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  • Interface for classes that have nothing in common

    - by Tomek Tarczynski
    Lets say I want to make few classes to determine behaviour of agents. The good practice would be to make some common interface for them, such interface (simplified) could look like this: interface IModel { void UpdateBehaviour(); } All , or at least most, of such model would have some parameters, but parameters from one model might have nothing in common with parameters of other model. I would like to have some common way of loading parameters. Question What is the best way to do that? Is it maybe just adding method void LoadParameters(object parameters) to the IModel? Or creating empty interface IParameters and add method void LoadParameters(IParameters parameters)? That are two ideas I came up with, but I don't like either of them.

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  • Blackberry - application settings save/load

    - by Max Gontar
    Hi! I know two ways to save/load application settings: use PersistentStore use filesystem (store, since SDCard is optional) I'd like to know what are you're practicies of working with application settings? Using PersistentStore to save/load application settings The persistent store provides a means for objects to persist across device resets. A persistent object consists of a key-value pair. When a persistent object is committed to the persistent store, that object's value is stored in flash memory via a deep copy. The value can then be retrieved at a later point in time via the key. Example of helper class for storing and retrieving settings: class PSOptions { private PersistentObject mStore; private LongHashtableCollection mSettings; private long KEY_URL = 0; private long KEY_ENCRYPT = 1; private long KEY_REFRESH_PERIOD = 2; public PSOptions() { // "AppSettings" = 0x71f1f00b95850cfeL mStore = PersistentStore.getPersistentObject(0x71f1f00b95850cfeL); } public String getUrl() { Object result = get(KEY_URL); return (null != result) ? (String) result : null; } public void setUrl(String url) { set(KEY_URL, url); } public boolean getEncrypt() { Object result = get(KEY_ENCRYPT); return (null != result) ? ((Boolean) result).booleanValue() : false; } public void setEncrypt(boolean encrypt) { set(KEY_ENCRYPT, new Boolean(encrypt)); } public int getRefreshPeriod() { Object result = get(KEY_REFRESH_PERIOD); return (null != result) ? ((Integer) result).intValue() : -1; } public void setRefreshRate(int refreshRate) { set(KEY_REFRESH_PERIOD, new Integer(refreshRate)); } private void set(long key, Object value) { synchronized (mStore) { mSettings = (LongHashtableCollection) mStore.getContents(); if (null == mSettings) { mSettings = new LongHashtableCollection(); } mSettings.put(key, value); mStore.setContents(mSettings); mStore.commit(); } } private Object get(long key) { synchronized (mStore) { mSettings = (LongHashtableCollection) mStore.getContents(); if (null != mSettings && mSettings.size() != 0) { return mSettings.get(key); } else { return null; } } } } Example of use: class Scr extends MainScreen implements FieldChangeListener { PSOptions mOptions = new PSOptions(); BasicEditField mUrl = new BasicEditField("Url:", "http://stackoverflow.com/"); CheckboxField mEncrypt = new CheckboxField("Enable encrypt", false); GaugeField mRefresh = new GaugeField("Refresh period", 1, 60 * 10, 10, GaugeField.EDITABLE|FOCUSABLE); ButtonField mLoad = new ButtonField("Load settings", ButtonField.CONSUME_CLICK); ButtonField mSave = new ButtonField("Save settings", ButtonField.CONSUME_CLICK); public Scr() { add(mUrl); mUrl.setChangeListener(this); add(mEncrypt); mEncrypt.setChangeListener(this); add(mRefresh); mRefresh.setChangeListener(this); HorizontalFieldManager hfm = new HorizontalFieldManager(USE_ALL_WIDTH); add(hfm); hfm.add(mLoad); mLoad.setChangeListener(this); hfm.add(mSave); mSave.setChangeListener(this); loadSettings(); } public void fieldChanged(Field field, int context) { if (field == mLoad) { loadSettings(); } else if (field == mSave) { saveSettings(); } } private void saveSettings() { mOptions.setUrl(mUrl.getText()); mOptions.setEncrypt(mEncrypt.getChecked()); mOptions.setRefreshRate(mRefresh.getValue()); } private void loadSettings() { mUrl.setText(mOptions.getUrl()); mEncrypt.setChecked(mOptions.getEncrypt()); mRefresh.setValue(mOptions.getRefreshPeriod()); } }

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  • Java: Is clone() really ever used? What about defensive copying in getters/setters?

