Search Results

Search found 11639 results on 466 pages for 'numerical methods'.

Page 424/466 | < Previous Page | 420 421 422 423 424 425 426 427 428 429 430 431  | Next Page >

• Find location using only distance and bearing?

  - by pinnacler

  Triangulation works by checking your angle to three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and it's to my right at 90 degrees." Repeat 2 more times for different targets and angles. Trilateration works by checking your distance from three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and I'm 100 meters away from that." Repeat 2 more times for different targets and ranges. But both of those methods rely on knowing WHAT you're looking at. Say you're in a forest and you can't differentiate between trees, but you know where key trees are. These trees have been hand picked as "landmarks." You have a robot moving through that forest slowly. Do you know of any ways to determine location based solely off of angle and range, exploiting geometry between landmarks? Note, you will see other trees as well, so you won't know which trees are key trees. Ignore the fact that a target may be occluded. Our pre-algorithm takes care of that. 1) If this exists, what's it called? I can't find anything. 2) What do you think the odds are of having two identical location 'hits?' I imagine it's fairly rare. 3) If there are two identical location 'hits,' how can I determine my exact location after I move the robot next. (I assume the chances of having 2 occurrences of EXACT angles in a row, after I reposition the robot, would be statistically impossible, barring a forest growing in rows like corn). Would I just calculate the position again and hope for the best? Or would I somehow incorporate my previous position estimate into my next guess? If this exists, I'd like to read about it, and if not, develop it as a side project. I just don't have time to reinvent the wheel right now, nor have the time to implement this from scratch. So if it doesn't exist, I'll have to figure out another way to localize the robot since that's not the aim of this research, if it does, lets hope it's semi-easy.

  Read the article

• The question about the basics of LINQ to SQL

  - by Alex

  I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer LINQ gets all customers from the database ("SELECT * FROM Customers"), moves them to the Customers array and then makes a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 && Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 && Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

  Read the article

• How to convert a 32bpp image to an indexed format?

  - by Ed Swangren

  So here are the details (I am using C# BTW): I receive a 32bpp image (JPEG compressed) from a server. At some point, I would like to use the Palette property of a bitmap to color over-saturated pixels (brightness 240) red. To do so, I need to get the image into an indexed format. I have tried converting the image to a GIF, but I get quality loss. I have tried creating a new bitmap in an index format by these methods: // causes a "Parameter not valid" error Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Indexed) // no error, but the resulting image is black due to information loss I assume Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Format8bppIndexed) I am at a loss now. The data in this image is changed constantly by the user, so I don't want to manually set pixels that have a brightness 240 if I can avoid it. If I can set the palette once when the image is created, my work is done. If I am going about this the wrong way to begin with please let me know. EDIT: Thanks guys, here is some more detail on what I am attempting to accomplish. We are scanning a tissue slide at high resolution (pathology application). I write the interface to the actual scanner. We use a line-scan camera. To test the line rate of the camera, the user scans a very small portion and looks at the image. The image is displayed next to a track bar. When the user moves the track bar (adjusting line rate), I change the overall intensity of the image in an attempt to model what it would look like at the new line rate. I do this using an ImageAttributes and ColorMatrix object currently. When the user adjusts the track bar, I adjust the matrix. This does not give me per pixel information, but the performance is very nice. I could use LockBits and some unsafe code here, but I would rather not rewrite it if possible. When the new image is created, I would like for all pixels with a brightness value of 240 to be colored red. I was thinking that defining a palette for the bitmap up front would be a clean way of doing this.

  Read the article

• Avoiding stack overflows in wrapper DLLs

  - by peachykeen

  I have a program to which I'm adding fullscreen post-processing effects. I do not have the source for the program (it's proprietary, although a developer did send me a copy of the debug symbols, .map format). I have the code for the effects written and working, no problems. My issue now is linking the two. I've tried two methods so far: Use Detours to modify the original program's import table. This works great and is guaranteed to be stable, but the user's I've talked to aren't comfortable with it, it requires installation (beyond extracting an archive), and there's some question if patching the program with Detours is valid under the terms of the EULA. So, that option is out. The other option is the traditional DLL-replacement. I've wrapped OpenGL (opengl32.dll), and I need the program to load my DLL instead of the system copy (just drop it in the program folder with the right name, that's easy). I then need my DLL to load the Cg framework and runtime (which relies on OpenGL) and a few other things. When Cg loads, it calls some of my functions, which call Cg functions, and I tend to get stack overflows and infinite loops. I need to be able to either include the Cg DLLs in a subdirectory and still use their functions (not sure if it's possible to have my DLLs import table point to a DLL in a subdirectory) or I need to dynamically link them (which I'd rather not do, just to simplify the build process), something to force them to refer to the system's file (not my custom replacement). The entire chain is: Program loads DLL A (named opengl32.dll). DLL A loads Cg.dll and dynamically links (GetProcAddress) to sysdir/opengl32.dll. I now need Cg.dll to also refer to sysdir/opengl32.dll, not DLL A. How would this be done? Edit: How would this be done easily without using GetProcAddress? If nothing else works, I'm willing to fall back to that, but I'd rather not if at all possible. Edit2: I just stumbled across the function SetDllDirectory in the MSDN docs (on a totally unrelated search). At first glance, that looks like what I need. Is that right, or am I misjudging? (off to test it now) Edit3: I've solved this problem by doing thing a bit differently. Instead of dropping an OpenGL32.dll, I've renamed my DLL to DInput.dll. Not only does it have the advantage of having to export one function instead of well over 120 (for the program, Cg, and GLEW), I don't have to worry about functions running back in (I can link to OpenGL as usual). To get into the calls I need to intercept, I'm using Detours. All in all, it works much better. This question, though, is still an interesting problem (and hopefully will be useful for anyone else trying to do crazy things in the future). Both the answers are good, so I'm not sure yet which to pick...

