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• Which class will be instantiated

  - by Michael

  Say I have 2 subclasses from UIViewController, class A and class B. In Main nib file an object is representing class A and it is set to load file from Secondary nib file. The owner of Secondary nib is of class B. The question is - from which class an object in Main nib file will be instanciated once the nib files unarchived in the memory? The reason this question arised is that I have to take care myself if such reference to external NIB file present, to ensure that the first nib's object and second nib's owner is same. Please correct me if my statement is wrong.

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• Best way to call other class view in iphone?

  - by aman-gupta

  Hi, Generally i call my other class view by creating a pointer of delegate and then call the other class by using its link as below:- First Way :- Mydelegate *ptr = (Mydelegate *)[[UIApplication sharedApplication]delegate]; [self.navigationController pushViewController:ptr.NextClasspointer animated:YES]; Second Way :- Create a pointer of that class which u want to call :-- NextClass *nextptr = [[NextClass alloc]initWithnibName:@"NextClass" bundle:nil]; [self.navigationController pushViewController:nextptr animated:YES]; [nextptr release]; nextptr = nil; These above two methods i generally used but my problem is that which one is best for big project so that my stack problem will be removed I mean memory issue will be solved.And is it necessary to release pointer in first and second case is the way i release is correct or wrong Please help me Thanks in Advance

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• UIScrollView with over 100 images

  - by tikkips

  I have implemented a UIScrollView on the iPhone that contains 100 image slots which I fill only the currently visible page, the one before it, and the one after it as the user scrolls. Everything works fine until we get up to image 97 or 98, the entire view disappears! The only thing I can do at that point is navigate back to the previous view. Nothing works as far as the scroll view after this. I am not receiving any memory warnings an the rest of the app functions fine. Any ideas? Has anyone created a UIScrollView in paging mode with over 100 pages? Rick

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• How to save multiple UIImage to a file iPad

  - by aron

  I have a PDF reader that displays pages of the document. What I want to do is allow the user to draw over the PDF in a transparent view. Then I want to save the drawing (UIImage) to disk. If at all possible, I don't want to have the documents folder filled with files like documentName_page01.png, documentName_page02.png for every page that is drawn over. However, I can't figure out how to store these UIImages into a single file without it becoming unwieldy and memory intensive. Any ideas appreciated.

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• What's the reason why core data takes care of the life-cycle of modeled properties?

  - by mystify

  The docs say that I should not release any modeled property in -dealloc. For me, that feels like violating the big memory management rules. I see a big retain in the header and no -release, because Core Data seems to do it at any other time. Is it because Core Data may drop the value of a property dynamically, at any time when needed? And what's Core Data doing when dropping an managed object? If there's no -dealloc, then how and when are the properties getting freed up?

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• Using UIImageViews for 'pages' in an iPhone/iPad storybook app?

  - by outtoplayinc

  I'm new to iPhone programming, and well, what seems obvious to me may seem silly to a seasoned coder. I did a few 'switching views' tutorials on Youtube, and basically, they seems to work nicely for adding pages to a storybook type app. You add a UIViewController and associated view for each page. My question is would this become insanely slow, or a memory hog if I continued this method for say....35+ pages? Each page would also have a sound file associated with it that would play narration when a page load and stops when we leave. Basically, think of a powerpoint type app, with sound, possibly animated image elements, next & back buttons. I'm probably thinking of this very simplistically, but that's where my experience is at for the moment. Any insight or tips as to better and or more efficient ways to proceed would be greatly appreciated.

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• C++ boost thread id and Singleton

  - by aaa

  hi. Sorry to flood so many questions this week. I assume thread index returned by thread.get_id is implementation specific. In case of the pthreads, is index reused? IE, if thread 0 runs and joins, is thread launched afterwords going to have a different ID? the reason I ask this is a need to implement Singleton pattern with a twist: each thread gets its own instance. I know it sounds very crazy, but threads control hardware (cuda) which does not permit device memory sharing. What is a good way to implement such pattern?

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• iPhone xcode array losing state after load

  - by Frames84

  Right i've had a search around and can't find anything. @synthesize list; // this is an NSArry -(void) viewDidLoad { NSArray *arr = [self getJSONFeed]; self.List = [arr retain]; // if i copy the access code into here it works fine. } -(void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSUInteger row = [indexPath row]; NSArray *vals = [list objectAtIndex:row] retain]; NSString *id = [vals valueForKey:@"id"]; // ERROR } right i've taken some of the code to try and provide it as simple as possible, ignore typo's and memory leaks this is sorted. Basically when I select a row I can't get data out of my 'list' array object. Please can anyone help me out?

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• Why does C++ allow variable length arrays that aren't dynamically allocated?

  - by Maulrus

  I'm relatively new to C++, and from the beginning it's been drilled into me that you can't do something like int x; cin >> x; int array[x]; Instead, you must use dynamic memory. However, I recently discovered that the above will compile (though I get a -pedantic warning saying it's forbidden by ISO C++). I know that it's obviously a bad idea to do it if it's not allowed by the standard, but I previously didn't even know this was possible. My question is, why does g++ allow variable length arrays that aren't dynamically allocated if it's not allowed by the standard? Also, if it's possible for the compiler to do it, why isn't it in the standard?

