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  • Wildcards vs. generic methods

    - by FredOverflow
    Is there any practical difference between the following approaches to print all elements in a range? public static void printA(Iterable<?> range) { for (Object o : range) { System.out.println(o); } } public static <T> void printB(Iterable<T> range) { for (T x : range) { System.out.println(x); } } Apparently, printB involves an additional checked cast to Object (see line 16), which seems rather stupid to me -- isn't everything an Object anyway? public static void printA(java.lang.Iterable); Code: 0: aload_0 1: invokeinterface #18, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator; 6: astore_2 7: goto 24 10: aload_2 11: invokeinterface #24, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object; 16: astore_1 17: getstatic #30; //Field java/lang/System.out:Ljava/io/PrintStream; 20: aload_1 21: invokevirtual #36; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V 24: aload_2 25: invokeinterface #42, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z 30: ifne 10 33: return public static void printB(java.lang.Iterable); Code: 0: aload_0 1: invokeinterface #18, 1; //InterfaceMethod java/lang/Iterable.iterator:()Ljava/util/Iterator; 6: astore_2 7: goto 27 10: aload_2 11: invokeinterface #24, 1; //InterfaceMethod java/util/Iterator.next:()Ljava/lang/Object; 16: checkcast #3; //class java/lang/Object 19: astore_1 20: getstatic #30; //Field java/lang/System.out:Ljava/io/PrintStream; 23: aload_1 24: invokevirtual #36; //Method java/io/PrintStream.println:(Ljava/lang/Object;)V 27: aload_2 28: invokeinterface #42, 1; //InterfaceMethod java/util/Iterator.hasNext:()Z 33: ifne 10 36: return

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  • Testing InlineFormset clean methods

    - by Rory
    I have a Django project, with 2 models, a Structure and Bracket, the Bracket has a ForeignKey to a Structure (i.e. one-to-many, one Structure has many Brackets). I created a TabularInline for the admin site, so that there would be a table of Brackets on the Structure. I added a custom formset with some a custom clean method to do some extra validation, you can't have a Bracket that conflicts with another Bracket on the same Structure etc. The admin looks like this: class BracketInline(admin.TabularInline): model = Bracket formset = BracketInlineFormset class StructureAdmin(admin.ModelAdmin): inlines = [ BracketInline ] admin.site.register(Structure, StructureAdmin) That all works, and the validation works. However now I want to write some unittest to test my complex formset validation logic. My first attempt to validate known-good values is: data = {'form-TOTAL_FORMS': '1', 'form-INITIAL_FORMS': '0', 'form-MAX_NUM_FORMS': '', 'form-0-field1':'good-value', … } formset = BracketInlineFormset(data) self.assertTrue(formset.is_valid()) However that doesn't work and raises the exception: ====================================================================== ERROR: testValid (appname.tests.StructureTestCase) ---------------------------------------------------------------------- Traceback (most recent call last): File "/paht/to/project/tests.py", line 494, in testValid formset = BracketInlineFormset(data) File "/path/to/django/forms/models.py", line 672, in __init__ self.instance = self.fk.rel.to() AttributeError: 'BracketInlineFormset' object has no attribute 'fk' ---------------------------------------------------------------------- The Django documentation (for formset validation) implies one can do this. How come this isn't working? How do I test the custom clean()/validation for my inline formset?

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  • MustOverride Shared Methods in .Net

    - by Ben
    Hi I have a few class's that inherit from a base class. I want to enforce that all of these Class's implement a shared method foo(). I am not able to create the following on the base class Public MustOvveride Shared Sub foo() as this is not allowed. I also cant create an Interface that defines a Shared Sub Foo() and implement that in my derrived class's, as this also is not allowed. Does anyone know how i should implement this? p.s i realise my example is in VB and i have also tagged C#, the same problem applies to both languages and presumably the same fix would apply.