    - by GreenieMeanie
    Do people practically ever use defensive getters/setters? To me, 99% of the time you intend for the object you set in another object to be a copy of the same object reference, and you intend for changes you make to it to also be made in the object it was set in. If you setDate(Date dt) and modify dt later, who cares? Unless I want some basic immutable data bean that just has primitives and maybe something simple like a Date, I never use it. As far as clone, there are issues as to how deep or shallow the copy is, so it seems kind of "dangerous" to know what is going to come out when you clone an Object. I think I have only used clone() once or twice, and that was to copy the current state of the object because another thread (ie another HTTP request accessing the same object in Session) could be modifying it. Edit - A comment I made below is more the question: But then again, you DID change the Date, so it's kind of your own fault, hence whole discussion of term "defensive". If it is all application code under your own control among a small to medium group of developers, will just documenting your classes suffice as an alternative to making object copies? Or is this not necessary, since you should always assume something ISN'T copied when calling a setter/getter?

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  • NHibernate dateTime as an ID Bad idea?

    - by Miau
    hi there I have an entity and it seems like using DateTime as the Id would be a good suit, however I there is this strange feeling that that it might be a terrible idea ( tho i cant come up with any logical reason as to why), This is an immutable object ( ie once the value is recorded it shouldn't really change ) So DateTime as id field in NHibernate yay or Nay? I would appreciate your comments on this

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  • [PHP] DOMDocument load on a page returning 400 Bad Request status

    - by PeteWilliams
    Hiya, I'm trying to use the Last.fm API for an application I'm creating, but am having some problems with validation. If an API request gives an error it returns a code and message in the response XML like this: <lfm status="failed"> <error code="6">No user with that name</error> </lfm> However, the request also returns an HTTP status of 400 (or in some cases 403) which DOMDocument considers an error and so then refuses to parse the XML. Is there any way round this, so that I can retrieve the error code and message? Thanks Pete

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  • Should I throw my own ArgumentOutOfRangeException or let one bubble up from below?

    - by Neil N
    I have a class that wraps List< I have GetValue by index method: public RenderedImageInfo GetValue(int index) { list[index].LastRetrieved = DateTime.Now; return list[index]; } If the user requests an index that is out of range, this will throw an ArgumentOutOfRangeException . Should I just let this happen or check for it and throw my own? i.e. public RenderedImageInfo GetValue(int index) { if (index >= list.Count) { throw new ArgumentOutOfRangeException("index"); } list[index].LastRetrieved = DateTime.Now; return list[index]; } In the first scenario, the user would have an exception from the internal list, which breaks mt OOP goal of the user not needing to know about the underlying objects. But in the second scenario, I feel as though I am adding redundant code. Edit: And now that I think of it, what about a 3rd scenario, where I catch the internal exception, modify it, and rethrow it?

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  • Best Practice - Removing item from generic collection in C#

    - by Matt Davis
    I'm using C# in Visual Studio 2008 with .NET 3.5. I have a generic dictionary that maps types of events to a generic list of subscribers. A subscriber can be subscribed to more than one event. private static Dictionary<EventType, List<ISubscriber>> _subscriptions; To remove a subscriber from the subscription list, I can use either of these two options. Option 1: ISubscriber subscriber; // defined elsewhere foreach (EventType event in _subscriptions.Keys) { if (_subscriptions[event].Contains(subscriber)) { _subscriptions[event].Remove(subscriber); } } Option 2: ISubscriber subscriber; // defined elsewhere foreach (EventType event in _subscriptions.Keys) { _subscriptions[event].Remove(subscriber); } I have two questions. First, notice that Option 1 checks for existence before removing the item, while Option 2 uses a brute force removal since Remove() does not throw an exception. Of these two, which is the preferred, "best-practice" way to do this? Second, is there another, "cleaner," more elegant way to do this, perhaps with a lambda expression or using a LINQ extension? I'm still getting acclimated to these two features. Thanks. EDIT Just to clarify, I realize that the choice between Options 1 and 2 is a choice of speed (Option 2) versus maintainability (Option 1). In this particular case, I'm not necessarily trying to optimize the code, although that is certainly a worthy consideration. What I'm trying to understand is if there is a generally well-established practice for doing this. If not, which option would you use in your own code?

