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• Problem understanding Inheritance

  - by dhruvbird

  I've been racking my brains over inheritance for a while now, but am still not completely able to get around it. For example, the other day I was thinking about relating an Infallible Human and a Fallible Human. Let's first define the two: Infallible Human: A human that can never make a mistake. It's do_task() method will never throw an exception Fallible Human: A human that will occasionally make a mistakes. It's do_task() method may occasionally throw a ErrorProcessingRequest Exception The question was: IS an infallible human A fallible human OR IS a fallible human AN infallible human? The very nice answer I received was in the form of a question (I love these since it gives me rules to answer future questions I may have). "Can you pass an infallible human where a fallible human is expected OR can you pass a fallible human where an infallible human is expected?" It seems apparent that you can pass an infallible human where a fallible human is expected, but not the other way around. I guess that answered my question. However, it still feels funny saying "An infallible human is a fallible human". Does anyone else feel queasy when they say it? It almost feels as if speaking out inheritance trees is like reading out statements from propositional calculus in plain English (the if/then implication connectives don't mean the same as that in spoken English). Does anyone else feel the same?

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• JQuery event that triggers after CSS is loaded?

  - by Dave

  (I posted this on the jquery forums but it's still awaiting moderation, so I thought I'd try my luck here since stackoverflow is so awesome. If I get an answer I'll post it here.) Maybe someone can help me with this, I have a couple of links on my page (inside a <div id="theme-selector">) which allow you to change the CSS stylesheets: $('#theme-selector a').click(function(){ var path = $(this).attr('href'); $('head link').remove(); $('head').append('<link type="text/css" href="'+path+'" rel="stylesheet" />'); return false; }); Now, after I've changed the style on the page, I want to get the new background color, using the following code (which I put after the $('head').append call): var bgcolor = $('body').css('background-color'); alert(bgcolor); The problem is, I think, that it takes some time for the browser to download the new stylesheet and I sometimes get the old background color in my alert message. Is there some event I can bind that will only alert me after all the stylesheets are loaded on the page? At the moment, all I can think of is using a setTimeout(function(){}, 5000); which isn't great, because what if it takes longer/shorter to load all the CSS on the page. Let me know if I need to clarify anything and I can provide more code. Thanks in advance.

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• Jquery dynamic dropdown event not firing

  - by kevin

  Hi i am trying to create dropdownlists dynamically and populating the contents via an ajax call, this sort of works in the sense that the drop down is created and populated as required but its 'change' event does not fire. I am posting the code below, if anyone can spot something obvious, can you please let me know regards $(document).ready(function () { $("#positions select").change(function (e) { alert("in"); var id = $("#category_id").val(); $.getJSON("/Category/GetSubCategories/" + id, function (data) { if (data.length > 0) { alert(data.length); var position = document.getElementById('positions'); var tr = position.insertRow(7); var td1 = tr.insertCell(-1); var td = tr.insertCell(-1); var sel = document.createElement("select"); sel.name = 'sel'; sel.id = 'sel'; sel.setAttribute('class', 'category'); td.appendChild(sel); $.each(data, function (GetSubCatergories, category) { $('#sel').append($("<option></option>"). attr("value", category.category_id). text(category.name)); }); } }); }); });

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• What job title should be most suitable for my object in resume and what salary range should I expect

