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• (nested) user controls within a mvp pattern causing sporadic problems

  - by LLEA

  hi everyone, I have a serious problem with nested user controls (UCs) in WinForms while trying to implement the mvp pattern (passive view). The project consists of one model (designed as a singleton) and a set of different presenters with corresponding view interfaces. To avoid one huge view interface and therefore an overloaded main UI, I decided to make use of a set of different UCs. Each UC has one view interface and one presenter that can access the model. But there are nested UCs: meaning that one specialised UC implements sort of a basic UC. The main UI just represents a container for all those UCs. So far, so good (if not, please ask)?! There are two problems that I am facing now (but I guess both are of the same origin): From time to time it is not possible anymore to load the UCs and test them within the Visual Studio 2008 User Control Test Container. The error message just says that a project with an output type of class library cannot be started directly etc. I can "handle" that by unloading all UC projects and reloading them afterwards. (I guess the references to all mvp components and other UCs are then updated). Assuming that the implementation of my mvp pattern is okay and all those UCs are testable within the VS Test Container at a certain time - there is the biggest problem still left: I am not able to add any UC (even the basic and unnested ones) to a simple Form (UI). The error message: error message.jpg Could it be that my basic UC causes all these Problems?! It consists of two simple ComboBoxes and implements a basic presenter and basic view interface. Whenever I add this UC to a different UC the VS designer adds two references to the public getter methods of the UC as resources. I then manually remove those resources from the resx-file and commend the corresponding lines in the designer file. thx in advance

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• How do I make JPA POJO classes + Netbeans forms play well together?

  - by Zak

  I started using netbeans to design forms to edit the instances of various classes I have made in a small app I am writing. Basically, the app starts, an initial set of objects is selected from the DB and presented in a list, then an item in the list can be selected for editing. When the editor comes up it has form fields for many of the data fields in the class. The problem I run into is that I have to create a controller that maps each of the data elements to the correct form element, and create an inordinate number of small conversion mapping lines of code to convert numbers into strings and set the correct element in a dropdown, then another inordinate amount of code to go back and update the underlying object with all the values from the form when the save button is clicked. My question is; is there a more directly way to make the editing of the form directly modify the contents of my class instance? I would like to be able to have a default mapping "controller" that I can configure, then override the getter/setter for a particular field if needed. Ideally, there would be standard field validation for things like phone numbers, integers, floats, zip codes, etc... I'm not averse to writing this myself, I would just like to see if it is already out there and use the right tool for the right job.

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• org.hibernate.PropertyNotFoundException

  - by niru

  hi i am new to hibernate, i m using the following code and getting the following error public class OperProfile { private String empId; private long age; private String name; public long getAge() { return age; } public void setAge(long age) { this.age = age; } public String getEmpId() { return empId; } public void setEmpId(String empId) { this.empId = empId; } public String getName() { return name; } public void setName(String name) { this.name = name; } } i am getting this error org.hibernate.PropertyNotFoundException: Could not find a getter for age in class com.fmr.OperProfile my hbm.xml file is <hibernate-mapping> <class name="com.fmr.OperProfile" table="EMPLOYEE" dynamic-update="true"> <id name="empId" type="java.lang.String" column="EMP_ID"> <generator class="assigned" /> </id> <property name="name" type="java.lang.String" column="NAME"/> <property name=" age" type="java.lang.Long" column="AGE" not-null="true" /> <property name="address1" type="java.lang.String" column="ADDRESS1" /> <property name="address2" type="java.lang.String" column="ADDRESS2" /> <property name="city" type="java.lang.String" column="CITY" /> <property name="state" type="java.lang.String" column="STATE" /> <property name="pincode" type="java.lang.Long" column="PINCODE" /> </class> </hibernate-mapping> please can anyone help me

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• Am I a discoverer of a bug in the WPF engine?

