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  • How to implement List, Set, and Map in null free design?

    - by Pyrolistical
    Its great when you can return a null/empty object in most cases to avoid nulls, but what about Collection like objects? In Java, Map returns null if key in get(key) is not found in the map. The best way I can think of to avoid nulls in this situation is to return an Entry<T> object, which is either the EmptyEntry<T>, or contains the value T. Sure we avoid the null, but now you can have a class cast exception if you don't check if its an EmptyEntry<T>. Is there a better way to avoid nulls in Map's get(K)? And for argument sake, let's say this language don't even have null, so don't say just use nulls.

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  • NullPointerException in javax.swing.text.SimpleAttributeSet.addAttribute

    - by Paul Reiners
    Has anyone ever seen an exception like this?: ERROR: java.lang.NullPointerException: null at java.util.Hashtable.put(null:-1) at javax.swing.text.SimpleAttributeSet.addAttribute(null:-1) at javax.swing.text.SimpleAttributeSet.addAttributes(null:-1) at javax.swing.text.StyledEditorKit.createInputAttributes(null:-1) at javax.swing.text.StyledEditorKit$AttributeTracker.updateInputAttributes(null:-1) at javax.swing.text.StyledEditorKit$AttributeTracker.caretUpdate(null:-1) at javax.swing.text.JTextComponent.fireCaretUpdate(null:-1) at javax.swing.text.JTextComponent$MutableCaretEvent.fire(null:-1) at javax.swing.text.JTextComponent$MutableCaretEvent.mouseReleased(null:-1) at java.awt.AWTEventMulticaster.mouseReleased(null:-1) at java.awt.AWTEventMulticaster.mouseReleased(null:-1) at java.awt.Component.processMouseEvent(null:-1) at javax.swing.JComponent.processMouseEvent(null:-1) at java.awt.Component.processEvent(null:-1) at java.awt.Container.processEvent(null:-1) at java.awt.Component.dispatchEventImpl(null:-1) at java.awt.Container.dispatchEventImpl(null:-1) at java.awt.Component.dispatchEvent(null:-1) at java.awt.LightweightDispatcher.retargetMouseEvent(null:-1) at java.awt.LightweightDispatcher.processMouseEvent(null:-1) at java.awt.LightweightDispatcher.dispatchEvent(null:-1) at java.awt.Container.dispatchEventImpl(null:-1) at java.awt.Window.dispatchEventImpl(null:-1) at java.awt.Component.dispatchEvent(null:-1) at java.awt.EventQueue.dispatchEvent(null:-1) at java.awt.EventDispatchThread.pumpOneEventForFilters(null:-1) at java.awt.EventDispatchThread.pumpEventsForFilter(null:-1) at java.awt.EventDispatchThread.pumpEventsForHierarchy(null:-1) at java.awt.EventDispatchThread.pumpEvents(null:-1) at java.awt.EventDispatchThread.pumpEvents(null:-1) at java.awt.EventDispatchThread.run(null:-1) I wish I could tell you an easy way to reproduce this, but I can’t. It’s happening in a Java Swing application I maintain. It happens infrequently and the application is quite complex. I know it’s a bit of a long shot just showing this stack trace, but I thought I’d try.

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  • Null Safe dereferencing in Java like ?. in Groovy using Maybe monad

    - by Sathish
    I'm working on a codebase ported from Objective C to Java. There are several usages of method chaining without nullchecks dog.collar().tag().name() I was looking for something similar to safe-dereferencing operator ?. in Groovy instead of having nullchecks dog.collar?.tag?.name This led to Maybe monad to have the notion of Nothing instead of Null. But all the implementations of Nothing i came across throw exception when value is accessed which still doesn't solve the chaining problem. I made Nothing return a mock, which behaves like NullObject pattern. But it solves the chaining problem. Is there anything wrong with this implementation of Nothing? [http://github.com/sathish316/jsafederef/blob/master/src/s2k/util/safederef/Nothing.java] As far as i can see 1. It feels odd to use mocking library in code 2. It doesn't stop at the first null. 3. How do i distinguish between null result because of null reference or name actually being null? How is it distinguished in Groovy code?

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  • Passing null as a param for replace() in javascript behaving weird?

    - by Babiker
    I have the follwing jQuery: $("#textArea").keyup(function(){ var textAreaValue = $("textArea"); if(!textArea.value.indexOf("some string")){ textArea.value = textArea.value.replace("some string",null); alert("It was there!"); } }); Is it normal for element.value.replace("some string",null); to replace "some string" with "null"as a string? And if normal can you please explain why? I have tested it with element.value.replace("some string",""), and that works fine, so what would be the difference between null and ""? Thanks in advance.

