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  • Public versus private inheritance when some of the parent's methods need to be exposed?

    - by Vorac
    Public inheritance means that all fields from the base class retain their declared visibility, while private means that they are forced to 'private' within the derived class's scope. What should be done if some of the parent's members (say, methods) need to be publicly exposed? I can think of two solution. Public inheritance somewhat breaks encapsulation. Furthermore, when you need to find out where is the method foo() defined, one needs to look at a chain of base classes. Private inheritance solves these problems, but introduces burden to write wrappers (more text). Which might be a good thing in the line of verbosity, but makes changes of interfaces incredibly cumbersome. What considerations am I missing? What constraints on the type of project are important? How to choose between the two (I am not even mentioning 'protected')? Note that I am targeting non-virtual methods. There isn't such a discussion for virtual methods (or is there).

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  • Using static methods in objects PHP - is it advantage?

    - by RePRO
    I was reading some articles and discussions on the use of static methods on objects and it struck me how much the views differ. Someone say that using static methods is an advantage. Someone says that use is a big mistake. I wonder how is it? My question is when to use static methods and when not? I would like to hear answers from experts in this field (PHP OOP). This is because I know how it really is. The following code should be analogous. Just call the static method is simpler (my opinion): <?php class A { public function write($a) { echo $a; } } class B { public static function write($a) { echo $a; } } $a = new A; $a->write(5); // 5 B::write(5); // 5 ?> Thank you.

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  • Centos/OVH: public IP on KVM virtual machine

    - by Sébastien
    Since a few days, I'm trying to configure my KVM vm to have a public IP address, without any success. First, I'm on OVH, and you need to know they don't allow networking from different mac addresses. I have so registered a virtual mac address associated with my failover IP Here's my configuration: Guest wanted IP: 46.105.40.x Host IP: 176.31.240.x Host configuration dummy0 interface: ifcfg-dummy0 BOOTPROTO=static IPADDR=10.0.0.1 NETMASK=255.0.0.0 ONBOOT=yes NM_CONTROLLED=no ARP=yes BRIDGE=br0 br0 bridge: ifcfg-br0 DEVICE=br0 TYPE=Bridge DELAY=0 ONBOOT=yes BOOTPROTO=static IPADDR=192.168.1.1 NETMASK=255.255.255.0 PEERDNS=yes NM_CONTROLLED=no ARP=yes Failover ip is redirected to the br0 bridge with ip route add 46.105.40.xxx dev br0 > cat /proc/sys/net/ipv4/ip_forward 1 > cat /proc/sys/net/ipv4/conf/vnet0/proxy_arp 1 > route -n Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 176.31.240.254 0.0.0.0 UG 0 0 0 eth0 46.105.40.x 0.0.0.0 255.255.255.255 UH 0 0 0 br0 176.31.240.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 br0 Guest configuration: KVM: <interface type='bridge'> <mac address='02:00:00:30:22:05'/> <source bridge='br0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/> </interface> I've borrowed most of the OVH configuration here (in french, http://guides.ovh.com/BridgeClient) for the guest configuration eth0 interface: ifcfg-eth0 DEVICE="eth0" BOOTPROTO=none HWADDR="02:00:00:30:22:05" NM_CONTROLLED="yes" ONBOOT="yes" TYPE="Ethernet" UUID="e9138469-0d81-4ee6-b5ab-de0d7d17d1c8" USERCTL=no PEERDNS=yes IPADDR=46.105.40.xxx NETMASK=255.255.255.255 GATEWAY=176.31.240.254 ARP=yes For the routes, I have in route-eth0: 176.31.240.254 dev eth0 default via 176.31.240.254 dev eth0 With this configuration, I don't have any access to the internet. The only thing I can do is to ping the public ip of the host, nothing more. My final conclusion is that the route does not work, because, when, on the guest, I run ping 8.8.8.8, I have, on the host: > tcpdump -i vnet0 icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on br0, link-type EN10MB (Ethernet), capture size 65535 bytes 13:38:09.009324 IP 46-105-40-xxx.kimsufi.com > google-public-dns-a.google.com: ICMP echo request, id 50183, seq 1, length 64 13:38:09.815344 IP 46-105-40-xxx.kimsufi.com > google-public-dns-a.google.com: ICMP echo request, id 50183, seq 2, length 64 I never get the ping reply, only the request. It seems Guest - Host communication is fine. On eth0: > tcpdump -i eth0 icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes 13:39:40.240561 IP 46-105-40-xxx.kimsufi.com > google-public-dns-a.google.com: ICMP echo request, id 50439, seq 1, length 64 13:39:40.250161 IP google-public-dns-a.google.com > 46-105-40-xxx.kimsufi.com: ICMP echo reply, id 50439, seq 1, length 64 I have the request and the reply on eth0, but reply is not forwarded to the bridge. I really don't understand why, I though it was the aim of the route to do that! IPtables is disabled on both host and guest. I really hope some of you will be able to help me! Many thanks in advance, Sébastien

