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  • Why does the assignment operator return a value and not a reference?

    - by Nick Lowman
    I saw the example below explained on this site and thought both answers would be 20 and not the 10 that is returned. He wrote that both the comma and assignment returns a value, not a reference. I don't quite understand what that means. I understand it in relation to passing variables into functions or methods i.e primitive types are passed in by value and objects by reference but I'm not sure how it applies in this case. I also understand about context and the value of 'this' (after help from stackoverflow) but I thought in both cases I would still be invoking it as a method, foo.bar() which would mean foo is the context but it seems both result in a function call bar(). Why is that and what does it all mean? var x = 10; var foo = { x: 20, bar: function () {return this.x;} }; (foo.bar = foo.bar)();//returns 10 (foo.bar, foo.bar)();//returns 10

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  • Read Core data in Serial Queue for iPhone app

    - by user1277209
    I have an app which uses Core data and the values are fetched from a link on internet. This runs absolutely fine when I am creating a serial queue in AppDelegate and I am not facing any problem with the same. Now, when I am trying to re-create similar scenario in a UITableViewController and executing the same in a serial queue but when the control reaches NSError *error; NSArray *match = [context executeFetchRequest:fetchRequest error:&error]; execution control disappears and then this code remains in the execution till eternity. Can anyone help me with what exactly is wrong here? FYI, I am passing the same ManagedObjectContext to the serial queue.

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  • C# Unit Testing: How do I set a Lazy<T>.ValueCreated to false?

    - by michael paul
    Basically, I have a unit test that gets a singleton instance of a class. Some of my tests required me to mock this singleton, so when I do Foo.Instance I get a different type of instance. The problem is that my checks are passing individually, but failing overall because one test is interfering with another. I tried to do a TestCleanup where I set: Foo_Accessor._instance = null; but that didn't work. What I really need is Foo_Accessor._instance.IsValueCreated = false; (_instance is a Lazy). Any way to unset the Lazy object that I didn't think of?

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  • best way to write a-> ..->[a] recursive functions in haskell

    - by Roman A. Taycher
    So I keep having this small problem where I have something like func :: a -> b -> [a] -- or basically any a-> ...-> [a] where ... is any types -> func x y = func' [x] y -- as long as they are used to generate a list of [a] from x func' :: [a] -> b -> [a] func = undefined --situation dependant generates a list from each element and returns it as one long list should I keep it like this? should I use func' hidden by a where? should I only use the [a] - b - [a] version and leave the responsibility of passing [variable] to the callee? I might well need to compose these functions and might want to mess around with the order so I'm leaning towards option 3. What do you think?

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  • What should I name instances of a twisted.internet.defer.Deferred?

    - by slacy
    I'm writing code using Twisted, and having trouble coming up with a sensible variable name for my twisted internet deferred's. Here are my candidates: d : Too generic, too short, violates pylint rule C0103. def : Conflicts with function defintion builtin. defer : Conflicts with module twisted.internet.defer deferred : OK but pretty long cb : Still too short, violates pylint C0103, conflicts with many callback method names. cback : Too Weird? callback : Conflicts with method Deferred.callback() I'm looking for other suggestions. It seems like most of the Twisted example code uses "d" which is fine for simple invocations, but when you're passing Deferred's around to methods and storing them as member variables, it's really far too descriptive.

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  • How can I declare constant strings for use in both an unmanaged C++ dll and in a C# application?

    - by Surfbutler
    Curently I'm passing my const string values up from my C++ into my C# at startup via a callback, but I'm wondering if there's a way of defining them in a C++ header file that I can then also refer to in C#. I already do this with enums as they are easy. I include a file in both my C++ library project (via a .h file with a pragma once at the top), and my C# application (as a link): #if _NET public #endif enum ETestData { First, Second }; I know it sounds messy, but it works :) But...how can I do the same with string constants - I'm initially thinking the syntax is too different between the platforms, but maybe there's a way? Using clever syntax involving #if _NET, #defines etc? Using resource files? Using a C++/CLI library? Any ideas?