  - by bitbonk

  We have a MFC 8 application compiled with /CLR that contains a larger amount of Windows Forms UserControls wich again contain WPF user controls using ElementHost. Due to the architecture of our software we can not use HwndHost directly. We observed an extremely strange behavior here that we can not make any sense of: When the CPU load is very high during startup of the application and there are a lot live of ElementHost instances, the whole property engine completely stops working. For example animations that usually just work fine now never update the values of the bound properties, they just stay at some random value after startup. When I set a property that is not bound to anything the value is correctly stored in the dependency property (calling the getter returns the new value) but the visual representation never reflects that. I set the background to red but the background color does not change. We tested this on a lot of different machines all running Windows XP SP2 and it is pretty reproducible. The funny thing here is, that there is in fact one situation where the bound properties actually pickup a new value from the animation and the visual gets updated based on the property values. It is when I resize the ElementHost or when I hide and reshow the parent native control. As soon as I do this, properties that are bound to an animation pickup a new value and the visuals rerender based on the new property values - but just once - if I want to see another update I have to resize the ElementHost. Do you have any explanation of what could be happening here or how I could approach this problem to find it out? What can I do to debug this? Is there a way I can get more information about what WPF actually does or where WPF might have crashed? To me it currently seems like a bug in WPF itself since it only happens at high CPU load at startup.

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• JavaEE: Question about design

  - by Harry Pham

  I have a JSF page that will create a new Comment. I have the managed bean of that page to be RequestScoped managed bean. @ManagedBean(name="PostComment") @RequestScoped public class PostComment { private Comment comment = null; @ManagedProperty(value="#{A}") private A a; //A is a ViewScoped Bean @ManagedProperty(value="#{B}") private B b; //B is a ViewScoped Bean @PostConstruct public void init(){ comment = new Comment(); } // setters and getters for comment and all the managed property variable public void postComment(String location){ //persist the new comment ... if(location.equals("A")){ //update the comment list on page A }else if(location.equals("B")){ //update the comment list on page B } } } As you can see from the code above, 2 ViewScoped bean A and B will both use method postComment(), and getter getComment() from bean PostComment. The problem I am having right now is that, if I am on A, constructor of A will load, but it will also load constructor of bean B. This make my page load twice as slow. What would be the best way to solve this problem?

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• Hibernate collection mapping challenge

  - by Geln Yang

  Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two character of its code : class Item{ string code; string name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <!--====================================== --> <many-to-one name="parent" class="Item" not-found="ignore"></many-to-one> <bag name="children"></bag> <!--====================================== --> </class> </hibernate-mapping> How to definition the mapping relationship? Thanks!

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• Binding ComboBoxes to enums... in Silverlight!

  - by Domenic

  So, the web, and StackOverflow, have plenty of nice answers for how to bind a combobox to an enum property in WPF. But Silverlight is missing all of the features that make this possible :(. For example: You can't use a generic EnumDisplayer-style IValueConverter that accepts a type parameter, since Silverlight doesn't support x:Type. You can't use ObjectDataProvider, like in this approach, since it doesn't exist in Silverlight. You can't use a custom markup extension like in the comments on the link from #2, since markup extensions don't exist in Silverlight. You can't do a version of #1 using generics instead of Type properties of the object, since generics aren't supported in XAML (and the hacks to make them work all depend on markup extensions, not supported in Silverlight). Massive fail! As I see it, the only way to make this work is to either Cheat and bind to a string property in my ViewModel, whose setter/getter does the conversion, loading values into the ComboBox using code-behind in the View. Make a custom IValueConverter for every enum I want to bind to. Are there any alternatives that are more generic, i.e. don't involve writing the same code over and over for every enum I want? I suppose I could do solution #2 using a generic class accepting the enum as a type parameter, and then create new classes for every enum I want that are simply class MyEnumConverter : GenericEnumConverter<MyEnum> {} What are your thoughts, guys?

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• Representing element as boolean with JAXB?

  - by Marcus

  We have this XML: <Summary> <ValueA>xxx</ValueA> <ValueB/> </Summary> <ValueB/> will never have any attributes or inner elements. It's a boolean type element - it exists (true) or it doesn't (false). JAXB generated a Summary class with a String valueA member, which is good. But for ValueB, JAXB generated a ValueB inner class and a corresponding member: @XmlElement(name = "ValueB") protected Summary.ValueB valueB; But what I'd like is a boolean member and no inner class: @XmlElement(name = "ValueB") protected boolean valueB; How can you do this? I'm not looking to regenerate the classes, I'd like to just make the code change manually. Update: In line with the accepted answer, we created a new method returning the boolean value conditional on whether valueB == null. As we are using Hibernate, we annotated valueB with @Transient and annotated the boolean getter with Hibernate's @Column annotation.