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  • virtual host setup: can't access wordpress site without www

    - by two7s_clash
    I would like to access my site both with and without using the www. Currently it only works with. Leaving out the www just goes to a blank page. Also, wp-admin just loads a blank page too. I have set an A record for mysite.com and www.mysite.com, both pointing to my static Bitnami IP. I also have a subdomain mapped to another directory that is working just fine (conference.mysite.com and www.conference.mysite.com). I'm using a Bitnami stack on an AWS EC2 micro instance. Here is my httpd.conf: ServerRoot "/opt/bitnami/apache2" Listen 80 LoadModule authn_file_module modules/mod_authn_file.so blah blah blah.... LoadModule php5_module modules/libphp5.so <IfModule !mpm_netware_module> <IfModule !mpm_winnt_module> User daemon Group daemon </IfModule> </IfModule> ServerAdmin [email protected] ServerName localhost:80 DocumentRoot "/opt/bitnami/apps/wordpress1/htdocs/" <Directory /> Options FollowSymLinks AllowOverride None Order deny,allow Allow from all </Directory> <Directory "/opt/bitnami/apps/wordpress1/htdocs/"> Options Indexes MultiViews +FollowSymLinks LanguagePriority en AllowOverride All Order allow,deny Allow from all </Directory> <IfModule dir_module> DirectoryIndex index.html index.php </IfModule> <FilesMatch "^\\.ht"> Order allow,deny Deny from all Satisfy All </FilesMatch> ErrorLog "logs/error_log" LogLevel warn <IfModule log_config_module> LogFormat "%h %l %u %t \\"%r\\" %>s %b \\"%{Referer}i\\" \\"%{User-Agent}i\\"" combined LogFormat "%h %l %u %t \\"%r\\" %>s %b" common <IfModule logio_module> LogFormat "%h %l %u %t \\"%r\\" %>s %b \\"%{Referer}i\\" \\"%{User-Agent}i\\" %I %O" combinedio </IfModule> CustomLog "logs/access_log" common </IfModule> <IfModule alias_module> ScriptAlias /cgi-bin/ "/opt/bitnami/apache2/cgi-bin/" </IfModule> <Directory "/opt/bitnami/apache2/cgi-bin"> AllowOverride None Options None Order allow,deny Allow from all </Directory> DefaultType text/plain <IfModule mime_module> TypesConfig conf/mime.types AddType application/x-compress .Z AddType application/x-gzip .gz .tgz </IfModule> Include conf/extra/httpd-mpm.conf <IfModule ssl_module> SSLRandomSeed startup builtin SSLRandomSeed connect builtin </IfModule> AddType application/x-httpd-php .php .phtml LoadModule wsgi_module modules/mod_wsgi.so WSGIPythonHome /opt/bitnami/python ServerSignature Off ServerTokens Prod AddType application/x-httpd-php .php PHPIniDir "/opt/bitnami/php/etc" Include "/opt/bitnami/apps/phpmyadmin/conf/phpmyadmin.conf" ExtendedStatus On <Location /server-status> SetHandler server-status Order Deny,Allow Deny from all Allow from localhost </Location> Include "/opt/bitnami/apache2/conf/bitnami/httpd.conf" Include "/opt/bitnami/apps/virtualhost.conf" Here is my virtual hosts file: NameVirtualHost *:80 <VirtualHost *:80> ServerAdmin xx DocumentRoot "/opt/bitnami/apps/wordpress1/htdocs" ServerName mbird.com ServerAlias www.mbird.com ErrorLog "logs/wordpress-error_log" CustomLog "logs/wordpress-access_log" common </VirtualHost> <Directory "/opt/bitnami/apps/wordpress1/htdocs"> Options Indexes MultiViews +FollowSymLinks AllowOverride All Order allow,deny Allow from all </Directory> ### WordPress conference.mbird.com configuration ### <VirtualHost *:80> ServerAdmin [email protected] DocumentRoot "/opt/bitnami/apps/wordpress/htdocs" ServerName conference.mbird.com ServerAlias www.conference.mbird.com ErrorLog "logs/confwordpress-error_log" CustomLog "logs/confwordpress-access_log" common </VirtualHost> <Directory "/opt/bitnami/apps/wordpress/htdocs"> Options Indexes MultiViews +FollowSymLinks AllowOverride All Order allow,deny Allow from all </Directory> ###

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  • Just a few questions about Hyper-V virtual machines and clustering