  - by user354177

  I was a classic asp developer in 2000. After a year of full-time employment, I left the field. I found a part-time position as an asp developer again in 2005 and taught myself vb.net. In 2007, I got the current full-time job as an Asp.net web developer. I taught myself C#, LING t0 SQL, Web Services, AJAX, and creating all kinds of reports with reporting services. One and half years ago, I sent myself to part-time graduate program in Database and Web Systems. I'll have two semesters to go and so far my GPA is 4.0/4.0. My job responsibility is to collect business requirements from other departments, design the database, write stored procedures, create aspx pages, and create reports. I love what I do and want to advance my career to the next level. What I enjoy most is to design the relational database. I would want to become an .Net Architect eventually. I got an interview. They were looking for asp.net web developer. But I was surprised and disappointed that position would only create aspx pages. I would not even have opportunity to write stored procedures, let alone design the database (those would be provided by another group). Furthermore, they asked me some detailed questions about web forms, some of which I did not know the answers. they might be disappointed as well. I am eager to learn and can apply what I learn to real projects right away. I believe no matter what specific skills I am lacking for a new position, I can catch up quickly. I am looking for $70k range job. The object in my resume is Experience C# Web Application Developer. Due to the experience from last interview, I wonder if the object is really what I want. Could somebody answer my questions? Thank you.

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• jQuery/Javascript Cookies and variable returning with value [object Object]

  - by user1706661

  I am attempting to set a cookie to a site using jQuery, ONLY if the user came from a specific site. In this case, lets use -http://referrersite.com- as the site they must come from for the cookie to be created as an example. The cookie value is being stored in a variable and everything up to this point is working fine. There is a conditional statement checking whether the user came from the referred site, if the cookie exists already and if the cookie doesn't exist and the user did not come from the referred site. If the user came from the referred site the cookie is created and stored in a variable. If the cookie already exists, it is then stored in a variable. If the cookie does not exist and the user did not come from the referred site I am assigning the variable a static string of characters - this is where the issue lies. When the variable is alerted from the non referred site and no existing cookie, it returns: [object Object], not the static string of characters. The code I am using is below: $(document).ready(function() { var referrer = document.referrer; if(referrer == "http://referrersite.com") { $.cookie("code","123456", { expires: 90, path: '/' }); cookieContainer = $.cookie("code"); alert(cookieContainer); } else if($.cookie("code")) { cookieContainer = $.cookie("code"); alert(cookieContainer); } else if($.cookie("code") == null && referrer != "http://referrersite.com") { cookieContainer = "67890"; alert(cookieContainer); } }); Please let me know if there is something I am missing as the code to me looks like it should work. Thanks!

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• Cryptography for P2P card game

  - by zephyr

  I'm considering writing a computer adaptation of a semi-popular card game. I'd like to make it function without a central server, and I'm trying to come up with a scheme that will make cheating impossible without having to trust the client. The basic problem as I see it is that each player has a several piles of cards (draw deck, current hand and discard deck). It must be impossible for either player to alter the composition of these piles except when allowed by the game rules (ie drawing or discarding cards), nor should players be able to know what is in their or their oppponent's piles. I feel like there should be some way to use something like public-key cryptography to accomplish this, but I keep finding holes in my schemes. Can anyone suggest a protocol or point me to some resources on this topic? [Edit] Ok, so I've been thinking about this a bit more, and here's an idea I've come up with. If you can poke any holes in it please let me know. At shuffle time, a player has a stack of cards whose value is known to them. They take these values, concatenate a random salt to each, then hash them. They record the salts, and pass the hashes to their opponent. The opponent concatenates a salt of their own, hashes again, then shuffles the hashes and passes the deck back to the original player. I believe at this point, the deck has been randomized and neither player can have any knowledge of the values. However, when a card is drawn, the opponent can reveal their salt, allowing the first player to determine what the original value is, and when the card is played the player reveals their own salt, allowing the opponent to verify the card value.

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• Custom collision

  - by bali182

  I was recently assigned to create a siple game using the Corona SDK. The main pillar of the game would be a simple event: the user should put a ball in a basket, and I should be able to handle this event. Here is a picture for better understanding: I successfully managed to create the collision shape for the basket, but i have trouble with the collision of the inside of this basket. My first thought was the following: create a new shape size and position it to fit the "belly" of this basket add it to the physics-world, and listen to the collision. With hybrid drawing it looks like this: But there is a problem: if i add this shape to the physics, it wouldn't let the ball fall into the, basket, it will handle this shape as a solid object as well. So my question is: How could I get this custom object to collide, without blocking the ball to fall through it? I have read a lots of forum post with similar questions but none of them got a proper answer. There must be a way to do this in an elegant way. And one note: Please don't suggest checking the collision manually, with rectangle intersection, because in this simple case it would work, but later I may need to change the shape of the basket, and then it will be useless!