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  • Creating a Mysql view to SELECT coloumns from different tables

    - by user330429
    I need help in constructing a VIEW on 4 tables. The view should contain coloumns: ER.ID, ER.EMPID, ER.CUSTID, ER.STATUS, ER.DATEREPORTED, ER.REPORT, EB.NAME, CR.CUSTNAME, CR.LOCID, CL.LOCNAME, DI.DEPTNAME ALIASES EMP_REPORT ER , EMP_BIO EB, CUST_RECORD CR, CUST_LOC CL, DEPT_ID DI THE DATA MODELS ARE: describe EMP_REPORT; +--------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+-------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | empid | int(11) | NO | | NULL | | | custid | int(11) | NO | | NULL | | | status | varchar(32) | NO | | NULL | | | datereported | bigint(20) | NO | | NULL | | | report | text | YES | | NULL | | +--------------+-------------+------+-----+---------+----------------+ describe EMP_BIO; +--------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | empid | int(11) | NO | PRI | NULL | | | name | varchar(56) | NO | | NULL | | | sex | char(1) | NO | | NULL | | | deptid | int(11) | NO | | NULL | | | email | varchar(32) | NO | | NULL | | | mobile | bigint(20) | YES | | NULL | | | gtlk | varchar(32) | YES | | NULL | | | skype | varchar(32) | YES | | NULL | | | cvid | int(11) | YES | | NULL | | +--------+-------------+------+-----+---------+-------+ describe CUST_RECORD; +----------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+----------------+ | custid | int(11) | NO | PRI | NULL | auto_increment | | custname | varchar(32) | NO | | NULL | | | address | varchar(255) | YES | | NULL | | | contactp | varchar(32) | YES | | NULL | | | mobile | bigint(20) | YES | | NULL | | | locid | int(11) | NO | | NULL | | | remarks | text | YES | | NULL | | | date | int(11) | YES | | NULL | | | addedby | int(11) | YES | | NULL | | +----------+--------------+------+-----+---------+----------------+ describe CUST_LOC; +---------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+-------------+------+-----+---------+-------+ | locid | int(11) | NO | PRI | 0 | | | locname | varchar(32) | NO | | NULL | | +---------+-------------+------+-----+---------+-------+ describe DEPT_ID; +----------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +----------+-------------+------+-----+---------+-------+ | deptid | int(11) | NO | | NULL | | | deptname | varchar(32) | YES | | NULL | | +----------+-------------+------+-----+---------+-------+ The table EMP_REPORT contains reports submitted by employees, all the coloumns in it needs to be fetched. The empid in this table should be used to fetch corresponding name in EMP_BIO (employee biodata) table. The custid in EMP_REPORT should be used to fetch corresponding locid in CUST_RECORD(customer record) which is used to fetch locname in CUST_LOC(customer location) table. The empid in EMP_REPORT is used to fetch corresponding deptid in EMP_BIO table which is then used to fetch corresponding deptname from DEPT_ID(department id) table. I tried constructing view using union of different select queries, but dint get proper results. Please help me. Thanks in advance. PS: sorry for my poor english

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  • How can I match a match a null byte (0x00) in the Visual Studio binary editor with a find using a re

    - by Paul K
    Open a file in the Visual Studio binary editor that contains a null byte (0x00), then use the Quick Find feature (Ctrl +F) to find null bytes. I would have thought I could use a regular expression such as \x00 to match null bytes but it doesn't work. Searching for any other hex value using this method works fine. Is this a VS bug, 'feature', or am I just missing something? Is there a work around?

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  • How to assign a value of a property to a var ONLY if the object isn't null

    - by Blankman
    In my code, is there a shorthand that I can use to assign a variable the value of a object's property ONLY if the object isn't null? string username = SomeUserObject.Username; // fails if null I know I can do a check like if(SomeUserObject != null) but I think I saw a shorthand for this kind of test. I tried: string username = SomeUserObject ?? "" : SomeUserObject.Username; But that doesn't work.

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  • How to check if my string is equal to null?

    - by Roman
    I want to perform some action ONLY IF my string has a meaningful value. So, I tried this. if (!myString.eqauls("")) { doSomething } and this if (!myString.eqauls(null)) { doSomething } and this if ( (!myString.eqauls("")) && (!myString.eqauls(null))) { doSomething } and this if ( (!myString.eqauls("")) && (myString!=null)) { doSomething } and this if ( myString.length()>0) { doSomething } And in all cases my program doSomething in spite on the fact that my string IS EMPTY. It equals to null. So, what is wrong with that?

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  • Using "null" in jQuery functions. Is this okay?

    - by Nick
    My database consists of some entries which are NULL (so they don't affect max, min, etc..). When I pull all of the data from the database, I need to repopulate form fields with the values. Using .val(value) where value = NULL seems to work without any problems, but I'm not sure if this is a valid way to go about this. It doesn't say anything in the jQuery documentation (that I can find) about using NULL as parameters to functions.