    - by René Kåbis
    I have been using Microsoft’s Hyper-V technology for a little while now, but I am just now dipping my toe into clustering. In particular, I am trying to implement a fault-tolerant SQL DB. This involves setting up two VMs, clustering them via Failover Cluster, and then installing SQL Server in some fashion. I have two physical machines - one high-end and rather beefy “heavy lifter” to contain the majority of the VMs, and another “backup” (a repurposed desktop) to hold the essential “secondary” (or failover) AD-DC, SQL and FS VMs. The main reason why I find the failover cluster at the VM level so attractive is that it presents a single IP and DNS entry to the network as a whole - if one machine (physical or virtual) goes down, you might loose some ping and the connections get reset, but the network applications (Microsoft RMS connection to backend SQL) can still connect to a viable DB without having to mess around with the settings at all. My first question is in terms of SQL Server itself. If I have a cluster between two VMs, does it make more sense to install the SQL Server in Failover Cluster configuration or should I simply install it in a stand-alone config and mirror the DBs? For example, this post suggests just mirroring the DBs, but do I just mirror standalone DBs on standalone VMs, or can I get the network and failover benefits of clustered VMs while still utilizing (on each clustered VM) standalone DBs that have been mirrored between each other? As well, I have come across a lot of documentation about SQL clustering, but most assume a number (#2) of physical machines to hold not only the actual SQL VMs but also the Quorum and Witness stores. I will not be able to muster more than two physical machines. As such, I will have to be satisfied with a VM cluster that does not exceed two VMs (one for each physical machine). Another issue involves MSDTC - the Distributed Transaction Coordinator. When attempting to install the SQL Failover Cluster (I never completed it for this reason) it threw a hissy fit because MSDTC had not been clustered. Search as I might, I have not yet found a way to do so under Windows Server 2012 R2. I have found plenty of docs for Windows 2008 and 2008 R2, but these instructions don’t align with 2012 R2 (at least, not in a way that allows me to successfully cluster MSDTC). Plus, some of the instructions that I have found for SQL Server Failover Cluster installation suggest that a third “network device” - shared network storage (a SAN) - is required for the DB itself (and other functionality). I do not have this, and won’t be getting this. Most of my storage exists on the “heavy lifter” that was designed for all of the “primary” VMs. If that physical machine goes down, so does the storage. The secondary server does have enough resources for an AD-DC Server, an SQL server and a File Server, so it will handle the “secondary” failover versions of those VMs (clustered or not). My final question involves file servers. If I cluster file servers between two VMs (one on my “heavy lifter” and another on my “backup”, how do I mirror the data between them? Clustering VMs only provides a single point of access on the network for a resource, it doesn’t exactly replicate data between the two - that is left to the services that serve up that data. I am unsure how I can ensure that file server data between two clustered file server VMs can be properly mirrored. Remember, I only have two devices to be used here - my primary machine and a backup secondary. There is no chance of me obtaining a SAN or any other type of network attached storage. What exists on the machines must act as the storage. Thanks in advance for any suggestions.

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  • DataContractSerializer does not properly deserialize, values for methods in object are missing

    - by sachin
    My SomeClass [Serializable] [DataContract(Namespace = "")] public class SomeClass { [DataMember] public string FirstName { get; set; } [DataMember] public string LastName { get; set; } [DataMember] private IDictionary<long, string> customValues; public IDictionary<long, string> CustomValues { get { return customValues; } set { customValues = value; } } } My XML File: <?xml version="1.0" encoding="UTF-8"?> <SomeClass> <FirstName>John</FirstName> <LastName>Smith</LastName> <CustomValues> <Value1>One</Value1> <Value2>Two</Value2> </CustomValues > </SomeClass> But my problem is for the class, i am only getting some of the data for my methods when i deserialize. var xmlRoot = XElement.Load(new StreamReader( filterContext.HttpContext.Request.InputStream, filterContext.HttpContext.Request.ContentEncoding)); XmlDictionaryReader reader = XmlDictionaryReader.CreateDictionaryReader(xmlRoot.CreateReader()); DataContractSerializer ser = new DataContractSerializer(typeof(SomeClass)); //Deserialize the data and read it from the instance. SomeClass someClass = (SomeClass)ser.ReadObject(reader, true); So when I check "someClass", FirstName will have the value john, But the LastName will be null. Mystery is how can i get some of the data and not all of the data for the class. So DataContractSerializer is not pulling up all the data from xml when deserializing. Am i doing something wrong. Any help is appreciated. Thanks in advance. Let me know if anyone has the same problem or any one has solution

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  • Constant NSDictionary/NSArray for class methods.