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• A way of allocating multidimensional arrays dynamically

  - by C77431

  salute.. I am learning dynamic allocations for multidimensional arrays in a book and I found some ways for that, And now haven't problem in it. But the author of the book shows us a way, but it doesn't work correctly. It is this: pbeans = new double [3][4]; // Allocate memory for a 3x4 array And this is the error: error C2440: '=' : cannot convert from 'int (*)[4]' to 'int *' how should i define pbeans ( if this type of coding is legal)? and what is the problem exactly? Regards.

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• Table Variables in SSIS

  - by aceinthehole

  In one SQL Task can I create a table variable DELCARE @TableVar TABLE (...) Then in another SQL Task or DataSource destination and select or insert into the table variable? The other option I have considered is using a Temp Table. CREATE TABLE #TempTable (...) I would prefer to use Table Variable so that it remains in memory. But can use temp table if it is not possible to use table variable. Also I cannot use the record set destination as I need to preform straight SQL tasks on it later on.

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• How do I write a Java text file viewer for big log files

  - by Hannes de Jager

  I am working on a software product with an integrated log file viewer. Problem is, its slow and unstable for really large files because it reads the whole file into memory when you view a log file. I'm wanting to write a new log file viewer that addresses this problem. What are the best practices for writing viewers for large text files? How does editors like notepad++ and VIM acomplish this? I was thinking of using a buffered Bi-directional text stream reader together with Java's TableModel. Am I thinking along the right lines and are such stream implementations available for Java?

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• Is the use of union in this matrix class completely safe?

  - by identitycrisisuk

  Unions aren't something I've used that often and after looking at a few other questions on them here it seems like there is almost always some kind of caveat where they might not work. Eg. structs possibly having unexpected padding or endian differences. Came across this in a math library I'm using though and I wondered if it is a totally safe usage. I assume that multidimensional arrays don't have any extra padding and since the type is the same for both definitions they are guaranteed to take up exactly the same amount of memory? template<typename T> class Matrix44T { ... union { T M[16]; T m[4][4]; } m; }; Are there any downsides to this setup? Would the order of definition make any difference to how this works?

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• FileInputStream and FileOutputStream to the same file: Is a read() guaranteed to see all write()s that "happened before"?

  - by user946850

  I am using a file as a cache for big data. One thread writes to it sequentially, another thread reads it sequentially. Can I be sure that all data that has been written (by write()) in one thread can be read() from another thread, assuming a proper "happens-before" relationship in terms of the Java memory model? Is this behavior documented? EDIT: In my JDK, FileOutputSream does not override flush(), and OutputStream.flush() is empty. That's why I'm wondering... EDIT^2: The streams in question are owned exclusively by a class that I have full control of. Each stream is guaranteed to be accesses by one thread only. My tests show that it works as expected, but I'm still wondering if this is guaranteed and documented. See also this related discussion: http://chat.stackoverflow.com/rooms/17598/discussion-between-hussain-al-mutawa-and-user946850

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• How to optimize indexing of large number of DB records using Zend_Lucene and Zend_Paginator

  - by jdichev

  So I have this cron script that is deployed and ran using Cron on a host and indexes all the records in a database table - the index is later used both for the front end of the site and the backed operations as well. After the operation, the index is about 3-4 MB. The problem is it takes a lot of resources (CPU: 30+ and a good chunk of memory) and slows the machine down. My question is about how to optimize the operation described below: First there is a select query built using the Zend Framework API, this query is then passed to a Paginator factory that returns a paginator which I am using to balance the current number of items being indexed and not iterate over too much items. The script is iterating over the current items in the paginator object using a foreach loop until reaching the end and then it starts from the beginning after getting items for the next page. I am suspecting this overhead is caused by the Zend_Lucene but no idea how this could be improved.

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• Address of array vs. address of array[0] - C language

  - by user324994

  My question is why does the address of an array differ from the address of its first position? I'm trying to write my own malloc, but to start out I'm just allocating a chunk of memory and playing around with the addresses. My code looks roughly like this: #define BUFF_SIZE 1024 static char *mallocbuff; int main(){ mallocbuff = malloc(BUFF_SIZE); printf("The address of mallocbuff is %d\n", &mallocbuff); printf("The address of mallocbuff[0] is %d\n", &mallocbuff[0]); } &mallocbuff is the same address every time I run it. &mallocbuff[0] is some random address every time. I was expecting the addresses to match each other. Can anyone explain why this isn't the case?

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• is it possible to write data to a collection in wpf?

  - by randyc

  Hello. In looking through samples I have seen a number of examples where it is possible to present data within a wpf applicaiton by binding to collections. However I was wondering is it possible to write to a collection from an applicaiton. Say for example i have 2 or more fields such as names and I wanted to have hte ability to add up to three names in my application ( all stored in memory). Will collections serve this purpose. In the past with asp.net I have done this by creating data tables and storing values on the fly or during the session. I am trying to learn WPF and I was wondering if collections work in the same fashion? If so could you please post an example or point me to references that show examples of this? Thank you in advance.

