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• How to Treat Race Condition of Session in Web Application?

  - by Morgan Cheng

  I was in a ASP.NET application has heavy traffic of AJAX requests. Once a user login our web application, a session is created to store information of this user's state. Currently, our solution to keep session data consistent is quite simple and brutal: each request needs to acquire a exclusive lock before being processed. This works fine for tradition web application. But, when the web application turns to support AJAX, it turns to not efficient. It is quite possible that multiple AJAX requests are sent to server at the same time without reloading the web page. If all AJAX requests are serialized by the exclusive lock, the response is not so quick. Anyway, many AJAX requests that doesn't access same session variables are blocked as well. If we don't have a exclusive lock for each requests, then we need to treat all race condition carefully to avoid dead lock. I'm afraid that would make the code complex and buggy. So, is there any best practice to keep session data consistent and keep code simple and clean?

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• How to implement a network protocol?

  - by gotch4

  Here is a generic question. I'm not in search of the best answer, I'd just like you to express your favourite practices. I want to implement a network protocol in Java (but this is a rather general question, I faced the same issues in C++), this is not the first time, as I have done this before. But I think I am missing a good way to implement it. In fact usually it's all about exchanging text messages and some byte buffers between hosts, storing the status and wait until the next message comes. The problem is that I usually end up with a bunch of switch and more or less complex if statements that react to different statuses / messages. The whole thing usually gets complicated and hard to mantain. Not to mention that sometimes what comes out has some "blind spot", I mean statuses of the protocol that have not been covered and that behave in a unpredictable way. I tried to write down some state machine classes, that take care of checking start and end statuses for each action in more or less smart ways. This makes programming the protocol very complicated as I have to write lines and lines of code to cover every possible situation. What I'd like is something like a good pattern, or a best practice that is used in programming complex protocols, easy to mantain and to extend and very readable. What are your suggestions?

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• Google App Engine - How to implement the activity stream in a social network

  - by spidee

  I want some ideas on the best practice to implement an activity stream for a social network im building in app engine (PYTHON) I first want to keep a log for all activities of each user - so that we have a history. i.e. someone became a friend, added a picture, changed their address etc. This way we have a users history available should we need it. Also mean we can remove friendship joins, change user data but have a historical log. I also want to stream a users activity to their friends. for this only the last X activities need to be kept - that is in the scenario that messages are sent to friends when an activity occurs. Its pretty straight forward designing a history log - ie: when, what, where. The complication comes as to how we notify friends of a user as to their activity. In our app friendships are not mutual - ie they are based on the twitter following model. Some accounts could have thousands of followers. What is the best approach to model this. using a many to many join table and doing a costly query - using a feed class that fired a copy of the activity to all the subscribers - maybe into mcache? As their maybe a need to fire thousands of messages i would imagine a cron job would need to be used. Any help ideas thoughts on this Thx

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• VB.NET Syntax Coding

  - by Yiu Korochko

  I know many people ask how some of these are done, but I do not understand the context in which to use the answers, so... I'm building a code editor for a subversion of Python language, and I found a very decent way of highlighting keywords in the RichTextBox through this: bluwords.Add(KEYWORDS GO HERE) If scriptt.Text.Length > 0 Then Dim selectStart2 As Integer = scriptt.SelectionStart scriptt.Select(0, scriptt.Text.Length) scriptt.SelectionColor = Color.Black scriptt.DeselectAll() For Each oneWord As String In bluwords Dim pos As Integer = 0 Do While scriptt.Text.ToUpper.IndexOf(oneWord.ToUpper, pos) >= 0 pos = scriptt.Text.ToUpper.IndexOf(oneWord.ToUpper, pos) scriptt.Select(pos, oneWord.Length) scriptt.SelectionColor = Color.Blue pos += 1 Loop Next scriptt.SelectionStart = selectStart2 End If (scriptt is the richtextbox) But when any decent amount of code is typed (or loaded via OpenFileDialog) chunks of the code go missing, the syntax selection falls apart, and it just plain ruins it. I'm looking for a more efficient way of doing this, maybe something more like visual studio itself...because there is NO NEED to highlight all text, set it black, then redo all of the syntaxing, and the text begins to over-right if you go back to insert characters between text. Also, in this version of Python, hash (#) is used for comments on comment only lines and double hash (##) is used for comments on the same line. Now I saw that someone had asked about this exact thing, and the working answer to select to the end of the line was something like: ^\'[^\r\n]+$|''[^\r\n]+$ which I cannot seem to get into practice. I also wanted to select text between quotes and turn it turquoise, such as between the first quotation mark and the second, the text is turquoise, and the same between the 3rd and 4th etcetera... Any help is appreciated!

