missing symbols - Page 486

Creating UTF-8 files in Java from a runnable Jar

- by RuntimeError

I have a little Java project where I've set the properties of the class files to UTF-8 (I use a lot of foreign characters not found on the default CP1252). The goal is to create a text file (in Windows) containing a list of items. When running the class files from Eclipse itself (hitting Ctrl+F11) it creates the file flawlessly and opening it in another editor (I'm using Notepad++) I can see the characters as I wanted. +--------------------------------------------------+ ¦ Universidade2010 (18/18)¦ ¦ hidden: 0¦ +--------------------------------------------------¦ But, when I export the project (using Eclipse) as a runnable Jar and run it using 'javaw -jar project.jar' the new file created is a mess of question marks ???????????????????????????????????????????????????? ? Universidade2010 (19/19)? ? hidden: 0? ???????????????????????????????????????????????????? I've followed some tips on how to use UTF-8 (which seems to be broken by default on Java) to try to correct this so now I'm using Writer w = new OutputStreamWriter(fos, "UTF-8"); and writing the BOM header to the file like in this question already answered but still without luck when exporting to Jar Am I missing some property or command-line command so Java knows I want to create UTF-8 files by default ?

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Custom bean instantiation logic in Spring MVC

- by Michal Bachman

I have a Spring MVC application trying to use a rich domain model, with the following mapping in the Controller class: @RequestMapping(value = "/entity", method = RequestMethod.POST) public String create(@Valid Entity entity, BindingResult result, ModelMap modelMap) { if (entity== null) throw new IllegalArgumentException("An entity is required"); if (result.hasErrors()) { modelMap.addAttribute("entity", entity); return "entity/create"; } entity.persist(); return "redirect:/entity/" + entity.getId(); } Before this method gets executed, Spring uses BeanUtils to instantiate a new Entity and populate its fields. It uses this: ... ReflectionUtils.makeAccessible(ctor); return ctor.newInstance(args); Here's the problem: My entities are Spring managed beans. The reason for this is to inject DAOs on them. Instead of calling new, I use EntityFactory.createEntity(). When they're retrieved from the database, I have an interceptor that overrides the public Object instantiate(String entityName, EntityMode entityMode, Serializable id) method and hooks the factories into that. So the last piece of the puzzle missing here is how to force Spring to use the factory rather than its own BeanUtils reflective approach? Any suggestions for a clean solution? Thanks very much in advance.

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Which C++ Standard Library wrapper functions do you use?

- by Neil Butterworth

This question, asked this morning, made me wonder which features you think are missing from the C++ Standard Library, and how you have gone about filling the gaps with wrapper functions. For example, my own utility library has this function for vector append: template <class T> std::vector<T> & operator += ( std::vector<T> & v1, const std::vector <T> & v2 ) { v1.insert( v1.end(), v2.begin(), v2.end() ); return v1; } and this one for clearing (more or less) any type - particularly useful for things like std::stack: template <class C> void Clear( C & c ) { c = C(); } I have a few more, but I'm interested in which ones you use? Please limit answers to wrapper functions - i.e. no more than a couple of lines of code.

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c++ templates and inheritance

- by Armen Ablak

Hey, I'm experiencing some problems with breaking my code to reusable parts using templates and inheritance. I'd like to achieve that my tree class and avltree class use the same node class and that avltree class inherits some methods from the tree class and adds some specific ones. So I came up with the code below. Compiler throws an error in tree.h as marked below and I don't really know how to overcome this. Any help appreciated! :) node.h: #ifndef NODE_H #define NODE_H #include "tree.h" template <class T> class node { T data; ... node() ... friend class tree<T>; }; #endif tree.h #ifndef DREVO_H #define DREVO_H #include "node.h" template <class T> class tree { public: //signatures tree(); ... void insert(const T&); private: node<T> *root; //missing type specifier - int assumed. Note: C++ does not support default-int }; //implementations #endif avl.h #ifndef AVL_H #define AVL_H #include "tree.h" #include "node.h" template <class T> class avl: public tree<T> { public: //specific int findMin() const; ... protected: void rotateLeft(node<T> *)const; private: node<T> *root; }; #endif avl.cpp (I tried separating headers from implementation, it worked before I started to combine avl code with tree code) #include "drevo" #include "avl.h" #include "vozlisce.h" template class avl<int>; //I know that only avl with int can be used like this, but currently this is doesn't matter :) //implementations ...