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• Hibernate collection mapping Problem

  - by Geln Yang

  Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two characters of its code : class Item{ String code; String name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <many-to-one name="parent" class="Item" not-found="ignore"> <formula> <![CDATA[ (select i.code,r.name from Item i where (case length(code) when 4 then i.code=SUBSTRING(code,1,2) else false end)) ]]> </formula> </many-to-one> <bag name="children"></bag> </class> </hibernate-mapping> I try to use formula to define the many-to-one relationship,but it doesn't work!Is there something wrong?Or is there other method? Thanks! ps,I use mysql database.

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• Hibernate mapping Problem

  - by Geln Yang

  Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two characters of its code : class Item{ String code; String name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <many-to-one name="parent" class="Item" not-found="ignore"> <formula> <![CDATA[ (select i.code,r.name from Item i where (case length(code) when 4 then i.code=SUBSTRING(code,1,2) else false end)) ]]> </formula> </many-to-one> <bag name="children"></bag> </class> </hibernate-mapping> I try to use formula to define the many-to-one relationship,but it doesn't work!Is there something wrong?Or is there other method? Thanks! ps,I use mysql database.

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• Entity framework generates values for NOT NULL columns which has default defined in db.

  - by Muhammad Kashif Nadeem

  Hi I have a table Customer. One of the columns in table is DateCreated. This column is NOT NULL but default values is defined for this column in db. When I add new Customer using EF4 from my code. var customer = new Customer(); customer.CustomerName = "Hello"; customer.Email = "[email protected]"; // Watch out commented out. //customer.DateCreated = DateTime.Now; context.AddToCustomers(customer); context.SaveChanges(); Above code generates following query. exec sp_executesql N'insert [dbo].[Customers]([CustomerName], [Email], [Phone], [DateCreated], [DateUpdated]) values (@0, @1, null, @2, null) select [CustomerId] from [dbo].[Customers] where @@ROWCOUNT > 0 and [CustomerId] = scope_identity() ',N'@0 varchar(100),@1 varchar(100),@2 datetime2(7) ',@0='Hello',@1='[email protected]',@2='0001-01-01 00:00:00' And throws following error The conversion of a datetime2 data type to a datetime data type resulted in an out-of-range value. The statement has been terminated. Can you please tell me how NOT NULL columns which has default values at db level should not have values generated by EF? DB: DateCreated DATETIME NOT NULL DateCreated Properties in EF: Nullable: False Getter/Setter: public Type: DateTime DefaultValue: None Thanks.

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• Are there any downsides in using C++ for network daemons?

  - by badcat

  Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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• Objective-C ref count and autorelease

  - by turbovince

  Hey guys, suppose the following code: int main (int argc, const char * argv[]) { //[...] Rectangle* myRect = [[Rectangle alloc] init]; Vector2* newOrigin = [[[Vector2 alloc] init] autorelease]; // ref count 1 [newOrigin setX: 50.0f]; [myRect setOrigin: newOrigin]; // ref count 2 [myRect.origin setXY: 25.0f :100.0f]; // ref count goes to 3... why ? [myRect release]; [pool drain]; return 0; } Rectangle's origin is declared as a (retain) synthesized property. Just wondering 2 things: Why does ref count goes to 3 when using the getter accessor of Rectangle's origin? Am I doing something wrong ? With a ref count of 3, I don't understand how this snippet of code cannot leak. Calling release on myRect will make it go down to 2 since I call release on the origin in dealloc(). But then, when does autorelease take effect? Thanks!

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• Is there any point in using a volatile long?

  - by Adamski

  I occasionally use a volatile instance variable in cases where I have two threads reading from / writing to it and don't want the overhead (or potential deadlock risk) of taking out a lock; for example a timer thread periodically updating an int ID that is exposed as a getter on some class: public class MyClass { private volatile int id; public MyClass() { ScheduledExecutorService execService = Executors.newScheduledThreadPool(1); execService.scheduleAtFixedRate(new Runnable() { public void run() { ++id; } }, 0L, 30L, TimeUnit.SECONDS); } public int getId() { return id; } } My question: Given that the JLS only guarantees that 32-bit reads will be atomic is there any point in ever using a volatile long? (i.e. 64-bit). Caveat: Please do not reply saying that using volatile over synchronized is a case of pre-optimisation; I am well aware of how / when to use synchronized but there are cases where volatile is preferable. For example, when defining a Spring bean for use in a single-threaded application I tend to favour volatile instance variables, as there is no guarantee that the Spring context will initialise each bean's properties in the main thread.

