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  • Proper Memory Management for Objective-C Method

    - by Justin
    Hi, I'm programming an iPhone app and I had a question about memory management in one of my methods. I'm still a little new to managing memory manually, so I'm sorry if this question seems elementary. Below is a method designed to allow a number pad to place buttons in a label based on their tag, this way I don't need to make a method for each button. The method works fine, I'm just wondering if I'm responsible for releasing any of the variables I make in the function. The application crashes if I try to release any of the variables, so I'm a little confused about my responsibility regarding memory. Here's the method: FYI the variable firstValue is my label, it's the only variable not declared in the method. -(IBAction)inputNumbersFromButtons:(id)sender { UIButton *placeHolderButton = [[UIButton alloc] init]; placeHolderButton = sender; NSString *placeHolderString = [[NSString alloc] init]; placeHolderString = [placeHolderString stringByAppendingString:firstValue.text]; NSString *addThisNumber = [[NSString alloc] init]; int i = placeHolderButton.tag; addThisNumber = [NSString stringWithFormat:@"%i", i]; NSString *newLabelText = [[NSString alloc] init]; newLabelText = [placeHolderString stringByAppendingString:addThisNumber]; [firstValue setText:newLabelText]; //[placeHolderButton release]; //[placeHolderString release]; //[addThisNumber release]; //[newLabelText release]; } The application works fine with those last four lines commented out, but it seems to me like I should be releasing these variables here. If I'm wrong about that I'd welcome a quick explanation about when it's necessary to release variables declared in functions and when it's not. Thanks.

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  • Use variables to decide which object in an array gets an attribute?

    - by DavidR
    I have a web app which has two text areas. When one text area receives a mousedown event, a variable "side" is set, either "left" or "right." When a user selects some text in a text area, three strings are made. One for the text before the beginning of the selection, the selection itself, and the text after the selection to the end. A function is set to return these like this: return { head: head_text, tail: tail_text, sel: sel_text, side: text_side } Now, I have created an array, and I want it to appear in such a way that we get, text.left({"head":"four score", "selection":"and seven", "tail":"years ago."}) I am assuming I would do this by text.side = getSelection(), but how do I get it to evaluate the variable "side" instead of thinking of it as an object within "text"? EDIT: Ok, just to clarify, I might be completely wrong in my ideas in how this works, but here it goes. I want to make it so that a function can look at "text" see within text two objects, "left" and "right," and then evaluate the head, sel, and tail of each object. Would it be easier for me to use two objects?

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  • C++, array declaration, templates, linker error

    - by justik
    There is a linker error in my SW. I am using the following structure based on h, hpp, cpp files. Some classes are templatized, some not, some have function templates. Declaration: test.h #ifndef TEST_H #define TEST_H class Test { public: template <typename T> void foo1(); void foo2 () }; #include "test.hpp" #endif Definition: test.hpp #ifndef TEST_HPP #define TEST_HPP template <typename T> void Test::foo1() {} inline void Test::foo2() {} //or in cpp file #endif CPP file: test.cpp #include "test.h" void Test::foo2() {} //or in hpp file as inline I have the following problem. The variable vars[] is declared in my h file test.h #ifndef TEST_H #define TEST_H char *vars[] = { "first", "second"...}; class Test { public: void foo(); }; #include "test.hpp" #endif and used as a local variable inside foo() method defined in hpp file as inline. test.hpp #ifndef TEST_HPP #define TEST_HPP inline void Test::foo() { char *var = vars[0]; //A Linker Error } #endif However, the following linker error occurs: Error 745 error LNK2005: "char * * vars" (?vars@@3PAPADA) already defined in test2.obj How and where to declare vars[] to avoid linker errors? After including #include "test.hpp" it is late to declare it...

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  • How do I put my return data from an asmx into JSON?