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IIS7.5 and MVC 2 : Implementing HTTP(S) security

- by Program.X

This is my first ASP.NET MVC application, and my first on an IIS 7.x installation whereby I have to do anything over and above the standard. I need to enforce Windows authentication on the /Index and /feeds/xxx.svc pages/services. In ASP.NET Web Forms, I would apply the Windows permissions on the files and remove Anonymous authentication in IIS 6. This needs to work over HTTP/S, but don't worry about that, that's in hand. What happens in MVC/IIS 7? I have tried modifying the permissions on the /Index.aspx view, which seems to block access. It asks me for a username/password, but does not grant access when I enter a valid username/password. Pressing Escape gives me an exception "*Access to the path 'E:\dev\xxx\xxx.ConsultantRegistration.Web.Admin\Views\ConsultantRegistration\index.aspx' is denied. *", which does get sent as a 401. So although the username/password does exist on the Index.aspx view, I can't use those credentials to access said view. I have in my web.config: What am I missing?

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Actionscript - combining AS2 assets into a single SWF

- by Justin Bachorik

Hi guys, I have a flash project that I'm trying to export as a single SWF. There's a main SWF file that loads about 6 other SWFs, and both the main and the child SWFs reference other external assets (images, sounds, etc). I'd like to package everything as a single .swf file so I don't have to tote the other assets around with the .swf. All the coding is done in the timeline, but the assets haven't been imported into the Flash Authoring environment and I don't have time to do that right now (there are too many references to them everywhere). I'm hoping that there's just an option I'm missing that allows this sort of packaged export, but I haven't found anything like that. I don't have access to Flex or mxmlc (and as the AS is timeline-based, they wouldn't necessarily help me). Any thoughts? Thanks! PS...if there's no way of doing exactly what I'm saying, I could deal with having all the assets in a "assets" folder or something like that, so I'd just be toting around main.swf and an assets folder. The problem here is that all the references to the assets assume that they're in the same folder as the main.swf file, so everything's assumed to be local...is there a way to change the scope of all external references in Flash (so, for example, all local references in the code are actually searched in /assets)?

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selecting text by ignoring inner Elements of div tag javascript

- by sugar

<html> <body> <script language="javascript"> function getSelectionHTML() { var div = document.getElementById("myDiv").childNodes; if (document.createRange) { var textNode=div.firstChild; var rangeObj=document.createRange(); rangeObj.setStart(textNode,0); rangeObj.setEnd(textNode,10); selRange.collapse(true); var elem = document.getElementById('myDiv') elem .innerHTML = elem .innerHTML.replace(rangeObj.toString(), '<span style="background-color: lime">'+rangeObj.toString()+'</span>') } } </script> <div id="myDiv"> asdf as<b>dfas df asf asdf sdfjk dvh a sjkh jhcdjkv</b> iof scjahjkv ahsjv hdjk biud fcsvjksdhf k </div> <form name="aform"> <input type="button" value="Get selection" onclick="getSelectionHTML()"> </body> </html> Ok. Let me explain - getSelectionHTML() method is for selection of characters from 0 to 10. I am getting the values by "myDiv" id. but inner bold, italic & other tags are putting me in trouble. In simple words, I just want to make selection of first ten characters (& apply them span tag) which are in "myDiv" tag. What exactly I am missing ? Can anyone help me ? Thanks in advance for sharing your knowledge. Sagar.

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are there requirements for Struts setters beyond variable name matching?