  Read the article

• PHP MVC Principles

  - by George

  I'm not using an off-the-shelf framework and don't particularly want to (nor d I want to go into the reasons why...). Anyway, onto my question(s), I hope it make sense.... I'm trying to get my head around what should go in the model and what should go in the controller. Originally I had the impression that a model class should represent an actual object (eg - a car from the cars table of a database) and model properties should mirror the database fields. However I'm now getting the feeling that I've got the wrong idea - should an instance of a model class represent an actual item, or should it contain a number of methods for doing stuff - sometimes to one car or sometimes to multiple cars based on my example earlier. For example I want to get all the cars from a the database and show them in the view. Am I right in think it should be along the lines of this? Controller File function list() { $cars = $this->model->get_all(); $this->view->add($cars); $this->view->render('cars-list'); } Model File function get_all() { // Use a database interaction class that I've written $cars = Database::select(); return $cars; } Now, if the car had a "status" field that was stored as an integer in the database and I wanted to change that to a string, where should that be done? By looping the SQL results array in the get_all() method in the model? Also, where should form validation live? I have written a validation class that works a little like this: $validator = new Validator(); $validator->check('field_name', 'required'); If the check fails, it adds an error message to the array in the Validator. This array of error messages would then get passed to the view. Should the use of my validator class go in model or the controller? Thanks in advance for for any help anyone can offer. If you know of any links to a simple MVC example / open source application that deals with basic CRUD, they would be much appreciated.

  Read the article

• Silverlight with MVVM Inheritance: ModelView and View matching the Model

  - by moonground.de

  Hello Stackoverflowers! :) Today I have a special question on Silverlight (4 RC) MVVM and inheritance concepts and looking for a best practice solution... I think that i understand the basic idea and concepts behind MVVM. My Model doesn't know anything about the ViewModel as the ViewModel itself doesn't know about the View. The ViewModel knows the Model and the Views know the ViewModels. Imagine the following basic (example) scenario (I'm trying to keep anything short and simple): My Model contains a ProductBase class with a few basic properties, a SimpleProduct : ProductBase adding a few more Properties and ExtendedProduct : ProductBase adding another properties. According to this Model I have several ViewModels, most essential SimpleProductViewModel : ViewModelBase and ExtendedProductViewModel : ViewModelBase. Last but not least, according Views SimpleProductView and ExtendedProductView. In future, I might add many product types (and matching Views + VMs). 1. How do i know which ViewModel to create when receiving a Model collection? After calling my data provider method, it will finally end up having a List<ProductBase>. It containts, for example, one SimpleProduct and two ExtendedProducts. How can I transform the results to an ObservableCollection<ViewModelBase> having the proper ViewModel types (one SimpleProductViewModel and two ExtendedProductViewModels) in it? I might check for Model type and construct the ViewModel accordingly, i.e. foreach(ProductBase currentProductBase in resultList) if (currentProductBase is SimpleProduct) viewModels.Add( new SimpleProductViewModel((SimpleProduct)currentProductBase)); else if (currentProductBase is ExtendedProduct) viewModels.Add( new ExtendedProductViewModels((ExtendedProduct)currentProductBase)); ... } ...but I consider this very bad practice as this code doesn't follow the object oriented design. The other way round, providing abstract Factory methods would reduce the code to: foreach(ProductBase currentProductBase in resultList) viewModels.Add(currentProductBase.CreateViewModel()) and would be perfectly extensible but since the Model doesn't know the ViewModels, that's not possible. I might bring interfaces into game here, but I haven't seen such approach proven yet. 2. How do i know which View to display when selecting a ViewModel? This is pretty the same problem, but on a higher level. Ended up finally having the desired ObservableCollection<ViewModelBase> collection would require the main view to choose a matching View for the ViewModel. In WPF, there is a DataTemplate concept which can supply a View upon a defined DataType. Unfortunately, this doesn't work in Silverlight and the only replacement I've found was the ResourceSelector of the SLExtensions toolkit which is buggy and not satisfying. Beside that, all problems from Question 1 apply as well. Do you have some hints or even a solution for the problems I describe, which you hopefully can understand from my explanation? Thank you in advance! Thomas

  Read the article

• iPhone noob - setting NSMutableDictionary entry inside Singleton?

  - by codemonkey

  Yet another iPhone/Objective-C noob question. I'm using a singleton to store app state information. I'm including the singleton in a Utilities class that holds it (and eventually other stuff). This utilities class is in turn included and used from various view controllers, etc. The utilities class is set up like this: // Utilities.h #import <Foundation/Foundation.h> @interface Utilities : NSObject { } + (id)GetAppState; - (id)GetAppDelegate; @end // Utilities.m #import "Utilities.h" #import "CHAPPAppDelegate.h" #import "AppState.h" @implementation Utilities CHAPPAppDelegate* GetAppDelegate() { return (CHAPPAppDelegate *)[UIApplication sharedApplication].delegate; } AppState* GetAppState() { return [GetAppDelegate() appState]; } @end ... and the AppState singleton looks like this: // AppState.h #import <Foundation/Foundation.h> @interface AppState : NSObject { NSMutableDictionary *challenge; NSString *challengeID; } @property (nonatomic, retain) NSMutableDictionary *challenge; @property (nonatomic, retain) NSString *challengeID; + (id)appState; @end // AppState.m #import "AppState.h" static AppState *neoAppState = nil; @implementation AppState @synthesize challengeID; @synthesize challenge; # pragma mark Singleton methods + (id)appState { @synchronized(self) { if (neoAppState == nil) [[self alloc] init]; } return neoAppState; } + (id)allocWithZone:(NSZone *)zone { @synchronized(self) { if (neoAppState == nil) { neoAppState = [super allocWithZone:zone]; return neoAppState; } } return nil; } - (id)copyWithZone:(NSZone *)zone { return self; } - (id)retain { return self; } - (unsigned)retainCount { return UINT_MAX; //denotes an object that cannot be released } - (void)release { // never release } - (id)init { if (self = [super init]) { challengeID = [[NSString alloc] initWithString:@"0"]; challenge = [NSMutableDictionary dictionary]; } return self; } - (void)dealloc { // should never be called, but just here for clarity [super dealloc]; } @end ... then, from a view controller I'm able to set the singleton's "challengeID" property like this: [GetAppState() setValue:@"wassup" forKey:@"challengeID"]; ... but when I try to set one of the "challenge" dictionary entry values like this: [[GetAppState() challenge] setObject:@"wassup" forKey:@"wassup"]; ... it fails giving me an "unrecognized selector sent..." error. I'm probably doing something really obviously dumb? Any insights/suggestions will be appreciated.

