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• Passing along variable inside link works only on first word in multiple-word-variables, why?

  - by Camran

  I have this code below. As you can see I am passing two variables along with the link. The second variabye (category) works whenever it consists of one word, but some categories are two words or more, and then on the receiving php page where I fetch the variable only the first word is fetched. Any ideas? Example: I pass along this: Rims & Tires Only this comes through: Rims $display_table .= "<a href='../ad.php?ad_id=$row[ad_id]&category=$row[category]' target='_parent'>"; Here is how I fetch it in the receiving php file (which the link is to): $cat = $_GET['category']; echo $cat; //displays only first word of multiple word categories. Thanks

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• How to default-initialize local variables of built-in types in C++?

  - by sharptooth

  How do I default-initialize a local variable of primitive type in C++? For example if a have a typedef: typedef unsigned char boolean;//that's Microsoft RPC runtime typedef I'd like to change the following line: boolean variable = 0; //initialize to some value to ensure reproduceable behavior retrieveValue( &variable ); // do actual job into something that would automagically default-initialize the variable - I don't need to assign a specific value to it, but instead I only need it to be intialized to the same value each time the program runs - the same stuff as with a constructor initializer list where I can have: struct Struct { int Value; Struct() : Value() {} }; and the Struct::Value will be default-initialized to the same value every time an instance is cinstructed, but I never write the actual value in the code. How can I get the same behavior for local variables?

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• emca fails with "Database instance is unavailable" though available

  - by Giri Mandalika

  The following example shows the symptoms of failure, and the exact error message. $ emca -repos create ... Password for SYSMAN user: Do you wish to continue? [yes(Y)/no(N)]: Y Nov 19, 2012 10:33:42 AM oracle.sysman.emcp.DatabaseChecks \ checkDbAvailabilityImpl WARNING: ORA-01034: ORACLE not available Nov 19, 2012 10:33:42 AM oracle.sysman.emcp.DatabaseChecks \ throwDBUnavailableException SEVERE: Database instance is unavailable. Fix the ORA error thrown and run EM Configuration Assistant again. Some of the possible reasons may be : 1) Database may not be up. 2) Database is started setting environment variable ORACLE_HOME with trailing '/'. Reset ORACLE_HOME and bounce the database. For eg. Database is started setting environment variable ORACLE_HOME=/scratch/db/ . Reset ORACLE_HOME=/scratch/db and bounce the database. Fix: Ensure that the ORACLE_HOME is pointing to the right location in $ORACLE_HOME/bin/emca file. Rather than installing from scratch, if ORACLE_HOME was copied over from another location, likely it results in wrong location for ORACLE_HOME in several Enterprise Manager (EM) specific scripts and files. It usually happens when the directory structure on the target machine is not identical to the structure on the original/source machine, including the top level directory location where Oracle RDBMS was installed properly using the installer.

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• Demantra Post Production Support Common Issues, Troubleshooting Tips, and Maintaining Your Instance

  - by Annemarie Provisero

  ADVISOR WEBCAST: Demantra Post Production Support Common Issues, Troubleshooting Tips, and Maintaining Your Instance PRODUCT FAMILY: Manufacturing - Demantra Solutions   March 2, 2011 at 8 am PT, 9 am MT, 11 am ET You have now gone live, or are preparing to go live, on Demantra. What you need to keep the application running smoothly? This one-hour session is recommended for functional users who give direction to the Demantra application and the technical users who support the application. TOPICS WILL INCLUDE: Key troubleshooting logs Keeping the database well maintained both in backup and performance When data should be removed and/or archived out of the Demantra application A short, live demonstration (only if applicable) and question and answer period will be included. Oracle Advisor Webcasts are dedicated to building your awareness around our products and services. This session does not replace offerings from Oracle Global Support Services. Click here to register for this session ------------------------------------------------------------------------------------------------------------- The above webcast is a service of the E-Business Suite Communities in My Oracle Support. For more information on other webcasts, please reference the Oracle Advisor Webcast Schedule.Click here to visit the E-Business Communities in My Oracle Support Note that all links require access to My Oracle Support.