- by slk

I have a model-driven Struts Web action: public class ModelDrivenAction<T extends Object> implements ModelDriven<T>, Preparable { protected Long id; protected T model; @Override public void prepare() {} public void setId(Long id) { this.id = id; } @Override public T getModel() { return model; } public void setModel(T model) { this.model = model; } } I have another action which is not currently model-driven: public class OtherAction implements Preparable { private ModelObj modelObj; private Long modelId; @Override public void prepare() { modelObj = repoService.retrieveModelById(modelId); } public void setModelId(Long modelId) { this.modelId = modelId; } } I wish to make it so, and would like to avoid having to track down all the instances in JavaScript where the action is passed a "modelId" parameter instead of "id" if at all possible. I thought this might work, so either modelId or id could be passed in: public class OtherAction extends ModelDrivenAction<ModelObj> { @Override public void prepare() { model = repoService.retrieveModelById(id); } public void setModelId(Long modelId) { this.id = modelId; } } However, server/path/to/other!method?modelId=123 is failing to set id. I thought so long as a setter matched a parameter name the Struts interceptor would call it on action invocation. Am I missing something here?

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Where should I put validation code?

- by D Lawson

I'm creating interfaces and abstract classes that represent a messaging framework for short text-based messages like SMS, email, twitter, xml, etc.. and I was wondering where I should put the message validation code. The thing is that I am only writing the superclasses and interfaces, so I'm not putting the actual implementation in, I'll just put the hooks in that allow others to validate the content of the messages. The way I see it, I could do it several ways: in the abstract superclass "Message", have an abstract method 'isValid'. A variation on this would be to have isValid be called when the Message constructor is called, throwing a MalformedMessageException if the message is formatted incorrectly. in the transport layer, immediately before sending, validate the message. I would have a send(Message) method that calls an isValid(Message) method immediately before it sends. have a singleton message validator with a static method isValid(Message) that is called at some point. I'm sure there are other options that I'm missing. Currently, I'm leaning towards the first one, but it doesn't feel right to me to have validation code in what should be a domain object.

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html in do_GET() method of a simple Python webserver

- by Meeri_Peeri

I am relatively new to Python but have been doing a lot of different things with it recently and I am liking it a lot. However, I ran into trouble/block with the following code. import http.server import socketserver import glob import random class Server(http.server.SimpleHTTPRequestHandler): def do_GET(self): self.send_response(200, 'OK') self.send_header('Content-type', 'html') self.end_headers() self.wfile.write(bytes("<html> <head><title> Hello World </title> </head> <body>", 'UTF-8')) images = glob.glob('*.jpg') rand = random.randint(0,len(images)-1) imagestring = "<img src = \"" + images[rand] + "\" height = 1028 width = 786 align = \"right\"/> </body> </html>" self.wfile.write(bytes(imagestring, 'UTF-8')) def serve_forever(port): socketserver.TCPServer(('', port), Server).serve_forever() if __name__ == "__main__": Server.serve_forever(8000) What I am trying to do here is grab a random image from multiple images in the directory and add it into the response to a web request. The code works fine but when I access the server via browser, the image is not displayed. The html of the page is as intended though. The permissions on the files are 755. Also I tried to create an index.html file in the do_GET method. That didn't work either. I mean the index.html was generated fine, but the response in the browser this time did not show anything (not even the hello world in the title). Am I missing anything very simple here? I was thinking should I overload the handle_request of the underlying SocketServer.BaseServer as the documentation says you should never override BaseHTTPServer's handle() method and should rather override the corresponding do_* method?

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Not Understanding Basics Of Dynamic DataBinding (bindPropety) In Flex

- by Joshua

I need to dynamically bind properties of components created at runtime. In this particular case please assume I need to use bindProperty. I don't quite understand why the following simplistic test is failing (see code). When I click the button, the label text does not change. I realize that there are simpler ways to go about this particular example using traditional non-dynamic binding, but I need to understand it in terms of using bindProperty. Can someone please help me understand what I'm missing? <?xml version="1.0" encoding="utf-8"?> <mx:WindowedApplication xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" xmlns:ns1="Tools.*" minWidth="684" minHeight="484" xmlns:ns2="*" creationComplete="Init();"> <mx:Script> <![CDATA[ import mx.collections.ArrayCollection; import mx.binding.utils.*; public var Available:ArrayCollection=new ArrayCollection(); public function get Value():String { return (Available.getItemAt(0).toString()); } public function Init():void { Available.addItemAt('Before', 0); BindingUtils.bindProperty(Lab, 'text', this, 'Value'); } public function Test():void { Available.setItemAt('After', 0); } ]]> </mx:Script> <mx:Label x="142" y="51" id="Lab"/> <mx:Button x="142" y="157" label="Button" click="Test();"/> </mx:WindowedApplication> Thanks in advance.