  Read the article

• Dependency Injection and Unit of Work pattern

  - by sunwukung

  I have a dilemma. I've used DI (read: factory) to provide core components for a homebrew ORM. The container provides database connections, DAO's,Mappers and their resultant Domain Objects on request. Here's a basic outline of the Mappers and Domain Object classes class Mapper{ public function __constructor($DAO){ $this->DAO = $DAO; } public function load($id){ if(isset(Monitor::members[$id]){ return Monitor::members[$id]; $values = $this->DAO->selectStmt($id); //field mapping process omitted for brevity $Object = new Object($values); return $Object; } } class User(){ public function setName($string){ $this->name = $string; //mark modified by means fair or foul } } The ORM also contains a class (Monitor) based on the Unit of Work pattern i.e. class Monitor(){ private static array modified; private static array dirty; public function markClean($class); public function markModified($class); } The ORM class itself simply co-ordinates resources extracted from the DI container. So, to instantiate a new User object: $Container = new DI_Container; $ORM = new ORM($Container); $User = $ORM->load('user',1); //at this point the container instantiates a mapper class //and passes a database connection to it via the constructor //the mapper then takes the second argument and loads the user with that id $User->setName('Rumpelstiltskin');//at this point, User must mark itself as "modified" My question is this. At the point when a user sets values on a Domain Object class, I need to mark the class as "dirty" in the Monitor class. I have one of three options as I can see it 1: Pass an instance of the Monitor class to the Domain Object. I noticed this gets marked as recursive in FirePHP - i.e. $this-Monitor-markModified($this) 2: Instantiate the Monitor directly in the Domain Object - does this break DI? 3: Make the Monitor methods static, and call them from inside the Domain Object - this breaks DI too doesn't it? What would be your recommended course of action (other than use an existing ORM, I'm doing this for fun...)

  Read the article

• Creating a spam list with a web crawler in python

  - by user313623

  Hey guys, I'm not trying to do anything malicious here, I just need to do some homework. I'm a fairly new programmer, I'm using python 3.0, and I having difficulty using recursion for problem-solving. I've been stuck on this question for quite a while. Here's the assignment: Write a recursive method spam(url, n) that takes a url of a web page as input and a non-negative integer n, collects all the email address contained in the web page and adds them to a global dictionary variable spam_dict, and then recursively calls itself on every http hyperlink contained in the web page. You will use a dictionary so only one copy of every email address is save; your dictionary will store (key,value) pairs (email, email). The recursive call should use the parameter n-1 instead of n. If n = 0, you should collect the email addresses but no recursive calls should be made. The parameter n is used to limit the recursion to at most depth n. You will need to use the solutions of the two above problems; you method spam() will call the methods links2() and emails() and possibly other functions as well. Notes: 1. running spam() directly will produce no output on the screen; to find your spam_dict, you will need to read the value of spam_dict, and you will also need to reset it to the empty dictionary before every run of spam. 2. Recall how global variables are used. Usage: spam_dict = {} spam('http://reed.cs.depaul.edu/lperkovic/csc242/test1.html',0) spam_dict.keys() dict_keys([]) spam_dict = {} spam('http://reed.cs.depaul.edu/lperkovic/csc242/test1.html',1) spam_dict.keys() dict_keys(['[email protected]', '[email protected]']) So far, I've written a function that traverses web pages and puts all the links in a nice little list, and what I wanted to do was call that functions. And why would I use recursion on a dictionary? And how? I don't understand how n ties into all of this. def links2(url): content = str(urlopen(url).read()) myparser = MyHTMLParser() myparser.feed(content) lst = myparser.get() mergelst = [] for link in lst: mergelst.append(urljoin(lst[0],link)) print(mergelst) Any input (except why spam is bad) would be greatly appreciated. Also, I realize that the above function could probably look better, if you have a way to do it, I'm all ears. However, all I need is the point is for the program to produce the proper output.

  Read the article

• In a DDD approach, is this example modelled correctly?

  - by Tag

  Just created an acc on SO to ask this :) Assuming this simplified example: building a web application to manage projects... The application has the following requirements/rules. 1) Users should be able to create projects inserting the project name. 2) Project names cannot be empty. 3) Two projects can't have the same name. I'm using a 4-layered architecture (User Interface, Application, Domain, Infrastructure). On my Application Layer i have the following ProjectService.cs class: public class ProjectService { private IProjectRepository ProjectRepo { get; set; } public ProjectService(IProjectRepository projectRepo) { ProjectRepo = projectRepo; } public void CreateNewProject(string name) { IList<Project> projects = ProjectRepo.GetProjectsByName(name); if (projects.Count > 0) throw new Exception("Project name already exists."); Project project = new Project(name); ProjectRepo.InsertProject(project); } } On my Domain Layer, i have the Project.cs class and the IProjectRepository.cs interface: public class Project { public int ProjectID { get; private set; } public string Name { get; private set; } public Project(string name) { ValidateName(name); Name = name; } private void ValidateName(string name) { if (name == null || name.Equals(string.Empty)) { throw new Exception("Project name cannot be empty or null."); } } } public interface IProjectRepository { void InsertProject(Project project); IList<Project> GetProjectsByName(string projectName); } On my Infrastructure layer, i have the implementation of IProjectRepository which does the actual querying (the code is irrelevant). I don't like two things about this design: 1) I've read that the repository interfaces should be a part of the domain but the implementations should not. That makes no sense to me since i think the domain shouldn't call the repository methods (persistence ignorance), that should be a responsability of the services in the application layer. (Something tells me i'm terribly wrong.) 2) The process of creating a new project involves two validations (not null and not duplicate). In my design above, those two validations are scattered in two different places making it harder (imho) to see whats going on. So, my question is, from a DDD perspective, is this modelled correctly or would you do it in a different way?