    - by Jeff B
    I am trying to code a global lookup table of sorts. I have game data that is stored in character/string format in a plist, but which needs to be in integer/id format when it is loaded. For instance, in the level data file, a "p" means player. In the game code a player is represented as the integer 1. This let's me do some bitwise operations, etc. I am simplifying greatly here, but trying to get the point across. Also, there is a conversion to coordinates for the sprite on a sprite sheet. Right now this string-integer, integer-string, integer-coordinate, etc. conversion is taking place in several places in code using a case statement. This stinks, of course, and I would rather do it with a dictionary lookup. I created a class called levelInfo, and want to define the dictionary for this conversion, and then class methods to call when I need to do a conversion, or otherwise deal with level data. NSString *levelObjects = @"empty,player,object,thing,doohickey"; int levelIDs[] = [0,1,2,4,8]; // etc etc @implementation LevelInfo +(int) crateIDfromChar: (char) crateChar { int idx = [[crateTypes componentsSeparatedByString:@","] indexOfObject: crateChar]; return levelIDs[idx]; } +(NSString *) crateStringFromID: (int) crateID { return [[crateTypes componentsSeparatedByString:@","] objectAtIndex: crateID]; } @end Is there a better way to do this? It feels wrong to basically build these temporary arrays, or dictionaries, or whatever for each call to do this translation. And I don't know of a way to declare a constant NSArray or NSDictionary. Please, tell me a better way....

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  • WPF: UnauthorizedAccessException using anonymous methods.

    - by Diego Pacheco Pedemonte
    Here is the thing, I want to create a simply app that copy many files from one site, and move them to another; but using async methods and create a new thread. private void button3_Click(object sender, RoutedEventArgs e) { //progressBar1.Maximum = _FileInfoArray.Count; DispatcherTimer dt1 = new DispatcherTimer(); foreach (FileInfo Fi in _FileInfoArray) { Thread t = new Thread(new ThreadStart(delegate() { DispatcherOperation _dispOp = progressBar1.Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(delegate() { File.Copy(txtdestino.Text, Fi.FullName, true); //progressBar1.Value = n; //txtstatus.Content = ("Copiados " + n.ToString() + " archivos"); //Thread.Sleep(100); } )); _dispOp.Completed += new EventHandler(_dispOp_Completed); } )); t.Start(); } } UnauthorizedAccessException is throw! It says that I can't access to txtdestino content. Some clues? -------------------------------------------------------------------------------Edited This is the version with all the changes, get the same error :( any clues? private void button4_Click(object sender, RoutedEventArgs e) { //First: Build mynames List<string> mynames = new List<string>(); foreach (FileInfo fi in _FileInfoArray) { mynames.Add(fi.FullName); } Thread t = new Thread(new ThreadStart(delegate() { foreach (string fullname in mynames) { DispatcherOperation _dispOp = progressBar1.Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(delegate() { string destino = System.IO.Path.Combine(@"C:\", System.IO.Path.GetFileName(fullname)); File.Copy(fullname, destino, true); //Some progressbar changes } )); _dispOp.Completed += new EventHandler(_dispOp_Completed); } } )); t.Start(); } File.Copy(txtdestino.Text, Fi.FullName, true); // here the exception is throw

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  • Twitter-OAuth update_profile_*_image methods problem [EpiTwitter]

    - by KPL
    People, I have been struggling over the two methods - Update Profile Image and Update Background Image I am using EpiTwitter library. I am uploading GIFs, Twitter returns the expected result for update_profile_background_image but returns 401 for update_profile_image , but the image is not changed. Here are the headers catched from $apiObj-headers in my case while using the update_profile_background_image Array ( [Date] = Sat, 24 Apr 2010 17:51:36 GMT [Server] = hi [Status] = 200 OK [X-Transaction] = 1272131495-55190-23911 [ETag] = b6a421c01936f3547802ae6b59ee7ef3" [Last-Modified] = Sat, 24 Apr 2010 17:51:36 GMT [X-Runtime] = 0.13990 [Content-Type] = application/json; charset=utf-8 [Content-Length] = 1272 [Pragma] = no-cache [X-Revision] = DEV [Expires] = Tue, 31 Mar 1981 05:00:00 GMT [Cache-Control] = no-cache, no-store, must-revalidate, pre- check=0, post-check=0 [Set-Cookie] = *REMOVED* [Vary] = Accept-Encoding [Connection] = close ) and for update_profile_image - Array ( [Date] => Sat, 24 Apr 2010 17:57:58 GMT [Server] => hi [Status] => 401 Unauthorized [WWW-Authenticate] => Basic realm="Twitter API" [X-Runtime] => 0.02263 [Content-Type] => text/html; charset=utf-8 [Content-Length] => 152 [Cache-Control] => no-cache, max-age=300 [Set-Cookie] => *REMOVED* [Expires] => Sat, 24 Apr 2010 18:02:58 GMT [Vary] => Accept-Encoding [Connection] => close ) Can somebody help me out?