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Data confusion - Selecting data in one DataGridView based on selection in another

- by Logan Young

This probably isn't the best way to do what I want, but I can't think of anything else to try... NB: I'm using Visual Basic.NET My form has 2 DataGridView controls. One of these is bound to a DataSet, the other isn't visible - at least not until the user selects a uniqueidentifier cell in the 1st grid. When the user makes this selection, the 2nd grid will become visible and display the row from another with the same id as the one selected in the 1st grid. So, basically, I want to dynamically display data in one grid based on user selection in another grid. My code looks like this so far... Private Sub RulesGrid_CellClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles RulesGrid.CellClick Try FlagsGrid.Visible = True ''// MsgBox(RulesGrid.CurrentCell.Value.ToString()) Dim sql As String = "SELECT * FROM ctblMKA_Status_Flags " + _ "WHERE intStatusID = '" & RulesGrid.CurrentCell.Value & "'" DSFlags = GetDS(sql) DSFlags.DataSetName = "FlagsDataSet" FlagsGrid.DataSource = DSFlags ProgressBar.Visible = False Catch ex As Exception MsgBox(ex.ToString) End Try End Sub I feel like I'm missing something here... Any ideas anyone?

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need to clean malformed tags using regular expression

- by Brian

Looking to find the appropriate regular expression for the following conditions: I need to clean certain tags within free flowing text. For example, within the text I have two important tags: <2004:04:12 and . Unfortunately some of tags have missing "<" or "" delimiter. For example, some are as follows: 1) <2004:04:12 , I need this to be <2004:04:12> 2) 2004:04:12>, I need this to be <2004:04:12> 3) <John Doe , I need this to be <John Doe> I attempted to use the following for situation 1: String regex = "<\\d{4}-\\d{2}-\\d{2}\\w*{2}[^>]"; String output = content.replaceAll(regex,"$0>"); This did find all instances of "<2004:04:12" and the result was "<2004:04:12 ". However, I need to eliminate the space prior to the ending tag. Not sure this is the best way. Any suggestions. Thanks

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App Engine - Query using a class member as parameter

- by Zach

I have a simple class, relevant details below: @PersistenceCapable(identityType = IdentityType.APPLICATION) public class SimpleCategory implements Serializable{ ... public static enum type{ Course, Category, Cuisine } @Persistent public type t; ... } I am attempting to query all SimpleCategory objects of the same type. public SimpleCategory[] getCategories(SimpleCategory.type type) { PersistenceManager pm = PMF.get().getPersistenceManager(); try{ Query q = pm.newQuery(SimpleCategory.class); q.setFilter("t == categoryType"); q.declareParameters("SimpleCategory.type categoryType"); List<SimpleCategory> cats = (List<SimpleCategory>) q.execute(type); ... } This results in a ClassNotResolvedException for SimpleCategory.type. The google hits I've found so far recommended to: Use query.declareImports to specify the class i.e. q.declareImports("com.test.zach.SimpleCategory.type"); Specify the fully qualified name of SimpleCategory in declareParameters Neither of these suggestions has worked. By removing .type and recompiling, I can verify that declareParameters can see SimpleCategory just fine, it simply cannot see the SimpleCategory.type, despite the fact that the remainder of the method has full visibility to it. What am I missing?