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  • javascript inherance? with Private vars and methods too

    - by Totty
    Hy i need to inherent a class from another. Parent has private var "_data" and private method "_test" and public method "add" Now the child have a public method "add", that uses the private method from the parent "_test" and the private var "_data". How do i do this? var Parent = function(){ var _data = {}; var _test = function(){alert('test')}; this.add = function(){alert('add from parent')} } var Child = function(){ this.add = function(){// here uses the _data and _test from the Parent class alert('add from child') } } // something to inherent Child from Parent // instance Child and use the add method And i think im miss the prototype concept (http://stackoverflow.com/questions/892467/javascript-inheritance)

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  • java thread - run() and start() methods

    - by JavaUser
    Please explain the output of the below code: If I call th1.run() ,the output is EXTENDS RUN RUNNABLE RUN If I call th1.start() , the output is : RUNNABLE RUN EXTENDS RUN Why this inconsistency . Please explain. class ThreadExample extends Thread{ public void run(){ System.out.println("EXTENDS RUN"); } } class ThreadExampleRunnable implements Runnable { public void run(){ System.out.println("RUNNABLE RUN "); } } class ThreadExampleMain{ public static void main(String[] args){ ThreadExample th1 = new ThreadExample(); //th1.start(); th1.run(); ThreadExampleRunnable th2 = new ThreadExampleRunnable(); th2.run(); } }

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  • mysql_close(): supplied argument is not a valid MySQL-Link resource

    - by Illes Peter
    Here's what I'm trying to do: I've got a db.php file that does all the db manipulation. It has 2 static methods, connect and deconnect. In my other file i simply use db::connect() and db::deconnect(). The mysql_close($con) in the deconnect method just doesn't know who $con is. Since I don't want to instantiate my class static is the only way to go. Declaring 'private $con' in class db doesn't seem to have an effect. Any ideas? class db { public static function connect() { $dbData = parse_ini_file($_SERVER['DOCUMENT_ROOT'].'/config.ini'); $con = mysql_connect($dbData['host'],$dbData['user'],$dbData['pass']); $db = mysql_select_db($dbData['db']); if ((!$con) || (!$db)) return 0; else return 1; } public static function deconnect() { mysql_close($con); } }

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  • Calling delegate methods and calling selectors

    - by Crystal
    I'm new to the concept of delegates and selectors when used with notifications. So my first question is, 1) Let's say you have a button that has a delegate that implements some doWork method. If you want the same functionality that's in the method, is it 'ok' to just call that method? I didn't know if that was considered good coding practices and/or if you should do that, or do something different in getting that type of functionality. Like if that is ok architecture? 2) Similarly, with NSNotificationCenter, I see some code that posts a notification. Then there's a HandleSegmentedControl:(NSNotification *)notification method. If I want to manually have that functionality, but without pressing the segment control, is it 'ok' to just take that functionality out of that method and put it in a new method so it would look like this: Original: - (void)HandleSegmentedControl:(NSNotification *)notification { NSDictionary *dict = [userInfo notification]; // do stuff with the dictionary } New: - (void)HandleSegmentedControl:(NSNotification *)notification { NSDictionary *dict = [userInfo notification]; [self newMethod:dict]; } - (void)newMethod:(NSDictionary *)dict { // do stuff with the dictionary } - (void)myOtherMethodThatNeedsTheSameFunctionality { NSDictionary *dict = // create some dictionary [self newMethod:dict]; } Sorry if these are basic questions. I'm not sure what the best practices are for things like this and wanted to start the right way. Thanks.

