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• What is the difference between using IDisposable vs a destructor in C#?

  - by j0rd4n

  When would I implement IDispose on a class as opposed to a destructor? I read this article, but I'm still missing the point. My assumption is that if I implement IDispose on an object, I can explicitly 'destruct' it as opposed to waiting for the garbage collector to do it. Is this correct? Does that mean I should always explicitly call Dispose on an object? What are some common examples of this?

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• replace values in a String from a Hashtable in Java

  - by Adnan

  My string looks like; String values = "I am from UK, and you are from FR"; and my hashtable; Hashtable countries = new Hashtable(); countries.put("United Kingdom", new String("UK")); countries.put("France", new String("FR")); What would be the most effective way to change the values in my string with the values from the hashtable accordingly. These are just 2 values to change, but in my case I will have 100+

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• how to merge ecommerce transaction data between two databases

  - by yamspog

  We currently run an ecommerce solution for a leisure and travel company. Everytime we have a release, we must bring the ecommerce site down as we update database schema and the data access code. We are using a custom built ORM where each data entity is responsible for their own CRUD operations. This is accomplished by dynamically generating the SQL based on attributes in the data entity. For example, the data entity for an address would be... [tableName="address"] public class address : dataEntity { [column="address1"] public string address1; [column="city"] public string city; } So, if we add a new column to the database, we must update the schema of the database and also update the data entity. As you can expect, the business people are not too happy about this outage as it puts a crimp in their cash-flow. The operations people are not happy as they have to deal with a high-pressure time when database and applications are upgraded. The programmers are upset as they are constantly getting in trouble for the legacy system that they inherited. Do any of you smart people out there have some suggestions?

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• Efficient storage/retrieval method for replayable comet style applications (Google Wave, Etherpad)

  - by Gareth Simpson

  I am considering a web application that would have the same kind of multi user, automatic saving, infinite undo / replay capabilities that you see in Google Wave and Etherpad (albeit on a drastically smaller scale and userbase). Before I go away and reinvent the wheel, is this something that has already been addressed as either a piece of technology or library, or even just a design pattern. I know this isn't necessarily the best Stack Overflow question as there is probably not a "right" answer, but my Google-fu has failed me and I'd just like a reading list! Ordinarily I would be developing under python/django but this is not a firm requirement just a preference :)

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• Communication between layers in an application

  - by Petar Minchev

  Hi guys! Let's assume we have the following method in the business layer. What's the best practice to tell the UI layer that something went wrong and give also the error message? Should the method return an empty String when it was OK, otherwise the error message, or should it throw another exception in the catch code wrapping the caught exception? If we choose the second variant then the UI should have another try,catch which is too much try,catch maybe. Here is a pseudocode for the first variant. public String updateSomething() { try { //Begin transaction here dataLayer.do1(); dataLayer.do2(); dataLayer.doN(); } catch(Exception exc) { //Rollback transaction code here return exc.message; } return ""; } Is this a good practice or should I throw another exception in the catch(then the method will be void)?

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• What's the standard behaviour for an out parameter when a TryXxxx method returns false?

  - by Matt Lacey

  Assuming a method with the following signature bool TryXxxx(object something, out int toReturn) What is it acceptable for toReturn to be if TryXxxx returns false? In that it's infered that toReturn should never be used if TryXxxx fails does it matter? If toReturn was a nulable type, then it would make sense to return null. But int isn't nullable and I don't want to have to force it to be. If toReturn is always a certain value if TryXxxx fails we risk having the position where 2 values could be considered to indicate the same thing. I can see this leading to potential possible confusion if the 'default' value was returned as a valid response (when TryXxxx returns true). From an implementation point if view it looks like having toReturn be a[ny] value is easiest, but is there anything more important to consider?

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• Migrating a simple application from Application Delegate to ViewController Class

  - by eco_bach

  Hi Frst of all wanted to send out a huge thanks for the great feedback and support. I have a simple application working, right now simply loads a sequence of images and alows the user to step thru the images by clicking a button. All of my logic is in my Application Delegate class, with the image loading, initialization of UIImage Views etc happening in my applicationDidFinishLaunching method. My next step is to migrate as much as possible all of the logic from this class to a ViewController, to take advantage of the extra functionality etc in viewcontrollers. All my images and imageViews are initialized like the following in my applicationDidFinishLaunching. img = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@image1.jpg" ofType:nil]]; imgView = [[UIImageView alloc] initWithImage:img]; How would I migrate this to a ViewController based application? Where would I put all of the logic currently in my applicationDidFinishLaunching method, or for loading of images, is it necessary to only load them here? Any feedback, tips, suggestions appreciated.