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get_bookmarks() object doesn't return link_category

- by ninja

I'm trying to fetch all link-categories from the built in Wordpress linklist (or bookmarks if you will). To do this, I simply stored all links in a variable like this: <?php $lists = get_bookmarks(); foreach($lists as $list) { $cats[] = $list->link_category; } ?> To my surprise even var_dump'ing $cats gave me "String(0)", so I var_dump'ed out $lists instead, and it gave me this: array(8) { [0]=> object(stdClass)#5126 (13) { ["link_id"]=> string(1) "1" ["link_url"]=> string(27) "http://codex.wordpress.org/" ["link_name"]=> string(13) "Documentation" ["link_image"]=> string(0) "" ["link_target"]=> string(0) "" ["link_description"]=> string(0) "" ["link_visible"]=> string(1) "Y" ["link_owner"]=> string(1) "1" ["link_rating"]=> string(1) "0" ["link_updated"]=> string(19) "0000-00-00 00:00:00" ["link_rel"]=> string(0) "" ["link_notes"]=> string(0) "" ["link_rss"]=> string(0) "" } Now, codex.wordpress.org is a default link that comes with wordpress, it's in a category called "Linklist", and as you can see, the object contains everything about that link, EXCEPT the categoryname. According to the codex this object should contain a field named "link_category", so I'm getting confused here. Am I missing something? Is the function broke? Regards NINJA

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Member function overloading/template specialization issue

- by Ferruccio

I've been trying to call the overloaded table::scan_index(std::string, ...) member function without success. For the sake of clarity, I have stripped out all non-relevant code. I have a class called table which has an overloaded/templated member function named scan_index() in order to handle strings as a special case. class table : boost::noncopyable { public: template <typename T> void scan_index(T val, std::function<bool (uint recno, T val)> callback) { // code } void scan_index(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code } }; Then there is a hitlist class which has a number of templated member functions which call table::scan_index(T, ...) class hitlist { public: template <typename T> void eq(uint fieldno, T value) { table* index_table = db.get_index_table(fieldno); // code index_table->scan_index<T>(value, [&](uint recno, T n)->bool { // code }); } }; And, finally, the code which kicks it all off: hitlist hl; // code hl.eq<std::string>(*fieldno, p1.to_string()); The problem is that instead of calling table::scan_index(std::string, ...), it calls the templated version. I have tried using both overloading (as shown above) and a specialized function template (below), but nothing seems to work. After staring at this code for a few hours, I feel like I'm missing something obvious. Any ideas? template <> void scan_index<std::string>(std::string val, std::function<bool (uint recno, std::string val)> callback) { // code }

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Has anyone ever successfully make index merge work for MySQL?

- by user198729

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git submodule svn external

- by Jason

Let's say I have 3 git repositories, each with a lib and tests folder in the root. All 3 repositories are part of what I want to be a single package, however it is important to me to keep the repositories separate. I am new to git coming from svn, so I have been reading up on submodules and how they differ from svn:externals. In SVN I could have a single lib/vendor/package directory, and inside package I could setup 3 externals pointing to each of my 3 repositories lib directory, renaming it appropriately like lib/vendor/package/a -> repo1/lib lib/vendor/package/b -> repo2/lib lib/vendor/package/c -> repo3/lib but from my understanding this is not possible with git. Am I missing something? Really I'm hoping this can be solved in one of two ways. Someone will point out how to create a 4th git repository which has the other 3 as submodules organized as I have mentioned above (where I can have an a, b, and c folder inside the root) Someone will point out how to set this up using svn:externals in combination with githubs svn support, referencing the lib directory within each git repository (from my understanding this is impossible)

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Windows Service Start-Up Error 1069

- by Gavin

Hello, I am installing a new windows service coded in C# on a server. I installed the service fine on the server, but once i manually start up the service on a server, with the same login credentials that our other services use, i get the fatal error message notification: "Could not start the %service name% on Local Computer. Error 1069: The Service did not start due to a logon failure." I looked in the event log and i got a 7038 and 7000 event id error in that order. 7038 event id message: "The %service name% service was unable to log on as %login% with the currently configured password due to the following error: Logon failure: unknown user name or bad password. To ensure that the service is configured properly, use the Services snap-in in Microsoft Management Console (MMC)." 7000 event id message: "The %service name% service failed to start due to the following error: The service did not start due to a logon failure. " I have other services that are using the same exact login account and they work fine. Is there something simple I could be missing? Thanks

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PHP extend a class method that is called from another class which extends it and calls the method wi