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  • virtual methods and template classes

    - by soxs060389
    Hi I got over a problem, I think a very specific one. I've got 2 classes, a B aseclass and a D erived class (from B aseclass). B is a template class ( or class template) and has a pure virtual method virutal void work(const T &dummy) = 0; The D erived class is supposed to reimplement this, but as D is Derived from B rather than D being another template class, the compiler spits at me that virtual functions and templates don't work at once. Any ideas how to acomplish what I want? I am thankfull for any thoughts and Ideas, especially if you allready worked out that problem this class is fixed aka AS IS, I can not edit this without breaking existing code base template <typename T> class B { public: ... virtual void work(const T &dummy) = 0; .. }; take int* as an example class D : public B<int*>{ ... virtual void work(const int* &dummy){ /* put work code here */ } .. }; Edit: The compiler tells me, that void B<T>::work(const T&) [with T = int*] is pure virtual within D

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  • Django Piston - how can I create custom methods?

    - by orokusaki
    I put my questions in the code comments for clarity: from piston.handler import AnonymousBaseHandler class AnonymousAPITest(AnonymousBaseHandler): fields = ('update_subscription',) def update_subscription(self, request, months): # Do some stuff here to update a subscription based on the # number of months provided. # How the heck can I call this method? return {'msg': 'Your subscription has been updated!'} def read(self, request): return { 'msg': 'Why would I need a read() method on a fully custom API?' }

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  • Resources and techniques/methods for SCJP preparation ?

    - by BenoitParis
    I am passing the SCJP 6 exam in a month. I have the "SCJP Sun Certified Programmer for Java 6 Exam 310-065" book. It seems great for the exam. But I want your advice on this. Getting the closest possible to 100% would be great. I have found a site that answered some of the questions you ask yourself when you go trough the book. Here is it : http://www.janeg.ca/java2.html As you can see it was written for Java 2 :/ I have written another specific question here on StackOverflow about the usefulness of JVM specification and Java compiler code for the SCJP. Will Update the results here. Here it is. Please share the resources you used in preparing the exam. Please also specify any resources that you think might help. Any type of resource is welcome: books, code, specs, sites, wikies, papers, online tests, grandmas... Please also share on any method/technique that helped you prepare the exam. Please also comment on the return you got from the resource and the method (for the learning process and for points in the exam) I'll begin: Book : "SCJP Sun Certified Programmer for Java 6 Exam 310-065". Seems like the official book for the preparation. Technique : Writing code in a text editor and compiling it with javac to test a question. NO IDEs! It helps you get a a straight answer to a question you have. It helps you pay attention to every word in the code (and this is very important in the SCJP) EDIT: Added dimension: Are there good, up-to-date online tests?

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  • Get annotations of return type in Java

    - by Apropos
    I'm using Spring MVC and am using aspects to advise my controllers. I'm running into one issue: controllers that return a value annotated with the @ResponseBody type. How are you able to find the annotations applied to the return type? @Around("myPointcut()") private Object checkAnnotations(ProceedingJoinPoint pjp) throws Throwable { Object result = pjp.proceed(); Method method = ((MethodSignature)pjp.getSignature()).getMethod(); System.out.println("Checking return type annotations."); for(Annotation annotation : method.getReturnType().getAnnotations()){ System.out.println(annotation.toString()); } System.out.println("Checking annotations on returned object."); for(Annotation annotation : result.getClass().getAnnotations()){ System.out.println(annotation.toString()); } return result; } Unfortunately, neither of these methods seem to have the desired effect. I can retrieve annotations on the type of object being returned, but not the ones being added at return time.

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  • How do I override methods of nested types?

    - by Mason Wheeler
    I've got a custom TObjectList descendant in Delphi 2009, and I'd like to play with its enumerator a bit and add some filtering functionality to the MoveNext method, to cause it to skip certain objects. MoveNext is called by DoMoveNext, which is a virtual method, so this shouldn't be difficult to override... except for one thing. The TEnumerator for TObjectList isn't its own class; it's declared as a nested type within the TObjectList declaration. Is there any simple way to override TEnumerator.DoMoveNext in my descendant class, or do I have to reimplement the whole TEnumerator? It's not a very big class, but I'd prefer to keep redundancies to a minimum if I can...