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  • inserting null values in datetime column and integer column

    - by reggie
    I am using C# and developing a winform application. I have a project class which has the project attributes. the constructor of the project class is as follows: newProject = new Project(GCD_ID.IsNull() ? (int?)null : Convert.ToInt32(GCD_ID), txt_Proj_Desc.Text, txt_Prop_Name.Text, ST.ID.ToString().IsNull() ? null: ST.ID.ToString(), cmbCentre.Text, SEC.ID.ToString().IsNull() ? null : SEC.ID.ToString(), cmbZone.Text, FD.ID.ToString().IsNull() ? null : FD.ID.ToString(), DT.ID.ToString().IsNull() ? null : DT.ID.ToString(), OP.ID.ToString().IsNull() ? null : OP.ID.ToString(), T.ID.ToString().IsNull() ? null : T.ID.ToString(), CKV.ID.ToString().IsNull() ? null : CKV.ID.ToString(), STAT.ID.ToString().IsNull() ? null : STAT.ID.ToString(), MW.IsNull() ? (Double?)null : Convert.ToDouble(MW), txt_Subject.Text, Ip_Num.IsNull() ? (int?)null : Convert.ToInt32(Ip_Num), H1N_ID.IsNull() ? (int?)null : Convert.ToInt32(H1N_ID), NOMS_Slip_Num.IsNull() ? (int?)null : Convert.ToInt32(NOMS_Slip_Num), NMS_Updated.IsNull() ? (DateTime?)null : Convert.ToDateTime(NMS_Updated), Received_Date.IsNull() ? (DateTime?)null : Convert.ToDateTime(Received_Date), Actual_IS_Date.IsNull() ? (DateTime?)null : Convert.ToDateTime(Actual_IS_Date), Scheduled_IS_Date.IsNull() ? (DateTime?)null : Convert.ToDateTime(Scheduled_IS_Date), UpSt.ID.ToString().IsNull() ? null : UpSt.ID.ToString(), UpFd.ID.ToString().IsNull() ? null : UpFd.ID.ToString(), txtHVCircuit.Text, cmbbxSIA.Text); My problem is that i cannot insert values into the database when the datetime variables and the integer variables are null. all this data are assigned to the variable from textboxes on the form.. bELOW is the database function which takes in all the variables and insert them into the database. public static void createNewProject(int? GCD_ID, string Project_Desc, string Proponent_Name, int Station_ID, string OpCentre, int Sector_ID, string PLZone, int Feeder, int DxTx_ID, int OpControl_ID, int Type_ID, int ConnKV_ID, int Status_ID, double? MW, string Subject, int? Ip_Num, int? H1N_ID, int? NOMS_Slip_Num, DateTime? NMS_Updated, DateTime? Received_Date, DateTime? Actual_IS_Date, DateTime? Scheduled_IS_Date, int UP_Station_ID, int UP_Feeder_ID, string @HV_Circuit, string SIA_Required) { SqlConnection conn = null; try { //Takes in all the employee details to be added to the database. conn = new SqlConnection(databaseConnectionString); conn.Open(); SqlCommand cmd = new SqlCommand("createNewProject", conn); cmd.CommandType = CommandType.StoredProcedure; cmd.Parameters.Add(new SqlParameter("GCD_ID", GCD_ID)); cmd.Parameters.Add(new SqlParameter("Project_Desc", MiscFunctions.Capitalize(Project_Desc))); cmd.Parameters.Add(new SqlParameter("Proponent_Name", MiscFunctions.Capitalize(Proponent_Name))); cmd.Parameters.Add(new SqlParameter("Station_ID", Station_ID)); cmd.Parameters.Add(new SqlParameter("OpCentre", OpCentre)); cmd.Parameters.Add(new SqlParameter("Sector_ID", Sector_ID)); cmd.Parameters.Add(new SqlParameter("PLZone", PLZone)); cmd.Parameters.Add(new SqlParameter("Feeder", Feeder)); cmd.Parameters.Add(new SqlParameter("DxTx_ID", DxTx_ID)); cmd.Parameters.Add(new SqlParameter("OpControl_ID", OpControl_ID)); cmd.Parameters.Add(new SqlParameter("Type_ID", Type_ID)); cmd.Parameters.Add(new SqlParameter("ConnKV_ID", ConnKV_ID)); cmd.Parameters.Add(new SqlParameter("Status_ID", Status_ID)); cmd.Parameters.Add(new SqlParameter("MW", MW)); cmd.Parameters.Add(new SqlParameter("Subject", Subject)); cmd.Parameters.Add(new SqlParameter("Ip_Num", Ip_Num)); cmd.Parameters.Add(new SqlParameter("H1N_ID", H1N_ID)); cmd.Parameters.Add(new SqlParameter("NOMS_Slip_Num", NOMS_Slip_Num)); cmd.Parameters.Add(new SqlParameter("NMS_Updated", NMS_Updated)); cmd.Parameters.Add(new SqlParameter("Received_Date", Received_Date)); cmd.Parameters.Add(new SqlParameter("Actual_IS_Date", Actual_IS_Date)); cmd.Parameters.Add(new SqlParameter("Scheduled_IS_Date", Scheduled_IS_Date)); cmd.Parameters.Add(new SqlParameter("UP_Station_ID", UP_Station_ID)); cmd.Parameters.Add(new SqlParameter("UP_Feeder_ID", UP_Feeder_ID)); cmd.Parameters.Add(new SqlParameter("HV_Circuit", HV_Circuit)); cmd.Parameters.Add(new SqlParameter("SIA_Required", SIA_Required)); cmd.ExecuteNonQuery(); } catch (Exception e) //returns if error incurred. { MessageBox.Show("Error occured in createNewProject" + Environment.NewLine + e.ToString()); } finally { if (conn != null) { conn.Close(); } } } My question is, how do i insert values into the database. please please help

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  • Why is this exception thrown in the visual studio C compiler?