- by dan.codes

I am trying to extend a class and override one of its methods. lets call that class A. My class, class B, is overiding a protected method. Class C extends class A and Class D extends class C. Inside of Class D, the method I am trying to overwrite is also extended here and that calls parent::mymethodimoverriding. That method does not exist in class C so it goes to it in class A. That is the method I am overiding in class B and obviously you can't extend A with B and have those changes show up in D since it does not fall in line with the class hierarchy. I might be wrong, so correct me please. so if my class b is called and ran then class D gets called it runs the method in A and overwrites what I had set. I am thinking there must be a way to get this to work, I am just missing something. here is an example, as you can see in class A there is a call to setTitle and it is set to "Example" In my class I set it to "NewExample". My class is getting called before class D so when class D is called it goes back to the parent and sets the title back to "Example" class A{ protected function _thefunction(){ setTitle("Example"); } } class B extends A{ protected function _thefunction(){ My new code here setTitle("NewExample"); } } class C extends A{ nothing that matters in here for what I am doing } class D extends C{ protected function _thefunction(){ parent::_thefunction(); additional code here } }

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Should I always import my file references into the database in drupal?

- by sprugman

I have a cck type with an image field, and a unique_id text field. The file name of the image is based on the unique_id. All of the content, including the image itself is being generated automatically via another process, and I'm parsing what that generates into nodes. Rather than creating separate fields for the id and the image, and doing an official import of the image into the files table, I'm tempted to only create the id field and create the file reference in the theme layer. I can think of pros and cons: 1) Theme Layer Approach Pros: makes the import process much less complex don't have to worry about syncing the db with the file system as things change more flexible -- I can move my images around more easily if I want Cons: maybe not as much The Drupal Way™ not as pure -- I'll wind up with more logic on the theme side. 2) Import Approach Pros: import method is required if we ever wanted to make the files private (we won't.) safer? Maybe I'll know if there's a problem with the image at import time, rather than view time. Since I'll be bulk importing, that might make a difference. if I delete a node through the admin interface, drupal might be able to delete the file for me, as well. Con: more complex import and maintenance All else being equal, simpler is always better, so I'm leaning toward #1. Are there any other issues I'm missing? (Since this is an open ended question, I guess I'll make it a community wiki, whatever that means.)

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Changing pointer of self

- by rob5408

I have an object that I alloc/init like normal just to get a instance. Later in my application I want to load state from disk for that object. I figure I could unarchive my class (which conforms to NSCoding) and just swap where my instance points to. To this end I use this code... NSString* pathForDataFile = [self pathForDataFile]; if([[NSFileManager defaultManager] fileExistsAtPath:pathForDataFile] == YES) { NSLog(@"Save file exists"); NSData *data = [[NSMutableData alloc] initWithContentsOfFile:pathForDataFile]; NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data]; [data release]; Person *tempPerson = [unarchiver decodeObjectForKey:@"Person"]; [unarchiver finishDecoding]; [unarchiver release]; if (tempPerson) { [self release]; self = [tempPerson retain]; } } Now when I sprinkled some NSLogs throughout my application I noticed self.person: <Person: 0x3d01a10> (After I create the object with alloc/init) self: <Person: 0x3d01a10> (At the start of this method) tempPerson: <Person: 0x3b1b880> (When I create the tempPerson) self: <Person: 0x3b1b880> (after i point self to the location of the tempPerson) self.person: <Person: 0x3d01a10> (After the method back in the main program) What am I missing?

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What's a good way to write batch scripts in C#?