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• A Newbie question regarding Software Development

  - by Sharif

  Hi, I'm going to complete my B.pharm (Hons.) degree and, you know, I don't have much knowledge about programing. I was wondering to build a software on my own. Could you guys tell me what to learn first for that? Is it too hard for a student of other discipline to build a software? Let me know please. The software I want to make is like a dictionary (or more specifically like "Physician's Desk Reference"). It should find the generic name, company name, indication, price etc. of a drug when I enter the brand name and vice versa. To build a software like that what programing language could help me most and what (and how many) language should I learn first? In my country, there is no practice of Community pharmacy (most of the pharmacy stores are run by unskilled people), that's why this type of thing could help them sell drugs. Would you please tell me what I'm to do and how tough it is? I'm very keen to learn programming. Thanks in advance NB: I started this post in ASKREDDIT section but it seems that was not the right place for poll type question, so I post it again in this section

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• Where should an application's default folder live?

  - by HotOil

  Hi: I'm creating a little app that configures a connected device and then saves the config information in a file. The filename cannot be chosen by the user, but its location can be chosen. Where is the best place for the app's default save-to folder? I have seen examples out there where it is the "MyDocuments" location (eg Visual Studio does this). I have seen a folder created right at the top of the C:\ drive. I find that to be a little obnoxious, personally. It could be in the Program Files[Manufacturer] or Program Files[Product Name], or wherever the app was installed. I have used this location in the past; I dislike it because Windows Explorer does not allow a user to browse to there very easily ('browsability'). Going with this last notion that 'browsability' is a factor, I suppose MyDocuments is the best choice. Is this the most common, most widely accepted practice? I think historically we have chosen the install folder because that co-locates the data with the device management utilities. But I would really like to get away from that. I don't want the user to have to go pawing through system files to find his/her data, esp if that person is not too Windows-savvy. Also, I am using the .NET WinForms FolderBrowserDialog, and the "Environment.SpecialFolders" enum isn't helpful in setting up the dialog to point into the Program Files folder. Thanks for your input! Suz.

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• Implementing a bitfield using java enums

  - by soappatrol

  Hello, I maintain a large document archive and I often use bit fields to record the status of my documents during processing or when validating them. My legacy code simply uses static int constants such as: static int DOCUMENT_STATUS_NO_STATE = 0 static int DOCUMENT_STATUS_OK = 1 static int DOCUMENT_STATUS_NO_TIF_FILE = 2 static int DOCUMENT_STATUS_NO_PDF_FILE = 4 This makes it pretty easy to indicate the state a document is in, by setting the appropriate flags. For example: status = DOCUMENT_STATUS_NO_TIF_FILE | DOCUMENT_STATUS_NO_PDF_FILE; Since the approach of using static constants is bad practice and because I would like to improve the code, I was looking to use Enums to achieve the same. There are a few requirements, one of them being the need to save the status into a database as a numeric type. So there is a need to transform the enumeration constants to a numeric value. Below is my first approach and I wonder if this is the correct way to go about this? class DocumentStatus{ public enum StatusFlag { DOCUMENT_STATUS_NOT_DEFINED(1<<0), DOCUMENT_STATUS_OK(1<<1), DOCUMENT_STATUS_MISSING_TID_DIR(1<<2), DOCUMENT_STATUS_MISSING_TIF_FILE(1<<3), DOCUMENT_STATUS_MISSING_PDF_FILE(1<<4), DOCUMENT_STATUS_MISSING_OCR_FILE(1<<5), DOCUMENT_STATUS_PAGE_COUNT_TIF(1<<6), DOCUMENT_STATUS_PAGE_COUNT_PDF(1<<7), DOCUMENT_STATUS_UNAVAILABLE(1<<8), private final long statusFlagValue; StatusFlag(long statusFlagValue) { this.statusFlagValue = statusFlagValue } public long getStatusFlagValue(){ return statusFlagValue } } /** * Translates a numeric status code into a Set of StatusFlag enums * @param numeric statusValue * @return EnumSet representing a documents status */ public EnumSet<StatusFlag> getStatusFlags(long statusValue) { EnumSet statusFlags = EnumSet.noneOf(StatusFlag.class) StatusFlag.each { statusFlag -> long flagValue = statusFlag.statusFlagValue if ( (flagValue&statusValue ) == flagValue ) { statusFlags.add(statusFlag) } } return statusFlags } /** * Translates a set of StatusFlag enums into a numeric status code * @param Set if statusFlags * @return numeric representation of the document status */ public long getStatusValue(Set<StatusFlag> flags) { long value=0 flags.each { statusFlag -> value|=statusFlag.getStatusFlagValue() } return value } public static void main(String[] args) { DocumentStatus ds = new DocumentStatus(); Set statusFlags = EnumSet.of( StatusFlag.DOCUMENT_STATUS_OK, StatusFlag.DOCUMENT_STATUS_UNAVAILABLE) assert ds.getStatusValue( statusFlags )==258 // 0000.0001|0000.0010 long numericStatusCode = 56 statusFlags = ds.getStatusFlags(numericStatusCode) assert !statusFlags.contains(StatusFlag.DOCUMENT_STATUS_OK) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_TIF_FILE) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_PDF_FILE) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_OCR_FILE) } }