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• PageableListView Not rendering my data as required

  - by Robin

  i am working on wicket, where i am supposed to show my data's under <tr> <td>Name</td> <td>Single Player Score</td> <td>Double Player Score</td> <td>Total Score</td> </tr> <tr wicket:id="data"> <td wicket:id="name"></td> <td wicket:id="singlePlayerScore"></td> <td wicket:id="doublePlayerScore"></td> <td wicket:id="totalScore"></td> </tr> My Player model class is as: Player class with attributes singlePlayerScore, doublePlayerScore(), name with getter and setter and also a list data obtained from database. Data from SQLQuery is as; name score gamemode A 200 singlePlayerMode A 100 doublePLayerMode B 400 singlePlayerMode B 300 doublePLayerMode dataList == player.getScoreList(); My PageableListView is as: final PageableListView listView = new PageableListView("data",dataList,10){ @Override protected void populateItem(Item item){ player = (Player)item.getModelObject(); item.add(Label("name",player.getName())); item.add(Label("singlePlayerScore",player.getName())); item.add(Label("doublePlayerScore",player.getName())); item.add(Label("totalScore",String.valueOf(player.getSinglePlayerScore()+player.getDoublePlayerScore()))); } } My Problem is as: What view i get is as: Name single Player Score Double Player Score Total Score A 0 100 100 A 200 0 200 B 0 300 300 B 400 0 400 How do i achieve below view on my webpage? Name single Player Score Double Player Score Total Score A 200 100 300 B 400 300 700 Please help me as to why is this happening? I guess my list has size four that's one reason why as to it is rendering the view? So what can i do to get as require rendering view?

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• @dynamic property needs setter with multiple behaviors

  - by ambertch

  I have a class that contains multiple user objects and as such has an array of them as an instance variable: NSMutableArray *users; The tricky part is setting it. I am deserializing these objects from a server via Objective Resource, and for backend reasons users can only be returned as a long string of UIDs - what I have locally is a separate dictionary of users keyed to UIDs. Given the string uidString of comma separated UIDs I override the default setter and populate the actual user objects: @dynamic users; - (void)setUsers:(id)uidString { users = [NSMutableArray arrayWithArray: [[User allUsersDictionary] objectsForKeys:[(NSString*)uidString componentsSeparatedByString:@","]]]; } The problem is this: I now serialize these to database using SQLitePO, which stores these as the array of user objects, not the original string. So when I retrieve it from database the setter mistakenly treats this array of user objects as a string! Where I actually want to adjust the setter's behavior when it gets this object from DB vs. over the network. I can't just make the getter serialize back into a string without tearing up large code that reference this array of user objects, and I tried to detect in the setter whether I have a string or an array coming in: if ([uidString respondsToSelector:@selector(addObject)]) { // Already an array, so don't do anything - just assign users = uidString but no success... so I'm kind of stuck - any suggestions? Thanks in advance!

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• Packages name conflicting with getters and setters?

  - by MrKishi

  Hello, folks. So, I've came across this compilation error a while ago.. As there's an easy fix and I didn't find anything relevant at the time, I eventually let it go. I just remembered it and I'm now wondering if this is really part of the language grammar (which I highly doubt) or if it's a compiler bug. I'm being purely curious about this -- it doesn't really affect development, but it would be nice to see if any of you have seen this already. package view { import flash.display.Sprite; public class Main extends Sprite { private var _view:Sprite = new Sprite(); public function Main() { this.test(); } private function test():void { trace(this.view.x, this.view.y); //1178: Attempted access of inaccessible property x through a reference with static type view:Main. //1178: Attempted access of inaccessible property y through a reference with static type view:Main. //Note that I got this due to the package name. //It runs just fine if I rename the package or getter. } public function get view():Sprite { return this._view; } } }

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• How to efficiently implement a strategy pattern with spring ?

  - by Anth0

  I have a web application developped in J2EE 1.5 with Spring framework. Application contains "dashboards" which are simple pages where a bunch of information are regrouped and where user can modify some status. Managers want me to add a logging system in database for three of theses dashboards. Each dashboard has different information but the log should be traced by date and user's login. What I'd like to do is to implement the Strategy pattern kind of like this : interface DashboardLog { void createLog(String login, Date now); } // Implementation for one dashboard class PrintDashboardLog implements DashboardLog { Integer docId; String status; void createLog(String login, Date now){ // Some code } } class DashboardsManager { DashboardLog logger; String login; Date now; void createLog(){ logger.log(login,now); } } class UpdateDocAction{ DashboardsManager dbManager; void updateSomeField(){ // Some action // Now it's time to log dbManagers.setLogger = new PrintDashboardLog(docId, status); dbManagers.createLog(); } } Is it "correct" (good practice, performance, ...) to do it this way ? Is there a better way ? Note :I did not write basic stuff like constructors and getter/setter.