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• BizTalk Pipeline Component Error: "Object reference not set to an instance of an object"

  - by Stuart Brierley

  Yesterday I posted about my BizTalk Archiving Pipeline Component, which can be found on Codeplex if anyone is interested in taking a look. During testing of this component I began to encounter an error whereby the component would throw an "Object reference not set to an instance of an object" error when processing as a part of a Custom Pipeline. This was occurring when the component was reading a ReadOnlySeekableStream so that the data can be archived to file, but the actual code throwing the error was somewhere in the depths of the Microsoft.BizTalk.Streaming stack. It turns out that there is a known issue where this exception can be thrown because the garbage collector has disposed of of the stream before execution of the custom pipeline has completed. To get around this you need to add the streams in your code to the pipeline context resource tracker.   So a block of my code goes from:                         originalStrm = bodyPart.GetOriginalDataStream();                         if (!originalStrm.CanSeek)                         {                             ReadOnlySeekableStream seekableStream = new ReadOnlySeekableStream(originalStrm);                             inmsg.BodyPart.Data = seekableStream;                             originalStrm = inmsg.BodyPart.Data;                         }                         fileArchive = new FileStream(FullPath, FileMode.Create, FileAccess.Write);                         binWriter = new BinaryWriter(fileArchive);                         byte[] buffer = new byte[bufferSize];                         int sizeRead = 0;                         while ((sizeRead = originalStrm.Read(buffer, 0, bufferSize)) != 0)                         {                             binWriter.Write(buffer, 0, sizeRead);                         } to                         originalStrm = bodyPart.GetOriginalDataStream();                         if (!originalStrm.CanSeek)                         {                             ReadOnlySeekableStream seekableStream = new ReadOnlySeekableStream(originalStrm);                             inmsg.BodyPart.Data = seekableStream;                             originalStrm = inmsg.BodyPart.Data;                         }                         pc.ResourceTracker.AddResource(originalStrm);                         fileArchive = new FileStream(FullPath, FileMode.Create, FileAccess.Write);                         binWriter = new BinaryWriter(fileArchive);                         byte[] buffer = new byte[bufferSize];                         int sizeRead = 0;                         while ((sizeRead = originalStrm.Read(buffer, 0, bufferSize)) != 0)                         {                             binWriter.Write(buffer, 0, sizeRead);                         } So far this seems to have solved the issue, the error is no more, and my archive component is continuing its way through testing.

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• When should a method of a class return the same instance after modifying itself?

  - by modiX

  I have a class that has three methods A(), B() and C(). Those methods modify the own instance. While the methods have to return an instance when the instance is a separate copy (just as Clone()), I got a free choice to return void or the same instance (return this;) when modifying the same instance in the method and not returning any other value. When deciding for returning the same modified instance, I can do neat method chains like obj.A().B().C();. Would this be the only reason for doing so? Is it even okay to modify the own instance and return it, too? Or should it only return a copy and leave the original object as before? Because when returning the same modified instance the user would maybe admit the returned value is a copy, otherwise it would not be returned? If it's okay, what's the best way to clarify such things on the method?

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• Very simple OOP question

  - by Mosty Mostacho

  I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works on constructions that are quite different one from each other but are still constructions. Note I've added one field for each class but there should be many more. Now, I thought this was the way to go but my partner told me that if in the future new construction classes appear we would have to modify the Company class, which is correct. So the new proposed class diagram would be this: Now I've been wondering: Should the fact that in no place of the application will there be mixed lists of planes and bridges affect the design in any way? When we have to list only planes for a company, how are we supposed to distinguish them from the other elements in the list without checking for their class names? Related to the previous question, is it correct to assume that this type of diagram should be high-level and this is something it shouldn't matter at this stage but rather be thought and decided at implementation time? Any comment will be appreciated.

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• Creating a Sandboxed Instance