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• Is Google Mock a good mocking framework ?

  - by des4maisons

  I am pioneering unit testing efforts at my company, and need need to choose a mocking framework to use. I have never used a mocking framework before. We have already chosen Google Test, so using Google Mock would be nice. However, my initial impressions after looking at Google Mock's tutorial are: The need for re-declaring each method in the mocking class with a MOCK_METHODn macro seems unnecessary and seems to go against the DRY principle. Their matchers (eg, the '_' in EXPECT_CALL(turtle, Forward(_));) and the order of matching seem almost too powerful. Like, it would be easy to say something you don't mean, and miss bugs that way. I have high confidence in google's developers, and low confidence in my own ability to judge mocking frameworks, never having used them before. So my question is: Are these valid concerns? Or is there no better way to define a mock object, and are the matchers intuitive to use in practice? I would appreciate answers from anyone who has used Google Mock before, and comparisons to other C++ frameworks would be helpful.

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• how to share a variable between two threads

  - by prmatta

  I just inherited some code, two threads within this code need to perform a system task. One thread should do the system task before the other thread. They should not be performing the system task together. The two threads do not have references to each other. Now, I know I can use some sort of a semaphore to achieve this. But my question is what is the right way to get both threads to access this semaphore. I could create a static variable/method a new class : public class SharedSemaphore { private static Semaphore s = new Semaphore (1, true); public static void performSystemTask () { s.acquire(); } public static void donePerformingSystemTask() { s.release(); } } This would work (right?) but this doesn't seem like the right thing to do. Because, the threads now have access to a semaphore, without ever having a reference to it. This sort of thing doesn't seem like a good programming practice. Am I wrong?

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• Why doesn't java.lang.Number implement Comparable?

  - by Julien Chastang

  Does anyone know why java.lang.Number does not implement Comparable? This means that you cannot sort Numbers with Collections.sort which seems to me a little strange. Post discussion update: Thanks for all the helpful responses. I ended up doing some more research about this topic. The simplest explanation for why java.lang.Number does not implement Comparable is rooted in mutability concerns. For a bit of review, java.lang.Number is the abstract super-type of AtomicInteger, AtomicLong, BigDecimal, BigInteger, Byte, Double, Float, Integer, Long and Short. On that list, AtomicInteger and AtomicLong to do not implement Comparable. Digging around, I discovered that it is not a good practice to implement Comparable on mutable types because the objects can change during or after comparison rendering the result of the comparison useless. Both AtomicLong and AtomicInteger are mutable. The API designers had the forethought to not have Number implement Comparable because it would have constrained implementation of future subtypes. Indeed, AtomicLong and AtomicInteger were added in Java 1.5 long after java.lang.Number was initially implemented. Apart from mutability, there are probably other considerations here too. A compareTo implementation in Number would have to promote all numeric values to BigDecimal because it is capable of accommodating all the Number sub-types. The implication of that promotion in terms of mathematics and performance is a bit unclear to me, but my intuition finds that solution kludgy.