    - by jphenow
    I want to return an array of javascript objects from my asp.net asmx file. ie. variable = [ { *value1*: 'value1', *value2*: 'value2', ..., }, { . . } ]; I seem have been having trouble reaching this. I'd put this into code but I've been hacking away at it so much it'd probably do more harm than good in having this answered. Basically I am using a web service to find names as people type the name. I'd use a regular text file or something but its a huge database that's always changing - and don't worry I've indexed the names so searching can be a little snappier - but I would really prefer to stick with this method and just figure out how to get usable JSON back to javascript. I've seen a few that sort of attempt to describe how one would approach this but I honestly think microsofts articles are damn near unreadable. Thanks in advance for assistance. EDIT: I'm using the $.ajax() function from jQuery - I've had it working but it seems like I was doing it in bad practice not returning and using actual JSON. Previously I'd take a string back and insert it into html to use the variable it set - very roundabout.

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  • CDN for Images in ASP.NET

    - by Chris
    I am in the process of moving all of the images in my web application over to a CDN but I want to easily be able to switch the CDN on or off without having to hard code the path to the images. My first thought was to add an HttpHandler for image extensions that depending whether a variable in the web.config (something like ) will serve the image from the server or from the CDN. But after giving this a little though I think I've essentially ruled this out as it will cause ASP.NET to handle the request for every single image, thus adding overhead, and it might actually completely mitigate the benefits of using a CDN. An alternative approach is, since all of my pages inherit from a base page class, I could create a function in the base class that determines what path to serve the files from based off the web.config variable. I would then do something like this in the markup: <img src='<%= GetImagePath()/image.png' /> I think this is probably what I'll have to end up doing, but it seems a little clunky to me. I also envision problems with the old .NET error of not being able to modify the control collection because of the "<%=" though the "<%#" solution will probably work. Any thoughts or ideas on how to implement this?

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  • Unable to Get values from Web Form to a PHP Class to Display

    - by kentrenholm
    I am having troubles getting the value from my variables submitted via a web form using a PHP class file. Here is my structure of the web page: Order Form Page Process.php Page Book.php Page I can easily get the user data entered (on Order Form Page), process, and display it on the Process.php page. The issue is that I must create a Book class and print the details of the data using the Book class. I have an empty constructor printing out "created" so I know my constructor is being called. I also am able to print the word "title" so I know I can print to the screen by using the Book class. My issue is that I can't get values in my variables in the Book class. Here is my variable declaration: private $title; Here is my printDetails function: public function printDetails () { echo "Title: " . $this->title . "<br />"; } Here is my new instance of the book class: $bookNow = new book; Here are my get and set functions: function __getTitle($title) { return $this->$title; } function __setTitle($title,$value) { $this->$title = $value; } I do have four other variables that I'm looking to display as well. Each of those have their own variable declaration, a line in printDetails, and their own setter and getter. Lastly, I also have a call to the Book class in my process PHP. It looks like this: function __autoload($book) { include $book . '.php'; } $bookNow = new book(); Any help, much appreciated. It must be something so very small (I'm hoping).

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  • In need of a Smarter Environmental Package Configuration

    - by Jeremy Liberman
    I am trying to set up a package template in SSIS, following the Wrox Programmer to Programmer book, SQL Server 2008 Integration Services: Problem - Design - Solution. I'm really liking this book even though it is 2008 and we're using SQL Server 2005. I've got a working package template that uses an Indirect XML package configuration to identify what environment (local developer, dev, QA, production, etc) the package is being run in. That locates the SQL Server package configuration for the environment. That set-up is great and all except for the environment variable at the very front of it all. My team would prefer it if the package could use the same environment resource locator as all our other applications and tools use, so we don't two environment markers with essentially the same information in them. Normally we look up a registry key in HKey_Local_Machine but the Registry Package Configuration type only lets you look up the HKey_Current_User registries. My first thought was to write a new Package Configuration Type class that extends the Registry type; after all we'd had such luck writing our own custom log provider. SSIS is super extendable, right? So there doesn't seem to be a way to write your own Package Configuration Types. Is there still some way I can configure my SSIS SQL Server package configuration from a HKLM registry key connection string? If this is not possible, what other workarounds are available? My idea is to write a PowerShell script that will create/modify the Environment Variable that the package will use by fetching the connection string from the registry. This way there's still two markers, but at least then it's automatically maintained and automated. Is this kind of workaround necessary? Thank you for your time.

