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  • Why do they initialize pointers this way?

    - by Rob
    In almost all of the books I read and examples I go through I see pointers initialized this way. Say that I have a class variable NSString *myString that I want to initialize. I will almost always see that done this way: -(id)init { if (self = [super init]) { NSString *tempString = [[NSString alloc] init]; myString = tempString; [tempString release]; } return self; } Why can't I just do the following? -(id)init { if (self = [super init]) { myString = [[NSString alloc] init]; } return self; } I don't see why the extra tempString is ever needed in the first place, but I could be missing something here with memory management. Is the way I want to do things acceptable or will it cause some kind of leak? I have read the Memory Management Guide on developer.apple.com and unless I am just missing something, I don't see the difference.

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  • why this with excel sheet reading?

    - by Lalit
    Hi, I am reading the excel sheet from c# interop services cell by cell. where as my excel sheet have Date cells. It generates some double values , I am converting them in date by : double dbl = Convert.ToDouble(((Excel.Range)worksheet.Cells[iRowindex, colIndex_q17]).Value2); string strDate3 = DateTime.FromOADate(dbl).ToShortDateString(); drRow[dtSourceEXLData.Columns[constants.VisualDate]] = strDate3; ok? but some time happening the value of ((Excel.Range)worksheet.Cells[iRowindex,colIndex_q17]).Value2 getting date formate.why this is happeing? plaease guide me. it throws excepion of "input string not in correct format".why it is not generating double value like other cell of same column?

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  • Why call iframe from javascript

    - by sammville
    I want to know why some ad codes or embed codes don't directly give you iframe code to embed on your site instead they give a javascript code which links to another javascript file on their server. The file on their server calls the iframe which serves the content. Why is this done and what are the benefits of this method. Example: this is the code issued by amazon: <script type="text/javascript" src="http://www.assoc-amazon.co.uk/s/ads.js"></script> Which opens another javascript file that calls the iframe.

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  • Why do I have to give an identifier?

    - by Knowing me knowing you
    In code: try { System.out.print(fromClient.readLine()); } catch(IOException )//LINE 1 { System.err.println("Error while trying to read from Client"); } In code line marked as LINE 1 compiler forces me to give an identifier even though I'm not using it. Why this unnatural constrain? And then if I type an identifier I'm getting warning that identifier isn't used. It just doesn't make sense to me, forcing a programmer to do something unnecesarry and surplus. And after me someone will revise this code and will be wondering if I didn't use this variable on purpouse or I just forgot. So in order to avoid that I have to write additional comment explaining why I do not use variable which is unnecessary in my code. Thanks

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  • why is there different syntax same outcome?

    - by Lizard
    Why is there different syntax same outcome? For example # Example 1 if($myCondition == true) : #my code here endif; if($myCondition == true) { #my code here } # Example 2 foreach($films as $film) : #my code here endforeach; foreach($films as $film) { #my code here } Also I have been using <?= for ages now and i now understand that is deprecated and I should be using <?php echo Is this the case and why? Its alot more annoying to have to write that out each time. What are your thoughts?

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  • Why should i POST data rather then GET?

    - by acidzombie24
    I know you dont want to POST a form with a username and password where anyone could use the history to see or situations where repeat actions may not be desired (refreshing a page = adding an item to a cart may not be desired). So i have an understanding when i may want to use one over the other. But i could always have the server redirect the url after a get to get around the cart problem and maybe most of my forms will work perfectly fine with get. WHY should i use POST over get? I dont understand the benefits of one over the other. I do notice post doesnt add data to the history/url and will warn you about refreshing the page but those are the only two differences i know of. Why as a developer might i want to use one over the other?

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  • Why is the output like this?

    - by javatechi
    class another { public void method(Object o) { System.out.println("This is in method which takes object"); } public void method(String s) { System.out.println("This is method which takes string"); } } public class NewClass { public static void main(String args[]) { another an = new another(); an.method(null); } } When I try to execute this, I get This is method which takes string as the output. Why not "This is in method which takes object"? Object can also be null and string can also be null, why doesn't it invoke first method?