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• Conversion between different template instantiation of the same template

  - by Naveen

  I am trying to write an operator which converts between the differnt types of the same implementation. This is the sample code: template <class T = int> class A { public: A() : m_a(0){} template <class U> operator A<U>() { A<U> u; u.m_a = m_a; return u; } private: int m_a; }; int main(void) { A<int> a; A<double> b = a; return 0; } However, it gives the following error for line u.m_a = m_a;. Error 2 error C2248: 'A::m_a' : cannot access private member declared in class 'A' d:\VC++\Vs8Console\Vs8Console\Vs8Console.cpp 30 Vs8Console I understand the error is because A<U> is a totally different type from A<T>. Is there any simple way of solving this (may be using a friend?) other than providing setter and getter methods? I am using Visual studio 2008 if it matters.

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• Hibernate JPA Caching Problem, Please help!

  - by Sameer Malhotra

  Ok, Here is my problem. I have a table named Master_Info_tbl. Its a lookup table: Here is the code for the table: @Entity @Table(name="MASTER_INFO_T") public class CodeValue implements java.io.Serializable { private static final long serialVersionUID = -3732397626260983394L; private Integer objectid; private String codetype; private String code; private String shortdesc; private String longdesc; private Integer dptid; private Integer sequen; private Timestamp begindate; private Timestamp enddate; private String username; private Timestamp rowlastchange; //getter Setter methods I have a service layer which calls the method       service.findbycodeType("Code1");   same way this table is queried for the other code types as well e.g. code2, code3 and so on till code10 which gets the result set from the same table and is shown into the drop down of the jsp pages since these drop downs are in 90% of the pages I am thinking to cache them globally. Any idea how to achieve this? FYI: I am using JPA and Hibernate with Struts2 and Spring. The database being used is DB2 UDB8.2 Please help!

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• unclear use of @property in window app using core data

  - by Matt

  Looking through a Window based application ive used to experiment with as a way of getting my head around core data, ive noticed that the appdelegate has the following code myAppDelegate.h #import <UIKit/UIKit.h> #import <CoreData/CoreData.h> @interface iCaptureFreeAppDelegate : NSObject <UIApplicationDelegate> { NSManagedObjectModel *managedObjectModel; NSManagedObjectContext *managedObjectContext; NSPersistentStoreCoordinator *persistentStoreCoordinator; UIWindow *window; UITabBarController *tabBarController; } myAppDelegate.m #import "myAppDelegate.h" @interface iCaptureFreeAppDelegate (PrivateCoreDataStack) @property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel; @property (nonatomic, retain) NSManagedObjectContext *managedObjectContext; @property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator; @end @implementation iCaptureFreeAppDelegate @synthesize window, tabBarController; // code .... // - (NSManagedObjectContext *) managedObjectContext { } - (NSManagedObjectModel *)managedObjectModel { } - (NSPersistentStoreCoordinator *)persistentStoreCoordinator { } // etc..... i want to understand a few things about what this project is doing why the properties in the category declaration? (if i delete the privateCoreDataStack category everything still works...) why the properties appear to be linked with the methods in the implementation ... managedObjectContext {} etc why the members in the .h file have the same name as the properties and the methods why code completion lets me use dot '.' to access the members but then fails on compilation say it cant find a getter thanks !

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• how to do validations when composing object of a class in other class ?

  - by haansi

  Hi, I have an IPAddress class which has one property named ip and in its setter I am validating data coming and if data is invalid it throws an error. (Its code is as the following): private string ip; public string IP { get { return ip; } set { string PartsOfIP = value.Split('.'); if (PartsOfIP.Length == 4) { foreach (string part in PartsOfIP) { int a = 0; bool result = int.TryParse(part, out a); if (result != true) { throw new Exception("Invalid IP"); } else { ip = value; } } } else { throw new Exception("Invalid IP"); } } In User Class I want to compose an object of IPAddress class. I am doing validations for properties of User in User class and validations of Ip in IPAddress class. My question is how I will compose IPAddress object in UserClass and what will be syntax for this ? If I again mention get and set here with IPAddress object in User class will my earlier mentioned (in IPAddress class) getter and setter work ? plz advice me in details thanks