  Read the article

• Wondering about a way to conserve memory in C# using List<> with structs

  - by Michael Ryan

  I'm not even sure how I should phrase this question. I'm passing some CustomStruct objects as parameters to a class method, and storing them in a List. What I'm wondering is if it's possible and more efficient to add multiple references to a particular instance of a CustomStruct if a equivalent instance it found. This is a dummy/example struct: public struct CustomStruct { readonly int _x; readonly int _y; readonly int _w; readonly int _h; readonly Enum _e; } Using the below method, you can pass one, two, or three CustomStruct objects as parameters. In the final method (that takes three parameters), it may be the case that the 3rd and possibly the 2nd will have the same value as the first. List<CustomStruct> _list; public void AddBackground(CustomStruct normal) { AddBackground(normal, normal, normal); } public void AddBackground(CustomStruct normal, CustomStruct hover) { AddBackground(normal, hover, hover); } public void AddBackground(CustomStruct normal, CustomStruct hover, CustomStruct active) { _list = new List<CustomStruct>(3); _list.Add(normal); _list.Add(hover); _list.Add(active); } As the method stands now, I believe it will create new instances of CustomStruct objects, and then adds a reference of each to the List. It is my understanding that if I instead check for equality between normal and hover and (if equal) insert normal again in place of hover, when the method completes, hover will lose all references and eventually be garbage collected, whereas normal will have two references in the List. The same could be done for active. That would be better, right? The CustomStruct is a ValueType, and therefore one instance would remain on the Stack, and the three List references would just point to it. The overall List size is determined not by the object Type is contains, but by its Capacity. By eliminating the "duplicate" CustomStuct objects, you allow them to be cleaned up. When the CustomStruct objects are passed to these methods, new instances are created each time. When the structs are added to the List, is another copy made? For example, if i pass just one CustomStruct, AddBackground(normal) creates a copy of the original variable, and then passes it three times to Addbackground(normal, hover, active). In this method, three copies are made of the original copy. When the three local variables are added to the List using Add(), are additional copies created inside Add(), and does that defeat the purpose of any equality checks as previously mentioned? Am I missing anything here?

  Read the article

• C# Extend array type to overload operators

  - by Episodex

  I'd like to create my own class extending array of ints. Is that possible? What I need is array of ints that can be added by "+" operator to another array (each element added to each), and compared by "==", so it could (hopefully) be used as a key in dictionary. The thing is I don't want to implement whole IList interface to my new class, but only add those two operators to existing array class. I'm trying to do something like this: class MyArray : Array<int> But it's not working that way obviously ;). Sorry if I'm unclear but I'm searching solution for hours now... UPDATE: I tried something like this: class Zmienne : IEquatable<Zmienne> { public int[] x; public Zmienne(int ilosc) { x = new int[ilosc]; } public override bool Equals(object obj) { if (obj == null || GetType() != obj.GetType()) { return false; } return base.Equals((Zmienne)obj); } public bool Equals(Zmienne drugie) { if (x.Length != drugie.x.Length) return false; else { for (int i = 0; i < x.Length; i++) { if (x[i] != drugie.x[i]) return false; } } return true; } public override int GetHashCode() { int hash = x[0].GetHashCode(); for (int i = 1; i < x.Length; i++) hash = hash ^ x[i].GetHashCode(); return hash; } } Then use it like this: Zmienne tab1 = new Zmienne(2); Zmienne tab2 = new Zmienne(2); tab1.x[0] = 1; tab1.x[1] = 1; tab2.x[0] = 1; tab2.x[1] = 1; if (tab1 == tab2) Console.WriteLine("Works!"); And no effect. I'm not good with interfaces and overriding methods unfortunately :(. As for reason I'm trying to do it. I have some equations like: x1 + x2 = 0.45 x1 + x4 = 0.2 x2 + x4 = 0.11 There are a lot more of them, and I need to for example add first equation to second and search all others to find out if there is any that matches the combination of x'es resulting in that adding. Maybe I'm going in totally wrong direction?

  Read the article

• Proper way to use Linq with WPF

  - by Ingó Vals

  I'm looking for a good guide into the right method of using Linq to Sql together with WPF. Most guides only go into the bare basics like how to show data from a database but noone I found goes into how to save back to the database. Can you answer or point out to me a guide that can answer these questions. I have a separate Data project because the same data will also be used in a web page so I have the repository method. That means I have a seperate class that uses the DataContext and there are methods like GetAllCompanies() and GetCompanyById ( int id ). 1) Where there are collections is it best to return as a IQueryable or should I return a list? Inside the WPF project I have seen reccomendations to wrap the collection in a ObservabgleCollection. 2) Why should I use ObservableCollection and should I use it even with Linq / IQueryable Some properties of the linq entities should be editable in the app so I set them to two-way mode. That would change the object in the observableCollection. 3) Is the object in the ObservableCollection still a instance of the original linq entity and so is the change reflected in the database ( when submitchanges is called ) I should have somekind of save method in the repository. But when should I call it? What happens if someone edits a field but decides not to save it, goes to another object and edits it and then press save. Doesn't the original change also save? When does it not remember the changes to a linq entity object anymore. Should I instance the Datacontext class in each method so it loses scope when done. 4) When and how to call the SubmitChanges method 5) Should I have the DataContext as a member variable of the repository class or a method variable To add a new row I should create a new object in a event ( "new" button push ) and then add it to the database using a repo method. 6) When I add the object to the database there will be no new object in the ObservableCollection. Do I refresh somehow. 7) I wan't to reuse the edit window when creating new but not sure how to dynamically changing from referencing selected item from a listview to this new object. Any examples you can point out.