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  • Accessing bean object methods from xhtml in RichFaces

    - by Mark Lewis
    Hello When I use (1) in my xhtml, I get an error as in (2). How can I access the size of an array in my bean? (1) A List of objects of a custom class type, accessed through the following h:outputText in a rich:column in a rich:subTable in a rich:dataTable: <h:outputText value="Info: #{f.filemask.size()}" /> (2) Caused by: com.sun.facelets.tag.TagAttributeException: /nodeConfig.xhtml @190,91 value="Info: #{f.filemask.size()" Error Parsing: Info:  #{f.filemask.size()} at com.sun.facelets.tag.TagAttribute.getValueExpression(TagAttribute.java:259) ... Caused by: org.apache.el.parser.ParseException: Encountered " "(" "( "" at line 1, column 41. Was expecting one of: "}" ... "." ... "[" ... ">" ... "gt" ... "<" ... "lt" ... ">=" ... "ge" ... "<=" ... "le" ... "==" ... "eq" ... "!=" ... "ne" ... "&&" ... "and" ... "||" ... "or" ... "*" ... "+" ... "-" ... "/" ... "div" ... "%" ... "mod" ... Any help greatly appreciated. I cannot seem to find references to using methods like this but this reference reported it working fine

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  • Call private methods and private properties from outside a class in PHP

    - by Pablo López Torres
    I want to access private methods and variables from outside the classes in very rare specific cases. I've seen that this is not be possible although introspection is used. The specific case is the next one: I would like to have something like this: class Console { final public static function run() { while (TRUE != FALSE) { echo "\n> "; $command = trim(fgets(STDIN)); switch ($command) { case 'exit': case 'q': case 'quit': echo "OK+\n"; return; default: ob_start(); eval($command); $out = ob_get_contents(); ob_end_clean(); print("Command: $command"); print("Output:\n$out"); break; } } } } This method should be able to be injected in the code like this: Class Demo { private $a; final public function myMethod() { // some code Console::run(); // some other code } final public function myPublicMethod() { return "I can run through eval()"; } private function myPrivateMethod() { return "I cannot run through eval()"; } } (this is just one simplification. the real one goes through a socket, and implement a bunch of more things...) So... If you instantiate the class Demo and you call $demo-myMethod(), you'll get a console: that console can access the first method writing a command like: > $this->myPublicMethod(); But you cannot run successfully the second one: > $this->myPrivateMethod(); Do any of you have any idea, or if there is any library for PHP that allows you to do this? Thanks a lot!

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  • Securely erasing a file using simple methods?

    - by Jason
    Hello, I am using C# .NET Framework 2.0. I have a question relating to file shredding. My target operating systems are Windows 7, Windows Vista, and Windows XP. Possibly Windows Server 2003 or 2008 but I'm guessing they should be the same as the first three. My goal is to securely erase a file. I don't believe using File.Delete is secure at all. I read somewhere that the operating system simply marks the raw hard-disk data for deletion when you delete a file - the data is not erased at all. That's why there exists so many working methods to recover supposedly "deleted" files. I also read, that's why it's much more useful to overwrite the file, because then the data on disk actually has to be changed. Is this true? Is this generally what's needed? If so, I believe I can simply write the file full of 1's and 0's a few times. I've read: http://www.codeproject.com/KB/files/NShred.aspx http://blogs.computerworld.com/node/5756 http://blogs.computerworld.com/node/5687 http://stackoverflow.com/questions/4147775/securely-deleting-a-file-in-c-net

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  • Synchronizing ASP.NET MVC action methods with ReaderWriterLockSlim

    - by James D
    Any obvious issues/problems/gotchas with synchronizing access (in an ASP.NET MVC blogging engine) to a shared object model (NHibernate, but it could be anything) at the Controller/Action level via ReaderWriterLockSlim? (Assume the object model is very large and expensive to build per-request, so we need to share it among requests.) Here's how a typical "Read Post" action would look. Enter the read lock, do some work, exit the read lock. public ActionResult ReadPost(int id) { // ReaderWriterLockSlim allows multiple concurrent writes; this method // only blocks in the unlikely event that some other client is currently // writing to the model, which would only happen if a comment were being // submitted or a new post were being saved. _lock.EnterReadLock(); try { // Access the model, fetch the post with specificied id // Pseudocode, etc. Post p = TheObjectModel.GetPostByID(id); ActionResult ar = View(p); return ar; } finally { // Under all code paths, we must release the read lock _lock.ExitReadLock(); } } Meanwhile, if a user submits a comment or an author authors a new post, they're going to need write access to the model, which is done roughly like so: [AcceptVerbs(HttpVerbs.Post)] public ActionResult SaveComment(/* some posted data */) { // try/finally omitted for brevity _lock.EnterWriteLock(); // Save the comment to the DB, update the model to include the comment, etc. _lock.ExitWriteLock(); } Of course, this could also be done by tagging those action methods with some sort of "synchronized" attribute... but however you do it, my question is is this a bad idea? ps. ReaderWriterLockSlim is optimized for multiple concurrent reads, and only blocks if the write lock is held. Since writes are so infrequent (1000s or 10,000s or 100,000s of reads for every 1 write), and since they're of such a short duration, the effect is that the model is synchronized , and almost nobody ever locks, and if they do, it's not for very long.