  - by Ricardo Peres

  In .NET 4.0 the policy APIs have changed a bit. Here's how you can create a sandboxed instance of a type, which must inherit from MarshalByRefObject: static T CreateRestrictedType<T>(SecurityZone zone, params Assembly [] fullTrustAssemblies) where T : MarshalByRefObject, new() { return(CreateRestrictedType<T>(zone, fullTrustAssemblies, new IPermission [0]); } static T CreateRestrictedType<T>(SecurityZone zone, params IPermission [] additionalPermissions) where T : MarshalByRefObject, new() { return(CreateRestrictedType<T>(zone, new Assembly [0], additionalPermissions); } static T CreateRestrictedType<T>(SecurityZone zone, Assembly [] fullTrustAssemblies, IPermission [] additionalPermissions) where T : MarshalByRefObject, new() { Evidence evidence = new Evidence(); evidence.AddHostEvidence(new Zone(zone)); PermissionSet evidencePermissionSet = SecurityManager.GetStandardSandbox(evidence); foreach (IPermission permission in additionalPermissions ?? new IPermission[ 0 ]) { evidencePermissionSet.AddPermission(permission); } StrongName [] strongNames = (fullTrustAssemblies ?? new Assembly[0]).Select(a = a.Evidence.GetHostEvidence<StrongName>()).ToArray(); AppDomainSetup adSetup = new AppDomainSetup(); adSetup.ApplicationBase = Path.GetDirectoryName(typeof(T).Assembly.Location); AppDomain newDomain = AppDomain.CreateDomain("Sandbox", evidence, adSetup, evidencePermissionSet, strongNames); ObjectHandle handle = Activator.CreateInstanceFrom(newDomain, typeof(T).Assembly.ManifestModule.FullyQualifiedName, typeof(T).FullName); return (handle.Unwrap() as T); } SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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• File permission issues after setting up an amazon ec2 instance

  - by Pardoner

  I've set up an amazon ec2 instance and I'm have some file permission issues. I've created myself a new user and added myself to the following groups: adm:x:4:me,ubuntu www-data:x:33:me,www-data ssh:x:108:me admin:x:111:me ubuntu:x:1000:www-data,me me:x:1001:me but when I cd /var/www I can't do simple commands without doing sudo first. So I chmod -R www-data:www-data /var/www to ensure that I'm in the owning group but I still have to type sudo for everything. If I sudo su www-data it works fine. Since I'm in the www-data group shouldn't I have the same privilages as www-data? One strange thing I'm noticing is that when I ls -l it list the owner but not the group names. Could this possibly be part of the issue? Is is posible for a directory to not be part of a group? drwxr-xr-x 4 www-data 4.0K Oct 24 16:39 . drwxr-xr-x 14 root 4.0K Oct 10 16:58 .. drwxrwxr-x 9 www-data 4.0K Oct 23 04:03 admin.mywebsite.com drwxrwxr-x 2 www-data 4.0K Oct 4 00:29 mywebsite.com drwxrwxr-x 9 www-data 4.0K Oct 23 04:03 staging.mywebsite.com

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• Why make JavaScript class based?

  - by Carnotaurus

  JavaScript is a prototype language. To turn it into a class based language adds little value? I am not talking about best-practice here. I remember reading an article from way back, which claimed that the class-based worldview is perceivably more flawed than the one of prototypes. My summary can be found here: http://carnotaurus.tumblr.com/post/3248631891/class-based-javascript-or-not. I am resisting to use the class-based jQuery add-on and other attempts at faciliating class-based JavaScript. Peer pressure is strong but is there a stronger theoretical or practical reason why I stop resisting?

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• Unable to Call Instantiate in Class Member Function

  - by onguarde

  The following javascript is attached to a gameObject. var instance : GameObject; class eg_class { function eg_func(){ var thePrefab : GameObject; instance = Instantiate(thePrefab); } } Error, Unknown identifier: 'instance'. Unknown identifier: 'Instantiate'. Questions, 1) Why is it that "instance" cannot be accessed within a class? Isn't it supposed to be a public variable? 2) "Instantiate" function works in Start()/Update() root functions. Is there a way to make it work from within member functions? Thanks in advance!

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• What alternative is better to diagram this scenario?

  - by Mosty Mostacho

  I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works on constructions that are quite different one from each other but are still constructions. Note I've added one field for each class but there should be many more. Now, I thought this was the way to go but my partner told me that if in the future new construction classes appear we would have to modify the Company class, which is correct. So the new proposed class diagram would be this: Now I've been wondering: Should the fact that in no place of the application will there be mixed lists of planes and bridges affect the design in any way? When we have to list only planes for a company, how are we supposed to distinguish them from the other elements in the list without checking for their class names? Related to the previous question, is it correct to assume that this type of diagram should be high-level and this is something it shouldn't matter at this stage but rather be thought and decided at implementation time? Any comment will be appreciated.

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• Class Versus Struct

  - by Prometheus87

  In C++ and other influenced languages there is a construct called Structure (struct) and we all know the class. Both are capable of holding functions and variables. some differences are 1. Class is given memory in heap and struct is given memory in stack 2. in class variable are private by default and in struct thy are public My question is that struct was somehow abandoned for Class. Why? other that abstraction, a struct can do all the same stuff a class does. Then why abandon it?