    - by Shane Larson
    Hello. I am trying to get more adept and my C programming and I was attempting to test out displaying a character from the input stream while inside of the loop that is getting the character. I am using the getchar() method. I am getting an exception thrown at the time that the printf statement in my code is present. (If I comment out the printf line in this function, the exception is not thrown). Exception: Unhandled exception at 0x611c91ad (msvcr90d.dll) in firstOS.exe: 0xC0000005: Access violation reading location 0x00002573. Here is the code... Any thoughts? Thank you. PS. I am using the stdio.h library. /*getCommandPromptNew - obtains a string command prompt.*/ void getCommandPromptNew(char s[], int lim){ int i, c; for(i=0; i < lim-1 && (c=getchar())!=EOF && c!='\n'; ++i){ s[i] = c; printf('%s', c); } }

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  • Programming Concepts: What should be done when an exception is thrown?

    - by Dooms101
    This does not really apply to any language specifically, but if it matters I am using VB.NET in Visual Studio 2008. I can't seem to find anything really that useful using Google about this topic, but I was wondering what is common practice when an exception is thrown and caught but since it has been thrown the application cannot continue operating. For example I have exceptions that are thrown by my FileLoader class when a file cannot be found or when a file is deemed corrupt. The exception is only thrown within the class and is not handled really. If the error is detected, then the exception is thrown and whatever function is was thrown is basically quits. So in the code trying to create that object or call one of its members I use a Try...Catch statement. However, I was wondering, what should even do when this exception is caught? My application needs these files to be intact, and if they are not, the application is almost useless. So far I just pop up a message box telling the user their is an error and to reinstall. What else can I do, or better, what's common practice in these situations?

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  • MySQL load data null values

    - by SP1
    Hello, I have a file that can contain from 3 to 4 columns of numerical values which are separated by comma. Empty fields are defined with the exception when they are at the end of the row: 1,2,3,4,5 1,2,3,,5 1,2,3 The following table was created in MySQL: +-------+--------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+--------+------+-----+---------+-------+ | one | int(1) | YES | | NULL | | | two | int(1) | YES | | NULL | | | three | int(1) | YES | | NULL | | | four | int(1) | YES | | NULL | | | five | int(1) | YES | | NULL | | +-------+--------+------+-----+---------+-------+ I am trying to load the data using MySQL LOAD command: load data infile '/tmp/testdata.txt' into table moo fields terminated by "," lines terminated by "\n"; The resulting table: +------+------+-------+------+------+ | one | two | three | four | five | +------+------+-------+------+------+ | 1 | 2 | 3 | 4 | 5 | | 1 | 2 | 3 | 0 | 0 | | 1 | 2 | 3 | NULL | NULL | +------+------+-------+------+------+ The problem lies with the fact that when a field is empty in the raw data and is not defined, MySQL for some reason does not use the columns default value (which is NULL) and uses zero. NULL is used correctly when the field is missing alltogether. Unfortunately, I have to be able to distinguish between NULL and 0 at this stage so any help would be appreciated. Thanks S.

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  • Is there a way in VS2008 (c#) to see all the possible exception types that can originate from a meth

    - by Matt
    Is there a way in VS2008 IDE for c# to see all the possible exception types that can possibly originate from a method call or even for an entire try-catch block? I know that intellisense or the object browser tells me this method can throw these types of exceptions but is there another way than using the object browser everytime? Something more accessible when coding? Furthermore, I don't think intellisense or the object browser do anything more than read the XML code comments. Shouldn't it be possible to scan a class's source and find all the exception types that can be thrown. (Forget path-ing based on method input, just scan the code for exception types) Am I wrong? Extending this idea, you should be able to hover over the 'try' or 'catch' keywords and present a tooltip with all the types of exceptions that can be thrown. My question boils down to, does a VS2008 add on like this exist? Does VS2010 do this perhaps? If not, could you implement it the way I've described, by scanning the class code for thrown exception types and would people find it useful. Exceptions bubble up so you have to scan every bit of code every method call, which I guess could be impractical, though I suppose you could build an index the first time and increase your speed that way. (It might be a cool little project....)