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• What are the general factors, that a developer should consider when he starts developing an applicat

  - by Oden

  Hey, I'm new to the development business, and I'm interested in the way, how other programmers start to develop, design an application. What are the main factors that I should consider when sitting down and starting to think about the app? How do you start planning a project?

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• Tips for documenting a web application?

  - by Pandiya Chendur

  I know that I can take my asp.net application and get it reversed to a UML document, but that doesn't tell the whole story of things like who can use what, what it calls in the way of stored procedures, what pages call what pages etc. etc. Does anyone know of an article where someone has a comprehensive way to document a web application/site? Or shall I just make up my own way?

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• What is the best way to identify which form has been submitted?

  - by Rupert

  Currently, when I design my forms, I like to keep the name of the submit button equal to the id of the form. Then, in my php, I just do if(isset($_POST['submitName'])) in order to check if a form has been submitted and which form has been submitted. Firstly, are there any security problems or design flaws with this method? One problem I have encountered is when I wish to overlay my forms with javascript in order to provide faster validation to the user. For example, whilst I obviously need to retain server side validation, it is more convenient for the user if an error message is displayed inline, upon blurring an input. Additionally, it would be good to provide entire form validation, upon clicking the submit button. Therefore, when the user clicks on the form's submit button, I am stopping the default action, doing my validation, and then attempting to renable the traditional submit functionality, if the validation passes. In order to do this, I am using the form.submit() method but, unfortunately, this doesn't send the submit button variable (as it should be as form.submit() can be called without any button being clicked). This means my PHP script fails to detect that the form has been submitted. What is the correct way to work around this? It seems like the standard solution is to add a hidden field into the form, upon passing validation, which has the name of form's id. Then when form.submit() is called, this is passed along in place of the submit button. However, this solution seems very ungraceful to me and so I am wondering whether I should: a) Use an alternative method to detect which form has been submitted which doesn't rely rely on passing the submit button. If so what alternative is there? Obviously, just having an extra hidden field from the start isn't any better. b) Use an alternative Javascript solution which allows me to retain my non-Javascript design. For example, is there an alternative to form.submit() which allows me to pass in extra data? c) Suck it up and just insert a hidden field using Javascript.

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• Tips for Using Multiple Development Systems

  - by Tim Lytle

  When I travel, I don't pack up the desktop I use in the office and take it with me. Maybe I should, but I don't. However, since I'm a contract programmer I like to be able to work wherever I am: I'm mostly thinking of web development here. Version Control goes a long way in keeping sane and working on multiple projects on multiple systems (two or three computers); however, there are the issues of: IDE settings - different display sizes mean the IDE settings can't be completely synced, if at all. Database - if the database is 'external' (even if it's running on the same system, it's not in version control), how do you maintain the needed syncs of structure. Development Stack - Some projects need non-standard extensions, libraries, etc installed. Just an overview of some of the hassle involved with developing on multiple systems. I'll probably end up asking some specific questions, but I thought a CW style tips might reveal some things I would even think to ask about. Update: I guess this would also address tips to make upgrading/replacing your development system easier (something I've just done). So, one tip per answer please, so the 'top' tips are easy to find. How do you make it easier to develop on multiple systems, or to transfer work after upgrading/replaceing a development system?

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• Debugging TestNG configuration failures

  - by Ula Karzelek

  I'm running testng from ant. I'm using my own test listeners. I'm refactoring the code and once a while I got [testng] Total tests run: 7, Failures: 0, Skips: 7 [testng] Configuration Failures: 1, Skips: 2 What will be the best approach to fix configuration failures?

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• How to code for Alternate Course AKA Rainy Day Scenary?

  - by janetsmith

  Alternate course is something when user doesn't do what you expected, e.g. key in wrong password, pressing back button, or database error. For any programming project, alternate course accounts for more than 50% of a project timeline. It is important. However, most computer books only focus on Basic Course (when everything goes fine). Basic course is rather simple, compared to Alternate course, because this is normally given by client. Alternate course is what we, as a programmer or Business Analyst needs to take care of. Java has some built-in mechanism (try-catch) to force us to handle those unexpected behavior. The question is, how to handle them? Any pattern to follow? Any guideline or industry practice for handling alternate course?