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  • Why do we need Web-Api? [closed]

    - by user437973
    I was just wondering what the deal is with Asp.net Web-Api. Why did we need a separate type of controller in order to facilitate varying content types for action results? Why wasn't this capability just baked into the ASP.Net MVC base controller? Anyway, I was just wondering if there was a compelling reason to use both types of controllers within the same project, assuming that the project was being freshly created, or if this project structure was due to an inherent technical limitation. Would it be possible to have ApiControllers fulfill the purpose of an MVC Controller in all cases by just serving HTML when that is the specified accept type? It just seems to me like a lot of unnecessary repetition to have to re-implement the same types of actions using both types of controllers if you want those actions to be available to your web application through the API and through the web interface.

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  • Why does this C program compile?

    - by AdmiralJonB
    I've just come across someone's C code that I'm confused as to why it is compiling. There are two points I don't understand. First, the function prototype has no parameters compared to the actual function definition. Secondly, the parameter in the function definition doesn't have an type. #include <stdio.h> int func(); int func(param) { return param; } int main() { int bla = func(10); printf("%d",bla); } Could someone please explain to me why this works? I've tested it in a couple of compilers and it works fine.

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  • Why the streams in C++?

    - by oh boy
    As you all know there are libraries using streams such as iostream and fstream. My question is: Why streams? Why didn't they stick with functions similar to print, fgets and so on (for example)? They require their own operators << and >> but all they do could be implemented in simple functions like above, also the function printf("Hello World!"); is a lot more readable and logical to me than cout << "Hello World"; I also think that all of those string abstractions in C++ all compile down to (less efficient) standard function calls in binary.

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  • Why Hadoop is tightly bound to linux?

    - by user1676346
    I am new with Hadoop. What are the specific reasons why Hadoop is so tightly bound with Linux, and the cluster it runs upon is homogeneous? I'm looking for really specific details that can tell me why Hadoop does not work well with windows, and if there are some libraries some specific scripts that are involved? My project is to deploy Hadoop without using Cygwin. I have already seen the article from Hayes Davis where he explained how to install Hadoop without Cygwin, but he said that there are some bugs. I might start from scratch to properly configure Hadoop on Windows, but if any one can explain what, specifically, are the reasons that Hadoop doesn't work well on windows that would be very helpful.

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  • Why my mysql DISTINCT doesn't work ?

    - by belaz
    Hello, Why the two query below return duplicate member_id and not the third ? i need the second query to work with distinct. Anytime i run a GROUP BY, this query is incredibly slow and the resultset doesn't return the same value as distinct (the value is wrong). SELECT member_id, id FROM ( SELECT * FROM table1 ORDER BY created_at desc ) as u LIMIT 5 +-----------+--------+ | member_id | id | +-----------+--------+ | 11333 | 313095 | | 141831 | 313094 | | 141831 | 313093 | | 12013 | 313092 | | 60821 | 313091 | +-----------+--------+ SELECT distinct member_id, id FROM ( SELECT * FROM table1 ORDER BY created_at desc ) as u LIMIT 5 +-----------+--------+ | member_id | id | +-----------+--------+ | 11333 | 313095 | | 141831 | 313094 | | 141831 | 313093 | | 12013 | 313092 | | 60821 | 313091 | +-----------+--------+ SELECT distinct member_id FROM ( SELECT * FROM table1 ORDER BY created_at desc ) as u LIMIT 5 +-----------+ | member_id | +-----------+ | 11333 | | 141831 | | 12013 | | 60821 | | 64980 | +-----------+ my table sample CREATE TABLE `table1` ( `id` int(11) NOT NULL AUTO_INCREMENT, `member_id` int(11) NOT NULL, `s_type_id` int(11) NOT NULL, `created_at` datetime DEFAULT NULL, PRIMARY KEY (`id`), KEY `s_FI_1` (`member_id`), KEY `s_FI_2` (`s_type_id`) ) ENGINE=InnoDB AUTO_INCREMENT=313096 DEFAULT CHARSET=utf8;

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  • Why does a non-constant offsetof expression work?

