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  • Creating objects and referencing before saving object to db

    - by Flexo
    Sorry about the vague title, but i didnt know how to ask the question in one line :) I have an order with nested itemgroups that again have nested items. the user specify the amount of item that he would like to have in each itemgroup. I would like to create these items in the create method of the orders controller when the order itself is being created. I kinda have 2 problems here. First, how do i set the reference of the items, or better yet, put the items into the @order object so they are saved when the @order is saved? the items are being stored in the db as the code is now, but the reference is not set because the order is not stored in the db yet so it doesnt have an id yet. Second, im not sure im using the correct way to get the id from my itemgroup. @order = Order.new(params[:order]) @order.itemgroups.each do |f| f.amount.times do @item = Item.new() @item.itemgroup_id = f.id @item.save end end

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  • Android Static Variable Scope and Lifetime

    - by Edison
    I have an application that has a Service uses a ArrayList to store in the background for a very long time, the variable is initialized when the service started. The service is in the background and there will be frequent access to the variable (that's why i don't want to use file management or settings since it will be very expensive for a file I/O for the sake of battery life). The variable will likely to be ~1MB-2MB over its life tie. Is it safe to say that it will never be nulled by GC or the system or is there any way to prevent it? Thanks.

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  • Using std::bad_alloc for C pointers

    - by otibom
    I'm using a library written in C in a C++ project. I'd like to use C++ exceptions to handle C errors. In particular, it would be nice to have an exception thrown if an allocation fails. I can do this in constructors of classes which hold C-style pointers to C structs : if (c_object == NULL) throw std::bad_alloc(); But if the class is responsible for several C objects they are no ways of free-ing all already allocated pointers since the destructor isn't called. I have a feeling I could use smart-pointers, but I don't have much experience with them. What's more, I have to have access to the original C pointers to use the C api properly. Is there an elegant solution to this ?

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  • Iphone release problem

    - by xger86x
    Hi, i have the following code in a .h @property (nonatomic, copy) NSString *username; Then, username is assigned in this way when the user enter text in a TextField: self.username = textField.text; And then, in dealloc method i call release: NSLog(@"%d",[username retainCount]); [username release]; NSLog(@"%d",[username retainCount]); But in the console it prints: 2011-01-11 23:09:52.468 IApp[2527:307] 1 2011-01-11 23:09:52.480 IApp[2527:307] 1 What is the problem? Thanks

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  • NSMutableArray accessing issue.

    - by Danegraphics
    I've searched and have no answer. I've created an NSMutableArray and am getting an EXC_BAD_ACCESS error in one place of access. Here. This is declaring in the .h file: NSMutableArray *buttons; ... @property (nonatomic, retain)NSMutableArray *buttons; And this is the synthesizing and implimenting: @synthesize buttons; ... - (id)init { self = [super init]; if(self != nil) { buttons = [[NSMutableArray alloc] init]; } return self; } ... -(void)addButtonWithImage:(Image*)image { Image *button = image; [buttons addObject:button]; [button release]; } ... -(void)replaceButtonAt:(int)num with:(Image*)image { Image *button = image; [buttons replaceObjectAtIndex:num withObject:button]; <<===EXC_BAD_ACCESS [button release]; } But when I use this: -(void)renderButton:(int)num atPoint:(CGPoint)point center:(BOOL)center{ Image *button = [buttons objectAtIndex:num]; [button renderAtPoint:point centerOfImage:center]; } It works

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  • Rails: Serializing objects in a database?

    - by keruilin
    I'm looking for some general guidance on serializing objects in a database. What are serialized objects? What are some best-practice scenarios for serializing objects in a DB? What attributes do you use when creating the column in the DB so you can use a serialized object? How to save a serialized object? And how to access the serialized object and its attributes? (Using hashes?)

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  • Is there an ORM with APIs to be used programatically?

    - by Kabeer
    Hello. Neither did not get any response for my previous question, nor enough views :) So here I am now framing my query afresh. Is there any ORM that offers APIs to be used programatically? In my situation, a user will be helped through a wizard to define some entities. Thereafter those entites will be created in a database in form of tables (there will of course be some improvization). I need an ORM that offers APIs for modeling and creating entities during application runtime and not just during design time. Mine is a .Net application, therefore I was looking at Entity Framework. However, to me it looked tied to Visual Studio (I may be wrong also as I am new to it). Any recommendations? Or alternative point of view?

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  • Released object crashes app

    - by John Smith
    I am using objective-C++ (+Boost) for iPhone development. I am in a rather tight loop and need to allocate and release a certain object. The code is something like this. for (int i=0;i<100;i++) { opt = [[FObj alloc] init]; //do stuff with opt [opt release]; } The FObj object is something like @interface FObj MyCPPObj * cppobj; @end In the implementation of FObj there is a dealloc method: -(void) dealloc { delete cppobj; //previously allocated with 'new' [super dealloc]; } I am afraid that if i don't release then the 'MyCPPObj's will just pile up. But releasing makes the app crash after the first loop. What am I doing wrong? Or perhaps should I make cppobj and boost::shared_ptr? (do boost shared pointers automatically release their objects when an objective-C++ object is deleted?)

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  • What does CPU Time consist of? [closed]

    - by Sid
    What does CPU time exactly consist of? For instance, is the time taken to access a page from the RAM (at which point, the CPU is most likely idling) part of the CPU time? I'm not talking about fetching the page from the disk here, just fetching it from the RAM. Thanks

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  • Release resources in .Net C#

    - by zaidwaqi
    Hi, I'm new to C# and .NET, ,and have been reading around about it. I need to know why and when do I need to release resources? Doesn't the garbage collector take care of everything? When do I need to implement IDisposable, and how is it different from destructor in C++? Also, if my program is rather small i.e. a screensaver, do I need to care about releasing resources? Thanks.