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  • Android sqlight problem always null

    - by yoav.str
    every time i am using the db its null and i just dont get it i use this code for the SQL when I have quarry : public class GameSQLHelper { static final String[] COUNTRIES = new String[] { "Afghanistan", "Albania", "Algeria", "American Samoa", "Andorra" }; private static final String DB_PATH = "/countryCityGame/databases/"; private static final String DATABASE_NAME = "events.db"; private static final int DATABASE_VERSION = 1; private final Context mCtx; // Table name public static final String TABLE = "myDataBase"; // Columns public static final String LETTER = "letter"; public static final String TYPE = "type"; public static final String VALUE = "value"; //my database SQLiteDatabase myDataBase; private static class DatabaseHelper extends SQLiteOpenHelper { private static final String TAG = null; DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { String sql = "create table " + TABLE + "( " + BaseColumns._ID + " integer primary key autoincrement, " + LETTER + " text not null, " + TYPE + " text not null," + VALUE + " text not null );"; Log.d("EventsData", "onCreate: " + sql); db.execSQL(sql); insertValuesToDB(db); } private void insertValuesToDB(SQLiteDatabase db) { if (db == null){ } else{ db.execSQL("INSERT INTO " + TABLE + " ("+LETTER+","+ TYPE +"," + VALUE +")" + " VALUES ('A', 'country', 'Angola');"); ContentValues initialValues = new ContentValues(); for (int i = 0 ; i < COUNTRIES.length ; i++){ Character tmp = (Character)COUNTRIES[i].charAt(0); initialValues.put(VALUE, COUNTRIES[i]); initialValues.put(TYPE, "country"); initialValues.put(LETTER,tmp.toString(tmp)); db.insert(TABLE, null, initialValues); } } } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS notes"); onCreate(db); } } /** * Constructor - takes the context to allow the database to be * opened/created * * @param ctx the Context within which to work */ public GameSQLHelper(Context ctx) { this.mCtx = ctx; } public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { if (oldVersion >= newVersion) return; String sql = null; if (oldVersion == 1) sql = "alter table " + TABLE + " add note text;"; if (oldVersion == 2) sql = ""; Log.d("EventsData", "onUpgrade : " + sql); if (sql != null) db.execSQL(sql); } public void openDataBase() throws SQLException{ //Open the database String myPath = DB_PATH + DATABASE_NAME; myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE); } public boolean existInDataBase(String serchStr ){ Cursor c = null ; try{ openDataBase(); c = myDataBase.query(true, TABLE, new String[] {TYPE }, VALUE + "=" + serchStr, null, null, null, null, null); } catch(Exception e){ Log.d("sqlExacption", e.getMessage()); } if (c == null) return false; return true; } } whenever i call this class (i hold an instace of him initialized : mDbHelper = new GameSQLHelper(this); where this is an activity ) i always get my mDbHelper as null how can i change it , its my first time working with sql outside of mysql platform so i am kind of having problmes understanding tje concept , and the android notepad example didnt help me .

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  • How to get javascript object references or reference count?

    - by Tauren
    How to get reference count for an object Is it possible to determine if a javascript object has multiple references to it? Or if it has references besides the one I'm accessing it with? Or even just to get the reference count itself? Can I find this information from javascript itself, or will I need to keep track of my own reference counters. Obviously, there must be at least one reference to it for my code access the object. But what I want to know is if there are any other references to it, or if my code is the only place it is accessed. I'd like to be able to delete the object if nothing else is referencing it. If you know the answer, there is no need to read the rest of this question. Below is just an example to make things more clear. Use Case In my application, I have a Repository object instance called contacts that contains an array of ALL my contacts. There are also multiple Collection object instances, such as friends collection and a coworkers collection. Each collection contains an array with a different set of items from the contacts Repository. Sample Code To make this concept more concrete, consider the code below. Each instance of the Repository object contains a list of all items of a particular type. You might have a repository of Contacts and a separate repository of Events. To keep it simple, you can just get, add, and remove items, and add many via the constructor. var Repository = function(items) { this.items = items || []; } Repository.prototype.get = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { return this.items[i]; } } } Repository.prototype.add = function(item) { if (toString.call(item) === "[object Array]") { this.items.concat(item); } else { this.items.push(item); } } Repository.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { this.removeIndex(i); } } } Repository.prototype.removeIndex = function(index) { if (items[index]) { if (/* items[i] has more than 1 reference to it */) { // Only remove item from repository if nothing else references it this.items.splice(index,1); return; } } } Note the line in remove with the comment. I only want to remove the item from my master repository of objects if no other objects have a reference to the item. Here's Collection: var Collection = function(repo,items) { this.repo = repo; this.items = items || []; } Collection.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { // Remove object from this collection this.items.splice(i,1); // Tell repo to remove it (only if no other references to it) repo.removeIndxe(i); return; } } } And then this code uses Repository and Collection: var contactRepo = new Repository([ {id: 1, name: "Joe"}, {id: 2, name: "Jane"}, {id: 3, name: "Tom"}, {id: 4, name: "Jack"}, {id: 5, name: "Sue"} ]); var friends = new Collection( contactRepo, [ contactRepo.get(2), contactRepo.get(4) ] ); var coworkers = new Collection( contactRepo, [ contactRepo.get(1), contactRepo.get(2), contactRepo.get(5) ] ); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 2, 5 coworkers.remove(2); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 5 friends.remove(4); contactRepo.items; // contains item ids 1, 2, 3, 5 friends.items; // contains item ids 2 coworkers.items; // contains item ids 1, 5 Notice how coworkers.remove(2) didn't remove id 2 from contactRepo? This is because it was still referenced from friends.items. However, friends.remove(4) causes id 4 to be removed from contactRepo, because no other collection is referring to it. Summary The above is what I want to do. I'm sure there are ways I can do this by keeping track of my own reference counters and such. But if there is a way to do it using javascript's built-in reference management, I'd like to hear about how to use it.

