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  • LINQ query to navigate an object hierachy

    - by TesterTurnedDeveloper
    Let's say I have an object graph of Countries / States / Cities, like below: public class City { public string Name { get; set; } } public class State { public List<City> Cities { get; set; } } public class Country { public List<State> States { get; set; } } Is there a simple way to query a List<Country> to get all the cities?

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  • Finding the specific type held in an ArrayList<Object> (ie. Object = String, etc.)

    - by Christopher Griffith
    Say I have an ArrayList that I have cast to an ArrayList of objects. I know that all the objects that were in the ArrayList I cast were of the same type, but not what the type was. Now, if the ArrayList is not empty, I could take one of the objects in it and use the instanceof operator to learn what the actual type is. But what of the case where the ArrayList is empty? How do I determine what type Object actually is then? Is it possible?

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  • Dynamic class_name for has_many relations

    - by vooD
    I'm trying to make has_many relation with dynamic class_name attribute class Category < ActiveRecord::Base has_many :ads, :class_name => ( lambda { return self.item_type } ) end or class Category < ActiveRecord::Base has_many :ads, :class_name => self.item_type end But i got errors: can't convert Proc into String or undefined method `item_type' for #<Class:0xb62c6c88> Thank you for any help!

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  • Exception in Google App Engine (Java) while trying to create Memcache Object

    - by Shreeni
    I am coming back to an old Google App Engine project on which I saw a bug. During this lag, I have been upgrading my AppEngine SDK and is now set at 1.3. When I try to run the same project again, I see the following exception: java.lang.NoSuchMethodError: com.google.apphosting.api.ApiProxy$Environment.getDefaultNamespace()Ljava/lang/String; at com.google.appengine.api.NamespaceManager.get(NamespaceManager.java:56) at com.google.appengine.api.memcache.MemcacheServiceImpl.setNamespace(MemcacheServiceImpl.java:181) at com.google.appengine.api.memcache.MemcacheServiceImpl.(MemcacheServiceImpl.java:145) at com.google.appengine.api.memcache.MemcacheServiceFactory.getMemcacheService(MemcacheServiceFactory.java:25) The line causing the problem is: CacheManager.getInstance().getCacheFactory().createCache(Collections.emptyMap()); (It is the same line as suggested by the AppEngine documentation to create a memcache object. It used to work fine previously. ) Any suggestions on how to fix it?

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  • Encapsulating a Windows.Forms.Button

    - by devoured elysium
    I want to define a special kind of button that only allows two possible labels: "ON" and "OFF". I decided to inherit from a Windows.Forms.Button to implement this but now I don't know I how should enforce this rule. Should I just override the Text property like this? public override string Text { set { throw new InvalidOperationException("Invalid operation on StartStopButton!"); } } The problem I see with this is that I am breaking the contract that all buttons should have. If any code tries something like foreach (Button button in myForm) { button.Text = "123"; } they will get an Exception if I have any of my special buttons on the form, which is something that isn't expectable. First, because people think of properties just as "public" variables, not methods, second, because they are used to using and setting whatever they want to buttons without having to worry with Exceptions. Should I instead just make the set property do nothing? That could also lead to awkward results: myButton.Text = "abc"; MessageBox.Show(abc); //not "abc"! The general idea from the OO world is to in this kind of cases use Composition instead of inheritance. public class MySpecialButton : <Some class from System.Windows.Forms that already knows how to draw itself on forms> private Button button = new Button(); //I'd just draw this button on this class //and I'd then only show the fields I consider //relevant to the outside world. ... } But to make the Button "live" on a form it must inherit from some special class. I've looked on Control, but it seems to already have the Text property defined. I guess the ideal situation would be to inherit from some kind of class that wouldn't even have the Text property defined, but that'd have position, size, etc properties available. Upper in the hierarchy, after Control, we have Component, but that looks like a really raw class. Any clue about how to achieve this? I know this was a long post :( Thanks

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  • syntax problem crating a method that returns an object (java)

    - by David
    I'm trying to create a method that will sum two timeO objects and return a new TimeO object called sum. Here is the relevant code snippet: public static TimeO add (TimeO t1, TimeO t2) { TimeO sum = new TimeO ; ... } When i try to compile it i get this error message: TimeO.java:15: '(' or '[' expected TimeO sum = new TimeO ; ^ 1 error i cant think of any reason why it would want me to open a set of parenthasies or brackets here but its possible that i dont' quite understand the syntax. Whats going wrong here?