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  • Use of malloc() and free() in C++

    - by Matt H
    Is there any reason to use malloc and free in C++ over their more modern counterparts? Occasionally I see this, and I can't see why some people do it. Are there any advantages/disadvantage, or is there no real difference, except that it's just better to use C++ constructs in C++?

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  • Implementing Barrier system solution in C or C++

    - by hardikpatel172
    Actually I have been assigned to implement Barrier system solution in either C or C++ programming language... But I have zero knowledge about it ... I know the problem as well as solution theoritically.. But I have no idea how to implement it.... How can it be possible in C++ to stop or run or wait any process.... Plz yaar... Anyone help me... It's urgent...

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  • C#: How to implement a smart cache

    - by Svish
    I have some places where implementing some sort of cache might be useful. For example in cases of doing resource lookups based on custom strings, finding names of properties using reflection, or to have only one PropertyChangedEventArgs per property name. A simple example of the last one: public static class Cache { private static Dictionary<string, PropertyChangedEventArgs> cache; static Cache() { cache = new Dictionary<string, PropertyChangedEventArgs>(); } public static PropertyChangedEventArgs GetPropertyChangedEventArgsa(string propertyName) { if (cache.ContainsKey(propertyName)) return cache[propertyName]; return cache[propertyName] = new PropertyChangedEventArgs(propertyName); } } But, will this work well? For example if we had a whole load of different propertyNames, that would mean we would end up with a huge cache sitting there never being garbage collected or anything. I'm imagining if what is cached are larger values and if the application is a long-running one, this might end up as kind of a problem... or what do you think? How should a good cache be implemented? Is this one good enough for most purposes? Any examples of some nice cache implementations that are not too hard to understand or way too complex to implement?

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  • How much RAM used by Python dict or list?

    - by Who8MyLunch
    My problem: I am writing a simple Python tool to help me visualize my data as a function of many parameters. Each change in parameters involves a non-trivial amount of time, so I would like to cache each step's resulting imagery and supporting data in a dictionary. But then I worry that this dictionary could grow too large over time. Most of my data is in the form of Numpy arrays. My question: How would one go about computing the total number of bytes used by a Python dictionary. The dictionary itself may contain lists and other dictionaries, each of which contain data stored in Numpy arrays. Ideas?

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  • How costly performance-wise are these actions in iPhone objective-C?

    - by Alex Gosselin
    This is really a few questions in one, I'm wondering what the performance cost is for these things, as I haven't really been following a best practice of any sort for these. The answers may also be useful to other readers, if somebody knows these. (1) If I need the core data managed object context, is it bad to use #import "myAppDelegate.h" //farther down in the code: NSManagedObjectContext *context = [(myAppDelegate.h*)[[UIApplication sharedApplication] delegate] managedObjectContext]; as opposed to leaving the warning you get if you don't cast the delegate? (2) What is the cheapest way to hard-code a string? I have been using return @"myString"; on occasion in some functions where I need to pass it to a variety of places, is it better to do it this way: static NSString *str = @"myString"; return str; (3) How costly is it to subclass an object i wrote vs. making a new one, in general? (4) When I am using core data and navigating through a hierarchy of some sort, is it necessary to turn things back into faults somehow after I read some info from them? or is this done automatically? Thanks for any help.

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  • Will this be garbage collected in JVM?

    - by stjowa
    I am running the following code every two minutes via a Timer: object = new Object(this); Potentially, this is a lot of objects being created and a lot of objects being overwritten. Do the overwritten objects get garbage collected, even with a reference to itself being used in the newly created object? I am using JDK 1.6.0_13. Thanks for the help.

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  • Static variables within functions in C++ - allocated even if function doesn't run?

    - by John C
    I've been reading up on C++ on the Internet, and here's one thing that I haven't been quite able to find an answer to. I know that static variables used within functions are akin to globals, and that subsequent invocations of that function will have the static variable retain its value between calls. However, if the function is never claled, does the static variable get allocated? Thanks

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  • What to throw in a C++ class wrapping a C library ?

    - by ereOn
    I have to create a set of wrapping C++ classes around an existing C library. For many objects of the C library, the construction is done by calling something like britney_spears* create_britney_spears() and the opposite function void free_britney_spears(britney_spears* brit). If the allocation of a britney_spears fails, create_britney_spears() returns NULL. This is, as far as I know, a very common pattern. Now I want to wrap this inside a C++ class. //britney_spears.hpp class BritneySpears { public: BritneySpears(); private: boost::shared_ptr<britney_spears> m_britney_spears; }; And here is the implementation: // britney_spears.cpp BritneySpears::BritneySpears() : m_britney_spears(create_britney_spears(), free_britney_spears) { if (!m_britney_spears) { // Here I should throw something to abort the construction, but what ??! } } So the question is in the code sample: What should I throw to abort the constructor ? I know I can throw almost anything, but I want to know what is usually done. I have no other information about why the allocation failed. Should I create my own exception class ? Is there a std exception for such cases ? Many thanks.

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  • How to do comments in Activity Stream? (like Facebook)

    - by fesja
    Hi, I'm starting to develop an activity stream. I've read both How to implement the activity stream in a social network and What’s the best manner of implementing a social activity stream?. What I haven't found is the best way to add comments to the activities. As in facebook, each comment can be commented by another person. If each activity comment is saved as another activity, then I would not be able to get the activity of that comment without doing a query. So the solution I'm thinking is to save the comments inside the serialize data field of each activity. If the user wants to delete his comment, I would have to update that activity. Is this the correct solution? Is there a better approach? Thanks!

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