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  • Replace <Unknown Source> in Java Rhino (JSR223) with actual file name

    - by Lord.Quackstar
    Hello everyone, In my code, all of the scripts are contained in .js files. Whenever one of the scripts contains an error, I get this: javax.script.ScriptException: sun.org.mozilla.javascript.internal.EcmaError: ReferenceError: "nonexistant" is not defined. (<Unknown source>#5) in <Unknown source> at line number 5 What bugs me is the <Unknown Source>. Multiple files are in one ScriptContext, and it can be hard to track down an error. It also looks horrible. Is there a way to replace <Unknown Source> with the actual file name? None of the methods I see support passing a File object, so I'm really confused here.

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  • Secure Webservice?

    - by cam
    I'm trying to create a secure webservice (that provides simple database data) with PHP that can be connected to through my Silverlight application. I don't know enough about PHP to be able to see another way to do this. The webservice should only be accessible through the client, and only with the proper username/password. The only two ways I can imagine to do this would be by passing the username/password hash via URL, or use a "hidden form" and do it via POST_. I'm just trying to get past this point, I'm the sole developer on this project and I'm just trying to get past this PHP webservice part so I can get back to being an application programmer :) Normally, I would learn PHP, but I'm on the clock, so I'm just looking for a point in the right direction on how to achieve this!

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  • How do check if PDO object is connected properly inside a different class?

    - by tgun926
    I want to fetch some information from my mysql database in a class, so I'm passing in the PDO object into a __construct function, and working from there. However, what's an elegant way of checking to see if the PDO object was correctly created, and that the connection is open when the Table class is instantiated? class Table{ public function __construct(PDO $db, $week){ try{ $query = $db -> query ("SELECT * FROM `table1` where `day` = 'monday'"); } catch(PDOExeption $e){ echo 'error: '. $e->getMessage(); //die(); } } } I don't think this code does what I want.

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  • Reference to an instance method of a particular object

    - by Andrey
    In the following code, if i try to pass method reference using the class name, works. But passing the reference variable compiler gives an error, i do not understand why? public class User { private String name; public User(String name) { this.name = name; } public void printName() { System.out.println(name); } } public class Main { public static void main(String[] args) { User u1 = new User("AAA"); User u2 = new User("BBB"); User u3 = new User("ZZZ"); List<User> userList = Arrays.asList(u1, u2, u3); userList.forEach(User::printName); // works userList.forEach(u1::printName); // compile error } } Thanks,

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  • Android ListView Item Visibility

    - by user1478754
    I'm trying to create a screen that displays multiples items. For this, I've created a listview but I'm not sure how to approach how to add/remove items from it. Since I'm using custom listview items, I've created my own listadapter but now I need a way to add items on a button click. Is there a way to create listview that can take an indefinite amount of items (instead of passing it in an fixed length array of View objects)? Also what's the best way to remove items from listviews? setVisibility?

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  • How to check if Google Street View available and display message?

    - by Vafello
    I am passing lat and lng variables and display google sreet view in a div. The problem is that when the StreetView is unavilable then nothing is displayed. I would like to check if there is a streetview for a given lat and lng and display a message. Here is my code: var myPano = new GStreetviewPanorama(document.getElementById("street2"), panoOpts); var location = new GLatLng(lat,lng) myPano.setLocationAndPOV(location); Maybe I should use something like: Event.addListener(myPano, "error", errorMessage()); Any ideas?

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  • How do you create a daemon in Python?

    - by DavidM
    Searching on Google reveals x2 code snippets. The first result is to this code recipe which has a lot of documentation and explanation, along with some useful discussion underneath. However, another code sample, whilst not containing so much documentation, includes sample code for passing commands such as start, stop and restart. It also creates a PID file which can be handy for checking if the daemon is already running etc. These samples both explain how to create the daemon. Are there any additional things that need to be considered? Is one sample better than the other, and why?