- by Scott Bilas

I would like to write simple scripts in C#. Stuff I would normally use .bat or 4NT .btm files for. Copying files, parsing text, asking user input, and so on. Fairly simple but doing this stuff right in a batch file is really hard (no exceptions for example). I'm familiar with command line "scripting" wrappers like AxScript so that gets me part of the way there. What I'm missing is the easy file-manipulation framework. I want to be able to do cd(".."), copy(srcFile, destFile) type functionality. Tools I have tried: NANT, which we use in our build process. Not a good scripting tool. Insanely verbose XML syntax and to add a simple function you must write an extension assembly. Can't do it inline. PowerShell. Looks great, but I just haven't been able to switch over to this as my primary shell. Too many differences from 4NT. Whatever I do needs to run from an ordinary command prompt and not require a special shell to run it through. Can PowerShell be used as a script executor? Perl/Python/Ruby. Really hate learning an entirely new language and framework just to do batch file operations. Haven't been able to dedicate the time I need to do this. Plus, we're a 99% .NET shop for our toolchain and I really want to leverage our existing experience and codebase. Are there frameworks out there that are trying to solve this problem of "make a batch file in C#" that you have used? I want the power of C#/.NET with the immediate-mode type functionality of a typical cmd.exe shell language. Am I alone in wanting something like this?

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using empty on inaccessible object with isset and get

- by David

<?php class Magic_Methods { protected $meta; public function __construct() { $this->meta = (object) array( 'test' => 1 ); } public function __isset($name) { echo "pass isset {$name} \n"; return isset($this->$name); } public function __get($name) { echo "pass get {$name} \n"; return $this->$name; } } $mm = new Magic_Methods(); $meta = empty($mm->meta->notExisting); var_dump($meta); echo "||\n"; $meta = empty($mm->meta); var_dump($meta); The snippet above does not work as expected for me. Why would the first empty() ommit the __isset? I get this: pass get meta bool(true) || pass isset meta pass get meta bool(false) I would expected identical results or another pass at the __isset, but not a direct call to __get. Or am I missing something here?

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Using list() to extract a data.table inside of a function

- by Nathan VanHoudnos

I must admit that the data.table J syntax confuses me. I am attempting to use list() to extract a subset of a data.table as a data.table object as described in Section 1.4 of the data.table FAQ, but I can't get this behavior to work inside of a function. An example: require(data.table) ## Setup some test data set.seed(1) test.data <- data.table( X = rnorm(10), Y = rnorm(10), Z = rnorm(10) ) setkey(test.data, X) ## Notice that I can subset the data table easily with literal names test.data[, list(X,Y)] ## X Y ## 1: -0.8356286 -0.62124058 ## 2: -0.8204684 -0.04493361 ## 3: -0.6264538 1.51178117 ## 4: -0.3053884 0.59390132 ## 5: 0.1836433 0.38984324 ## 6: 0.3295078 1.12493092 ## 7: 0.4874291 -0.01619026 ## 8: 0.5757814 0.82122120 ## 9: 0.7383247 0.94383621 ## 10: 1.5952808 -2.21469989 I can even write a function that will return a column of the data.table as a vector when passed the name of a column as a character vector: get.a.vector <- function( my.dt, my.column ) { ## Step 1: Convert my.column to an expression column.exp <- parse(text=my.column) ## Step 2: Return the vector return( my.dt[, eval(column.exp)] ) } get.a.vector( test.data, 'X') ## [1] -0.8356286 -0.8204684 -0.6264538 -0.3053884 0.1836433 0.3295078 ## [7] 0.4874291 0.5757814 0.7383247 1.5952808 But I cannot pull a similar trick for list(). The inline comments are the output from the interactive browser() session. get.a.dt <- function( my.dt, my.column ) { ## Step 1: Convert my.column to an expression column.exp <- parse(text=my.column) ## Step 2: Enter the browser to play around browser() ## Step 3: Verity that a literal X works: my.dt[, list(X)] ## << not shown >> ## Step 4: Attempt to evaluate the parsed experssion my.dt[, list( eval(column.exp)] ## Error in `rownames<-`(`*tmp*`, value = paste(format(rn, right = TRUE), (from data.table.example.R@1032mCJ#7) : ## length of 'dimnames' [1] not equal to array extent return( my.dt[, list(eval(column.exp))] ) } get.a.dt( test.data, "X" ) What am I missing? Update: Due to some confusion as to why I would want to do this I wanted to clarify. My use case is when I need to access a data.table column when when I generate the name. Something like this: set.seed(2) test.data[, X.1 := rnorm(10)] which.column <- 'X' new.column <- paste(which.column, '.1', sep="") get.a.dt( test.data, new.column ) Hopefully that helps.

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