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• Is it okay to violate the principle that collection properties should be readonly for performance?

  - by uriDium

  I used FxCop to analyze some code I had written. I had exposed a collection via a setter. I understand why this is not good. Changing the backing store when I don't expect it is a very bad idea. Here is my problem though. I retrieve a list of business objects from a Data Access Object. I then need to add that collection to another business class and I was doing it with the setter method. The reason I did this was that it is going to be faster to make an assignment than to insert hundreds of thousands of objects one at a time to the collection again via another addElement method. Is it okay to have a getter for a collection in some scenarios? I though of rather having a constructor which takes a collection? I thought maybe I could pass the object in to the Dao and let the Dao populate it directly? Are there any other better ideas?

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• Does Entity Framework saves related classes automatically?

  - by herbatnic

  Let's assume that we have such classes public class A{ string someField { get; set; } public virtual B B {get; set; } } public class B { int someIntField {get; set; } [ForeignKey("Id")] [Required] public virtual A A { get; set; } } In code I create new instances for both of them and making relation like: A a = new A () { someField = "abcd"}; B b = new B () { someIntField = 42 }; A.B = b; B.A = a; Should I using DBContext to save both classes like that: using (var db = new myDbContext()) { myDbContext.As.Add(A); myDbContext.Bs.Add(B); myDBContext.SaveChanges(); } Or saving it like that: using (var db = new myDbContext()) { myDbContext.As.Add(A); myDbContext.SaveChanges(); } is enough to store related objects into database?

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• How is machine code understood by the machine

  - by Kraken

  I have a very naive question here, and I would like you to correct me on whatever wrong concepts I put out here. The question is as follows: I have ubuntu installed on my machine, now I write a helloWorld.c program in C language. Now, on the operating system I have a compiler installed, when I execute my helloWorld.c program, the OS schedules the compiler and that basically compiles my code into machine code, which eventually, I execute. Now my kernel code is written in C, then how does my machine interprets that code? Say my kernel code is helloWorld.c, now would not I require any compiler, to compile this code. Also, if I hardcode a compiler in maybe ROM or something, then what language is it written in? Assembly language? Let me know if I have made myself clear with the problem. Thanks. EDIT: By kernel code I mean, the code for operating system. Operating System code. I guess it is written in C right?

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• Dependency Injection: How to pass DB around?

  - by Stephane

  Edit: This is a conceptual question first and foremost. I can make applications work without knowing this, but I'm trying to learn the concept. I've seen lots of videos with related classes and that makes sense, but when it comes to classes wrapping around other classes, I can't seem to grasp where things should be instantiated/passed around. =-=-=-=-=-=-= Question: Let's say I have a simple page that loads data from a table, manipulates the result and displays it. Simple. I'm going to use '=' for instantiating a class and '-' for passing a class in using constructor injection. It seems to me that the database has to be passed from one end of the application to the other which doesn't seem right. Here's how I would do it if I wanted to separate concerns: index =>Controller =>Model Layer =>Database =>DAO->Database I have this rule in my head that says I'm not supposed to create objects inside other objects. So what do I do with the Database? Or even the Model for that matter? I'm obviously missing something so basic about this. I would love a simplified example so that I can move forward in my code. I feel really hamstrung by this.