  Read the article

• MKMap showing detail of annotations

  - by yeohchan

  I have encountered a problem of populating the description for each annotation. Each annotation works, but there is somehow an area when trying to click on it. Here is the code. the one in bold is the one that has the problem. -(void)viewDidLoad{ FlickrFetcher *fetcher=[FlickrFetcher sharedInstance]; NSArray *rec=[fetcher recentGeoTaggedPhotos]; for(NSDictionary *dic in rec){ NSLog(@"%@",dic); NSDictionary *string = [fetcher locationForPhotoID:[dic objectForKey:@"id"]]; double latitude = [[string objectForKey:@"latitude"] doubleValue]; double longitude = [[string objectForKey:@"longitude"]doubleValue]; if(latitude !=0 && latitude != 0 ){ CLLocationCoordinate2D coordinate1 = { latitude,longitude }; **NSDictionary *adress=[NSDictionary dictionaryWithObjectsAndKeys:[dic objectForKey:@"owner"],[dic objectForKey:@"title"],nil];** MKPlacemark *anArea=[[MKPlacemark alloc]initWithCoordinate:coordinate1 addressDictionary:adress]; [mapView addAnnotation:anArea]; } } } Here is what the Flickr class does: #import <Foundation/Foundation.h> #define TEST_HIGH_NETWORK_LATENCY 0 typedef enum { FlickrFetcherPhotoFormatSquare, FlickrFetcherPhotoFormatLarge } FlickrFetcherPhotoFormat; @interface FlickrFetcher : NSObject { NSManagedObjectModel *managedObjectModel; NSManagedObjectContext *managedObjectContext; NSPersistentStoreCoordinator *persistentStoreCoordinator; } // Returns the 'singleton' instance of this class + (id)sharedInstance; // // Local Database Access // // Checks to see if any database exists on disk - (BOOL)databaseExists; // Returns the NSManagedObjectContext for inserting and fetching objects into the store - (NSManagedObjectContext *)managedObjectContext; // Returns an array of objects already in the database for the given Entity Name and Predicate - (NSArray *)fetchManagedObjectsForEntity:(NSString*)entityName withPredicate:(NSPredicate*)predicate; // Returns an NSFetchedResultsController for a given Entity Name and Predicate - (NSFetchedResultsController *)fetchedResultsControllerForEntity:(NSString*)entityName withPredicate:(NSPredicate*)predicate; // // Flickr API access // NOTE: these are blocking methods that wrap the Flickr API and wait on the results of a network request // // Returns an array of Flickr photo information for photos with the given tag - (NSArray *)photosForUser:(NSString *)username; // Returns an array of the most recent geo-tagged photos - (NSArray *)recentGeoTaggedPhotos; // Returns a dictionary of user info for a given user ID. individual photos contain a user ID keyed as "owner" - (NSString *)usernameForUserID:(NSString *)userID; // Returns the photo for a given server, id and secret - (NSData *)dataForPhotoID:(NSString *)photoID fromFarm:(NSString *)farm onServer:(NSString *)server withSecret:(NSString *)secret inFormat:(FlickrFetcherPhotoFormat)format; // Returns a dictionary containing the latitue and longitude where the photo was taken (among other information) - (NSDictionary *)locationForPhotoID:(NSString *)photoID; @end

  Read the article

• What's the standard algorithm for syncing two lists of objects?

  - by Oliver Giesen

  I'm pretty sure this must be in some kind of text book (or more likely in all of them) but I seem to be using the wrong keywords to search for it... :( A common task I'm facing while programming is that I am dealing with lists of objects from different sources which I need to keep in sync somehow. Typically there's some sort of "master list" e.g. returned by some external API and then a list of objects I create myself each of which corresponds to an object in the master list. Sometimes the nature of the external API will not allow me to do a live sync: For instance the external list might not implement notifications about items being added or removed or it might notify me but not give me a reference to the actual item that was added or removed. Furthermore, refreshing the external list might return a completely new set of instances even though they still represent the same information so simply storing references to the external objects might also not always be feasible. Another characteristic of the problem is that both lists cannot be sorted in any meaningful way. You should also assume that initializing new objects in the "slave list" is expensive, i.e. simply clearing and rebuilding it from scratch is not an option. So how would I typically tackle this? What's the name of the algorithm I should google for? In the past I have implemented this in various ways (see below for an example) but it always felt like there should be a cleaner and more efficient way. Here's an example approach: Iterate over the master list Look up each item in the "slave list" Add items that do not yet exist Somehow keep track of items that already exist in both lists (e.g. by tagging them or keeping yet another list) When done iterate once more over the slave list Remove all objects that have not been tagged (see 4.) Update Thanks for all your responses so far! I will need some time to look at the links. Maybe one more thing worthy of note: In many of the situations where I needed this the implementation of the "master list" is completely hidden from me. In the most extreme cases the only access I might have to the master list might be a COM-interface that exposes nothing but GetFirst-, GetNext-style methods. I'm mentioning this because of the suggestions to either sort the list or to subclass it both of which is unfortunately not practical in these cases unless I copy the elements into a list of my own and I don't think that would be very efficient. I also might not have made it clear enough that the elements in the two lists are of different types, i.e. not assignment-compatible: Especially, the elements in the master list might be available as interface references only.

  Read the article

• C# problem with two threads and hardware access

  - by mack369

  I'm creating an application which communicates with the device via FT2232H USB/RS232 converter. For communication I'm using FTD2XX_NET.dll library from FTDI website. I'm using two threads: first thread continuously reads data from the device the second thread is the main thread of the Windows Form Application I've got a problem when I'm trying to write any data to the device while the receiver's thread is running. The main thread simply hangs up on ftdiDevice.Write function. I tried to synchronize both threads so that only one thread can use Read/Write function at the same time, but it didn't help. Below code responsible for the communication. Note that following functions are methods of FtdiPort class. Receiver's thread private void receiverLoop() { if (this.DataReceivedHandler == null) { throw new BackendException("dataReceived delegate is not set"); } FTDI.FT_STATUS ftStatus = FTDI.FT_STATUS.FT_OK; byte[] readBytes = new byte[this.ReadBufferSize]; while (true) { lock (FtdiPort.threadLocker) { UInt32 numBytesRead = 0; ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead); if (ftStatus == FTDI.FT_STATUS.FT_OK) { this.DataReceivedHandler(readBytes, numBytesRead); } else { Trace.WriteLine(String.Format("Couldn't read data from ftdi: status {0}", ftStatus)); Thread.Sleep(10); } } Thread.Sleep(this.RXThreadDelay); } } Write function called from main thread public void Write(byte[] data, int length) { if (this.IsOpened) { uint i = 0; lock (FtdiPort.threadLocker) { this.ftdiDevice.Write(data, length, ref i); } Thread.Sleep(1); if (i != (int)length) { throw new BackendException("Couldnt send all data"); } } else { throw new BackendException("Port is closed"); } } Object used to synchronize two threads static Object threadLocker = new Object(); Method that starts the receiver's thread private void startReceiver() { if (this.DataReceivedHandler == null) { return; } if (this.IsOpened == false) { throw new BackendException("Trying to start listening for raw data while disconnected"); } this.receiverThread = new Thread(this.receiverLoop); //this.receiverThread.Name = "protocolListener"; this.receiverThread.IsBackground = true; this.receiverThread.Start(); } The ftdiDevice.Write function doesn't hang up if I comment following line: ftStatus = ftdiDevice.Read(readBytes, this.ReadBufferSize, ref numBytesRead);

  Read the article

• Java: omitting a data member from the equals method.