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  • PHP Header redirection problem within page called by cURL

    - by Das123
    I have a site that uses cURL to access some pages, stores the returned results in variables, and then uses these variables within its own page. The script works well except where the target cURL page has a header('Location: ...') command inside it. It seems to just ignore this header command. The cURL command is as follows... //Load result page into variable so portions can be allocated to correct variables $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); # URL to post to curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1 ); # return into a variable curl_setopt($ch, CURLOPT_HEADER, 0); curl_setopt($ch, CURLOPT_POST, true); curl_setopt($ch, CURLOPT_POSTFIELDS, $postfields); $loaded_result = curl_exec( $ch ); # run! curl_close($ch); I've tried changing the CURLOPT_HEADER to 1 but it doesn't do anything. So how can I allow script redirection within the target urls using cURL to grab the results? By the way, the pages work fine if accessed other than via cURL but iFrames are not an option in this instance.

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  • Haskell: Dealing With Types And Exceptions

    - by Douglas Brunner
    I'd like to know the "Haskell way" to catch and handle exceptions. As shown below, I understand the basic syntax, but I'm not sure how to deal with the type system in this situation. The below code attempts to return the value of the requested environment variable. Obviously if that variable isn't there I want to catch the exception and return Nothing. getEnvVar x = do { var <- getEnv x; Just var; } `catch` \ex -> do { Nothing } Here is the error: Couldn't match expected type `IO a' against inferred type `Maybe String' In the expression: Just var In the first argument of `catch', namely `do { var <- getEnv x; Just var }' In the expression: do { var <- getEnv x; Just var } `catch` \ ex -> do { Nothing } I could return string values: getRequestURI x = do { requestURI <- getEnv x; return requestURI; } `catch` \ex -> do { return "" } however, this doesn't feel like the Haskell way. What is the Haskell way?

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  • How make this jquery function reusable?

    - by Pandiya Chendur
    Comsider this jquery function, function showresults(jsonobj) { $.each(jsonobj, function(i, employee) { divs += '<div class="resultsdiv"><br /><span style="display: inline-block;width:150px;" class="resultName">' + employee.Emp_Name + '</span><span class="resultfields" style="padding-left:100px;">Category&nbsp;:</span>&nbsp;<span class="resultfieldvalues">' + employee.Desig_Name + '</span><br /><br /><span id="SalaryBasis" class="resultfields">Salary Basis&nbsp;:</span>&nbsp;<span class="resultfieldvalues">' + employee.SalaryBasis + '</span><span class="resultfields" style="padding-left:25px;">Salary&nbsp;:</span>&nbsp;<span class="resultfieldvalues">' + employee.FixedSalary + '</span><span style="font-size:110%;font-weight:bolder;padding-left:25px;">Address&nbsp;:</span>&nbsp;<span class="resultfieldvalues">' + employee.Address + '</span></div>'; }); } Here i am iterating my json data and drawing div elements.... As you see these div elements are hardcoded how to pass these html div elements dynamically by a variable... var divs=<div></div> function showresults(jsonobj,divs) { $.each(jsonobj, function(i, employee) { divs += divs Is this correct way of doing but there will be an error employee object wont be there know when my divs variable declared outside the function... Any suggestion...

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  • GADTs and Scrap your Boilerplate

    - by finnsson
    I'm writing a XML (de)serializer using Text.XML.Light and Scrap your Boilerplate (at http://github.com/finnsson/Text.XML.Generic) and so far I got working code for "normal" ADTs but I'm stuck at deserializing GADTs. I got the GADT data DataBox where DataBox :: (Show d, Eq d, Data d) => d -> DataBox and I'm trying to get this to compile instance Data DataBox where gfoldl k z (DataBox d) = z DataBox `k` d gunfold k z c = k (z DataBox) -- not OK toConstr (DataBox d) = toConstr d dataTypeOf (DataBox d) = dataTypeOf d but I can't figure out how to implement gunfold for DataBox. The error message is Text/XML/Generic.hs:274:23: Ambiguous type variable `b' in the constraints: `Eq b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Show b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Data b' arising from a use of `k' at Text/XML/Generic.hs:274:18-30 Probable fix: add a type signature that fixes these type variable(s) It's complaining about not being able to figure out the data type of b. I'm also trying to implement dataCast1 and dataCast2 but I think I can live without them (i.e. an incorrect implementation). I guess my questions are: Is it possible to combine GADTs with Scrap your Boilerplate? If so: how do you implement gunfold for a GADT?