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  • C++ int vector to c#

    - by Stefan Koenen
    I'm doing a C# project and I want to call next_permutation from the algorithm library in C++. I found the way to call c++ functions in c# but i dont know how to get vectors from c++ and use it in c# (cause next_permutation require a int vector...) this is what I'm trying at the moment: extern void NextPermutation(vector<int>& permutation) { next_permutation (permutation.begin(),permutation.end()); } [DllImport("PEDLL.dll", CallingConvention = CallingConvention.Cdecl)] private static extern void NextPermutation(IntPtr test);

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  • Review of a locked part of an function in C#.NET

    - by Lieven Cardoen
    Is this piece of code where I lock a part of the function correct? Or can it have use drawbacks when multiple sessions ask concurrently for the same Exam? Purpose is that client that first asks for the Exam will assemble it, all next clients will get the cached version. public Exam GetExamByExamDto(ExamDTO examDto, int languageId) { Log.Warn("GetExamByExamDto"); lock (LockString) { if (!ContainsExam(examDto.id, languageId)) { Log.Warn("Assembling ExamDto"); var examAssembler = new ExamAssembler(); var exam = examAssembler.createExam(examDto); if (AddToCache(exam)) { _examDictionary.Add(examDto.id + "_" + languageId, exam); } Log.Warn("Returning non cached ExamDto"); return exam; } } Log.Warn("Returning cached ExamDto"); return _examDictionary[examDto.id + "_" + languageId]; } I have a feeling that this isn't the way to do it.

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  • Help with implementing a function to change size of dynamic array

    - by iRobot
    I'm trying to write a function that will change the size of a dynamic array to a new size. In my header file, I have: Image **images; //pointer to a dynamic array of image pointers int maximum; //size I want to do this by allocating a new array and copying the values over without changing their indices. If there are non-null pointers outside the range newmax, then we cant do this. So heres what I have: There are no compilation or runtime errors. However, I find that the new array isnt getting sized right. When I run the following test case: I should get an index out of bounds error, but instead the system lets it slide. Can anyone see the mistake? I've looked for hours but cant find anything.

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  • Assign parameters to function according to parameter names

    - by Korcholis
    I have an assoc array with a list of what are parameters to me. Here's an example: array( 'param1' => 'value1', 'param4' => 'value4', 'param3' => 'value3', 'param2' => 'value2', ); Note that they may come unsorted. Now, is there a way I can make a call (static or from an instance, using call_user_func_array or similar) and correctly pass each value to each parameter? Just to be sure, an example function I'd like to call using that parameter array is one such this: exampleFunction($param1, $param2, $param3, $param4) { ... } PS: Reflection is great, but I'm concerned about execution times (which, at least, in Java tends to increase a lot when using Reflection). If you know any other way to do so, it would be awesome.

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  • One UI for two business objects

    - by JC
    I have an order edit and quote edit screen that are very similar. I want to try to avoid code like this: if (order is Order) SetupScreenForOrder(); if (order is Quote) SetupScreenForQuote(); But maintaining two screens is not good either. If I create some common interface between a Quote and Order then how do you deal with fields like OrderNumber or QuoteDate? What's the best way to handle this?

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  • Java ME Runnable object takes up memory although not made an instance yet

    - by user1646684
    I am facing a strange problem with memory in Java ME. here is a part of my code: int variable=1; while (true) { if (variable==2) { display = Display.getDisplay(this); MyCanvas mc = new MyCanvas(this); // MyCanvas is a runnable object mcT = new Thread(mc); // new thread for MyCanvas mc.repaint(); display.setCurrent(mc); mcT.start(); // run thread } if (variable==1) { // Do some other stuff } } The problem is that although still the variable is set to 1, so it does not come through the if (variable==2) condition the program consumes 300kB more memory than when I delete the code after condition if (variable==2). As far as I know the code should by executed and the objects shall be created only when I set variable to value 2. But it consumes the memory also when the code after condition "if (variable==2)" is not executed. Why does this happen?

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  • How to split the definition of template friend funtion within template class?