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• Form doesn't resize smoothly with a timer event

  - by BDotA

  I have a grid control at the bottom of my form and it can be shown or hidden if user wants to show/hide it. So one way was to well use AutoSize of the form and change the Visuble property of that grid to true or false,... But I thought let's make it a little cooler! so I wanted the form to resize a little more slowly, like a garage door! So I dropped a Timer on the form and started increasing the height of the form little by little while the timer ticks... so something like this when user says show/hide the grid: timer1.Enabled = true; timer1.Start(); and something like this on the timer_click event: this.Height = this.Height + 5; if(this.Height -10 > ErrorsGrid.Bottom ) timer1.Stop(); It kind of works but still not perfect. For example it lags at the very beginning, stop a like a second and then start moving it...So now with this idea in mind what alterations do you suggest I should do to make this thing look and work better?

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• Best Approach for Checking and Inserting Records

  - by nevets1219

  In one of our existing C programs which purpose is: Open connection to DB for record in all_record: if record contain certain data: if record is NOT in table A: // see #1 insert record information into table A and B // see #2 Close connection to DB select field from table where field=XXX 2 inserts This is typically done every X months to sync everything up or so I'm told. I've also been told that this process takes roughly a couple of days. There is (currently) at most 2.5million records (though not necessarily all 2.5m will be inserted). One of the table contains 10 fields and the other 5 fields. There isn't much to be done about iterating through the records since that part can't be changed at the moment. What I would like to do is speed up the part where I query MySQL. I'm not sure if I have left out any important details -- please let me know! I'm also no SQL expert so feel free to point out the obvious. I thought about: Putting all the inserts into a transaction (at the moment I'm not sure how important it is for the transaction to be all-or-none or if this affects performance) Using Insert X Where Not Exists Y LOAD DATA INFILE (but that would require I create a (possibly) large temp file) I read that (hopefully someone can confirm) I should drop indexes so they aren't re-calculated. mysql Ver 14.7 Distrib 4.1.22, for sun-solaris2.10 (sparc) using readline 4.3

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• How can I use SQL Server's full text search across multiple rows at once?

  - by Morbo

  I'm trying to improve the search functionality on my web forums. I've got a table of posts, and each post has (among other less interesting things): PostID, a unique ID for the individual post. ThreadID, an ID of the thread the post belongs to. There can be any number of posts per thread. Text, because a forum would be really boring without it. I want to write an efficient query that will search the threads in the forum for a series of words, and it should return a hit for any ThreadID for which there are posts that include all of the search words. For example, let's say that thread 9 has post 1001 with the word "cat" in it, and also post 1027 with the word "hat" in it. I want a search for cat hat to return a hit for thread 9. This seems like a straightforward requirement, but I don't know of an efficient way to do it. Using the regular FREETEXT and CONTAINS capabilities for N'cat AND hat' won't return any hits in the above example because the words exist in different posts, even though those posts are in the same thread. (As far as I can tell, when using CREATE FULLTEXT INDEX I have to give it my index on the primary key PostID, and can't tell it to index all posts with the same ThreadID together.) The solution that I currently have in place works, but sucks: maintain a separate table that contains the entire concatenated post text of every thread, and make a full text index on THAT. I'm looking for a solution that doesn't require me to keep a duplicate copy of the entire text of every thread in my forums. Any ideas? Am I missing something obvious?

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• Not getting an array as result (calling a webservice by AJAX-JSON)

  - by Pasargad

  I'm trying to get the result of my web service as an array and then loop over the result to fetch all of the data; what I have done so far: In my web service when I return the result I use return json_encode($newFiles); and the result is as following: "[{\"path\":\"c:\\\\my_images\\\\123.jpg\",\"ID\":\"123\",\"FName\":\"John\",\"LName\":\"Brown\",\"dept\":\"Hr\"}]" tehn in my Web application I'm calling the rest web service by the following code in the RestService class: public function getNewImages($time) { $url = $this->rest_url['MyService'] . "?action=getAllNewPhotos&accessKey=" . $this->rest_key['MyService'] . "&lastcheck=" . $time; $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); $data = curl_exec($ch); if ($data) { return json_decode($data); } else { return null; } } and then in my controller I have the following code: public function getNewImgs($time="2011-11-03 14:35:08") { $newImgs = $this->restservice->getNewImages($time); echo json_encode$newImgs; } and I'm calling this `enter code here`controller method by AJAX: $("#searchNewImgManually").click(function(e) { e.preventDefault(); $.ajax({ type: "POST", async: true, datatype: "json", url: "<?PHP echo base_url("myProjectController/getNewImgs"); ?>", success: function(imgsResults) { alert(imgsResults[0]); } }); }); but instead of giving me the first object it is just giving me quotation mark (the first charachter of the result) " Why is that? I'm passing in JSON format and in AJAX I mentioned datatype as "JSON" ! Please let me know if you need more clarification! Thanks :)