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  • ruby on rails basics help

    - by CHID
    Hi, i created a scaffolded application in rails by the name of product. The product_controller.rb file contains the following. class ProductsController ApplicationController def new @product = Product.new respond_to do |format| format.html # new.html.erb format.xml { render :xml = @product } end end def create @product = Product.new(params[:product]) respond_to do |format| if @product.save flash[:notice] = 'Product was successfully created.' format.html { redirect_to(@product) } format.xml { render :xml = @product, :status = :created, :location = @product } else format.html { render :action = "new" } format.xml { render :xml = @product.errors, :status = :unprocessable_entity } end end end Now when the url http://localhost:3000/products/create is given Where new product link is clicked, control is transferred to new definition in the controller class and then an instance variable @product is created. BUT WHERE IS THIS VARIABLE PASSED? The funtion inturn calls new.rhtml which contains <% form_for(@product) do |f| % #all form elments declaration <% f.submit "Create" % <%= end % Here @product is initialized in the controller file and passed to this new.rhtml. So where does form_for(@product) gets the data? How does the control gets tranfered to create function in controller file when submit button is clicked? No where action is specified to the controller file. in the create function, wat does redirec_to(@product) specify where @product is an object received from the new.html file... I am very much confused on the basics of ROR. Somone pls help me clarify this. pardon me for making such a big post. I have lots of doubts in this single piece of code

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  • Javascript style variables with "-" in their name aren't able to be changed?

    - by William
    Okay, so this bug has cost me quite a bit of time and embarrassment. It seems that any style variable with a - in it's name can't be modified by javascript. As seen here: <!DOCTYPE html> <html lang="en"> <head> <title>Class Test</title> <meta charset="utf-8" /> <style> body { text-align: center; background-color: #ffffff;} #box { position: absolute; left: 610px; top: 80px; height: 50px; width: 50px; background-color: #ff0000; color: #000000;} </style> <script type="text/javascript"> var box = 0; </script> </head> <body> <div id="box" ></div> <script type="text/javascript"> box = document.getElementById('box'); box.style.background-color = "#0000ff"; </script> </body> </html> The box in said example will just remain red. So how do I change a style variable with a - in it's name?

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  • Confusion in MIPS code

    - by Haya Hallian
    While going through the MIPS code I got some confusion. Code is shown as follows .data key: .ascii "key: " # "key: \n" char: .asciiz " \n" .text .globl main main: jal getchar la $a0, char # $a0 contains address of char variable (" \n") sb $v0, ($a0) # replace " " in char with v0, which is read_character (X) la $a0, key # now a0 will contain, address of "key: " "X\n" What I dont understand is that how load address instruction works. First a0 contained address of char variable. In next line we are storing value of v0 in that location. there is no offset with ($a0), is that assumed to be 0 like in 0($a0)? Why only the " " empty space is replaced with v0, and why not the "\n" get replaced? or It may also have been the case that both the empty space and \n character get replced by v0. Secondly when we load the address of key in a0, the previous address should be overwritten. a0 should have contained the address of key only, but from comment it seems that the two strings are concatenated. How does that happen.

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  • iMX31 dependencies?