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  • Methods for Lazy Initialization with properties

    - by Stuart Pegg
    I'm currently altering a widely used class to move as much of the expensive initialization from the class constructor into Lazy Initialized properties. Below is an example (in c#): Before: public class ClassA { public readonly ClassB B; public void ClassA() { B = new ClassB(); } } After: public class ClassA { private ClassB _b; public ClassB B { get { if (_b == null) { _b = new ClassB(); } return _b; } } } There are a fair few more of these properties in the class I'm altering, and some are not used in certain contexts (hence the Laziness), but if they are used they're likely to be called repeatedly. Unfortunately, the properties are often also used inside the class. This means there is a potential for the private variable (_b) to be used directly by a method without it being initialized. Is there a way to make only the public property (B) available inside the class, or even an alternative method with the same initialized-when-needed? This is reposted from Programmers (not subjective enough apparently): http://programmers.stackexchange.com/questions/34270/best-methods-for-lazy-initialization-with-properties

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  • Speed vs security vs compatibility over methods to do string concatenation in Python

    - by Cawas
    Similar questions have been brought (good speed comparison there) on this same subject. Hopefully this question is different and updated to Python 2.6 and 3.0. So far I believe the faster and most compatible method (among different Python versions) is the plain simple + sign: text = "whatever" + " you " + SAY But I keep hearing and reading it's not secure and / or advisable. I'm not even sure how many methods are there to manipulate strings! I could count only about 4: There's interpolation and all its sub-options such as % and format and then there's the simple ones, join and +. Finally, the new approach to string formatting, which is with format, is certainly not good for backwards compatibility at same time making % not good for forward compatibility. But should it be used for every string manipulation, including every concatenation, whenever we restrict ourselves to 3.x only? Well, maybe this is more of a wiki than a question, but I do wish to have an answer on which is the proper usage of each string manipulation method. And which one could be generally used with each focus in mind (best all around for compatibility, for speed and for security). Thanks.

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  • Naming convention for non-virtual and abstract methods

    - by eagle
    I frequently find myself creating classes which use this form (A): abstract class Animal { public void Walk() { // TODO: do something before walking // custom logic implemented by each subclass WalkInternal(); // TODO: do something after walking } protected abstract void WalkInternal(); } class Dog : Animal { protected override void WalkInternal() { // TODO: walk with 4 legs } } class Bird : Animal { protected override void WalkInternal() { // TODO: walk with 2 legs } } Rather than this form (B): abstract class Animal { public abstract void Walk(); } class Dog : Animal { public override void Walk() { // TODO: do something before walking // custom logic implemented by each subclass // TODO: walk with 4 legs // TODO: do something after walking } } class Bird : Animal { public override void Walk() { // TODO: do something before walking // custom logic implemented by each subclass // TODO: walk with 2 legs // TODO: do something after walking } } As you can see, the nice thing about form A is that every time you implement a subclass, you don't need to remember to include the initialization and finalization logic. This is much less error prone than form B. What's a standard convention for naming these methods? I like naming the public method Walk since then I can call Dog.Walk() which looks better than something like Dog.WalkExternal(). However, I don't like my solution of adding the suffix "Internal" for the protected method. I'm looking for a more standardized name. Btw, is there a name for this design pattern?

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  • AS3 - Can't access properties or methods of a MC child that has been added in script

    - by Chris
    Hi All - I am still a bit of a beginner at AS3, so bear with me, please. I have created a loop to instantiate tiles on a board. In the following example, "Gametiles" is an array containing objects of class "Tile" which is a class that extends MovieClip. "Game" is a MC that I added to the stage in the flash developing environment. for(var i:uint=0;i < Gametiles.length;i++){ var pulledTile = Gametiles[i]; var tilename:String = "I_Tile_" + pulledTile.grid_y + "_" + pulledTile.grid_x; var createdTile = new InteractiveTile(); pulledTile.addAnims(createdTile); Game.addChildAt(pulledTile, 0); Game.getChildAt(0).name = tilename; } The above code works - but with a tricky problem. If I did something like the following: trace(Game.I_Tile_1_3.x); I get "TypeError: Error #1010: A term is undefined and has no properties." However, I am able to access theses children in the following manner: var testing = Game.getChildByName("I_Tile_1_3") trace(testing.x); This method is a bit cumbersome though. I really don't want to have to create a var and call getChildByName every time I want to interact with these properties or methods. How can I set up these children so that I can access them directly without the extra steps?

