link would stop the distributing etc. Is that true or do i need to include another license and dual license my Themes. So to sum it up i want to use a license to stop others from selling and distributing my themes, while at the same time letting others use the code if they want to.

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  • Facebook page design is not working in IE8 [closed]

    - by PrateekSaluja
    Hello Experts, We have designed a face book page.It is working fine in all browser including IE7 but it is not working in IE8.We checked then we got if we run our code outside the face book page it works in IE8 but when we put our code into face book page its not working.Here is the css code what we are using for IE8. <!--[if lt IE 8]> <style> .nv_a { width:90px; height:27px; float:left; text-align:center; padding-top:8px; } .nvt_a { width:66px; height:27px; float:left; text-align:center; padding-top:8px; } .nv_a a { width:90px; height:27px; float:left; padding-top:8px; text-align:center; color:#000; display:inline-block; text-decoration:none; background-color:#e0e0e0; border-top:solid 1px #999; border-left:solid 1px #999; border-right:solid 1px #999; border-bottom:solid 1px #999; } .nv_a a:hover { width:90px; height:27px; padding-top:8px; float:left; color:#000; text-align:center; background-color:#ccc; } .nvt_a a { width:66px; height:27px; float:left; padding-top:8px; text-align:center; color:#000; display:inline-block; text-decoration:none; background-color:#e0e0e0; border-top:solid 1px #999; border-left:solid 1px #999; border-right:solid 1px #999; border-bottom:solid 1px #999; border:1px solid red; } Please help us to solve the issue.

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  • C Problem with Compiler?

    - by Solomon081
    I just started learning C, and wrote my hello world program: #include <stdio.h> main() { printf("Hello World"); return 0; } When I run the code, I get a really long error: Apple Mach-O Linker (id) Error Ld /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug/CProj normal x86_64 cd /Users/Solomon/Desktop/C/CProj setenv MACOSX_DEPLOYMENT_TARGET 10.7 /Developer/usr/bin/clang -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.7.sdk -L/Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug -F/Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug -filelist /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Intermediates/CProj.build/Debug/CProj.build/Objects-normal/x86_64/CProj.LinkFileList -mmacosx-version-min=10.7 -o /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug/CProj ld: duplicate symbol _main in /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Intermediates/CProj.build/Debug/CProj.build/Objects-normal/x86_64/helloworld.o and /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Intermediates/CProj.build/Debug/CProj.build/Objects-normal/x86_64/main.o for architecture x86_64 Command /Developer/usr/bin/clang failed with exit code 1 I am running xCode Should I reinstall DevTools?

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  • How to explain to non-technical person why the task will take much longer then they think?

    - by Mag20
    Almost every developer has to answer questions from business side like: Why is going to take 2 days to add this simple contact form? When developer estimates this task, they may divide it into steps: make some changes to Database optimize DB changes for speed add front end HTML write server side code add validation add client side javascript use unit tests make sure SEO is setup is working implement email confirmation refactor and optimize the code for speed ... These maybe hard to explain to non-technical person, who basically sees the whole task as just putting together some HTML and creating a table to store the data. To them it could be 2 hours MAX. So is there a better way to explain why the estimate is high to non-developer?

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  • Performing user authentication in a CodeIgniter controller constructor?

    - by msanford
    In "The Clean Code Talks -- Unit Testing" (http://youtu.be/wEhu57pih5w), Miško Hevery mentions that "as little work as possible should be done in constructors [to make classes more easily testable]'. It got me thinking about the way I have implemented my user authentication mechanism. Having delved into MVC development through CodeIgniter, I designed my first web application to perform user authentication for protected resources in controllers' constructors in cases where every public function in that controller requires the user to be authenticated. For controllers with public methods having mixed authentication requirements, I would naturally move the authentication from the constructor to each method requiring authentication (though I don't currently have a need for this). I made this choice primarily to keep the controller tight, and to ensure that all resources in the controller are always covered. As for code longevity and maintainability: given the application structure, I can't foresee a situation in which one of the affected controllers would need a public method that didn't require user authentication, but I can see this as a potential drawback in general with this implementation (i.e., requiring future refactoring). Is this a good idea?

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  • What are the software design essentials? [closed]

    - by Craig Schwarze
    I've decided to create a 1 page "cheat sheet" of essential software design principles for my programmers. It doesn't explain the principles in any great depth, but is simply there as a reference and a reminder. Here's what I've come up with - I would welcome your comments. What have I left out? What have I explained poorly? What is there that shouldn't be? Basic Design Principles The Principle of Least Surprise – your solution should be obvious, predictable and consistent. Keep It Simple Stupid (KISS) - the simplest solution is usually the best one. You Ain’t Gonna Need It (YAGNI) - create a solution for the current problem rather than what might happen in the future. Don’t Repeat Yourself (DRY) - rigorously remove duplication from your design and code. Advanced Design Principles Program to an interface, not an implementation – Don’t declare variables to be of a particular concrete class. Rather, declare them to an interface, and instantiate them using a creational pattern. Favour composition over inheritance – Don’t overuse inheritance. In most cases, rich behaviour is best added by instantiating objects, rather than inheriting from classes. Strive for loosely coupled designs – Minimise the interdependencies between objects. They should be able to interact with minimal knowledge of each other via small, tightly defined interfaces. Principle of Least Knowledge – Also called the “Law of Demeter”, and is colloquially summarised as “Only talk to your friends”. Specifically, a method in an object should only invoke methods on the object itself, objects passed as a parameter to the method, any object the method creates, any components of the object. SOLID Design Principles Single Responsibility Principle – Each class should have one well defined purpose, and only one reason to change. This reduces the fragility of your code, and makes it much more maintainable. Open/Close Principle – A class should be open to extension, but closed to modification. In practice, this means extracting the code that is most likely to change to another class, and then injecting it as required via an appropriate pattern. Liskov Substitution Principle – Subtypes must be substitutable for their base types. Essentially, get your inheritance right. In the classic example, type square should not inherit from type rectangle, as they have different properties (you can independently set the sides of a rectangle). Instead, both should inherit from type shape. Interface Segregation Principle – Clients should not be forced to depend upon methods they do not use. Don’t have fat interfaces, rather split them up into smaller, behaviour centric interfaces. Dependency Inversion Principle – There are two parts to this principle: High-level modules should not depend on low-level modules. Both should depend on abstractions. Abstractions should not depend on details. Details should depend on abstractions. In modern development, this is often handled by an IoC (Inversion of Control) container.

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