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• Extend footer wrap to width of page.

  - by hawkeye126

  I've made a footer wrap outside the content wrap (which everything else is in). I would like to make the footer wrap extend to fill the width of the page and I would like it to be fixed on the bottom. Here's the code: footerWrap { background-color:#000; width: auto; } footer { margin: auto; text-align:center; width:965px; height:150px; background-color:#000; border:#000 inset medium; } The website is item9andthemadhatters.com please let me know if you need any other code or info. Thanks!! update: html { padding:0; height:100%; width: 100%; } body{ margin: -1px 0 0 0; background-color:#FFF; font-family: calibri; background-image:url(images/item9HeaderSideFiller.gif); background-repeat: repeat-x; padding:0; height:100%; width: 100%; } wrap { width: 965px; margin:auto auto; min-height:462px; max-height:4000 px; footerWrap { background-color:#000; position:absolute; bottom:0; width:100% } footer { margin: auto; text-align:center; width:965px; height:150px; background-color:#000; } }

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• What choices do I have for a future in software development?

  - by user354892

  After graduating from college with a degree in mathematics and a minor in computer science, I took over a year to find my first programming job. I very much enjoy my work environment, but sometimes I feel like I'm not developing professionally as quickly as I am capable of. My company does mostly web programming. The project that I work on is basically a front-end for a SQL database. The entire project is (AFAIK) coded is VB.NET. I've been working on the back-end logic of the program. After some time on the job, we decided that designing web pages is not my cup of tea. It seems like the thing that I spend more time on than anything else is searching the web and SO for information about poorly documented .net and web APIs. This does not make me happy; is this normal for a programming job; I don't think it is. It really hit me the other day when i saw a question about math asked here and I didn't know the answer; I feel like my knowledge is going stale! I was previously almost hired by another company where they design graphic-intensive battle simulations for the military. I sometimes wonder what my life might be like if I had that job. I feel like my math and problem solving skills might have been a better fit at this other company. Within the wide field of software development, there are a number of directions in which to go as evidenced by the huge variety of topics discussed here on StackOverflow. I would like to feel like I'm going in the direction where I will make the most of my skills and have a satisfying career. Let me word this question as clearly as possible: given the wide breadth of the field of software development, how does it break down into sub-fields and what are the considerations for developing a software development career. I do not want to manage my career by default.

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• byte and short data types in Java can accept the value outside the range by explicit cast. The higher data types however can not. Why?

  - by Lion

  Let's consider the following expressions in Java. byte a = 32; byte b = (byte) 250; int i = a + b; This is valid in Java even though the expression byte b = (byte) 250; is forced to assign the value 250 to b which is outside the range of the type byte. Therefore, b is assigned -6 and consequently i is assigned the value 26 through the statement int i = a + b;. The same thing is possible with short as follows. short s1=(short) 567889999; Although the specified value is outside the range of short, this statement is legal. The same thing is however wrong with higher data types such int, double, folat etc and hence, the following case is invalid and causes a compile-time error. int z=2147483648; This is illegal, since the range of int in Java is from -2,147,483,648 to 2147483647 which the above statement exceeds and issues a compile-time error. Why is such not wrong with byte and short data types in Java?

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• What does Postgres do when BEGIN is run on a connection in autocommit mode?