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• Perl - Using hashes in classes

  - by brydgesk

  I have a class with several variables, one of which is a hash (_runs): sub new { my ($class, $name) = @_; my $self = { _name => $name, ... _runs => (), _times => [], ... }; bless ($self, $class); return $self; } Now, all I'm trying to do is create an accessor/mutator, as well as another subroutine that pushes new data into the hash. But I'm having a hell of a time getting all the referencing/dereferencing/$self calls working together. I've about burned my eyes out with "Can't use string ("blah") as a HASH ref etc etc" errors. For the accessor, what is 'best practice' for returning hashes? Which one of these options should I be using (if any)?: return $self->{_runs}; return %{ $self->{_runs} }; return \$self->{_runs}; Further, when I'm using the hash within other subroutines in the class, what syntax do I use to copy it? my @runs = $self->{_runs}; my @runs = %{ $self->{_runs} }; my @runs = $%{ $self->{_runs} }; my @runs = $$self->{_runs}; Same goes for iterating over the keys: foreach my $dt (keys $self->{_runs}) foreach my $dt (keys %{ $self->{_runs} }) And how about actually adding the data? $self->{_runs}{$dt} = $duration; %{ $self->{_runs} }{$dt} = $duration; $$self->{_runs}{$dt} = $duration; You get the point. I've been reading articles about using classes, and articles about referencing and dereferencing, but I can't seem to get my brain to combine the knowledge and use both at the same time. I got my _times array working finally, but mimicking my array syntax over to hashes didn't work.

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• Structuring the UI code of a single-page EXTjs Web app using Rails?

  - by Daniel Beardsley

  I’m in the process of creating a large single-page web-app using ext-js for the UI components with Rails on the backend. I’ve come to good solutions for transferring data using Whorm gem and Rails support of RESTful Resources. What I haven’t come to a conclusion on is how to structure the UI and business logic aspects of the application. I’ve had a look at a few options, including Netzke but haven’t seen anything that I really think fits my needs. How should a web-application that uses ext-js components, layouts, and controls in the browser and Rails on the server best implement UI component re-use, good organization, and maintainability while maintaining a flexible layout design. Specifically I’m looking for best-practice suggestions for structuring the code that creates and configures UI components (many UI config options will be based on user data) Should EXT classes be extended in static JS for often re-used customizations and then instantiated with various configuration options by generated JS within html partials? Should partials create javascript blocks that instantiate EXT components? Should partials call helpers that return ruby hashes for EXT component config which is then dumped to Json? Something else entirely? There are many options and I'd love to hear from people who've been down this road and found some methodology that worked for them.

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• Using an embedded Word document to create a new instance of that document.

  - by jim

  For a variety of reasons that are immutable ... I have a Word document which contains a VBA application (the 'app document') which creates a new document based on another document (the 'template') which contains the framework for the new document. I want to embed the 'template' into the 'app document' so that I deliver one file and I know I am using the correct version of the 'template'. I have, so far, embedded the 'template' file into the 'app document' and can find it by looping through "ThisDocument.InlineShapes", looking at .Field.OleFormat.IconLabel to find the 'template' by its name. The inlineShape.Field.OleFormat.Object is the 'template' document itself, and I can .Activate it, which causes it to appear as a regular document. I try to do SaveAs, and it does in fact save the file as the name I give it, however, that saved-as file is not left open, just the embedded file. I can not .Activate the file and just save it, then open the saved file, but that seems more work than necessary. So ... is the way I am doing this "the way", or I have missed some obvious practice? TIA

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• php form submit and the resend infromation screen

  - by Para

  Hello, I want to ask a best practice question. Suppose I have a form in php with 3 fields say name, email and comment. I submit the form via POST. In PHP I try and insert the date into the database. Suppose the insertion fails. I should now show the user an error and display the form filled in with the data he previously inserted so he can correct his error. Showing the form in it's initial state won't do. So I display the form and the 3 fields are now filled in from PHP with echo or such. Now if I click refresh I get a message saying "Are you sure you want to resend information?". OK. Suppose after I insert the data I don't carry on but I redirect to the same page but with the necessary parameters in the query string. This makes the message go away but I have to carry 3 parameters in the query string. So my question is: How is it better to do this? I want to not carry around lots of parameters in the query string but also not get that error. How can this be done? Should I use cookies to store the form information.