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  • Adding custom methods to a subclassed NSManagedObject

    - by CJ
    I have a Core Data model where I have an entity A, which is an abstract. Entities B, C, and D inherit from entity A. There are several properties defined in entity A which are used by B, C, and D. I would like to leverage this inheritance in my model code. In addition to properties, I am wondering if I can add methods to entity A, which are implemented in it's sub-entities. For example: I add a method to the interface for entity A which returns a value and takes one argument I add implementations of this method to A, B, C, D Then, I call executeFetchRequest: to retrieve all instances of B I call the method on the objects retrieved, which should call the implementation of the method contained in B's implementation I have tried this, but when calling the method, I receive: [NSManagedObject methodName:]: unrecognized selector sent to instance I presume this is because the objects returned by executeFetchRequest: are proxy objects of some sort. Is there any way to leverage inheritance using subclassed NSManagedObjects? I would really like to be able to do this, otherwise my model code would be responsible for determining what type of NSManagedObject it's dealing with and perform special logic according to the type, which is undesirable. Any help is appreciated, thanks in advance.

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  • How to feature-detect/test for specific jQuery (and Javascript) methods/functions used

    - by Zildjoms
    good day everyone, hope yer all doin awesome am very new to javascript and jquery, and i (think) i have come up with a simple fade-in/out implementation on a site am workin on (check out http://www.s5ent.com/expandjs.html - if you have the time to check it for inefficiency or what that'd be real sweet). i use the following functions/methods/collections and i would like to do a feature test before using them. uhm.. how? or is there a better way to go about this? jQuery $ .fadeIn([duration]) .fadeOut([duration]) .attr(attributeName,value) .append(content) .each(function(index,Element)) .css(propertyName,value) .hover(handlerIn(eventObject),handlerOut(eventObject)) .stop([clearQueue],[jumpToEnd]) .parent() .eq(index) JavaScript setInterval(expression,timeout) clearInterval(timeoutId) setTimeout(expression,timeout) clearTimeout(timeoutId) i tried looking into jquery.support for the jquery ones, but i find myself running into conceptual problems with it, i.e. for fadein/fadeout, i (think i) should test for $.support.opacity, but that would be false in ie whereas ie6+ could still fairly render the fades. also am using jquery 1.2.6 coz that's enough for what i need. the support object is in 1.3. so i'm hoping to avoid dragging-in more unnecessary code if i can. i also worked with browser sniffing, no matter how frowned-upon. but that's also a bigger problem for me because of non-standard ua strings and spoofing and everything else am not aware of. so how do you guys think i should go about this? or should i even? is there a better way to go about making sure that i don't run code that'll eventually break the page? i've set it up to degrade into a css hover when javascript ain't there.. expertise needed. much appreciated, thanks guyz!

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  • ArrayList in Java, adding code to methods

    - by yaz
    Why am I getting a compile time error for the two method headers at the end of my code in my class ArrayListTest? ArrayListTest: http://pastebin.com/dUHn9vPr Student: http://pastebin.com/3Vz1Aytr I have a compiler error at the two lines: delete(CS242, s3) replace(CS242, s, s4); When I try to run the code it states: Exception in thread "main" java.lang.Error: Unresolved compilation problems: The method replace(ArrayList<Student>, Student, Student)in the type ArrayListTest is not applicable for the arguments (List<Student>, Student, Student) The method delete(ArrayList<Student>, Student) in the type ArrayListTest is not applicable for the arguments (List<Student>, Student) at ArrayListTest.main(ArrayListTest.java:54) I fixed the compile time errors since I use Eclipse and Eclipse gives options of code you can use to fix the compile time error. I chose to "Change method to 'replace(ArrayList, Student, Student)' to 'replace(List, Student, Student)' Although it fixed that compile time error, I don't understand why I was getting a compile time error to begin with and why that effectively fixed the error I don't really know what missing code I need to write to correct these two methods below: public static void replace(List<Student> cS242, Student oldItem, Student newItem) { public static void delete(List<Student> cS242, Student target){

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  • Using Rails Helper Methods within ActionRecord Queries?

    - by Pygmalion
    I have a table of events (in a sqlite3 database for what it's worth) with a column called "when" that contains a timestamp detailing precisely when the event that particular row denotes is set to occur. Right now, I have @events = Event.find(:all) in my controller and I am using template helper methods to calculate where to place each event on my display page based on the day of the week it occurs on. For example: <% if(event.when.wday == 6) %> # DO SOMETHING <% end %> I want to abstract this logic to the controller however. My idea was to do the following: @thursday_events = Event.find(:all, :conditions => ["when.wday=4"]) Obviously (I guess?) this didn't work. Throwing the error "SQLite3::SQLException: near "when": syntax error: SELECT * FROM "events" WHERE (when.wday=4)". I'm assuming this is because I tried to use a helper method within a find condition but I don't know a better way to do this. Any advice? Thanks!

