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  • C++ containers on classes, returning pointers

    - by otneil
    Hello, I'm having some trouble to find the best way to accomplish what I have in mind due to my inexperience. I have a class where I need to a vector of objects. So my first question will be: is there any problem having this: vector< AnyType container* and then on the constructor initialize it with new (and deleting it on the destructor)? Another question is: if this vector is going to store objects, shouldn't it be more like vector< AnyTipe* so they could be dynamically created? In that case how would I return an object from a method and how to avoid memory leaks (trying to use only STL)?

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  • Detect if Java Swing component has been hidden

    - by kayahr
    Assume we have the following Swing application: final JFrame frame = new JFrame(); final JPanel outer = new JPanel(); frame.add(outer); JComponent inner = new SomeSpecialComponent(); outer.add(inner); So in this example we simply have an outer panel in the frame and a special component in the panel. This special component must do something when it is hidden and shown. But the problem is that setVisible() is called on the outer panel and not on the special component. So I can't override the setVisible method in the special component and I also can't use a component listener on it. I could register the listener on the parent component but what if the outer panel is also in another panel and this outer outer panel is hidden? Is there an easier solution than recursively adding componentlisteners to all parent components to detect a visibility change in SomeSpecialComponent?

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  • C++ struct, public data members and inheritance

    - by Marius
    Is it ok to have public data members in a C++ class/struct in certain particular situations? How would that go along with inheritance? I've read opinions on the matter, some stated already here http://stackoverflow.com/questions/952907/practices-on-when-to-implement-accessors-on-private-member-variables-rather-than http://stackoverflow.com/questions/670958/accessors-vs-public-members or in books/articles (Stroustrup, Meyers) but I'm still a little bit in the shade. I have some configuration blocks that I read from a file (integers, bools, floats) and I need to place them into a structure for later use. I don't want to expose these externally just use them inside another class (I actually do want to pass these config parameters to another class but don't want to expose them through a public API). The fact is that I have many such config parameters (15 or so) and writing getters and setters seems an unnecessary overhead. Also I have more than one configuration block and these are sharing some of the parameters. Making a struct with all the data members public and then subclassing does not feel right. What's the best way to tackle that situation? Does making a big struct to cover all parameters provide an acceptable compromise (I would have to leave some of these set to their default values for blocks that do not use them)?

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  • Haskell type classes and type families (cont'd)

    - by Giuseppe Maggiore
    I need some help in figuring a compiler error which is really driving me nuts... I have the following type class: infixl 7 --> class Selectable a s b where type Res a s b :: * (-->) :: (CNum n) => (Reference s a) -> (n,(a->b),(a->b->a)) -> Res a s b which I instance twice. First time goes like a charm: instance Selectable a s b where type Res a s b = Reference s b (-->) (Reference get set) (_,read,write) = (Reference (\s -> let (v,s') = get s in (read v,s')) (\s -> \x -> let (v,s') = get s v' = write v x (_,s'') = set s' v' in (x,s''))) since the type checker infers (-->) :: Reference s a -> (n,a->b,a->b->a) -> Reference s b and this signature matches with the class signature for (--) since Res a s b = Reference s b Now I add a second instance and everything breaks: instance (Recursive a, Rec a ~ reca) => Selectable a s (Method reca b c) where type Res a s (Method reca b c) = b -> Reference s c (-->) (Reference get set) (_,read,write) = \(x :: b) -> from_constant( Constant(\(s :: s)-> let (v,s') = get s :: (a,s) m = read v ry = m x :: Reference (reca) c (y,v') = getter ry (cons v) :: (c,reca) v'' = elim v' (_,s'') = set s' v'' in (y,s''))) :: Reference s c the compiler complains that Couldn't match expected type `Res a s (Method reca b c)' against inferred type `b -> Reference s c' The lambda expression `\ (x :: b) -> ...' has one argument, which does not match its type In the expression: \ (x :: b) -> from_constant (Constant (\ (s :: s) -> let ... in ...)) :: Reference s c In the definition of `-->': --> (Reference get set) (_, read, write) = \ (x :: b) -> from_constant (Constant (\ (s :: s) -> ...)) :: Reference s c reading carefully the compiler is telling me that it has inferred the type of (--) thusly: (-->) :: Reference s a -> (n,a->(Method reca b c),a->(Method reca b c)->a) -> (b -> Reference s c) which is correct since Res a s (Method reca b c) = b -> Reference s c but why can't it match the two definitions? Sorry for not offering a more succint and standalone example, but in this case I cannot figure how to do it...