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  • How to properly close a socket after an exception is caught?

    - by marco
    Hello, after my last project I had the problem that the client was expecting an object from the server, but while processing the clients input an exception that forces the server to close the socket for security reasons is caught. This causes the client to terminate in a very unpleasant way, the way I decided to deal with this was sending the client a Input status message after each recieved input so that he knows if his input was processed properly or if he needs to throw an exception. So my question: Is there a better/cleaner way to close the socket after an exception is caught?? thanks,

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  • [Word2007] How to showing "only number" in picture cross-reference

    - by kornelijepetak
    I have many pictures in a document and I reference them very often in text. I don't want to lose the order so I am using Insert - Cross-reference. This opens the cross-reference dialog where I can set Reference type to Picture. For "Insert reference to", there are 5 choices: - Entire caption - List item - Only label and number - Only caption text - Page number, Above/below What I need is a reference that would be inserted like this: [4], and not like this: [Picture 4]; None of these options enable me to do it. Is there any way to make Word 2007 insert a reference to only Caption Number? Note: The document is written in Croatian language which has 7 declension cases, so using "Picture 4" would not be valid in all cases. Actually caption label Picture is set to croatian word "Slika" and when I need to say say "in the picture" I can't because it would be "na Slici 5." and not "na Slika 5." (like Word would make me do). That's why I need to reference only the caption number. Is that possible in Word 2007?

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  • Changing the namespace for a Web Reference in a Project to be Made Into a VS Project Template

    - by kdmurray
    When I add a web reference to a project, it comes up with a default namespace of: com.wpdevs.myservice. This is the namespace I'd have expected it to use in the application. When I add the using statement to the project, I have to add: using MyProject.com.wpdevs.myservice; I'd like to find a way to eliminate having to reference the project name in the using statement. The project I'm putting together now is destined to be converted into a VS Project template and having that rather strange reference in there, or even having a per-project reference, isn't something I'd like to have in the project.

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  • Are there any Python reference counting/garbage collection gotchas when dealing with C code?

    - by Jason Baker
    Just for the sheer heck of it, I've decided to create a Scheme binding to libpython so you can embed Python in Scheme programs. I'm already able to call into Python's C API, but I haven't really thought about memory management. The way mzscheme's FFI works is that I can call a function, and if that function returns a pointer to a PyObject, then I can have it automatically increment the reference count. Then, I can register a finalizer that will decrement the reference count when the Scheme object gets garbage collected. I've looked at the documentation for reference counting, and don't see any problems with this at first glance (although it may be sub-optimal in some cases). Are there any gotchas I'm missing? Also, I'm having trouble making heads or tails of the cyclic garbage collector documentation. What things will I need to bear in mind here? In particular, how do I make Python aware that I have a reference to something so it doesn't collect it while I'm still using it?

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  • visual studio 2010 add reference version missing

    - by Noel
    In VS2008 when I add a reference to a dll e.g log4Net I get the following in csproj <Reference Include="log4net, Version=1.2.10.0, Culture=neutral, PublicKeyToken=1b44e1d426115821, processorArchitecture=MSIL"> <SpecificVersion>False</SpecificVersion> <HintPath>..\..\lib\log4net\log4net.dll</HintPath> </Reference> In VS2010 when I add a reference to a dll for the first time e.g log4Net I get the following in csproj (i.e no version number etc) <Reference Include="log4net"> <HintPath>..\..\lib\log4net\log4net.dll</HintPath> </Reference> If I remove reference and add a second time the same details as in VS2008 is there (Version etc) Anyone know why version number etc not present the first time I add a reference and why it is present on secound time reference added?

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  • FETCH INTO doesn't raise an exception if the set is empty, does it?

    - by Cade Roux
    Here is some actual code I'm trying to debug: BEGIN OPEN bservice (coservice.prod_id); FETCH bservice INTO v_billing_alias_id, v_billing_service_uom_id, v_summary_remarks; CLOSE bservice; v_service_found := 1; -- An empty fetch is expected for some services. EXCEPTION WHEN OTHERS THEN v_service_found := 0; END; When the parametrized cursor bservice(prod_id) is empty, it fetches NULL into the three variables and does not throw an exception. So whoever wrote this code expecting it to throw an exception was wrong, right? The comment seems to imply that and empty fetch is expected and then it sets a flag for later handling, but I think this code cannot possibly have been tested with empty sets either. Obviously, it should use bservice%NOTFOUND or bservice%FOUND or similar.