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  • [Java] Nested methods vs "piped" methods, which is better?

    - by Michael Mao
    Hi: Since uni, I've programming in Java for 3 years, although I am not fully dedicated to this language, I have spent quite some time in it, nevertheless. I understand both ways, just curious which style do you prefer. public class Test{ public static void main(String[] args) { System.out.println(getAgent().getAgentName()); } private static Agent getAgent() { return new Agent(); }} class Agent{ private String getAgentName() { return "John Smith"; }} I am pretty happy with nested method calls such like the following public class Test{ public static void main(String[] args) { getAgentName(getAgent()); } private static void getAgentName(Agent agent) { System.out.println(agent.getName()); } private static Agent getAgent() { return new Agent(); }} class Agent { public String getName(){ return "John Smith"; }} They have identical output I saw "John Smith" twice. I wonder, if one way of doing this has better performance or other advantages over the other. Personally I prefer the latter, since for nested methods I can certainly tell which starts first, and which is after. The above code is but a sample, The code that I am working with now is much more complicated, a bit like a maze... So switching between the two styles often blows my head in no time.

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  • Combining cache methods - memcache/disk based

    - by Industrial
    Hi! Here's the deal. We would have taken the complete static html road to solve performance issues, but since the site will be partially dynamic, this won't work out for us. What we have thought of instead is using memcache + eAccelerator to speed up PHP and take care of caching for the most used data. Here's our two approaches that we have thought of right now: Using memcache on all<< major queries and leaving it alone to do what it does best. Usinc memcache for most commonly retrieved data, and combining with a standard harddrive-stored cache for further usage. The major advantage of only using memcache is of course the performance, but as users increases, the memory usage gets heavy. Combining the two sounds like a more natural approach to us, even though the theoretical compromize in performance. Memcached appears to have some replication features available as well, which may come handy when it's time to increase the nodes. What approach should we use? - Is it stupid to compromize and combine the two methods? Should we insted be focusing on utilizing memcache and instead focusing on upgrading the memory as the load increases with the number of users? Thanks a lot!

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  • ruby/datamapper: Refactor class methods to module

    - by DeSchleib
    Hello, i've the following code and tried the whole day to refactor the class methods to a sperate module to share the functionality with all of my model classes. Code (http://pastie.org/974847): class Merchant include DataMapper::Resource property :id, Serial [...] class << self @allowed_properties = [:id,:vendor_id, :identifier] alias_method :old_get, :get def get *args [...] end def first_or_create_or_update attr_hash [...] end end end I'd like to archive something like: class Merchant include DataMapper::Resource include MyClassFunctions [...] end module MyClassFunctions def get [...] def first_or_create_or_update[...] end => Merchant.allowed_properties = [:id] => Merchant.get( :id=> 1 ) But unfortunately, my ruby skills are to bad. I read a lot of stuff (e.g. here) and now i'm even more confused. I stumbled over the following two points: alias_method will fail, because it will dynamically defined in the DataMapper::Resource module. How to get a class method allowed_properties due including a module? What's the ruby way to go? Many thanks in advance.

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  • How to call different methods from single webservices class

    - by pointer
    I have a following RESTful webservice, I have two methods for http get. One function signs in and other function signs out a user from an application. Following is the code: import javax.ws.rs.core.Context; import javax.ws.rs.core.UriInfo; import javax.ws.rs.PathParam; import javax.ws.rs.Consumes; import javax.ws.rs.PUT; import javax.ws.rs.Path; import javax.ws.rs.GET; import javax.ws.rs.POST; import javax.ws.rs.Produces; import javax.ws.rs.QueryParam; /** * REST Web Service * * @author Pointer */ @Path("generic") public class GenericResource { @Context private UriInfo context; /** * Creates a new instance of GenericResource */ public GenericResource() { } /** * Retrieves representation of an instance of * com.ef.apps.xmpp.ws.GenericResource * * @return an instance of java.lang.String */ @GET @Produces("text/html") public String SignIn(@QueryParam("username") String username, @QueryParam("password") String password, @QueryParam("extension") String extension) { //TODO return proper representation object return "Credentials " + username + " : " + password + " : " + extension; } @GET @Produces("text/html") public String SignOut(@QueryParam("username") String username, @QueryParam("password") String password, @QueryParam("extension") String extension) { //TODO return proper representation object return "Credentials " + username + " : " + password + " : " + extension; } } Now, where would I specify that which function I want to call for http get?

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