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• Single (class) Instances in Multi-tenant Web Application

  Need and implementation of single instance (class)

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• How to flag a class as under development in Java

  - by Usavich

  I'm working on a internship project, but I have to leave before I can finish up everything. I have 1 class that is not stable enough for production use. I want to mark/flag this class so that other people will not accidentally use it in production. I have already put the notice in Javadoc, but that doesn't seem enough. Some compiler error or warning would be better. The code is organized like this: [Package] | company.foo.bar.myproject |-- Class1.java |-- Class2.java |-- Class3.java <--(not stable) If there was a single factory class that calls those classes in public methods, I could have set the method to class3 as private. However the API is NOT exposed that way. Users will directly use those class, e.g. new Class1();, but I can't make a top-level class private. What's the best practice to deal with this situation?

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• Passing class names or objects?

  - by nischayn22

  I have a switch statement switch ( $id ) { case 'abc': return 'Animal'; case 'xyz': return 'Human'; //many more } I am returning class names,and use them to call some of their static functions using call_user_func(). Instead I can also create a object of that class, return that and then call the static function from that object as $object::method($param) switch ( $id ) { case 'abc': return new Animal; case 'xyz': return new Human; //many more } Which way is efficient? To make this question broader : I have classes that have mostly all static methods right now, putting them into classes is kind of a grouping idea here (for example the DB table structure of Animal is given by class Animal and so for Human class). I need to access many functions from these classes so the switch needs to give me access to the class

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• Variable names for Contact Information bits

  - by RustyTheBoyRobot

  I am in the middle of refactoring code and would like to get some ideas on variable naming so that my new names clearly represent the data they hold. I have a class called ContactMethod which makes sense to me; each instance is a different way to contact someone. My problem comes when naming the properties of ContactMethod. For example, one instance might be a Fax number of 555-555-5555 while another could be an Email address of [email protected]; I've got a property called contactMethodType to hold the values "fax" or "email", but I don't know what to call the "555-555-5555" or "[email protected]" part. Has anyone here created a good generic name for this piece of contact information? (PS - the old convention was to call it a "Phone" with fields "phoneType" holding the "fax"/"email" value and "phoneId" holding the number/address. Yuck.)

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• Name for this antipattern? Fields as local variables

  - by JSB????

  In some code I'm reviewing, I'm seeing stuff that's the moral equivalent of the following: public class Foo { private Bar bar; public MethodA() { bar = new Bar(); bar.A(); bar = null; } public MethodB() { bar = new Bar(); bar.B(); bar = null; } } The field bar here is logically a local variable, as its value is never intended to persist across method calls. However, since many of the methods in Foo need an object of type Bar, the original code author has just made a field of type Bar. This is obviously bad, right? Is there a name for this antipattern?

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• Specifying a Postfix Instance to send outbound email