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  • explain this macro

    - by deostroll
    #define __T(x) L ## x Found in code from one of the MFC source header file. It is mostly used for converting strings to ........ (I don't know what). If I am correct it converts strings to LPCTSTR...don't know what that type is either... I can't seem to convert char* into LPCTSTR. While MFC file handling, the following code will always return error while trying to open the file... char* filepath = "C:\\Program Files\\Microsoft Office\\Office12\\BITMAPS\\STYLES\\GLOBE.WMF"; if( !file.Open((LPCTSTR)filepath , CFile::modeRead, &fexp) ) { fexp.ReportError(); return 1; } But instead if I wrote it this way, it doesn't give error: if( !file.Open( _T("C:\\Program Files\\Microsoft Office\\Office12\\BITMAPS\\STYLES\\GLOBE.WMF") , CFile::modeRead, &fexp) ) { fexp.ReportError(); return 1; } I am looking at passing a variable as the first argument to the CFile::Open() method.

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  • iPhone view architecture question

    - by Joe
    So I have (for instance) three views: A: root view B: a view functionally identical to root C: a data entry view which collects a few piece of info What I'm trying to do is reuse C to supply the data it collects to either A or B. It should supply the data to whichever of the two it is pushed onto. The data for A is similar, but functionally distinct, to what collects for B. Right now, I'm passing data from C to A or B via a singleton class. What I'm trying to avoid is having two instances of C, one to supply data to A and B (because, in actuality, the program will have 5 total views like C. Does the question make sense?

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  • Call function based off of a string in Lisp

    - by powerj1984
    I am passing in command line arguments to my Lisp program and they are formatted like this when they hit my main function: ("1 1 1" "dot" "2 2 2") I have a dot function and would like to call it directly from the argument, but this isn't possible because something like (funcall (second args)...) receives "dot" and not dot as the function name. I tried variations of this function: (defun remove-quotes (s) (setf (aref s 0) '"")) to no avail, before realizing that the quotes were not really a part of the string. Is there a simple way to do this, or should I just check each string and then call the appropriate function? Thanks!

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  • CakePHP accessing other controllers

    - by James
    CakePHP Newbie :) I am having trouble accessing another controller and passing that data to a view in one of my controllers: In controllers/landings_controller.php: var $uses = 'User'; function home() { $userdata = $this->User->read(); $this->set(compact('userdata')); } In views/landings/home.ctp: <?php echo $this->userdata; ?> When accessing /landings/home I get the following error: Notice (8): Undefined property: View::$userdata [APP/views/landings/home.ctp, line 38] I don't know what I am doing wrong. Any help? Thanks!

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  • Do fields need to be explicitly final to have a "proper" immutable object?

    - by Yishai
    You often read about immutable objects requiring final fields to be immutable in Java. Is this in fact the case, or is it simply enough to have no public mutability and not actually mutate the state? For example, if you have an immutable object built by the builder pattern, you could do it by having the builder assign the individual fields as it builds, or having the builder hold the fields itself and ultimately return the immutable object by passing the values to its (private) constructor. Having the fields final has the obvious advantage of preventing implementation errors (such as allowing code to retain a reference to the builder and "building" the object multiple times while in fact mutating an existing object), but having the Builder store its data inside the object as it is built would seem to be DRYer. So the question is: Assuming the Builder does not leak the Object early and stops itself from modifying the object once built (say by setting its reference to the object as null) is there actually anything gained (such as improved thread safety) in the "immutability" of the object if the object's fields were made final instead?