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• WPF binding to a boolean on a control

  - by Jose

  I'm wondering if someone has a simple succinct solution to binding to a dependency property that needs to be the converse of the property. Here's an example I have a textbox that is disabled based on a property in the datacontext e.g.: <TextBox IsEnabled={Binding CanEdit} Text={Binding MyText}/> The requirement changes and I want to make it ReadOnly instead of disabled, so without changing my ViewModel I could do this: In the UserControl resources: <UserControl.Resources> <m:NotConverter x:Key="NotConverter"/> </UserControl.Resources> And then change the TextBox to: <TextBox IsReadOnly={Binding CanEdit,Converter={StaticResource NotConverter}} Text={Binding MyText}/> Which I personally think is EXTREMELY verbose I would love to be able to just do this(notice the !): <TextBox IsReadOnly={Binding !CanEdit} Text={Binding MyText}/> But alas, that is not an option that I know of. I can think of two options. Create an attached property IsNotReadOnly to FrameworkElement(?) and bind to that property If I change my ViewModel then I could add a property CanEdit and another CannotEdit which I would be kind of embarrassed of because I believe it adds an irrelevant property to a class, which I don't think is a good practice. The main reason for the question is that in my project the above isn't just for one control, so trying to keep my project as DRY as possible and readable I am throwing this out to anyone feeling my pain and has come up with a solution :)

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• jquery callback functions failing to finish execution

  - by calumbrodie

  I'm testing a jquery app i've written and have come across some unexpected behaviour $('button.clickme').live('click',function(){ //do x (takes 2 seconds) //do y (takes 4 seconds) //do z (takes 0.5 seconds) }) The event can be triggered by a number of buttons. What I'm finding is that when I click each button slowly (allowing 10 seconds between clicks) - my callback function executes correctly (actions x, y & z complete). However If I rapidly click buttons on my page it appears that the function sometimes only completes up to step x or y before terminating. My question: Is it the case that if this function is fired by a clicking second DOM element, while the first callback function is completing - will jQuery terminate the first callback and start over again? Do I have to write my callback function explicitly outside the event handler and then call it?? function doStuff() { //do x //do y //do z ( } $('button.clickme).live('click',doStuff()) If this is the case can someone explain why this is happening or give me a link to some advice on best practice on closures etc - I'd like to know the BEST way to write jQuery to improve performance etc. Thanks

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• XSD, restrictions and code generation

  - by bob

  Hello, I'm working on some code generation for an existing project and I want to start from a xsd. So I can use tools as Xsd2Code / xsd.exe to generate the code and also the use the xsd to validate the xml. That part works without any problems. I also want to translate some of the restrictions to DataAnnotations (enrich Xsd2Code). For example xs:minInclusive / xs:maxInclusive I can translate to a RangeAttribute. But what to do with custom validation attributes that we created? Can I add custom facets / restrictions? And how? Or is there another solution / best practice. I would like to collect everything in a single (xsd) file so that one file contains the structure of the class (model) including the validation (attributes) that has to be added. <xs:element name="CertainValue"> <xs:simpleType> <xs:restriction base="xs:double"> <xs:minInclusive value="1" /> <xs:maxInclusive value="100" /> <xs_custom:customRule attribute="value" /> </xs:restriction> </xs:simpleType> </xs:element>

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• Better way to implement custom views in a listview with simpleadapter?

  - by jonaz

  I have a value called tags which is a comma separated list of words. I want to put this into nicely designed "tag-buttons". The below works. However the line ((LinearLayout) view).removeAllViews(); seems like an ugly fix for not adding the tags multiple times every time adapter.notifyDataSetChanged(); is called after i load more rows with a setOnScrollListener() Any suggestion to "best practice" here, or at least a more good looking solution? adapter = new SimpleAdapter(activity,data, R.layout.list_transactions, new String[] {"comment", "amount","date","tags","category"}, new int[] { R.id.comment, R.id.amount,R.id.date,R.id.tags_container,R.id.category } ); SimpleAdapter.ViewBinder binder = new SimpleAdapter.ViewBinder() { @Override public boolean setViewValue(View view, Object object, String value) { //Log.d(TAG,"view.toString()= "+ view.toString()); if (view.getId() == R.id.tags_container) { String[] tags = value.split(","); ((LinearLayout) view).removeAllViews(); for (String tag : tags) { View v = createTagView(activity.getLayoutInflater(),tag); ((LinearLayout) view).addView(v); } return true; } return false; } };

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• Validating JSP's and HTML Forms, Server-side or Client-side, or both?