  - by Catherine Jefferson

  I have a CentOS 6.5 server running Postfix 2.6x (the default distribution) with five public IPv4 IPs bound to it. Each IP has DNS and rDNS set separately. Each uses a different hostname at a different domain. I have five Postfix instances, one bound to each IP, like this example: 192.168.34.104 red.example.com /etc/postfix 192.168.36.48 green.example.net /etc/postfix-green 192.168.36.49 pink.example.org /etc/postfix-pink 192.168.36.50 orange.example.info /etc/postfix-orange 192.168.36.51 blue.example.us /etc/postfix-blue I've tested each IP by telneting to port 25. Postfix answers and banners properly with the correct hostname. Email is received on all of these instances with no problems and is routed to the correct place. This setup, minus the final instance, has existed for a couple of years and works. I never bothered to set up outbound email to go through any but the main instance, however; there was no need. Now I need to send email from blue.example.us that actually leaves from that interface and IP, such that the Received headers show blue.example.us as the sending mailhost, so that SPF and DKIM validate, etc etc. The email that will be sent from blue.example.com is a feedback loop sent by a single shell account on the server (account5), an account that is dedicated to sending this email. The account receives the feedback loop emails from servers on other networks, saves the bodies of those emails, and then generates a new outbound email header, appends the saved body, and sends the email. It's sending by piping each email to sendmail -oi -t. We're doing it this way to mask the identities of the initial servers. The procmail script that processes these emails works correctly. However, I cannot configure this account to send email through the proper Postfix instance/IP/interface. The exact same account and script sends email through the main Postfix instance /etc/postfix without any issues. When I change MAIL_CONFIG to point to /etc/postfix-blue in either .bash_profile or the Procmail script that handles this email, though, I get this error: sendmail: fatal: User account5(###) is not allowed to submit mail I've read the manuals on Postfix.org, searched Google, and tried the suggestions in three previous answers here on ServerFault.com: Postfix - specify interface to deliver outbound mail on Postfix user is not allowed to submit mail Postfix rejects php mails I have been careful to stop and restart Postfix after each configuration change, and tested the results. Nothing has worked. The main postfix instance happily accepts outbound email from account5. The postfix-blue instance continues to reject email from account5 with the sendmail error above. As tempting as it is to blame machine hostility, I know that I must be missing something or doing something wrong. Does anybody have any suggestions as to what it might be? Please feel free to ask for further information about my setup if you need it. =-=-=-=-=-=-=-=-=-= At the request of the responder, here are main.cf and master.cf for a) the main postfix instance ("red.example.com") and b) the FBL instance ("blue.example.us") [NOTE: All parameters not specified below were left at the default Postfix 2.6 settings] MAIN: master.cf smtp inet n - n - - smtpd main.cf myhostname = red.example.com mydomain = example.com inet_interfaces = $myhostname, localhost inet_protocols = all lmtp_host_lookup = native smtp_host_lookup = native ignore_mx_lookup_error = yes mydestination = $myhostname, localhost.$mydomain, localhost local_recipient_maps = mynetworks = 192.168.34.104/32 relay_domains = example.com, example.info, example.net, example.org, example.us relayhost = [192.168.34.102] # Separate physical server, main mailserver. relay_recipient_maps = hash:/etc/postfix/relay_recipients alias_maps = hash:/etc/aliases alias_database = hash:/etc/aliases smtpd_banner = $myhostname ESMTP $mail_name multi_instance_wrapper = ${command_directory}/postmulti -p -- multi_instance_enable = yes multi_instance_directories = /etc/postfix-green /etc/postfix-pink /etc/postfix-orange /etc/postfix-blue FBL: master.cf 184.173.119.103:25 inet n - n - - smtpd main.cf myhostname = blue.example.us mydomain = blue.example.us <= Deliberately set to subdomain only. myorigin = $mydomain inet_interfaces = $myhostname lmtp_host_lookup = native smtp_host_lookup = native ignore_mx_lookup_error = yes mydestination = $myhostname local_recipient_maps = unix:passwd.byname $alias_maps $virtual_alias_maps mynetworks = 192.168.36.51/32, 192.168.35.20/31 <= Second IP is backup MX servers relay_domains = $mydestination recipient_canonical_maps = hash:/etc/postfix-blue/canonical virtual_alias_maps = hash:/etc/postfix-fbl/virtual alias_maps = hash:/etc/aliases, hash:/etc/postfix-blue/canonical alias_maps = hash:/etc/aliases, hash:/etc/postfix-blue/canonical mailbox_command = /usr/bin/procmail -a "$EXTENSION" DEFAULT=$HOME/Mail/ MAILDIR=$HOME/Mail smtpd_banner = $myhostname ESMTP $mail_name authorized_submit_users = multi_instance_name = postfix-blue multi_instance_enable = yes

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• How to map hash keys to methods for an encapsulated Ruby class (tableless model)?

  - by user502052

  I am using Ruby on Rails 3 and I am tryng to map a hash (key, value pairs) to an encapsulated Ruby class (tableless model) making the hash key as a class method that returns the value. In the model file I have class Users::Account #< ActiveRecord::Base def initialize(attributes = {}) @id = attributes[:id] @firstname = attributes[:firstname] @lastname = attributes[:lastname] end end def self.to_model(account) JSON.parse(account) end My hash is hash = {\"id\":2,\"firstname\":\"Name_test\",\"lastname\":\"Surname_test\"} I can make account = Users::Account.to_model(hash) that returns (debugging) --- id: 2 firstname: Name_test lastname: Surname_test That works, but if I do account.id I get this error NoMethodError in Users/accountsController#new undefined method `id' for #<Hash:0x00000104cda410> I think because <Hash:0x00000104cda410> is an hash (!) and not the class itself. Also I think that doing account = Users::Account.to_model(hash) is not the right approach. What is wrong? How can I "map" those hash keys to class methods?

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• How do I dynamically instantiate a class in javascript?