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  • How to unit test generic classes

    - by Rowland Shaw
    I'm trying to set up some unit tests for an existing compact framework class library. However, I've fallen at the first hurdle, where it appears that the test framework is unable to load the types involved (even though they're both in the class library being tested) Test method MyLibrary.Tests.MyGenericClassTest.MyMethodTest threw exception: System.MissingMethodException: Could not load type 'MyLibrary.MyType' from assembly 'MyLibrary, Version=1.0.3778.36113, Culture=neutral, PublicKeyToken=null'.. My code is loosely: public class MyGenericClass<T> : List<T> where T : MyType, new() { public bool MyMethod(T foo) { throw new NotImplementedException(); } } With test methods: public void MyMethodTestHelper<T>() where T : MyType, new() { MyGenericClass<T> target = new MyGenericClass<T>(); foo = new T(); expected = true; actual = target.MyMethod(foo); Assert.AreEqual(expected, actual); } [TestMethod()] public void MyMethodTest() { MyMethodTestHelper<MyType>(); } I'm a bit stumped though, as I can't even get it to break in the debugger to get to the inner exception, so what else do I check? EDIT this does seem to be something specific to the Compact Framework - recompiling the class libraries and the unit tests for the full framework, gives the expected output (i.e. the debugger stops when I'm going to throw a NotImplementedException).

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  • Why can't you call a non-static method from a static method?

    - by VoodooChild
    I have a static method [Method1] in my class, which calls another method [Method2] in the same class and is not a static method. But this is a no-no. I get this error: An object reference is required for the non-static field, method, or property "ClassName.MethodName()" Can someone please briefly describe why? including other things that might be related to this.

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  • Pass in a value into Python Class through command line

    - by chrissygormley
    Hello, I have got some code to pass in a variable into a script from the command line. The script is: import sys, os def function(var): print var class function_call(object): def __init__(self, sysArgs): try: self.function = None self.args = [] self.modulePath = sysArgs[0] self.moduleDir, tail = os.path.split(self.modulePath) self.moduleName, ext = os.path.splitext(tail) __import__(self.moduleName) self.module = sys.modules[self.moduleName] if len(sysArgs) > 1: self.functionName = sysArgs[1] self.function = self.module.__dict__[self.functionName] self.args = sysArgs[2:] except Exception, e: sys.stderr.write("%s %s\n" % ("PythonCall#__init__", e)) def execute(self): try: if self.function: self.function(*self.args) except Exception, e: sys.stderr.write("%s %s\n" % ("PythonCall#execute", e)) if __name__=="__main__": test = test() function_call(sys.argv).execute() This works by entering ./function <function> <arg1 arg2 ....>. The problem is that I want to to select the function I want that is in a class rather than just a function by itself. The code I have tried is the same except that function(var): is in a class. I was hoping for some ideas on how to modify my function_call class to accept this. Thanks for any help.

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  • Can I use memcpy in C++ to copy classes that have no pointers or virtual functions

    - by Shane MacLaughlin
    Say I have a class, something like the following; class MyClass { public: MyClass(); int a,b,c; double x,y,z; }; #define PageSize 1000000 MyClass Array1[PageSize],Array2[PageSize]; If my class has not pointers or virtual methods, is it safe to use the following? memcpy(Array1,Array2,PageSize*sizeof(MyClass)); The reason I ask, is that I'm dealing with very large collections of paged data, as decribed here, where performance is critical, and memcpy offers significant performance advantages over iterative assignment. I suspect it should be ok, as the 'this' pointer is an implicit parameter rather than anything stored, but are there any other hidden nasties I should be aware of?

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  • Python base classes share attributes?

    - by tad
    Code in test.py: class Base(object): def __init__(self, l=[]): self.l = l def add(self, num): self.l.append(num) def remove(self, num): self.l.remove(num) class Derived(Base): def __init__(self, l=[]): super(Derived, self).__init__(l) Python shell session: Python 2.6.5 (r265:79063, Apr 1 2010, 05:22:20) [GCC 4.4.3 20100316 (prerelease)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import test >>> a = test.Derived() >>> b = test.Derived() >>> a.l [] >>> b.l [] >>> a.add(1) >>> a.l [1] >>> b.l [1] >>> c = test.Derived() >>> c.l [1] I was expecting "C++-like" behavior, in which each derived object contains its own instance of the base class. Is this still the case? Why does each object appear to share the same list instance?

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  • Storing Instances of Classes in Flex Shared Objects

    - by babyangel86
    Is it possible to store instances of a class in a cookie or in shared objects. Basically in my application I have an object "Diagram" that the user can create. If they hit save, I want to store the current instance as a cookie and allows them to reload it later. Alternatively, I could see about getting them to store the saved version on the hard disk. But even then, all I want to save and retreive is my actionscript object. Is this possible? I've tried storing the object to SharedObject.data.diag, but when I try to retrieve the object from the cookie doing SharedObject.data.diag as Diag returns null.

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  • How to use rails routes in external classes?

    - by wesgarrison
    I'm using prawn to generate pdfs, set up ala http://wiki.github.com/sandal/prawn/using-prawn-in-rails I'd like to access my routes so I can generate links in my pdfs, but now I'm not in a template like I used to do with prawnto, so I don't have access to the named routes. class MyPdf < Prawn::Document def to_pdf text root_path end end How can I include my named routes?

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  • jquery :last missing multiple classes

    - by mickyjtwin
    I have an unordered list, and am using jquery to find the last ul and apply a class. jQuery("ul.class1:last").addClass("lastUi"); The html is as follows: <ul class="class1"></ul> <ul class="class1"></ul> This is working fine, however it has now changed in that another class is being added to the list so the html looks like: <ul class="class1"></ul> <ul class="class1 class2"></ul> <ul class="class1"></ul> <ul class="class1 class2"></ul> The jQuery code is now not picking up the last ul with both class1 and class2 as the last element and isn't adding the lastUI class.