  - by cchampion

  public class GamePiece { public GamePiece(char cLetter, int nPointValue) { m_cLetter=cLetter; m_nPointValue=nPointValue; m_nTurnPlaced=0; //has not been placed on game board yet. } public char GetLetter() {return m_cLetter;} public int GetPointValue() {return m_nPointValue;} public int GetTurnPlaced() {return m_nTurnPlaced;} public void SetTurnPlaced(int nTurnPlaced) { m_nTurnPlaced=nTurnPlaced; } @Override public boolean equals(Object obj) { /*NOTE to keep this shorter I omitted some of the null checking and instanceof stuff. */ GamePiece other = (GamePiece) obj; //not case sensitive, and I don`t think we want it to be here. if(m_cLetter != other.m_cLetter) { return false; } if(m_nPointValue != other.m_nPointValue) { return false; } /* NOTICE! m_nPointValue purposely omitted. It does not affect hashcode or equals */ return true; } @Override public int hashCode() { /* NOTICE! m_nPointValue purposely omitted. It should not affect hashcode or equals */ final int prime = 41; return prime * (prime + m_nPointValue + m_cLetter); } private char m_cLetter; private int m_nPointValue; private int m_nTurnPlaced;//turn which the game piece was placed on the game board. Does not affect equals or has code! } Consider the given piece of code. This object has been immutable until the introduction of the m_nTurnPlaced member (which can be modified by the SetTurnPlaced method, so now GamePiece becomes mutable). GamePiece is used in an ArrayList, I call contains and remove methods which both rely on the equals method to be implemented. My question is this, is it ok or common practice in Java for some members to not affect equals and hashcode? How will this affect its use in my ArrayList? What type of java Collections would it NOT be safe to use this object now that it is mutable? I've been told that you're not supposed to override equals on mutable objects because it causes some collections to behave "strangely" (I read that somewhere in the java documentation).

  Read the article

• How safe is my safe rethrow?

  - by gustafc

  (Late edit: This question will hopefully be obsolete when Java 7 comes, because of the "final rethrow" feature which seems like it will be added.) Quite often, I find myself in situations looking like this: do some initialization try { do some work } catch any exception { undo initialization rethrow exception } In C# you can do it like this: InitializeStuff(); try { DoSomeWork(); } catch { UndoInitialize(); throw; } For Java, there's no good substitution, and since the proposal for improved exception handling was cut from Java 7, it looks like it'll take at best several years until we get something like it. Thus, I decided to roll my own: (Edit: Half a year later, final rethrow is back, or so it seems.) public final class Rethrow { private Rethrow() { throw new AssertionError("uninstantiable"); } /** Rethrows t if it is an unchecked exception. */ public static void unchecked(Throwable t) { if (t instanceof Error) throw (Error) t; if (t instanceof RuntimeException) throw (RuntimeException) t; } /** Rethrows t if it is an unchecked exception or an instance of E. */ public static <E extends Exception> void instanceOrUnchecked( Class<E> exceptionClass, Throwable t) throws E, Error, RuntimeException { Rethrow.unchecked(t); if (exceptionClass.isInstance(t)) throw exceptionClass.cast(t); } } Typical usage: public void doStuff() throws SomeException { initializeStuff(); try { doSomeWork(); } catch (Throwable t) { undoInitialize(); Rethrow.instanceOrUnchecked(SomeException.class, t); // We shouldn't get past the above line as only unchecked or // SomeException exceptions are thrown in the try block, but // we don't want to risk swallowing an error, so: throw new SomeException("Unexpected exception", t); } private void doSomeWork() throws SomeException { ... } } It's a bit wordy, catching Throwable is usually frowned upon, I'm not really happy at using reflection just to rethrow an exception, and I always feel a bit uneasy writing "this will not happen" comments, but in practice it works well (or seems to, at least). What I wonder is: Do I have any flaws in my rethrow helper methods? Some corner cases I've missed? (I know that the Throwable may have been caused by something so severe that my undoInitialize will fail, but that's OK.) Has someone already invented this? I looked at Commons Lang's ExceptionUtils but that does other things. Edit: finally is not the droid I'm looking for. I'm only interested to do stuff when an exception is thrown. Yes, I know catching Throwable is a big no-no, but I think it's the lesser evil here compared to having three catch clauses (for Error, RuntimeException and SomeException, respectively) with identical code. Note that I'm not trying to suppress any errors - the idea is that any exceptions thrown in the try block will continue to bubble up through the call stack as soon as I've rewinded a few things.

  Read the article

• MacRuby + Interface Builder: How to display, then close, then display a window again

  - by Derick Bailey

  I'm a complete n00b with MacRuby and Cocoa, though I've got more than a year of Ruby experience, so keep that in mind when answering - I need lots of details and explanation. :) I've set up a simple project that has 2 windows in it, both of which are built with Interface Builder. The first window is a simple list of accounts using a table view. It has a "+" button below the table. When I click the + button, I want to show an "Add New Account" window. I also have an AccountsController < NSWindowController and a AddNewAccountController class, set up as the delegates for these windows, with the appropriate button click methods wired up, and outlets to reference the needed windows. When I click the "+" button in the Accounts window, I have this code fire: @add_account.center @add_account.display @add_account.makeKeyAndOrderFront(nil) @add_account.orderFrontRegardless this works great the first time I click the + button. Everything shows up, I'm able to enter my data and have it bind to my model. however, when I close the add new account form, things start going bad. if I set the add new account window to release on close, then the second time I click the + button, the window will still pop up but it's frozen. i can't click any buttons, enter any data, or even close the form. i assume this is because the form's code has been released, so there is no message loop processing the form... but i'm not entirely sure about this. if i set the add new account window to not release on close, then the second time i click the + button, the window shows up fine and it is usable - but it still has all the data that i had previously entered... it's still bound to my previous Account class instance. what am I doing wrong? what's the correct way to create a new instance of the Add New Account form, create a new Account model, bind that model to the form and show the form, when I click the + button on the Accounts form? ... this is all being done on OSX 10.6.6, 64bit, with XCode 3.2.4