  - by Adam

  I'm starting out with classes in Javascript and have hit a wall. I've looked all over for a tutorial that goes a little further than simply how to construct a class (usually Animal) then extend the class and have a Method do something (Dog alert('Bark');). I have created a class that I want a user to be able to instantiate (is that the right word)? For example the first stage in my program is for the user to give the class a name, and then start to populate the various variables in the class. When they've done that they may do it again many times. So if: var className = new MyObject(); How do I dynamically create the name of the new object className and then refer to it later in the code?

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• Ruby - Possible to pass a block as a param as an actual block to another function?

  - by Markus O'Reilly

  This is what I'm trying to do: def call_block(in_class = "String", &block) instance = eval("#{in_class}.new") puts "instance class: #{instance.class}" instance.instance_eval{ block.call } end # --- TEST EXAMPLE --- # This outputs "class: String" every time "sdlkfj".instance_eval { puts "class: #{self.class}" } # This will only output "class: Object" every time # I'm trying to get this to output "class: String" though call_block("String") { puts "class: #{self.class}" } On the line where it says "instance.instance_eval{ block.call }", I'm trying to find another way to make the new instance variable run instance eval on the block. The only way I can think of to get it to do that is to pass instance_eval the original block, not as a variable or anything, but as a real block like in the test example. Any tips?

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• Can't see *all* databases in a remote SQL Server instance

  - by George

  Yesterday I posted a related question on StackOverflow. This problem involved not being able to see a SQL Server 2008 instance on another PC. I am not sure why adding the port number enabled me to see a SQL Server that I could not otherwise see, since the port number that I specified was, after all, the default port. Now I notice that I have another problem. While I can connect to the remote SQL 2008 Server instance, I cannot see all the databases in the instance. I am trying to connect to the 2008 instance from another PC using SQL Server 2008 Mgt Studio. I am connecting from a Windows 7 Ultimate PC to a Windows XP Pro PC. I suspect that my problem has something to do with not all database in the remote instance having the same version. For example, I "upgraded" a a SL 2005 database to 2008 by doing a backup frm 2005 and importing it into 2008. When I realized that this was not one of the database that I could see from my other PC, I noticed that the compatability level of the imported was still 2005, so I changed it to 2008. Still I could not see the database. I am sure that this is relevant: I just noticed that on my remote server, the sql node instance node, named "sql2008" says "version 10" when I am on the remote serfver, but when I connect to the sql2008 remote instance fron my local PC, the connection is shown locally as being a "SQL Servr version 8.0" instance. I suspect that locally, I am only being shown databases that are somehow in the remote 2008 instance but have not been upgraded. I guess I don't know what constitutes an upgraded database and I don not know who to connect to see all the databases, even if this requires multiple connections from the source PC.

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• Checking instance of non-class constrained type parameter for null in generic method

  - by casperOne

  I currently have a generic method where I want to do some validation on the parameters before working on them. Specifically, if the instance of the type parameter T is a reference type, I want to check to see if it's null and throw an ArgumentNullException if it's null. Something along the lines of: // This can be a method on a generic class, it does not matter. public void DoSomething<T>(T instance) { if (instance == null) throw new ArgumentNullException("instance"); Note, I do not wish to constrain my type parameter using the class constraint. I thought I could use Marc Gravell's answer on "How do I compare a generic type to its default value?", and use the EqualityComparer<T> class like so: static void DoSomething<T>(T instance) { if (EqualityComparer<T>.Default.Equals(instance, null)) throw new ArgumentNullException("instance"); But it gives a very ambiguous error on the call to Equals: Member 'object.Equals(object, object)' cannot be accessed with an instance reference; qualify it with a type name instead How can I check an instance of T against null when T is not constrained on being a value or reference type?

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• Django: Can class-based views accept two forms at a time?

  - by Hooman

  If I have two forms: class ContactForm(forms.Form): name = forms.CharField() message = forms.CharField(widget=forms.Textarea) class SocialForm(forms.Form): name = forms.CharField() message = forms.CharField(widget=forms.Textarea) and wanted to use a class based view, and send both forms to the template, is that even possible? class TestView(FormView): template_name = 'contact.html' form_class = ContactForm It seems the FormView can only accept one form at a time. In function based view though I can easily send two forms to my template and retrieve the content of both within the request.POST back. variables = {'contact_form':contact_form, 'social_form':social_form } return render(request, 'discussion.html', variables) Is this a limitation of using class based view (generic views)? Many Thanks

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