    - by Chris J. Kiick
    Why does this work: #include <sys/types.h> #include <stdio.h> #include <stddef.h> typedef struct x { int a; int b[128]; } x_t; int function(int i) { size_t a; a = offsetof(x_t, b[i]); return a; } int main(int argc, char **argv) { printf("%d\n", function(atoi(argv[1]))); } If I remember the definition of offsetof correctly, it's a compile time construct. Using 'i' as the array index results in a non-constant expression. I don't understand how the compiler can evaluate the expression at compile time. Why isn't this flagged as an error?

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  • Why is rails called a dsl?

    - by b_ayan
    Recently, when I tried to explain why Rails is a DSL to an intern at my organisation, I was not able to articulate my reasonings to the effect I would like to. Maybe I do not understand the space well enough to teach the nuances. Redirecting him to Martin Fowler' article or the google ranked one InfoQ or other material has not helped much either. Can some explain why Rails is a DSL with an example / parallel situation which is not voodoo stuff for someone who is fairly new to the world of code? Understanding the ideology might also help in elaborating the intricacies of the rails ecosystem?

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  • Why do I get Bind Variable "DeliveryDate_Variable" is NOT DECLARED(Completely New TO Oracle)

    - by GigaPr
    Hi, I have the following script in Oacle I do not understand why i get Bind Variable "DeliveryDate_Variable" is NOT DECLARED Everything looks ok to me VARIABLE RollingStockTypeId_Variable NUMBER := 1; VARIABLE DeliveryDate_Variable DATE := (to_date('2010/8/25:12:00:00AM', 'yyyy/mm/dd:hh:mi:ssam')); SELECT DISTINCT rs.Id, rs.SerialNumber, rsc.Name AS Category, (SELECT COUNT(Id) from ROLLINGSTOCKS WHERE ROLLINGSTOCKCATEGORYID = rsc.id) as "Number Owened", (SELECT COUNT(rs.Id) FROM ROLLINGSTOCKS rs WHERE rs.ID NOT IN( select RollingStockId from ROLLINGSTOCK_ORDER WHERE :DeliveryDate_Variable BETWEEN DEPARTUREDATE AND DELIVERYDATE) AND rs.RollingStockCategoryId IN (Select Id from RollingStockCategories Where RollingStockTypeId = :RollingStockTypeId_Variable) AND rs.RollingStockCategoryId = rsc.Id) AS "Number Available" FROM ROLLINGSTOCKS rs JOIN RollingStockCategories rsc ON rsc.Id = rs.RollingStockCategoryId WHERE rs.ID NOT IN( select RollingStockId from ROLLINGSTOCK_ORDER WHERE :DeliveryDate_Variable BETWEEN DEPARTUREDATE AND DELIVERYDATE ) AND rs.RollingStockCategoryId IN ( Select Id from RollingStockCategories Where RollingStockTypeId = :RollingStockTypeId_Variable ) ORDER BY rsc.Name

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  • MEF Why is ComposePart an extension method?

    - by ILovePaperTowels
    CompositionContainer.ComposePart is an extension method. why is that? Looking into the System.Componentmodel.Composition assembly, it looks like it's because it is ONLY meant to work with the attributed programming model while the .Compose() method is able to take in exports as long as it is a composablepart. ComposePart is even hosted in the 'AttributedModelServices' class which makes me think I'm correct. Am I correct on this? If not, why is it an extension method and not a method in the container class?

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  • Why javabeans framework create the IndexedPropertyDescriptor for the NON index method

    - by George Macus
    I'm not familiar with java beans framework, in the below scenario, I got the IndexedPropertyDescriptor for the method getFooWithX, could someone explain why? public class IntrospectorTest { public static void main(String[] args) throws IntrospectionException { BeanInfo info = Introspector.getBeanInfo(SubClass.class); PropertyDescriptor[] descriptors = info.getPropertyDescriptors(); for (int i = 0; i < descriptors.length; i++) { System.out.println(descriptors[i].getClass().getName() + ":" + descriptors[i].getName()); } } } abstract class BaseClass { public abstract Object getFoo(); } abstract class SubClass extends BaseClass { public Object getFooWithX(int x) { return null; } } and the result will be: java.beans.PropertyDescriptor:class java.beans.PropertyDescriptor:foo java.beans.IndexedPropertyDescriptor:fooWithX Why?

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