  - by DNS

  I'm trying to better understand the concept of 'autocommit' when working with a Postgres (psycopg) connection. Let's say I have a fresh connection, set its isolation level to ISOLATION_LEVEL_AUTOCOMMIT, then run this SQL directly, without using the cursor begin/rollback methods (as an exercise; not saying I actually want to do this): INSERT A INSERT B BEGIN INSERT C INSERT D ROLLBACK What happens to INSERTs C & D? Is autocommit is purely an internal setting in psycopg that affects how it issues BEGINs? In that case, the above SQL is unafected; INSERTs A & B are committed as soon as they're done, while C & D are run in a transaction and rolled back. What isolation level is that transaction run under? Or is autocommit a real setting on the connection itself? In that case, how does it affect the handling of BEGIN? Is it ignored, or does it override the autocommit setting to actually start a transaction? What isolation level is that transaction run under? Or am I completely off-target?

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• Hibernate OneToMany and ManyToOne confusion! Null List!

  - by squizz

  I have two tables... For example - Company and Employee (let's keep this real simple) Company( id, name ); Employee( id, company_id ); Employee.company_id is a foreign key. My entity model looks like this... Employee @ManyToOne(cascade = CascadeType.PERSIST) @JoinColumn(name = "company_id") Company company; Company @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER) @JoinColumn(name = "company_id") List<Employee> employeeList = new ArrayList<Employee>(); So, yeah I want a list of employees for a company. When I do the following... Employee e = new Employee(); e.setCompany(c); //c is an Company that is already in the database. DAO.insertEmployee(e); //this works fine! If I then get my Company object it's list is empty! Ive tried endless different ways from the Hibernate documentation! Obviously not tried the correct one yet! I just want the list to be populated for me or find out a sensible alternative. Help would be greatly appreciated, thanks!

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• How to implement the "System.out.println(ClassName::MethodName <then my message>)" of Eclipse in Netbeans?

  - by Sen

  I would like to know if there is the same feature as in eclipse to automatically generate and print the System.out.println(ClassName::MethodName <then my message>) functionality (which will print the class name and method name for debugging in the console) in Netbeans also. For example, in Eclipse Editor, Typing syst + Ctrl+ Space will auto generate a System.out.println(ClassName::MethodName ) type output in the console. Is such a method available in Netbeans? As of now, I have only two methods here in Netbeans: sout + Tab (System.out.println()) and soutv + Tab (System.out.println(prints the variable used just above the line)) automatically. Let me rephrase, instead of myMethod1, I want to get the enclosing method name. Eg. : public class X { public void myMethod1(int a) { System.out.println(X::myMethod1()); // This should be produced when I type the Code-Template abbreviation (example: syst) and press tab (or corresponding key). } } public class Y { public void myMethod2(int b) { System.out.println(Y::myMethod2()); // This should be produced when I type the Code-Template abbreviation (example: syst) and press tab (or corresponding key). } } Update: With the following code template: syst = System.out.println("${classVar editable="false" currClassName default="getClass()"}"); I am able to print the classname, but still no clue for the Method name.

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• How to display controllers with proper aligning in iPhone screen ?

  - by chatcja

  I have a issue of displaying information in iPhone screen. Case is as follows. I crated a view-based application in Xcode name as myView. Then open myViewViewController.xib interface builder, change back groung color and added label at top-let (0, 0) of the view. Then I add new file named as myView2ViewController, which is subclass of UIViewController and corresponding XIB also generated. Open myView2ViewController in IB and added a label at top-left as previous. Also changed the background color. In the "applicationDidFinishLaunching" of AppDeligate do following myView2ViewController *mView = [[myView2ViewController alloc] initWithNibName:@"myView2ViewController" bundle:nil]; [window addSubview:mView.view]; When I run the application, it is shown as upper part of the Label is sheared. It seems as whole UI has been moved 20 px upper (Because, there is a horizontal space in the bottom). I guess this is due to some positioning. But still I could not found any way to fix it. Hope somebody will help me to identify this issue !!