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  • Avoiding Service Locator with AutoFac 2

    - by Page Brooks
    I'm building an application which uses AutoFac 2 for DI. I've been reading that using a static IoCHelper (Service Locator) should be avoided. IoCHelper.cs public static class IoCHelper { private static AutofacDependencyResolver _resolver; public static void InitializeWith(AutofacDependencyResolver resolver) { _resolver = resolver; } public static T Resolve<T>() { return _resolver.Resolve<T>(); } } From answers to a previous question, I found a way to help reduce the need for using my IoCHelper in my UnitOfWork through the use of Auto-generated Factories. Continuing down this path, I'm curious if I can completely eliminate my IoCHelper. Here is the scenario: I have a static Settings class that serves as a wrapper around my configuration implementation. Since the Settings class is a dependency to a majority of my other classes, the wrapper keeps me from having to inject the settings class all over my application. Settings.cs public static class Settings { public static IAppSettings AppSettings { get { return IoCHelper.Resolve<IAppSettings>(); } } } public interface IAppSettings { string Setting1 { get; } string Setting2 { get; } } public class AppSettings : IAppSettings { public string Setting1 { get { return GetSettings().AppSettings["setting1"]; } } public string Setting2 { get { return GetSettings().AppSettings["setting2"]; } } protected static IConfigurationSettings GetSettings() { return IoCHelper.Resolve<IConfigurationSettings>(); } } Is there a way to handle this without using a service locator and without having to resort to injecting AppSettings into each and every class? Listed below are the 3 areas in which I keep leaning on ServiceLocator instead of constructor injection: AppSettings Logging Caching

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  • Best practice for installing python modules from an arbitrary VCS repository

    - by fmark
    I'm newish to the python ecosystem, and have a question about module editing. I use a bunch of third-party modules, distributed on PyPi. Coming from a C and Java background, I love the ease of easy_install <whatever>. This is a new, wonderful world, but the model breaks down when I want to edit the newly installed module for two reasons: The egg files may be stored in a folder or archive somewhere crazy on the file system. Using an egg seems to preclude using the version control system of the originating project, just as using a debian package precludes development from an originating VCS repository. What is the best practice for installing modules from an arbitrary VCS repository? I want to be able to continue to import foomodule in other scripts.

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  • How to learn as a lone developer?

    - by fearofawhackplanet
    I've been lucky to work in a small team with a couple of experienced and knowledgeable developers for the first year of my career. I've learned a huge amount. But I'm now getting transferred within my company, and will be working on solo projects. I'll cope, but I know I'll make mistakes and won't always produce the best solutions without someone to guide me and review my output. I'm wondering if anyone has any tips in this situation. How can I keep learning? What's the best way to monitor and asses the quality of my work? How can I ensure that my career and skills don't stagnate?

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  • exc_bad_access on insertNewObjectForEntityForName:inManagedObjectContext