  - by CitadelCSAlum

  I am aware that I can Google "HTML Form Validation" and would get a billion tutorials. I am well aware that I can use simple JavaScript to validate form input, but I have been told that this is not necessarily an efficient method. I have also heard that it is a best practice to validate both client and server-side code. OK! Well, What exactly does this mean besides writing code on both? Does it mean I do some with JavaScript and other with Servlet's or does it mean that I write identical validation methods on both? My real question is can anybody give me insight and direction as how to go about validation my HTML forms. I am using JSP's and Servlet's and I have tons of form validation to do. I have already done minor form validation with regex in Java, but want to figure out if Im heading in the right track before I write any more code. Only productive answers please, If I wanted negative feedback on how inexperienced I was, I would have gone to Reddit. Thanks!

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• Best way to unit test Collection?

  - by limc

  I'm just wondering how folks unit test and assert that the "expected" collection is the same/similar as the "actual" collection (order is not important). To perform this assertion, I wrote my simple assert API:- public void assertCollection(Collection<?> expectedCollection, Collection<?> actualCollection) { assertNotNull(expectedCollection); assertNotNull(actualCollection); assertEquals(expectedCollection.size(), actualCollection.size()); assertTrue(expectedCollection.containsAll(actualCollection)); assertTrue(actualCollection.containsAll(expectedCollection)); } Well, it works. It's pretty simple if I'm asserting just bunch of Integers or Strings. It can also be pretty painful if I'm trying to assert a collection of Hibernate domains, say for example. The collection.containsAll(..) relies on the equals(..) to perform the check, but I always override the equals(..) in my Hibernate domains to check only the business keys (which is the best practice stated in the Hibernate website) and not all the fields of that domain. Sure, it makes sense to check just against the business keys, but there are times I really want to make sure all the fields are correct, not just the business keys (for example, new data entry record). So, in this case, I can't mess around with the domain.equals(..) and it almost seems like I need to implement some comparators for just unit testing purposes instead of relying on collection.containsAll(..). Are there some testing libraries I could leverage here? How do you test your collection? Thanks.

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• is it better to test if a function is needed inside or outside of it?

  - by b0x0rz

  what is the best practice? call a function then return if you test for something, or test for something then call? i prefer the test inside of function because it makes an easier viewing of what functions are called. for example: protected void Application_BeginRequest(object sender, EventArgs e) { this.FixURLCosmetics(); } and private void FixURLCosmetics() { HttpContext context = HttpContext.Current; if (!context.Request.HttpMethod.ToString().Equals("GET", StringComparison.OrdinalIgnoreCase)) { // if not a GET method cancel url cosmetics return; }; string url = context.Request.RawUrl.ToString(); bool doRedirect = false; // remove > default.aspx if (url.EndsWith("/default.aspx", StringComparison.OrdinalIgnoreCase)) { url = url.Substring(0, url.Length - 12); doRedirect = true; } // remove > www if (url.Contains("//www")) { url = url.Replace("//www", "//"); doRedirect = true; } // redirect if necessary if (doRedirect) { context.Response.Redirect(url); } } is this good: if (!context.Request.HttpMethod.ToString().Equals("GET", StringComparison.OrdinalIgnoreCase)) { // if not a GET method cancel url cosmetics return; }; or should that test be done in Application_BeginRequest? what is better? thnx

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• Large ListView containing images in Android

  - by Marco W.

  For various Android applications, I need large ListViews, i.e. such views with 100-300 entries. All entries must be loaded in bulk when the application is started, as some sorting and processing is necessary and the application cannot know which items to display first, otherwise. So far, I've been loading the images for all items in bulk as well, which are then saved in an ArrayList<CustomType> together with the rest of the data for each entry. But of course, this is not a good practice, as you're very likely to have an OutOfMemoryException then: The references to all images in the ArrayList prevent the garbage collector from working. So the best solution is, obviously, to load only the text data in bulk whereas the images are then loaded as needed, right? The Google Play application does this, for example: You can see that images are loaded as you scroll to them, i.e. they are probably loaded in the adapter's getView() method. But with Google Play, this is a different problem, anyway, as the images must be loaded from the Internet, which is not the case for me. My problem is not that loading the images takes too long, but storing them requires too much memory. So what should I do with the images? Load in getView(), when they are really needed? Would make scrolling sluggish. So calling an AsyncTask then? Or just a normal Thread? Parametrize it? I could save the images that are already loaded into a HashMap<String,Bitmap>, so that they don't need to be loaded again in getView(). But if this is done, you have the memory problem again: The HashMap stores references to all images, so in the end, you could have the OutOfMemoryException again. I know that there are already lots of questions here that discuss "Lazy loading" of images. But they mainly cover the problem of slow loading, not too much memory consumption.