    - by Abhi
    Dear all I am beginner in an silverlight application. So at first i looked on demo application which is provided by wince 6.0 r3 at location WINCE600\PUBLIC\COMMON\OAK\DEMOS\XAMLPERF - this contains c++ code and WINCE600\PUBLIC\COMMON\OAK\FILES\XAMLPERF - this contains xaml file with the images Now before running this application in an emulator. I at first proceeded with the following: I have first taken my workspace went to catalog item and added "Silverlight for Windows Embedded" from the drop down menu of an catalog item Then right clicked on solution explorer and choosed on properties and under configuration in drop down menu i have selected environment variables where i have added new variable called "sysgen_samplexamlperf" and assigned value as 1 for that variable. Now after rebuiding the application, i have dumped the image into emulator and i found that at desktop of device emulator i can see the exe file to which i run and i can see the application is working fine with 3d effects. Now same thing i proceeded in iMX31 hardware and i was not able to see the application running in a proper manner as it was performing in an emulator. So now what i feel is that there be any dependency when we run the application on hardware. So what can be the dependency? Also in this location "WINCE600\PUBLIC\COMMON\OAK\FILES\XAMLPERF" the images are in png format. So is there any dependency with an image format? Thanks and regards

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  • How to throw meaningful data in exceptions ?

    - by ZeroCool
    I would like to throw exceptions with meaningful explanation ! I thought of using variable arguments worked fine but lately I figured out it's impossible to extend the class in order to implement other exception types. So I figured out using an std::ostreamstring as a an internal buffer to deal with formatting ... but doesn't compile! I guess it has something to deal with copy constructors. Anyhow here is my piece of code: class Exception: public std::exception { public: Exception(const char *fmt, ...); Exception(const char *fname, const char *funcname, int line, const char *fmt, ...); //std::ostringstream &Get() { return os_ ; } ~Exception() throw(); virtual const char *what() const throw(); protected: char err_msg_[ERRBUFSIZ]; //std::ostringstream os_; }; The variable argumens constructor can't be inherited from! this is why I thought of std::ostringstream! Any advice on how to implement such approach ?

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  • Using placeholders/variables in a sed command

    - by jesse_galley
    I want to store a specific part of a matched result as a variable to be used for replacement later. I would like to keep this in a one liner instead of finding the variable I need before hand. when configuring apache, and use mod_rewrite, you can specificy specific parts of patterns to be used as variables,like this: RewriteRule ^www.example.com/page/(.*)$ http://www.example.com/page.php?page=$1 [R=301,L] the part of the pattern match that's contained inside the parenthesis is stored as $1 for use later. So if the url was www.example.com/page/home, it would be replaced with www.example.com/page.php?page=home. So the "home" part of the match was saved in $1 because it was the part of the pattern inside the parenthesis. I want something like this functionality with a sed command, I need to automatically replace many strings in a SQL dump file, to add drop table if exist commands before each create table, but I need to know the table name to do this, so if the dump file contains something like: ... CREATE TABLE `orders` ... I need to run something like: cat dump.sql | sed "s/CREATE TABLE `(.*)`/DROP TABLE IF EXISTS $1\N CREATE TABLE `$1`/g" to get the result of: ... DROP TABLE IF EXISTS `orders` CREATE TABLE `orders` ... I'm using the mod_rewrite syntax in the sed command as a logical example of what I'm trying to do. Any suggestions?

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  • How to iterate properly across a const set?

    - by Jared
    I'm working on a program that's supposed to represent a graph. My issue is in my printAdjacencyList function. Basically, I have a Graph ADT that has a member variable "nodes", which is a map of the nodes of that graph. Each Node has a set of Edge* to the edges it is connected to. I'm trying to iterate across each node in the graph and each edge of a node. void MyGraph::printAdjacencyList() { std::map<std::string, MyNode*>::iterator mit; std::set<MyEdge*>::iterator sit; for (mit = nodes.begin(); mit != nodes.end(); mit++ ) { std::cout << mit->first << ": {"; const std::set<MyEdge*> edges = mit->second->getEdges(); for (sit = edges.begin(); sit != edges.end(); sit++) { std::pair<MyNode*, MyNode*> edgeNodes = *sit->getEndpoints(); } } std::cout << " }" << std::endl; } getEdges is declared as: const std::set<MyEdge*>& getEdges() { return edges; }; and get Endpoints is declared as: const std::pair<MyNode*, MyNode*>& getEndpoints() { return nodes; }; The compiler error I'm getting is: MyGraph.cpp:63: error: request for member `getEndpoints' in `*(&sit)->std::_Rb_tree_const_iterator<_Tp>::operator-> [with _Tp = MyEdge*]()', which is of non-class type `MyEdge* const' MyGraph.cpp:63: warning: unused variable 'edgeNodes' I have figured out that this probably means I'm misusing const somewhere, but I can't figure out where for the life of me. Any information would be appreciated. Thanks!