    - by matthewc
    I have a garbage collected Cocoa application built on 10.5 frameworks. In an NSOperation In a loop I am quickly creating hundreds of NSManagedObjects. Frequently the creation of those NSManagedObejcts will crash with a exc_bad_access error. for (offsetCount; offsetCount < [parsedData count]; offsetCount++) { NSManagedObject *child = [NSEntityDescription insertNewObjectForEntityForName:@"Thread" inManagedObjectContext:[self moc]]; Thumbnail *thumb = [Thumbnail insertInManagedObjectContext:[self moc]]; Image *image = [Image insertInManagedObjectContext:[self moc]]; ... } Thumbnail and Image are both subclasses of NSManagedObject generated with mogenerator. insertInManagedObjectContext: looks like NSParameterAssert(moc_); return [NSEntityDescription insertNewObjectForEntityForName:@"Thumbnail" inManagedObjectContext:moc_]; NSParameterAssert(moc_); return [NSEntityDescription insertNewObjectForEntityForName:@"Image" inManagedObjectContext:moc_]; The NSManagedObjectContext returned by [self moc] is created for the NSOperation with NSPersistentStoreCoordinator *coord = [(MyApp_AppDelegate *)[[NSApplication sharedApplication] delegate] persistentStoreCoordinator]; self.moc = [[NSManagedObjectContext alloc] init]; [self.moc setPersistentStoreCoordinator:coord]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(contextDidSave:) name:NSManagedObjectContextDidSaveNotification object:self.moc]; [self.moc setMergePolicy:NSMergeByPropertyObjectTrumpMergePolicy]; [self.moc setUndoManager:nil]; [self.moc setRetainsRegisteredObjects:YES]; moc is defined as (nonatomic, retain) and synthesized. As far as I can tell it, the persistent store and my appDelegate have no reason to be and are not being garbage collected. The stack trace looks like Thread 2 Crashed: Dispatch queue: com.apple.root.default-priority 0 libauto.dylib 0x00007fff82d63600 auto_zone_root_write_barrier + 688 1 libobjc.A.dylib 0x00007fff826f963b objc_assign_strongCast_gc + 59 2 com.apple.CoreFoundation 0x00007fff88677068 __CFBasicHashAddValue + 504 3 com.apple.CoreFoundation 0x00007fff88676d2f CFBasicHashAddValue + 191 4 com.apple.CoreData 0x00007fff82bdee5e -[NSManagedObjectContext(_NSInternalAdditions) _insertObjectWithGlobalID:globalID:] + 190 5 com.apple.CoreData 0x00007fff82bded24 -[NSManagedObjectContext insertObject:] + 148 6 com.apple.CoreData 0x00007fff82bbd75c -[NSManagedObject initWithEntity:insertIntoManagedObjectContext:] + 716 7 com.apple.CoreData 0x00007fff82bdf075 +[NSEntityDescription insertNewObjectForEntityForName:inManagedObjectContext:] + 101 8 com.yourcompany.MyApp 0x000000010002c7a7 +[_Thumbnail insertInManagedObjectContext:] + 256 (_Thumbnail.m:14) 9 com.yourcompany.MyApp 0x000000010002672d -[ThreadParse main] + 10345 (B4ChanThreadParse.m:174) 10 com.apple.Foundation 0x00007fff85ee807e -[__NSOperationInternal start] + 698 11 com.apple.Foundation 0x00007fff85ee7d23 ____startOperations_block_invoke_2 + 99 12 libSystem.B.dylib 0x00007fff812bece8 _dispatch_call_block_and_release + 15 13 libSystem.B.dylib 0x00007fff8129d279 _dispatch_worker_thread2 + 231 14 libSystem.B.dylib 0x00007fff8129cbb8 _pthread_wqthread + 353 15 libSystem.B.dylib 0x00007fff8129ca55 start_wqthread + 13 My app is crashing in other places with exc_bad_access but this is code that it happens most with. All of the stack traces look similar and have something to do with CFHash. Any help would be appreciated.

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  • Objective-C categories in static library

    - by Vladimir
    Can you guide me how to properly link static library to iphone project. I use staic library project added to app project as direct dependency (target - general - direct dependecies) and all works OK, but categories. A category defined in static library is not working in app. So my question is how to add static library with some categories into other project? And in general, what is best practice to use in app project code from other projects?

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  • jQuery - bad div size in IE

    - by Tomek
    hello, I have a problem with sizes of divs - in Firefox everything is fine, but IE messes things up, I use only jquery show hide function which open div with other divs nested in it, you can see what I mean on www.custos.pl/v1 - by choosing any option on the bottom, a div opens up, where you have a submenu opening up jScrollPanes, the whole div should stay within the photo background, but in IE it goes vertically way beyond it, Id appreciate your help

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  • When should you use intermediate variables for expressions?

    - by froadie
    There are times that one writes code such as this: callSomeMethod(someClass.someClassMethod()); And other times when one would write the same code like this: int result = someClass.someClassMethod(); callSomeMethod(result); This is just a basic example to illustrate the point. My question isn't if you should use an intermediate variable or not, as that depends on the code and can sometimes be a good design decision and sometimes a terrible one. The question is - when would you choose one method over the other? What factors would you consider when deciding whether to use an intermediate step? (I'd assume length and understandability of the fully inlined code would have something to do with it...)

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  • PDO update with conditional?

    - by dmontain
    I have a PDO mysql that updates 3 fields. $update = $mypdo->prepare("UPDATE tablename SET field1=:field1, field2=:field2, field3=:field3 WHERE key=:key"); But I want field3 to be updated only when $update3 = true; Is this possible to accomplish with a single query? I could do it with 2 queries where I update field1 and field2 then check the boolean and update field3 if needed in a separate query. But hopefully there is a way to accomplish this in 1 query?