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• Is it bad to explicitly compare against boolean constants e.g. if (b == false) in Java?

  - by polygenelubricants

  Is it bad to write: if (b == false) //... while (b != true) //... Is it always better to instead write: if (!b) //... while (!b) //... Presumably there is no difference in performance (or is there?), but how do you weigh the explicitness, the conciseness, the clarity, the readability, etc between the two? Note: the variable name b is just used as an example, ala foo and bar.

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• What is a good practice to access class attributes in class methods?

  - by Clem

  I always wonder about the best way to access a class attribute from a class method in Java. Could you quickly convince me about which one of the 3 solutions below (or a totally different one :P) is a good practice? public class Test { String a; public String getA(){ return this.a; } public setA(String a){ this.a = a; } // Using Getter public void display(){ // Solution 1 System.out.println(this.a); // Solution 2 System.out.println(getA()); // Solution 3 System.out.println(this.getA()); } // Using Setter public void myMethod(String b, String c){ // Solution 1 this.a = b + c; // Solution 2 setA(b + c); // Solution 3 this.setA(b + c); } }

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• Is there a way to express Django admin settings inside the models, instead of admin.py?

  - by Off Rhoden

  Talking about Django 1.1.1. I thought at one time (0.96) the kinds of things put inside of the admin.py file were part of an inner class of the model. There's a certain beauty in having all of this in one place. But I don't know if this change was out of necessity. Any compelling reasons one way or the other?

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• Multiple Actions (Forms) on one Page - How not to lose master data, after editing detail data?

  - by nWorx

  Hello all, I've got a form where users can edit members of a group. So they have the possibilty to add members or remove existing members. So the Url goes like ".../Group/Edit/4" Where 4 is the id of the group. the view looks like this <% using (Html.BeginForm("AddUser", "Group")) %> <%{%> <label for="newUser">User</label> <%=Html.TextBox("username")%> <input type="submit" value="Add"/> </div> <%}%> <% using (Html.BeginForm("RemoveUser", "Group")) %> <%{%> <div class="inputItem"> <label for="groupMember">Bestehende Mitglieder</label> <%= Html.ListBox("groupMember", from g in Model.GetMembers() select new SelectListItem(){Text = g}) %> <input type="submit" value="Remove" /> </div> <%}%> The problem is that after adding or removing one user i lose the id of the group. What is the best solution for solving this kind of problem? Should I use hidden fields to save the group id? Thanks in advance.

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• How to call superconstructor in a neat way

  - by sandis

  So here is my code: public MyClass (int y) { super(y,x,x); //some code } My problem is that in this case i want to generate a 'x' and sent to the super constructor. However the call to the superconstructor must be the first line in this constructor. Of course I could do something like this: int x; { x = generateX(); } But this feels ugly, and then the code will run no matter what constructor I use, which feels not so nice. Right now I am consider encapsulating my whole object in another object that only calculates x and then starts this object. Is this the best approach?

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• What Getters and Setters should and shouldn't do.

  - by cyclotis04

  I've run into a lot of differing opinions on Getters and Setters lately, so I figured I should make it into it's own question. A previous question of mine received an immediate comment (later deleted) that stated setters shouldn't have any side effects, and a SetProperty method would be a better choice. Indeed, this seems to be Microsoft's opinion as well. However, their properties often raise events, such as Resized when a form's Width or Height property is set. OwenP also states "you shouldn't let a property throw exceptions, properties shouldn't have side effects, order shouldn't matter, and properties should return relatively quickly." Yet Michael Stum states that exceptions should be thrown while validating data within a setter. If your setter doesn't throw an exception, how could you effectively validate data, as so many of the answers to this question suggest? What about when you need to raise an event, like nearly all of Microsoft's Control's do? Aren't you then at the mercy of whomever subscribed to your event? If their handler performs a massive amount of information, or throws an error itself, what happens to your setter? Finally, what about lazy loading within the getter? This too could violate the previous guidelines. What is acceptable to place in a getter or setter, and what should be kept in only accessor methods?

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• Is it bad practice to use an enum that maps to some seed data in a Database?