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  • Model View Control Issue: Null Pointer Initialization Question

    - by David Dimalanta
    Good morning again. This is David. Please, I need an urgent help regarding control model view where I making a code that uniquely separating into groups: An Activity Java Class to Display the Interface A View and Function Java Class for Drawing Cards and Display it on the Activity Class The problem is that the result returns a Null Pointer Exception. I have initialize for the ID for Text View and Image View. Under this class "draw_deck.java". Please help me. Here's my code for draw_deck.java: package com.bodapps.inbetween.model; import android.content.Context; import android.view.View; import android.widget.ImageView; import android.widget.TextView; import com.bodapps.inbetween.R; public class draw_deck extends View { public TextView count_label; public ImageView draw_card; private int count; public draw_deck(Context context) { super(context); // TODO Auto-generated constructor stub //I have initialized two widgets for ID. I still don't get it why I got forced closed by Null Pointer Exception thing. draw_card = (ImageView) findViewById(R.id.IV_Draw_Card); count_label = (TextView) findViewById(R.id.Text_View_Count_Card); } public void draw(int s, int c, String strSuit, String strValue, Pile pile, Context context) { //super(context); //Just printing the card drawn from pile int suit, value = 1; draw_card = (ImageView) findViewById(R.id.IV_Draw_Card); count_label = (TextView) findViewById(R.id.Text_View_Count_Card); Card card; if(!pile.isEmpty()) //Setting it to IF statement displays the card one by one. { card = pile.drawFromPile(); //Need to check first if card is null. if (card != null) { //draws an extra if (card != null) { //Get suit of card to print out. suit = card.getSuit(); switch (suit) { case CardInfo.DIAMOND: strSuit = "DIAMOND"; s=0; break; case CardInfo.HEART: strSuit = "HEART"; s=1; break; case CardInfo.SPADE: strSuit = "SPADE"; s=2; break; case CardInfo.CLUB: strSuit = "CLUB"; s=3; break; } //Get value of card to print out. value = card.getValue(); switch (value) { case CardInfo.ACE: strValue = "ACE"; c=0; break; case CardInfo.TWO: c=1; break; case CardInfo.THREE: strValue = "THREE"; c=2; break; case CardInfo.FOUR: strValue = "FOUR"; c=3; break; case CardInfo.FIVE: strValue = "FIVE"; c=4; break; case CardInfo.SIX: strValue = "SIX"; c=4; break; case CardInfo.SEVEN: strValue = "SEVEN"; c=4; break; case CardInfo.EIGHT: strValue = "EIGHT"; c=4; break; case CardInfo.NINE: strValue = "NINE"; c=4; break; case CardInfo.TEN: strValue = "TEN"; c=4; break; case CardInfo.JACK: strValue = "JACK"; c=4; break; case CardInfo.QUEEN: strValue = "QUEEN"; c=4; break; case CardInfo.KING: strValue = "KING"; c=4; break; } } } }// //Below two lines of code, this is where issued the Null Pointer Exception. draw_card.setImageResource(deck[s][c]); count_label.setText(new StringBuilder(strValue).append(" of ").append(strSuit).append(String.valueOf(" " + count++)).toString()); } //Choice of Suits in a Deck public Integer[][] deck = { //Array Group 1 is [0][0] (No. of Cards: 4 - DIAMOND) { R.drawable.card_dummy_1, R.drawable.card_dummy_2, R.drawable.card_dummy_4, R.drawable.card_dummy_5, R.drawable.card_dummy_3 }, //Array Group 2 is [1][0] (No. of Cards: 4 - HEART) { R.drawable.card_dummy_1, R.drawable.card_dummy_2, R.drawable.card_dummy_4, R.drawable.card_dummy_5, R.drawable.card_dummy_3 }, //Array Group 3 is [2][0] (No. of Cards: 4 - SPADE) { R.drawable.card_dummy_1, R.drawable.card_dummy_2, R.drawable.card_dummy_4, R.drawable.card_dummy_5, R.drawable.card_dummy_3 }, //Array Group 4 is [3][0] (No. of Cards: 4 - CLUB) { R.drawable.card_dummy_1, R.drawable.card_dummy_2, R.drawable.card_dummy_4, R.drawable.card_dummy_5, R.drawable.card_dummy_3 }, }; } And this one of the activity class, Player_Mode_2.java: package com.bodapps.inbetween; import java.util.Random; import android.app.Activity; import android.app.Dialog; import android.content.Context; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.ImageView; import android.widget.TextView; import android.widget.Toast; import com.bodapps.inbetween.model.Card; import com.bodapps.inbetween.model.Pile; import com.bodapps.inbetween.model.draw_deck; /* * * Public class for Two-Player mode. * */ public class Player_Mode_2 extends Activity { //Image Views private ImageView draw_card; private ImageView player_1; private ImageView player_2; private ImageView icon; //Buttons private Button set_deck; //Edit Texts private EditText enter_no_of_decks; //text Views private TextView count_label; //Integer Data Types private int no_of_cards, count; private int card_multiplier; //Contexts final Context context = this; //Pile Model public Pile pile; //Card Model public Card card; //create View @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.play_2_player_mode); //-----[ Search for Views ]----- //Initialize for Image View draw_card = (ImageView) findViewById(R.id.IV_Draw_Card); player_1 = (ImageView) findViewById(R.id.IV_Player_1_Card); player_2 = (ImageView) findViewById(R.id.IV_Player_2_Card); //Initialize for Text view or Label count_label = (TextView) findViewById(R.id.Text_View_Count_Card); //-----[ Adding Values ]----- //Integer Values count = 0; no_of_cards = 0; //-----[ Adding Dialog ]----- //Initializing Dialog final Dialog deck_dialog = new Dialog(context); deck_dialog.setContentView(R.layout.dialog); deck_dialog.setTitle("Deck Dialog"); //-----[ Initializing Views for Dialog's Contents ]----- //Initialize for Edit Text enter_no_of_decks = (EditText) deck_dialog.findViewById(R.id.Edit_Text_Set_Number_of_Decks); //Initialize for Button set_deck = (Button) deck_dialog.findViewById(R.id.Button_Deck); //-----[ Setting onClickListener() ]----- //Set Event Listener for Image view draw_card.setOnClickListener(new Draw_Card_Model()); //Set Event Listener for Setting the Deck set_deck.setOnClickListener(new OnClickListener() { public void onClick(View v) { if(card_multiplier <= 8) { //Use "Integer.parseInt()" method to instantly convert from String to int value. card_multiplier = Integer.parseInt(enter_no_of_decks.getText().toString()); //Shuffling cards... pile = new Pile(card_multiplier); //Multiply no. of decks //Dismiss or close the dialog. deck_dialog.dismiss(); } else { Toast.makeText(getApplicationContext(), "Please choose a number from 1 to 8.", Toast.LENGTH_SHORT).show(); } } }); //Show dialog. deck_dialog.show(); } //Shuffling the Array public void Shuffle_Cards(Integer[][] Shuffle_Deck) { Random random = new Random(); for(int i = Shuffle_Deck[no_of_cards].length - 1; i >=0; i--) { int Index = random.nextInt(i + 1); //Simple Swapping Integer swap = Shuffle_Deck[card_multiplier-1][Index]; Shuffle_Deck[card_multiplier-1][Index] = Shuffle_Deck[card_multiplier-1][i]; Shuffle_Deck[card_multiplier-1][i] = swap; } } //Private Class for Random Card Draw private class Draw_Card_Model implements OnClickListener { public void onClick(View v) { //Just printing the card drawn from pile int suit = 0, value = 0; String strSuit = "", strValue = ""; draw_deck draw = new draw_deck(context); //This line is where issued the Null Pointer Exception. if (count == card_multiplier*52) { // A message shows up when all cards are draw out. Toast.makeText(getApplicationContext(), "All cards have been used up.", Toast.LENGTH_SHORT).show(); draw_card.setEnabled(false); } else { draw.draw(suit, value, strSuit, strValue, pile, context); count_label.setText(count); //This is where I got force closed error, although "int count" have initialized the number. This was supposed to accept in the setText() method. count++; } } } } Take note that the issues on Null Pointer Exception is the Image View and the Edit Text. I got to test it. Thanks. If you have any info about my question, let me know it frankly.