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• Regarding C Static/Non Static Float Arrays (Xcode, Objective C)

  - by user1875290

  Basically I have a class method that returns a float array. If I return a static array I have the problem of it being too large or possibly even too small depending on the input parameter as the size of the array needed depends on the input size. If I return just a float array[arraysize] I have the size problem solved but I have other problems. Say for example I address each element of the non-static float array individually e.g. NSLog(@"array[0] %f array[1] %f array[2] %f",array[0],array[1],array[2]); It prints the correct values for the array. However if I instead use a loop e.g. for (int i = 0; i < 3; i++) { NSLog(@"array[%i] %f",i,array[i]); } I get some very strange numbers (apart from the last index, oddly). Why do these two things produce different results? I'm aware that its bad practice to simply return a non static float, but even so, these two means of addressing the array look the same to me. Relevant code from class method (for non-static version)... float array[arraysize]; //many lines of code later if (weShouldStoreValue == true) { array[index] = theFloat; index = index + 1; } //more lines of code later return array; Note that it returns a (float*).

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• What characters are NOT escaped with a mysqli prepared statement?

  - by barfoon

  Hey everyone, I'm trying to harden some of my PHP code and use mysqli prepared statements to better validate user input and prevent injection attacks. I switched away from mysqli_real_escape_string as it does not escape % and _. However, when I create my query as a mysqli prepared statement, the same flaw is still present. The query pulls a users salt value based on their username. I'd do something similar for passwords and other lookups. Code: $db = new sitedatalayer(); if ($stmt = $db->_conn->prepare("SELECT `salt` FROM admins WHERE `username` LIKE ? LIMIT 1")) { $stmt->bind_param('s', $username); $stmt->execute(); $stmt->bind_result($salt); while ($stmt->fetch()) { printf("%s\n", $salt); } $stmt->close(); } else return false; Am I composing the statement correctly? If I am what other characters need to be examined? What other flaws are there? What is best practice for doing these types of selects? Thanks,

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• Extremely CPU Intensive Alarm Clock

  - by SoulBeaver

  For some reason my program, a console alarm clock I made for laughs and practice, is extremely CPU intensive. It consumes about 2mB RAM, which is already quite a bit for such a small program, but it devastates my CPU with over 50% resources at times. Most of the time my program is doing nothing except counting down the seconds, so I guess this part of my program is the one that's causing so much strain on my CPU, though I don't know why. If it is so, could you please recommend a way of making it less, or perhaps a library to use instead if the problem can't be easily solved? /* The wait function waits exactly one second before returning to the * * called function. */ void wait( const int &seconds ) { clock_t endwait; // Type needed to compare with clock() endwait = clock() + ( seconds * CLOCKS_PER_SEC ); while( clock() < endwait ) {} // Nothing need be done here. } In case anybody browses CPlusPlus.com, this is a genuine copy/paste of the clock() function they have written as an example for clock(). Much why the comment //Nothing need be done here is so lackluster. I'm not entirely sure what exactly clock() does yet. The rest of the program calls two other functions that only activate every sixty seconds, otherwise returning to the caller and counting down another second, so I don't think that's too CPU intensive- though I wouldn't know, this is my first attempt at optimizing code. The first function is a console clear using system("cls") which, I know, is really, really slow and not a good idea. I will be changing that post-haste, but, since it only activates every 60 seconds and there is a noticeable lag-spike, I know this isn't the problem most of the time. The second function re-writes the content of the screen with the updated remaining time also only every sixty seconds. I will edit in the function that calls wait, clearScreen and display if it's clear that this function is not the problem. I already tried to reference most variables so they are not copied, as well as avoid endl as I heard that it's a little slow compared to \n.

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