    - by ~joke
    The following example compiles fine but I can't figure out how to separate declaration and definition of operator<<() is this particular case. Every time I try to split the definition friend is causing trouble and gcc complains the operator<<() definition must take exactly one argument. #include <iostream> template <typename T> class Test { public: Test(const T& value) : value_(value) {} template <typename STREAM> friend STREAM& operator<<(STREAM& os, const Test<T>& rhs) { os << rhs.value_; return os; } private: T value_; }; int main() { std::cout << Test<int>(5) << std::endl; }

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  • Singletons and constants

    - by devoured elysium
    I am making a program which makes use of a couple of constants. At first, each time I needed to use a constant, I'd define it as //C# private static readonly int MyConstant = xxx; //Java private static final int MyConstant = xxx; in the class where I'd need it. After some time, I started to realise that some constants would be needed in more than one class. At this time, I had 3 choises: To define them in the different classes that needed it. This leads to repetition. If by some reason later I need to change one of them, I'd have to check in all classes to replace them everywhere. To define a static class/singleton with all the constants as public. If I needed a constant X in ClassA, ClassB and ClassC, I could just define it in ClassA as public, and then have ClassB and ClassC refer to them. This solution doesn't seem that good to me as it introduces even more dependencies as the classes already have between them. I ended up implementing my code with the second option. Is that the best alternative? I feel I am probably missing some other better alternative. What worries me about using the singleton here is that it is nowhere clear to a user of the class that this class is using the singleton. Maybe I could create a ConstantsClass that held all the constants needed and then I'd pass it in the constructor to the classes that'd need it? Thanks

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  • How can I use Amazon's API in PHP to search for books?

    - by TerranRich
    I'm working on a Facebook app for book sharing, reviewing, and recommendations. I've scoured the web, searched Google using every search phrase I could think of, but I could not find any tutorials on how to access the Amazon.com API for book information. I signed up for an AWS account, but even the tutorials on their website didn't help me one bit. They're all geared toward using cloud computing for file storage and processing, but that's not what I want. I just want to access their API to search info on books. Kind of like how http://openlibrary.org/ does it, where it's a simple URL call to get information on a book (but their databases aren't nearly as populated as Amazon's). Why is it so hard to find the information I need on Amazon's AWS site? If anybody could help, I would greatly appreciate it.

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  • Trouble accessing Mutable array

    - by Jared Gross
    Im having trouble with my for loop where I am trying to index user names. I am able to separate my original array into individual objects but am not able to send the value to a new array that I need to reference later on. The value and count for userNames in my self.userNamesArray = userNames; line is correct. But right after that when I log self.userNamesArray, I get (null). Any tips cause I'm not completely sure I'm cheers! .h @property (nonatomic, copy) NSMutableArray *userNamesArray; .m - (void)viewWillAppear:(BOOL)animated { self.friendsRelation = [[PFUser currentUser] objectForKey:@"friendsRelation"]; PFQuery *query = [self.friendsRelation query]; [query orderByAscending:@"username"]; [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) { if (error) { NSLog(@"Error: %@ %@", error, [error userInfo]); } else { self.friends = objects; NSArray *users = [self.friends valueForKey:@"username"]; NSLog(@"username:%@", users); //Create an array of name wrappers and pass to the root view controller. NSMutableArray *userNames = [[NSMutableArray alloc] initWithCapacity:[self.friends count]]; for (NSString *user in users) { componentsSeparatedByCharactersInSet:charSet]; NSArray *nameComponents = [user componentsSeparatedByString:@" "]; UserNameWrapper *userNameWrapper = [[UserNameWrapper alloc] initWithUserName:nil nameComponents:nameComponents]; [userNames addObject:userNameWrapper]; } self.userNamesArray = userNames; NSLog(@"userNamesArray:%@",self.userNamesArray); [self.tableView reloadData]; } Here's the code where I need to reference the self.userNamesArray where again, it is comping up nil. - (void)setUserNamesArray:(NSMutableArray *)newDataArray { if (newDataArray != self.userNamesArray) { self.userNamesArray = [newDataArray mutableCopy]; if (self.userNamesArray == nil) { self.sectionsArray = nil; NSLog(@"user names empty"); } else { [self configureSections]; } } }

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  • how to convert the string into json object?