  - by skb

  I have a table in my database called "OrderItemType" which has about 5 records for the different OrderItemTypes in my system. Each OrderItem contains an OrderItemType, and this gives me referential integrity. In my middletier code, I also have an enum which matches the values in this table so that I can have business logic for the different types. My dev manager says he hates it when people do this, and I am not exactly sure why. Is there a better practice I should be following?

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• How to set default values to all wrong or null parameters of method?

  - by Roman

  At the moment I have this code (and I don't like it): private RenderedImage private RenderedImage getChartImage (GanttChartModel model, String title, Integer width, Integer height, String xAxisLabel, String yAxisLabel, Boolean showLegend) { if (title == null) { title = ""; } if (xAxisLabel == null) { xAxisLabel = ""; } if (yAxisLabel == null) { yAxisLabel = ""; } if (showLegend == null) { showLegend = true; } if (width == null) { width = DEFAULT_WIDTH; } if (height == null) { height = DEFAULT_HEIGHT; } ... } How can I improve it? I have some thoughts about introducing an object which will contain all these parameters as fields and then, maybe, it'll be possible to apply builder pattern. But still don't have clear vision how to implement that and I'm not sure that it's worth to be done. Any other ideas?

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• What are the reasons for casting a void pointer?

  - by Maulrus

  I'm learning C++ from scratch, and as such I don't have an expert understanding of C. In C++, you can't cast a void pointer to whatever, and I understand the reasons behind that. However, I know that in C, you can. What are the possible reasons for this? It just seems like it's be a huge hole in type safety, which (to me) seems like a bad thing.

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• Efficiently Serving Dynamic Content in Google App Engine

  - by awegawef

  My app on google app engine returns content items (just text) and comments on them. It works like this (pseudo-ish code): query: get keys of latest content #query to datastore for each item in content if item_dict in memcache: use item_dict else: build_item_dict(item) #by fetching from datastore store item_dict in memcache send all item_dicts to template Sorry if the code isn't understandable. I get all of the content dictionaries and send them to the template, which uses them to create the webpage. My problem is that if the memcache has expired, for each item I want to display, I have to (1) lookup item in memcache, (2) since no memcache exists I must fetch item from the datastore, and (3) store the item in memcache. These calls build up quickly. I don't set an expire time for the entries to the memcache, so this really only happens once in the morning, but the webpage takes long enough to load (~1 sec) that the browser reports it as not existing. Regularly, my webpages take about 50ms to load. This approach works decently for frequent visits, but it has its flaws as shown above. How can I remedy this? The entries are dynamic enough that I don't think it would be in my best interest to cache my initial request. Thanks in advance

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• Self-Configuring Classes W/ Command Line Args: Pattern or Anti-Pattern?

  - by dsimcha

  I've got a program where a lot of classes have really complicated configuration requirements. I've adopted the pattern of decentralizing the configuration and allowing each class to take and parse the command line/configuration file arguments in its c'tor and do whatever it needs with them. (These are very coarse-grained classes that are only instantiated a few times, so there is absolutely no performance issue here.) This avoids having to do shotgun surgery to plumb new options I add through all the levels they need to be passed through. It also avoids having to specify each configuration option in multiple places (where it's parsed and where it's used). What are some advantages/disadvantages of this style of programming? It seems to reduce separation of concerns in that every class is now doing configuration stuff, and to make programs less self-documenting because what parameters a class takes becomes less explicit. OTOH, it seems to increase encapsulation in that it makes each class more self-contained because no other part of the program needs to know exactly what configuration parameters a class might need.

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• "Special case" records for foreign key constraints

  - by keithjgrant

  Let's say I have a mysql table, called foo with a foreign key option_id constrained to the option table. When I create a foo record, the user may or may not have selected an option, and 'no option' is a viable selection. What is the best way to differentiate between 'null' (i.e. the user hasn't made a selection yet) and 'no option' (i.e. the user selected 'no option')? Right now, my plan is to insert a special record into the option table. Let's say that winds up with an id of 227 (this table already has a number of records at this point, so '1' isn't available). I have no need to access this record at a database level, and it would act as nothing more than a placeholder that the foreign key in the foo table can reference. So do I just hard-code '227' in my codebase when I'm creating 'foo' records where the user has selected 'no option'? The hard-coded id seems sloppy, and leaves room for error as the code is maintained down the road, but I'm not really sure of another approach.

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