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  • REST doesn't work with Sever-Client-Client setup

    - by drozzy
    I am having a problem with my current RESTful api design. What I have is a REST api which is consumed by Django web-server, which renders the HTML templates. REST api > Django webserver > HTML The problem I am encountering is that I have to reconstruct all the URLS like mysite.com/main/cities/<id>/streets/ into equivalent rest api urls on my web-server layer: api.com/cities/<id>/streets/ Thus I have a lot of mapping back and forth, but as far as I know REST says that the client (in this case my web-server) should NOT need to know how to re-construct the urls. Can REST be used for such a setup and how? Or is it only viable for Server-Client architecture. Thanks

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  • MVC Localization of Default Model Binder

    - by Dai Bok
    Hi, I am currently trying to figure out how to localize the error messages generated by MVC. Let me use the default model binder as an example, so I can explain the problem. Assuming I have a form, where a user enters thier age. The user then enters "ten" in to the form, but instead of getting the expected error of "Age must be beween 18 and 25." the message "The value 'ten' is not valid for Age." is displayed. The entity's age property is defined below: [Range(18, 25, ErrorMessageResourceType = typeof (Errors), ErrorMessageResourceName = "Age", ErrorMessage = "Range_ErrorMessage")] public int Age { get; set; } After some digging, I notice that this error text comes from the System.Web.Mvc.Resources.DefaultModelBinder_ValueInvalid in the MvcResources.resx file. Now, how can create localized versions of this file? As A solution, for example, should I download MVC source and add MvcResources.en_GB.resx, MvcResources.fr_FR.resx, MvcResources.es_ES.resx and MvcResources.de_DE.resx, and then compile my own version of MVC.dll? But I don't like this idea. Any one else know a better way?

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  • controlling if exceptions are swallowed by a static boolean

    - by sandis
    So we are a few guys developing this product that is communicating with a really unstable server. It often returns very strange and corrupt data. During testing we want the resulting crashes to be loud, so we discover them. But every other day we need to demonstrate our product for a potential customer. To the customer the errors will go undiscovered if we just swallow them. I am thinking about implementing something like this around all server communication to quickly switch between swallowing exceptions and crashing: try { apiCall(); } catch (Exception e) { if(!SWALLOW_EXCEPTION) { throw e; } } Is this an awesome idea, or can it be done in a better way?

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  • do I need to use partial?

    - by wiso
    I've a general function, for example (only a simplified example): def do_operation(operation, a, b, name): print name do_something_more(a,b,name, operation(a,b)) def operation_x(a,b): return a**2 + b def operation_y(a,b): return a**10 - b/2. and some data: data = {"first": {"name": "first summation", "a": 10, "b": 20, "operation": operation_x}, "second": {"name": "second summation", "a": 20, "b": 50, "operation": operation_y}, "third": {"name": "third summation", "a": 20, "b": 50, "operation": operation_x}, # <-- operation_x again } now I can do: what_to_do = ("first", "third") # this comes from command line for sum_id in what_to_do: do_operation(data["operation"], data["a"], data["b"], data["name"]) or maybe it's better if I use functools.partial? from functools import partial do_operation_one = do_operation(name=data["first"]["name"], operation=data["first"]["operation"], a=data["first"]["a"], b=data["first"]["b"]) do_operation_two = do_operation(name=data["second"]["name"], operation=data["second"]["operation"] a=data["second"]["a"], b=data["second"]["b"]) do_operation_three = do_operation(name=data["third"]["name"], operation=data["third"]["operation"] a=data["third"]["a"], b=data["third"]["b"]) do_dictionary = { "first": do_operation_one, "second": do_operation_two, "third": do_operation_three } for what in what_to_do: do_dictionary[what]()

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  • Blackberry User Interface Design - Customizable UI?

    - by John Stewart
    I am trying to design a Blackberry Application and I am wondering if there are any resources on how to create custom user interface elements, skin existing ones and what other possibilities are there? I have developed a few iPhone applications with custom UI and stuff, so not sure what BB world offers in terms of UI development. Any tips, suggestions or ideas would be great.

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