    - by Holicreature
    I use the ajax which sends back a string.. I want to convert the responsetext into a json object to process. I tried eval and also , but doesn't works... Wht to do? My code is function handleResponse() { if(httpa.readyState == 4){ var response = httpa.responseText; if(response!='empty') { alert(response); var foo = eval('(' +strJSON+ ')'); alert (foo); } } } // response alerts [{"id":"1","name":"Pepsodent 100g","selling_price":"28.75"},{"id":"2","name":"Pepsodent 40g","selling_price":"18.90"},{"id":"3","name":"Pepsodent brush","selling_price":"19.50"}]

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  • What is wrong in this c++ code?

    - by narayanpatra
    Why this coder do not show error #include <iostream> int main() { using namespace std; unsigned short int myInt = 99; unsigned short int * pMark = 0; cout << myInt << endl; pMark = &myInt; *pMark = 11; cout << "*pMark:\t" << *pMark << "\nmyInt:\t" << myInt << endl; return 0; } But this one shows : #include<iostream> using namespace std; int addnumber(int *p, int *q){ cout << *p = 12 << endl; cout << *q = 14 << endl; } #include<iostream> using namespace std; int addnumber(int *p, int *q){ cout << *p = 12 << endl; cout << *q = 14 << endl; } int main() { int i , j; cout << "enter the value of first number"; cin >> i; cout << "enter the value of second number"; cin >> j; addnumber(&i, &j); cout << i << endl; cout << j << endl; } In both the code snippets, I am assigning *pointer=somevalue. In first code it do not show any error but it shows error in the line cout << *p = 12 << endl; cout << *q = 14 << endl; What mistake I am doing ?

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  • Test if a method is an override?

    - by Water Cooler v2
    Is there a way to tell if a method is an override? For e.g. public class Foo { public virtual void DoSomething() {} public virtual int GimmeIntPleez() { return 0; } } public class BabyFoo: Foo { public override int GimmeIntPleez() { return -1; } } Is it possible to reflect on BabyFoo and tell if GimmeIntPleez is an override?

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  • Can I just release the top object (iPhone)?

    - by yar
    If I release the object that's holding a reference to the variable that I need to release, is that sufficient? Or must I release at every level of the containment hierarchy? I fear that my logic comes from working with a garbage collector for too long. For instance, I assigned to this property of a UIPickerView instance by hand instead of using IB @property(nonatomic, assign) id<UIPickerViewDelegate> delegate Since it's an assign property, I can't just release the reference after I assign it. When I finally release my UIPickerView instance, do I need to do this: [singlePicker.delegate release]; [singlePicker release]; or is the second line sufficient? Also: Are these assign properties the norm, or is that mostly for Interface Builder? I thought that retain properties were the normal thing to expect.

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  • Makefile won't copy .o to obj/ and target to bin/ folders

    - by about blank
    I'm trying to write a Makefile which will copy its target and objects to bin/ and obj/ directories, respectively. Yet, when I try to run it I get the following error: nasm -f elf64 -g -F stabs main.asm -l spacelander.lst ld -o spacelander obj/main.o ld: cannot find obj/main.o: No such file or directory make: *** [spacelander] Error 1 Why is this happening? Update I noticed when I posted the error that it was due to white spacing errors. After taking care of those, I still get the new error I replaced with the old one I mentioned prior. What is this?? Update 2 Posted -d flag output below Makefile source. Source ASM := nasm ARGS := -f FMT := elf64 OPT := -g -F stabs SRC := main.asm OBJDIR := obj TARGETDIR := bin OBJ := $(addprefix $(OBJDIR)/,$(patsubst %.asm, %.o, $(wildcard *.asm))) TARGET := spacelander .PHONY: all clean all: $(OBJDIR) $(TARGET) $(OBJDIR): mkdir $(OBJDIR) $(OBJDIR)/%.o: $(SRC) $(ASM) $(ARGS) $(FMT) $(OPT) $(SRC) -l $(TARGET).lst $(TARGET): $(OBJ) ld -o $(TARGET) $(OBJ) clean: @rm -f $(TARGET) $(wildcard *.o) @rm -rf $(OBJDIR) make -d Output - NOTE: output is too many characters for body, thus is pastebinned http://pastebin.com/3bctGJxs

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