  Read the article

• How to do a search from a list with non-prefix keywords

  - by aNui

  First of all, sorry if my english or my post got any mistakes. I am programming a program to search the name from the list and I need to find them if the keyword is not in front of the names (that's what I mean non-prefix) e.g. if I my list is the music instruments and I type "guit" to the search textbox. It should find the names "Guitar, Guitarrón, Acoustic Guitar, Bass Guitar, ..." or something like this Longdo Dictionary's search suggestion. here is my simple and stupid algorithm (that's all I can do) const int SEARCHROWLIMIT = 30; private string[] DoSearch(string Input, string[] ListToSearch) { List<string> FoundNames = new List<string>(); int max = 0; bool over = false; for (int k = 0; !over; k++) { foreach (string item in ListToSearch) { max = (max > item.Length) ? max : item.Length; if (k > item.Length) continue; if (k >= max) { over = true; break; } if (!Input.Equals("Search") && item.Substring(k, item.Length - k).StartsWith(Input, StringComparison.OrdinalIgnoreCase)) { bool exist = false; int i = 0; while (!exist && i < FoundNames.Count) { if (item.Equals(FoundNames[i])) { exist = true; break; } i++; } if (!exist && FoundNames.Count < SEARCHROWLIMIT) FoundNames.Add(item); else if (FoundNames.Count >= SEARCHROWLIMIT) over = true; } } } return FoundNames.ToArray(); } I think this algorithm is too slow for a large number of names and after several trial-and-error, I decided to add SEARCHROWLIMIT to breaks the operation And I also think there're some readymade methods that can do that. And another problem is I need to search music instruments by a category like strings, percussions, ... and by the country of origins. So I need to search them with filter by type and country. please help me. P.S. Me and my friends are just student from Thailand and developing the project to compete in Microsoft Imagine Cup 2010 and please become fan on our facebook page [KRATIB][3]. And we're so sorry we don't have much information in English but you can talk to us in English.

  Read the article

• Is it possible to reliably auto-decode user files to Unicode? [C#]

  - by NVRAM

  I have a web application that allows users to upload their content for processing. The processing engine expects UTF8 (and I'm composing XML from multiple users' files), so I need to ensure that I can properly decode the uploaded files. Since I'd be surprised if any of my users knew their files even were encoded, I have very little hope they'd be able to correctly specify the encoding (decoder) to use. And so, my application is left with task of detecting before decoding. This seems like such a universal problem, I'm surprised not to find either a framework capability or general recipe for the solution. Can it be I'm not searching with meaningful search terms? I've implemented BOM-aware detection (http://en.wikipedia.org/wiki/Byte_order_mark) but I'm not sure how often files will be uploaded w/o a BOM to indicate encoding, and this isn't useful for most non-UTF files. My questions boil down to: Is BOM-aware detection sufficient for the vast majority of files? In the case where BOM-detection fails, is it possible to try different decoders and determine if they are "valid"? (My attempts indicate the answer is "no.") Under what circumstances will a "valid" file fail with the C# encoder/decoder framework? Is there a repository anywhere that has a multitude of files with various encodings to use for testing? While I'm specifically asking about C#/.NET, I'd like to know the answer for Java, Python and other languages for the next time I have to do this. So far I've found: A "valid" UTF-16 file with Ctrl-S characters has caused encoding to UTF-8 to throw an exception (Illegal character?) (That was an XML encoding exception.) Decoding a valid UTF-16 file with UTF-8 succeeds but gives text with null characters. Huh? Currently, I only expect UTF-8, UTF-16 and probably ISO-8859-1 files, but I want the solution to be extensible if possible. My existing set of input files isn't nearly broad enough to uncover all the problems that will occur with live files. Although the files I'm trying to decode are "text" I think they are often created w/methods that leave garbage characters in the files. Hence "valid" files may not be "pure". Oh joy. Thanks.

  Read the article

• Executing a .NET Managed Assembly from SQL Server 2008 - Pro's, Con's & Recommendations

  - by RPM1984

  Hi guys, looking for opinions/recommendations/links for the following scenario im currently facing. The Platform: .NET 4.0 Web Application SQL Server 2008 The Task: Overhaul a component of the system that performs (fairly) complex mathematical operations based on a specific user activity, and updates numerous tables in the database. A common user activity might be "Bob" decides to post a forum topic. This results in (the end-solution) needing to look at various factors (about the post he did), then after doing some math based on lookup values/ratios as well as other data in the database, inserting some other data as a result of these operations. The Options: Ok - so here's what im thinking. Although it would be much easier to do this in C# (LINQ-SQL) it doesnt make much sense as the majority of the computations are based on values in the db, and it will get difficult to control/optimize/debug the LINQ over time. Hence, im leaning towards created a managed assembly (C# Class Library) that contains the lookup values (constants) as well as leveraging the math classes in the existing .NET BCL. Basically i'd expose a few methods that can be called by the T-SQL Stored Procedures. This to me has the following advantages: Simplicity of math. Do complex math in .NET vs complex math in T-SQL. No brainer. =) Abstraction of computatations, configurable "lookup" values and business logic from raw T-SQL. T-SQL only needs to care about the data, simplifying the stored procedures and making it easier to maintain. When it needs to do math it delegates off to the managed assembly. So, having said that - ive never done this before (call .NET assmembly from T-SQL), and after some googling the best site i could come up with is here, which is useful but outdated. So - what am i asking? Well, firstly - i need some better references on how to actually do this. "This" being how to call a C# .NET 4 Assembly from within T-SQL Stored Procedures in SQL Server 2008. Secondly, who out there has done this, what problems (if any) did you face? Realize this may be difficult to provide a "correct answer", so ill try to give it to whoever gives me the answer with a combination of good links and a list of pro's/con's/problems with this implementation. Cheers!

  Read the article

• passing custom object as parameter to a webmethod of asp.net web service

  - by Jon

  Hi, I have a custom class declared as follows (in vb.net) <Serializable()> _ Public Class NumInfo Public n As String Public f As Integer Public fc As char() Public t As Integer Public tc As char() Private validFlag As Boolean = True Public Sub New() End Sub 'I also have public properties(read/write) for all the public variablesEnd Class In my service.asmx codebehind class I have a webmethod as follows: <WebMethod()> _ <XmlInclude(GetType(NumInfo))> _ Public Function ConvertTo(ByVal info As NumInfo) As String Return mbc(info)'mbc is another function defined in my service.asmx "service" class End Function The problem is that when I start debugging it to test it, the page that I get does not contain any fields where I could input the values for the public fields of numInfo. How do I initialise the class? There is no "Invoke" button either. All I see are soap details as below: ConvertToTestThe test form is only available for methods with primitive types as parameters.SOAP 1.1The following is a sample SOAP 1.1 request and response. The placeholders shown need to be replaced with actual values.POST /Converter/BC.asmx HTTP/1.1Host: localhostContent-Type: text/xml; charset=utf-8Content-Length: lengthSOAPAction: "http://Services/ConvertTo"<?xml version="1.0" encoding="utf-8"?> <soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Body> <ConvertTo xmlns="http://Services/"> <info> <n>string</n> <f>int&lt/f> <fc> <char>char</char> <char>char>/char> </fc>..etc.. What am I doing wrong? For the record I tried replacing char() with string to see if it was the array causing problems but that didn't help either. I'm fairly new to web services. I tried replacing the custom object parameter with a primitive parameter just to check how things worked and it rendered a page with an input field and invoke button. I just can't seem to get it working with custom object. Help!