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• Best loose way to get objects with common base class

  - by Michael Teper

  I struggled to come up with a good title for this question, so suggestions are welcome. Let's say we have an abstract base class ActionBase that looks something like this: public abstract class ActionBase { public abstract string Name { get; } public abstract string Description { get; } // rest of declaration follows } And we have a bunch of different actions defined, like a MoveFileAction, WriteToRegistryAction, etc. These actions get attached to Worker objects: public class Worker { private IList<ActionBase> _actions = new List<ActionBase>(); public IList<ActionBase> Actions { get { return _actions; } } // worker stuff ... } So far, pretty straight-forward. Now, I'd like to have a UI for setting up Workers, assigning Actions, setting properties, and so on. In this UI, I want to present a list of all available actions, along with their properties, and for that I'd want to first gather up all the names and descriptions of available actions (plus the type) into a collection of the following type of item: public class ActionDescriptor { public string Name { get; } public string Description { get; } poblic Type Type { get; } } Certainly, I can use reflection to do this, but is there a better way? Having Name and Description be instance properties of ActionBase (as opposed to statics on derived classes) smells a bit, but there isn't an abstract static in C#. Thank you!

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• Safe way for getting/finding a vertex in a graph with custom properties -> good programming practice

  - by Shadow

  Hi, I am writing a Graph-class using boost-graph-library. I use custom vertex and edge properties and a map to store/find the vertices/edges for a given property. I'm satisfied with how it works, so far. However, I have a small problem, where I'm not sure how to solve it "nicely". The class provides a method Vertex getVertex(Vertexproperties v_prop) and a method bool hasVertex(Vertexproperties v_prop) The question now is, would you judge this as good programming practice in C++? My opinion is, that I have first to check if something is available before I can get it. So, before getting a vertex with a desired property, one has to check if hasVertex() would return true for those properties. However, I would like to make getVertex() a bit more robust. ATM it will segfault when one would directly call getVertex() without prior checking if the graph has a corresponding vertex. A first idea was to return a NULL-pointer or a pointer that points past the last stored vertex. For the latter, I haven't found out how to do this. But even with this "robust" version, one would have to check for correctness after getting a vertex or one would also run into a SegFault when dereferencing that vertex-pointer for example. Therefore I am wondering if it is "ok" to let getVertex() SegFault if one does not check for availability beforehand?

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• Correct way to initialize dynamic Array in C++

  - by mef

  Hey guys, I'm currently working on a C++ project, where dynamic arrays often appear. I was wondering, what could be the correct way to initialize a dynamic array using the new-operator? A colleague of mine told me that it's a no-no to use new within the constructor, since a constructor is a construct that shouldn't be prone to errors or shouldn't fail at all, respectively. Now let's consider the following example: We have two classes, a more or less complex class State and a class StateContainer, which should be self-explained. class State { private: unsigned smth; public: State(); State( unsigned s ); }; class StateContainer { private: unsigned long nStates; State *states; public: StateContainer(); StateContainer( unsigned long n ); virtual ~StateContainer(); }; StateContainer::StateContainer() { nStates = SOME_DEFINE_N_STATES; states = new State[nStates]; if ( !states ) { // Error handling } } StateContainer::StateContainer( unsigned long n ) { nStates = n; try { states = new State[nStates] } catch ( std::bad_alloc &e ) { // Error handling } } StateContainer::~StateContainer() { if ( states ) { delete[] states; states = 0; } } Now actually, I have two questions: 1.) Is it ok, to call new within a constructor, or is it better to create an extra init()-Method for the State-Array and why? 2.) Whats the best way to check if new succeeded: if (!ptr) std::cerr << "new failed." or try { /*new*/ } catch (std::bad_alloc) { /*handling*/ } 3.) Ok its three questions ;o) Under the hood, new does some sort of ptr = (Struct *)malloc(N*sizeof(Struct)); And then call the constructor, right?

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