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  • Aspect Oriented Programming vs List<IAction> To execute methods based on conditions

    - by David Robbins
    I'm new to AOP so bear with me. Consider the following scenario: A state machine is used in a workflow engine, and after the state of the application is changed, a series of commands are executed. Depending on the state, different types of commands should be executed. As I see it, one implementation is to create List<IAction> and have each individual action determine whether it should execute. Would a Aspect Oriented process work as well? That is, could you create an aspect that notifies a class when a property changes, and execute the appropriate processes from that class? Would this help centralize the state specific rules?

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  • Is There A Central Repository of Javascript Information?

    - by Brian
    For example, if you want information of PHP functions, you can go to http://www.php.net/ . If you want information of Perl functions you can to to http://www.cpan.org/ and/or use perldoc. If you want information on Java you can go to http://java.sun.com and/or use javadoc. However, if you want information on Javascript methods/functions and their attributes, return values, etc. where do you go? The reason I ask is I was playing with the "focus()" method and wondering if it could be passed any values or if it returned anything when called. I have done a cursory Google search but haven't found much. Does such a beast exist or am I out of luck? Thanks for reading, and have a good day.

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  • Error handling in C++, constructors vs. regular methods

    - by Dennis Ritchie
    I have a cheesesales.txt CSV file with all of my recent cheese sales. I want to create a class CheeseSales that can do things like these: CheeseSales sales("cheesesales.txt"); //has no default constructor cout << sales.totalSales() << endl; sales.outputPieChart("piechart.pdf"); The above code assumes that no failures will happen. In reality, failures will take place. In this case, two kinds of failures could occur: Failure in the constructor: The file may not exist, may not have read-permissions, contain invalid/unparsable data, etc. Failure in the regular method: The file may already exist, there may not be write access, too little sales data available to create a pie chart, etc. My question is simply: How would you design this code to handle failures? One idea: Return a bool from the regular method indicating failure. Not sure how to deal with the constructor. How would seasoned C++ coders do these kinds of things?

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  • Application settings methods? c++

    - by flyout
    I am thinking about adding configurable settings to an application, and I think the easiest ways are an external file or win registry (its a win only app). Which way would be better? I was wondering, an user with not enough permissions may not be able to create/write the config file. And in the case of the registry, would todays antivirus allow me to add/edit/remove keys? Or they only monitor certain keys? Also, if someone knows a class/lib to manage config settings (in pure win32) in vc++ please post it.

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  • Using a singleton database class in functions and multiple scripts(PHP) - best use methods

    - by dscher
    I have a singleton db connection which I get with: $dbConnect = myDatabase::getInstance(); which is easy enough. My question is what is the least rhetorical and legitimate way of using this connection in functions and classes? It seems silly to have to declare the variable global, pass it into every single function, and/or recreate this variable within every function. Is there another answer for this? Obviously I'm a noob and I can work my way around this problem 10 different ways, none of which is really attractive to me. It would be a lot easier if I could have that $dbConnect variable accessible in any function without needing to declare it global or pass it in. I do know I can add the variable to the $_SERVER array...is there something wrong with doing this? It seems somewhat inappropriate to me. Another quick question: Is it bad practice to do this: $result = myDatabase::getInstance()-query($query); from directly within a function?

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  • Is a function kind of like a static method?

    - by lkm
    I'm a java programmer and am trying to understand the difference between a method (java methods) and a function (such as in c++). I used to think that they are the same, just different naming conventions for different programming languages. But now that I know they are not, I am having trouble understanding the difference. I know that a method relates to an instance of a class and has access to class data (member variables), while a function does not (?). So is a function kind of like a static method? See here for explanations I read which led me to think this.

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  • in c# are methods private by default?

    - by Eli Perpinyal
    If I have a method that does not specify its Accessibility Level will it be Private by default? void Item_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) { throw new NotImplementedException(); } Is the above method private?

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