  Read the article

• How to copy DispatcherObject (BitmapSource) into different thread?

  - by Tomáš Kafka

  Hi, I am trying to figure out how can I copy DispatcherObject (in my case BitmapSource) into another thread. Use case: I have a WPF app that needs to show window in a new thread (the app is actually Outlook addin and we need to do this because Outlook has some hooks in the main UI thread and is stealing certain hotkeys that we need to use - 'lost in translation' in interop of Outlook, WPF (which we use for UI), and Winforms (we need to use certain microsoft-provided winforms controls)). With that, I have my implementation of WPFMessageBox, that is configured by setting some static properties - and and one of them is BitmapSource for icon. This is used so that in startup I can set WPFMessageBox.Icon once, and since then, every WPFMessageBox will have the same icon. The problem is that BitmapSource, which is assigned into icon, is a DispatcherObject, and when read, it will throw InvalidOperationException: "The calling thread cannot access this object because a different thread owns it.". How can I clone that BitmapSource into the actual thread? It has Clone() and CloneCurrentValue() methods, which don't work (they throw the same exception as well). It also occured to me to use originalIcon.Dispatcher.Invoke( do the cloning here ) - but the BitmapSource's Dispatcher is null, and still - I'd create a copy on a wrong thread and still couldnt use it on mine. BitmapSource.IsFrozen == true. Any idea on how to copy the BitmapSource into different thread (without completely reconstructing it from an image file in a new thread)? EDIT: So, freezing does not help: In the end I have a BitmapFrame (Window.Icon doesn't take any other kind of ImageSource anyway), and when I assign it as a Window.Icon on a different thread, even if frozen, I get InvalidOperationException: "The calling thread cannot access this object because a different thread owns it." with a following stack trace: WindowsBase.dll!System.Windows.Threading.Dispatcher.VerifyAccess() + 0x4a bytes WindowsBase.dll!System.Windows.Threading.DispatcherObject.VerifyAccess() + 0xc bytes PresentationCore.dll!System.Windows.Media.Imaging.BitmapDecoder.Frames.get() + 0xe bytes PresentationFramework.dll!MS.Internal.AppModel.IconHelper.GetIconHandlesFromBitmapFrame(object callingObj = {WPFControls.WPFMBox.WpfMessageBoxWindow: header}, System.Windows.Media.Imaging.BitmapFrame bf = {System.Windows.Media.Imaging.BitmapFrameDecode}, ref MS.Win32.NativeMethods.IconHandle largeIconHandle = {MS.Win32.NativeMethods.IconHandle}, ref MS.Win32.NativeMethods.IconHandle smallIconHandle = {MS.Win32.NativeMethods.IconHandle}) + 0x3b bytes > PresentationFramework.dll!System.Windows.Window.UpdateIcon() + 0x118 bytes PresentationFramework.dll!System.Windows.Window.SetupInitialState(double requestedTop = NaN, double requestedLeft = NaN, double requestedWidth = 560.0, double requestedHeight = NaN) + 0x8a bytes PresentationFramework.dll!System.Windows.Window.CreateSourceWindowImpl() + 0x19b bytes PresentationFramework.dll!System.Windows.Window.SafeCreateWindow() + 0x29 bytes PresentationFramework.dll!System.Windows.Window.ShowHelper(object booleanBox) + 0x81 bytes PresentationFramework.dll!System.Windows.Window.Show() + 0x48 bytes PresentationFramework.dll!System.Windows.Window.ShowDialog() + 0x29f bytes WPFControls.dll!WPFControls.WPFMBox.WpfMessageBox.ShowDialog(System.Windows.Window owner = {WPFControlsTest.MainWindow}) Line 185 + 0x10 bytes C#

  Read the article

• Adding NavigationControl to a TabBar Application containing UITableViews

  - by kungfuslippers

  Hi, I'm new to iPhone dev and wanted to get advice on the general design pattern / guide for putting a certain kind of app together. I'm trying to build a TabBar type application. One of the tabs needs to display a TableView and selecting a cell from within the table view will do something else - maybe show another table view or a web page. I need a Navigation Bar to be able to take me back from the table view/web page. The approach I've taken so far is to: Create an app based around UITabBarController as the rootcontroller i.e. @interface MyAppDelegate : NSObject <UIApplicationDelegate> { IBOutlet UIWindow *window; IBOutlet UITabBarController *rootController; } Create a load of UIViewController derived classes and associated NIBs and wire everything up in IB so when I run the app I get the basic tabs working. I then take the UIViewController derived class and modify it to the following: @interface MyViewController : UIViewController<UITableViewDataSource, UITableViewDelegate> { } and I add the delegate methods to the implementation of MyViewController - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return 2; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } if (indexPath.row == 0) { cell.textLabel.text = @"Mummy"; } else { cell.textLabel.text = @"Daddy"; } return cell; } Go back to IB , open MyViewController.xib and drop a UITableView onto it. Set the Files Owner to be MyViewController and then set the delegate and datasource of the UITableView to be MyViewController. If I run the app now, I get the table view appearing with mummy and daddy working nicely. So far so good. The question is how do I go about incorporating a Navigation Bar into my current code for when I implement: - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath() { // get row selected NSUInteger row = [indexPath row]; if (row == 0) { // Show another table } else if (row == 1) { // Show a web view } } Do I drop a NavigationBar UI control onto MyControllerView.xib ? Should I create it programmatically? Should I be using a UINavigationController somewhere ? I've tried dropping a NavigationBar onto my MyControllerView.xib in IB but its not shown when I run the app, only the TableView is displayed.

  Read the article

< Previous Page | 420 421 422 423 424 425 426 427 428 429 430 431  | Next Page >