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  • get_called_class hack not working with eval-code.

    - by Ekampp
    Hi there. I am using a ge_called_class hack for allowing late static binding in php version 5.2 (found here). I have the following in my code: # db_record.php $ac = "ForumThread"; $objects = $ac::find("all"); This will not work in php 5.2 for some reason, so I have done this: # db_record.php $ac = "ForumThread"; eval("\$objects = {$ac}::find('all');"); This on the other hand will not work with the get_called_class function. I get an error that the file function can't read the evaled section of code. So how do I solve this problem? Best regards.

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  • Creating An Utilities Class?

    - by Soo
    Hello SO, I'm very new to OOP and am trying my hardest to keep things strictly class based, while using good coding priciples. I'm a fair ways into my project now and I have a lot of general use methods I want to put into an utilities class. Is there a best way to create an utilities class? public class Utilities { int test; public Utilites() { } public int sum(int number1, int number2) { test = number1+number2; } return test; } After creating this Utilities class, do I just create an Utilities object, and run the methods of my choosing? Do I have this Utilities class idea correct?

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  • Classes and Objects in C++

    - by anurag18294
    class anurag { private: int rollno; char name[50]; int marks; float percen; void percentage(int num) { percen=(num/500)*100; } public: void getdata(void) { cout<<"\n\nEnter the name of the student:"; gets(name); cout<<"\n\nEnter the roll no: and the marks:"; cin>>rollno>>marks; percentage(marks); } void display(void) { cout<<"\n\nThe name of the student is:"; cout.write(name,50); cout<<"\n\nThe roll no: of the student is:"; cout<<rollno; cout<<"\n\n The marks obtained is:"<<marks; cout<<"\n\nThe percentage is:"<<percen; }}; void main() { clrscr(); anurag F; F.getdata(); F.display(); getch(); } why the following code is not giving the desired output?

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  • importing classes python

    - by Richard
    Just wondering why import sys exit(0) gives me this error: Traceback (most recent call last): File "<pyshell#1>", line 1, in ? exit(0) TypeError: 'str' object is not callable but from sys import exit exit(0) works fine?

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  • managing classes when everything is relative to a user in nhibernate (orm)

    - by Schotime
    Firstly I have three entities. Users, Roles, Items A user can have multiple Roles. An item gets assigned to one or more roles. Therefore a user will have access to a distinct set of items. Now there is a few ways I can see this working. There is a Collection on Users which has Roles via a many-to-many assoc. Then each Role in this collection will have its own collection of Items. So for each user I would have to get the User (using nhib and fetch the roles and items with it) then either do a selectMany on the Items in each Role to get all the Items for the user or do a couple of foreach's to port the data to a view or dto model. Create a db trigger to automatically insert into another table that just has the relationship between user and items so that on my User entity I only have a Items collections which has all the items assigned to me. Some other way that i can't think of yet, because I'm new to nHibernate. Now i know that the trigger doesn't feel right but I'm not sure how to do this. We also have some hierarchy later where a user may be in charge of a group of users. If anyone could shed some light on how they go about these scenarios in nhibernate or another orm that would be great, or point be in a direction. I know that in the past you would have to enter all combinations into a table so that the query worked, but when you know sql its not too bad. If you need any other info then let me know. Cheers

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  • Generics and Derived Classes .NET 3.5

    - by Achilles
    Consider the following where class "Circle" inherits from "Shape": dim objListOfCircles as new List(of Circle) DrawShapes(objListOfCirlces) Private sub DrawShapes(byref objListOfShapes as List(of Shape)) for each objShape as Shape in objListOfShapes objShape.Draw() next end sub I can't get this to work. What is the explaination as to why this doesn't work?

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  • How to implement callback methods inside classes (PHP)

    - by sombe
    I need to use a class callback method on an array inside another method (the callback function belongs to the class). class Database { public function escape_string_for_db($string){ return mysql_real_escape_string($string); } public function escape_all_array($array){ return array_filter($array,"$this->escape_string_for_db"); } } Is this the right way to go about that? (I mean, in terms of the second parameter passed to array_filter)

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  • Is it possible to create custom methods in entity classes in linq to sql

    - by doekman
    I have a table Site in SQL with (amongst others) three properties idReviewer1, idReviewer2, idReviewer3. Now I would like to create a methods on the entity class of Site to check if a user is a reviewer: partial class Site { public bool IsReviewer(int idUser) { return idReviewer1 == idUser || idReviewer2 == idUser || idReviewer3 == idUser; } } and I use it like this: return from s in db.Sites where s.IsReviewer(user) select s; However, Linq to SQL doesn't know how to translate this to SQL. I get the following error message: Method 'Boolean IsReviewer(Int32)' has no supported translation to SQL. I'd rather not write this: return from s in db.Sites where idReviewer1 == idUser || idReviewer2 == idUser || idReviewer3 == idUser select s; Is there any way to put this functionality in one place, without resorting to SQL?

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