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  • doubt in - Function Objects - c++

    - by Eternal Learner
    I have a class class fobj{ public: fobj(int i):id(i) {} void operator()() { std::cout<<"Prints"<<std::endl; } private: int id; }; template<typename T> void func(T type) { type(); } My Doubt is if I invoke func like Method 1: func(fobj(1); the message I wanted to print is printed. I was always thinking I needed to do something like Method 2: fobj Iobj(1); // create an instance of the fobj class func(Iobj); //call func by passing Iobj(which is a function object) How does Method 1 work? I mean what exactly happens? and how is a call made to the operator() in class fobj ?

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  • is it a good idea to write tests for environments other than development?

    - by jcollum
    Let's say I have a (fairly typical) set of environments: PROD, UAT, QA, DEV. Is it a good idea to run your tests across all environments? Here's what I'm thinking of. I have a proc in SQL that my code depends on, I'll call it proc_getActiveCustomers. If that proc isn't present my app will go south real fast. So I write a test that checks for the existence of this proc in the database. Nothing new here. But when I then deploy my app to the QA environment, would I also want to have a test that checks that environment for the existence of proc_getActiveCustomers? I think this is a good idea but I've never heard much about testing in environments outside of development. Makes me wonder if there's some downside I'm not aware of. The direction that I'm going is to have a list of environments in code and then passing that environment into my unit test.

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  • Data validation between SQL replicated tables

    - by Vikram
    Hi All, I am trying to figure out a way to validate the data in my publisher and subscriber in SQL 2005 replication. I thought of using sp_publication_validation, but it needs db_owner permission and we are not allowed to have it in our company. So I did bit more reading and found out about two other SPs that I think work for me. First one is sp_article_validation, which I plan to run on the publisher. For each article that I call this SP, its gonna give the row count and a checksum. With that info, I intend to call sp_table_validation on the subscriber, passing the row count and checksum from the previous SP, there by validating both tables. What do you guys think? Is this a proven way to validate data in replication? There is very little documentation on these SPs. Here is the link: sp_table_validation - http://msdn.microsoft.com/en-us/library/aa239370(v=sql.80).aspx sp_article_validation - http://msdn.microsoft.com/en-us/library/ms177511(v=SQL.90).aspx Thanks for

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  • What is "with" used for in PHP?

    - by Jason
    I have come across this line in the eloquent ORM library: return with(new static)->newQuery(); I've never seen "with" used before, and cannot find it in the PHP documentation. I'm guessing "with" is a stop-word in most searches, so I am not even getting close. Never having encountered "with" in many years of programming PHP, I feel like I'm missing out. What does it do? I did come across one passing comment regarding the ORM, that mentioned "with" is no longer needed in PHP-5.4, but that was as much as was said.

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  • how to view all images in android's built- in gallery from a php page

    - by ramz
    Hi, I am developing an application to display all the images in android's built-in gallery in to a php page. I posted the uri(content://media/extrenal/images/media) of the gallery images to the php page. I was not able to recreate images by using webView function loadUrl(). Should i need to upload the whole gallery to another directory and display the images? Or passing the bitmap itself will do? Please suggest me an idea to solve the problem.

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  • Best way to create a Unique ID field for an enum

    - by jax
    What is the best way to get a Unique ID from an ENUM that will stay consistent between repeated execution of the program? Currently I am doing this manually by passing an ID to the enum constructor. I don't really want to do this is I can help it. Another option would be to use a static field that gets incremented for each enum value. The problem is that if later I decide to move the enum fields around or delete some this will cause problems with my program as the ID will be saved into user preferences. The ID can be any basic type or a String.

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  • How should nested components interact with model in a GUI application?

    - by fig-gnuton
    Broad design/architecture question. If you have nested components in a GUI, what's the most common way for those components to interact with data? For example, let's say a component receives a click on one of its buttons to save data. Should the save request be delegated up that component's ancestors, with the uppermost ancestor ultimately passing the request to a controller? Or are models/datastores in a GUI application typically singletons, so that a component at any level of a hierarchy can directly get/set data? Or is a controller injected as a dependency down the hierarchy of components, so that any given component is only one intermediary away from the datastore/model?

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