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  • $_SERVER['HTTP_REFERER'] not working with Header

    - by EmmyS
    I have a site that allows public access to some pages, but requires a login for others. I have a link to the login from all pages, and what I'd like to do after a successful login is send the user back to the page they were on when they clicked the login link. I know the HTTP_REFERER can be spoofed, and sometimes stripped out by certain hosts and proxies, but since it's strictly within my own site, and only a convenience for users, I'm not too worried about it. I am curious about why it isn't working in conjunction with a redirect, though. I've set a visible field to contain the value of the http referer, and it displays correctly. So the page is getting the value of the referrer variable. But when I try this: $home_url = $_SERVER['HTTP_REFERER']; header('Location: ' . $home_url); it doesn't work. This, on the other hand, does: $home_url = 'http://' . $_SERVER['HTTP_HOST'].dirname($_SERVER['PHP_SELF']).'/discussions.php'; header('Location: ' . $home_url); So I know the header location part works. Any idea why it doesn't want to work in conjunction with the http_referer variable? (Also, does it drive anyone else nuts that referer is spelled incorrectly? I keep mistyping it using the OED spelling, silly me...)

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  • Why is my Perl script that calls FTP all of a sudden failing?

    - by Mel
    I have a script that has been running for over a year and now it is failing: It is creating a command file: open ( FTPFILE, ">get_list"); print FTPFILE "dir *.txt"\n"; print FTPFILE "quit\n"; close FTPFILE; Then I run the system command: $command = "ftp ".$Server." < get_list | grep \"\^-\" >new_list"; $code = system($command); The logic the checks: if ($code == 0) { do stuff } else { log error } It is logging an error. When I print the $code variable, I am getting 256. I used this command to parse the $? variable: $exit_value = $? >> 8; $signal_num = $? & 127; $dumped_core = $? & 128; print "Exit: $exit_value Sig: $signal_num Core: $dumped_core\n"; Results: Exit: 1 Sig: 0 Core: 0 Thanks for any help/insight.

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  • How can multiple variables be passed to a function cleanly in C?

    - by aquanar
    I am working on an embedded system that has different output capabilities (digital out, serial, analog, etc). I am trying to figure out a clean way to pass many of the variables that will control those functions. I don't need to pass ALL of them too often, but I was hoping to have a function that would read the input data (in this case from a TCP network), and then parse the data (IE, the 3rd byte contains the states of 8 of the digital outputs (according to which bit in that byte is high or low)), and put that into a variable where I can then use elsewhere in the program. I wanted that function to be separate from the main() function, but to do so would require passing pointers to some 20 or so variables that it would be writing to. I know I could make the variables global, but I am trying to make it easier to debug by making it obvious when a function is allowed to edit that variable, by passing it to the function. My best idea was a struct, and just pass a pointer to it, but wasn't sure if there was a more efficient way, especially since there is only really 1 function that would need to access all of them at once, while most others only require parts of the information that will be stored in this bunch of state variables. So anyway, is there a clean way to send many variables between functions at once that need to be edited?

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  • Problem in displaying image in FireFox

    - by Param-Ganak
    Hello friends, I have a JSP page on which I have a div tag in which there is a a IMG tag. Using this IMG tag I want to show an image in it. Here the source path of an image is comes from database so I assigned a JSP variable using JSP scriplet. This JSP variable have the source path of an image. This path of image may be of different machine or of same machine i.e. images are stored on different machine or on same machine i.e. on local machine on different drive. The problem is that how to give path of image stored on different machine as well as on same machine. I have tried different ways like by giving ip address of that machine. Here is the path that of local machine where the image is stored img src= file:\localhost\D:\ScannedSheets\testproj/batch1/IMG001.jpg style="z-index:1; position:absolute; top:0; left:0; width:850; height:1099" With this syntax the image is visible in Internet Explorer but With the same syntax Its not visible in FireFox, Google Chrome etc. Please Guide me in friends. Also tell me that how to give path of the image stored on different machine which works In Internet Explorer, FireFox, Google chrome etc.