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• C++ Virtual Methods for Class-Specific Attributes or External Structure

  - by acanaday

  I have a set of classes which are all derived from a common base class. I want to use these classes polymorphically. The interface defines a set of getter methods whose return values are constant across a given derived class, but vary from one derived class to another. e.g.: enum AVal { A_VAL_ONE, A_VAL_TWO, A_VAL_THREE }; enum BVal { B_VAL_ONE, B_VAL_TWO, B_VAL_THREE }; class Base { //... virtual AVal getAVal() const = 0; virtual BVal getBVal() const = 0; //... }; class One : public Base { //... AVal getAVal() const { return A_VAL_ONE }; BVal getBVal() const { return B_VAL_ONE }; //... }; class Two : public Base { //... AVal getAVal() const { return A_VAL_TWO }; BVal getBVal() const { return B_VAL_TWO }; //... }; etc. Is this a common way of doing things? If performance is an important consideration, would I be better off pulling the attributes out into an external structure, e.g.: struct Vals { AVal a_val; VBal b_val; }; storing a Vals* in each instance, and rewriting Base as follows? class Base { //... public: AVal getAVal() const { return _vals->a_val; }; BVal getBVal() const { return _vals->b_val; }; //... private: Vals* _vals; }; Is the extra dereference essentially the same as the vtable lookup? What is the established idiom for this type of situation? Are both of these solutions dumb? Any insights are greatly appreciated

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• Problems with binding to Window Height and Width

  - by D.H.

  I have some problems when I try to bind the height and width of a window to properties in my view model. Here is a small sample app to illustrate the problem. This is the code in app.xaml.xs public partial class App : Application { protected override void OnStartup(StartupEventArgs e) { base.OnStartup(e); MainWindow mainWindow = new MainWindow(); MainWindowViewModel mainWindowViewModel = new MainWindowViewModel(); mainWindow.DataContext = mainWindowViewModel; mainWindow.Show(); } } This is MainWindow.xaml: <Window x:Class="TestApp.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Height="{Binding WindowHeight}" Width="{Binding WindowWidth}" BorderThickness="{Binding WindowBorderThickness}"> </Window> And this is the view model: public class MainWindowViewModel { public int WindowWidth { get { return 100; } } public int WindowHeight { get { return 200; } } public int WindowBorderThickness { get { return 8; } } } When the program is started the getters of WindowHeight and WindowBorderThickness (but not WindowWidth) are called, so the height and the border of the window is set properly, but not the width. I then add button that will trigger PropertyChanged for all properties, so that the view model now looks like this: public class MainWindowViewModel : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; public void TriggerPropertyChanges() { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs("WindowWidth")); PropertyChanged(this, new PropertyChangedEventArgs("WindowHeight")); PropertyChanged(this, new PropertyChangedEventArgs("WindowBorderThickness")); } } public ICommand ButtonCommand { get { return new RelayCommand(delegate { TriggerPropertyChanges(); }); } } public int WindowWidth { get { return 100; } } public int WindowHeight { get { return 200; } } public int WindowBorderThickness { get { return 8; } } } Now, when I click the button, the getter of WindowBorderThickness is called, but not the ones for WindowWidth and WindowHeight. It all just seems very weird and inconsistent to me. What am I missing?

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• How to use accessors within the same class in Objective C?

  - by Azeworai

  Hi, I have a few properties defined in my header file like so @property (assign) bool connectivity_N; @property (assign) bool isConnected_N; In my implementation file I have an init and the synthesized properties like so @implementation Map @synthesize connectivity_N; @synthesize isConnected_N; a init to set the initial values like so -(id) init { if( (self=[super init]) ) { //initialise default properties self.connectivity_N=NO; self.isConnected_N=NO; } return self; } I'm running into an error that states Error: accessing unknown 'connectivity_N' class method. In this public method within the class +(bool) isConnectable:(directions) theDirection{ bool isTheDirectionConnectable= NO; switch (theDirection) { case north: isTheDirectionConnectable= self.connectivity_N; break; I'm not sure why is this so as I'm trying to grab the value of the property. According to the apple developer documentation "The default names for the getter and setter methods associated with a property are propertyName and setPropertyName: respectively—for example, given a property “foo”, the accessors would be foo and setFoo:" That has given me a clue that I've done something wrong here, I'm fairly new to objective C so would appreciate anyone who spends the time to explain this to me. Thanks!

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