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  • Throwing exception from a property when my object state is invalid

    - by Rumi P.
    Microsoft guidelines say: "Avoid throwing exceptions from property getters", and I normally follow that. But my application uses Linq2SQL, and there is the case where my object can be in invalid state because somebody or something wrote nonsense into the database. Consider this toy example: [Table(Name="Rectangle")] public class Rectangle { [Column(Name="ID", IsPrimaryKey = true, IsDbGenerated = true)] public int ID {get; set;} [Column(Name="firstSide")] public double firstSide {get; set;} [Column(Name="secondSide")] public double secondSide {get; set;} public double sideRatio { get { return firstSide/secondSide; } } } Here, I could write code which ensures that my application never writes a Rectangle with a zero-length side into the database. But no matter how bulletproof I make my own code, somebody could open the database with a different application and create an invalid Rectangle, especially one with a 0 for secondSide. (For this example, please forget that it is possible to design the database in a way such that writing a side length of zero into the rectangle table is impossible; my domain model is very complex and there are constraints on model state which cannot be expressed in a relational database). So, the solution I am gravitating to is to change the getter to: get { if(firstSide > 0 && secondSide > 0) return firstSide/secondSide; else throw new System.InvalidOperationException("All rectangle sides should have a positive length"); } The reasoning behind not throwing exceptions from properties is that programmers should be able to use them without having to make precautions about catching and handling them them. But in this case, I think that it is OK to continue to use this property without such precautions: if the exception is thrown because my application wrote a non-zero rectangle side into the database, then this is a serious bug. It cannot and shouldn't be handled in the application, but there should be code which prevents it. It is good that the exception is visibly thrown, because that way the bug is caught. if the exception is thrown because a different application changed the data in the database, then handling it is outside of the scope of my application. So I can't do anything about it if I catch it. Is this a good enough reasoning to get over the "avoid" part of the guideline and throw the exception? Or should I turn it into a method after all? Note that in the real code, the properties which can have an invalid state feel less like the result of a calculation, so they are "natural" properties, not methods.

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