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  • Number of characters recommended for a statement

    - by liaK
    Hi, I have been using Qt 4.5 and so do C++. I have been told that it's a standard practice to maintain the length of each statement in the application to 80 characters. Even in Qt creator we can make a right border visible so that we can know whether we are crossing the 80 characters limit. But my question is, Is it really a standard being followed? Because in my application, I use indenting and all, so it's quite common that I cross the boundary. Other cases include, there might be a error statement which will be a bit explanatory one and which is in an inner block of code, so it too will cross the boundary. Usually my variable names look bit lengthier so as to make the names meaningful. When I call the functions of the variable names, again I will cross. Function names will not be in fewer characters either. I agree a horizontal scroll bar shows up and it's quite annoying to move back and forth. So, for function calls including multiple arguments, when the boundary is reached I will make the forth coming arguments in the new line. But besides that, for a single statement (for e.g a very long error message which is in double quotes " " or like longfun1()->longfun2()->...) if I use an \ and split into multiple lines, the readability becomes very poor. So is it a good practice to have those statement length restrictions? If this restriction in statement has to be followed? I don't think it depends on a specific language anyway. I added C++ and Qt tags since if it might. Any pointers regarding this are welcome.

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  • Elements of a Java Object Array are created but without correct names

    - by Greenhouse Gases
    Hi all Im having rather an annoying problem. I have a class called Person and a class called Event which serve to create objects to be used for competitors that compete in a certain event. When I add a competitor thats fine and the GUI list updates accordingly, however when I add an event the element in the array does not take on the value of the instance variable name in the class Event and so the GUI does not show the event name, though it is being added in the array correctly. How can I make it so that the event object in each element of the listOfEvents array (which is an array of event objects) has the name of the event. I should add this is for university though this isnt the part for which we will be assessed, it is somethign i have come across and due to not being able to see the code for the GUI, I've hit the proverbial brick wall. I wont include the whole load of code Ive been writing but hopefully my description and snippets below will suffice. Any advice I would appreciate greatly. No doubt I have overlooked something simple! Many thanks. listOfEvents is declared as: Event[] listOfEvents = new Event[20]; A snippet from the Event class: public class Event { String name; Person[] participants = new Person[10]; // array of competitors for the event public Event(String name) { this.name = name; } } and its use in the addEvent method (p is a global variable): public void addEvent(String eventName) { listOfEvents[p] = new Event(eventName); p++; }

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  • "for" loop from program 7.6 from Kochan's "Programming in Objective-C"

    - by Mr_Vlasov
    "The sigma notation is shorthand for a summation. Its use here means to add the values of 1/2^i, where i varies from 1 to n. That is, add 1/2 + 1/4 + 1/8 .... If you make the value of n large enough, the sum of this series should approach 1. Let’s experiment with different values for n to see how close we get." #import "Fraction.h" int main (int argc, char *argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; Fraction *aFraction = [[Fraction alloc] init]; Fraction *sum = [[Fraction alloc] init], *sum2; int i, n, pow2; [sum setTo: 0 over: 1]; // set 1st fraction to 0 NSLog (@"Enter your value for n:"); scanf ("%i", &n); pow2 = 2; for (i = 1; i <= n; ++i) { [aFraction setTo: 1 over: pow2]; sum2 = [sum add: aFraction]; [sum release]; // release previous sum sum = sum2; pow2 *= 2; } NSLog (@"After %i iterations, the sum is %g", n, [sum convertToNum]); [aFraction release]; [sum release]; [pool drain]; return 0; } Question: Why do we have to create additional variable sum2 that we are using in the "for" loop? Why do we need "release previous sum" here and then again give it a value that we just released? : sum2 = [sum add: aFraction]; [sum release]; // release previous sum sum = sum2; Is it just for the sake of avoiding memory leakage? (method "add" initializes a variable that is stored in sum2)

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