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• How do I read UTF-8 characters via a pointer?

  - by Jen

  Suppose I have UTF-8 content stored in memory, how do I read the characters using a pointer? I presume I need to watch for the 8th bit indicating a multi-byte character, but how exactly do I turn the sequence into a valid Unicode character? Also, is wchar_t the proper type to store a single Unicode character? This is what I have in mind: wchar_t readNextChar (char** p) { char ch = *p++; if (ch & 128) { // This is a multi-byte character, what do I do now? // char chNext = *p++; // ... but how do I assemble the Unicode character? ... } ... }

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• Replacing the Import Table in PE file by standart LoadLibrary...

  - by user308368

  Hello. I have an executable (PE) file that load a dll file as represented in the Import table... let say: PEFile.exe Modules.dll my question is how can i remove Modules.dll's import_descriptor from the imports and do its work by loadLibrary without the rely on the import table and without destroy the file???... My bigger problem his i could not understand exactly how the Import thing works... after the loader read the information he needs to do the import's thing, i believe he use the LoadLibrary, GetProcAddress APIs... but i couldn't understated what he doing with the pointers he get... he putting them somewhere in memory... and then what just call them?!? all the papers i found in the net explain the structure of the import table, but i didn't found a paper that explain how it is really work and get used... i hope you cold understand my Gibberish English... Thank you!

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• Program visible to Linux as normal directory

  - by Xam

  I'm trying to write program to work as programmable directory, in other words: User, or other systems open that directory and read/write files or dirs. I try to create program to cache most used files in memory (less I/O to HDD), but right now I don't know how to achive that. There are probably some docs about this but I can't find them. I know that there is FUSE, NFS and others, but reading their source is quite difficult. If any one has info about implementation in C lang I'll be very grateful. Sorry for my English..

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• C string program

  - by mrblippy

  Hi, i have been given a task to do ar school that must read three strings in, store the third string in dynamically allocated memory and print out the last 4 letters of the first word alphabetically. Here is the program i have so far but the strings are all stored in different variables, making them hard to sort. if anyone could give me a hand and help me finish this program i would be very grateful. thanks #include <stdio.h> #include <stdlib.h> #include <string.h> int main() { char word1[101]; char word2[101]; char* word3; char buffer[101]; scanf("%s", word1); scanf("%s", word2); scanf("%s", buffer); word3 = (char *) malloc(strlen(buffer)+1); strcpy(word3, buffer); return 0; }

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• Android app crashes on second run

  - by Nick

  I have been working on my app and it runs on the simulator fine. I loaded it into my phone and now I have a problem. It runs fine when I first start it and also if I pick home and then restart it; however, if I use the back arrow and then restart it it crashes on that time, but will work out the next time I start it. I think it has to do with some kind of memory build up, but I verified onDestroy is being called, I figured that deletes everything my program created, right?

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• what mysql table structure is better

  - by Sergey

  I have very complicated search algorithm on my site, so i decided to make a table with cache or maybe all possible results. I wanna ask what structure would be better, or maybe not the one of them? (mySQL) 1) word VARCHAR, results TEXT or BLOB where i'll store ids of found objects (for example 6 chars for each id) 2) word VARCHAR, result INT, but words are not unique now i think i'll have about 200 000 rows in 1) with 1000-10000 ids each row or 200 000 000+ rows in 2) First way takes more storage memory but i think it would be much faster to find 1 unique row among 200 000, than 1000 rows among 200 mln non unique rows i think about index on word column and no sphinx. So that do YOU think? p.s. as always, sorry for my english if it's not very good.

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• Improving the performance of an nHibernate Data Access Layer.

  - by Amitabh

  I am working on improving the performance of DataAccess Layer of an existing Asp.Net Web Application. The scenerios are. Its a web based application in Asp.Net. DataAccess layer is built using NHibernate 1.2 and exposed as WCF Service. The Entity class is marked with DataContract. Lazy loading is not used and because of the eager-fetching of the relations there is huge no of database objects are loaded in the memory. No of hits to the database is also high. For example I profiled the application using NHProfiler and there were about 50+ sql calls to load one of the Entity object using the primary key. I also can not change code much as its an existing live application with no NUnit test cases at all. Please can I get some suggestions here?

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• SQL Server Compact Edition 3.5 performance

  - by Wili

  I am using SQL Server CE 3.5 SP1 in one of my client applications. When a user loads the program and starts using it, performance is fine. If the user lets the program sit idle for a while, it takes a considerable amount of time (10 or more seconds) for the program to respond. Every time the user asks for a new screen, a call is made to the SQL CE database to get the data for that screen. It seems like the hard drive may be going to sleep and then when the database is accessed, the hard drive has to wake back up. Is it possible to load the entire database into memory and work from that? Are there any other suggestions on how to increase performance?

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