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  • Free Memory Occupied by Std List, Vector, Map etc

    - by Graviton
    Coming from a C# background, I have only vaguest idea on memory management on C++-- all I know is that I would have to free the memory manually. As a result my C++ code is written in such a way that objects of the type std::vector, std::list, std::map are freely instantiated, used, but not freed. I didn't realize this point until I am almost done with my programs, now my code is consisted of the following kinds of patterns: struct Point_2 { double x; double y; }; struct Point_3 { double x; double y; double z; }; list<list<Point_2>> Computation::ComputationJob(list<Point_3> pts3D, vector<Point_2> vectors) { map<Point_2, double> pt2DMap=ConstructPointMap(pts3D); vector<Point_2> vectorList = ConstructVectors(vectors); list<list<Point_2>> faceList2D=ConstructPoints(vectorList , pt2DMap); return faceList2D; } My question is, must I free every.single.one of the list usage ( in the above example, this means that I would have to free pt2DMap, vectorList and faceList2D)? That would be very tedious! I might just as well rewrite my Computation class so that it is less prone to memory leak. Any idea how to fix this?

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  • Referencing object's identity before submitting changes in LINQ

    - by Axarydax
    Hi, is there a way of knowing ID of identity column of record inserted via InsertOnSubmit beforehand, e.g. before calling datasource's SubmitChanges? Imagine I'm populating some kind of hierarchy in the database, but I wouldn't want to submit changes on each recursive call of each child node (e.g. if I had Directories table and Files table and am recreating my filesystem structure in the database). I'd like to do it that way, so I create a Directory object, set its name and attributes, then InsertOnSubmit it into DataContext.Directories collection, then reference Directory.ID in its child Files. Currently I need to call InsertOnSubmit to insert the 'directory' into the database and the database mapping fills its ID column. But this creates a lot of transactions and accesses to database and I imagine that if I did this inserting in a batch, the performance would be better. What I'd like to do is to somehow use Directory.ID before commiting changes, create all my File and Directory objects in advance and then do a big submit that puts all stuff into database. I'm also open to solving this problem via a stored procedure, I assume the performance would be even better if all operations would be done directly in the database.

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  • JSF Float Conversion

    - by Phill Sacre
    I'm using JSF 1.2 with IceFaces 1.8 in a project here. I have a page which is basically a big edit grid for a whole bunch of floating-point number fields. This is implemented with inputText fields on the page pointing at a value object with primitive float types Now, as a new requirement sees some of the fields be nullable, I wanted to change the value object to use Float objects rather than primitive types. I didn't think I'd need to do anything to the page to accomodate this. However, when I make the change I get the following error: /pages/page.xhtml @79,14 value="#{row.targetValue}": java.lang.IllegalArgumentException: argument type mismatch And /pages/page.xhtml @79,14 value="#{row.targetValue}": java.lang.IllegalArgumentException: java.lang.ClassCastException@1449aa1 The page looks like this: <ice:inputText value="#{row.targetValue}" size="4"> <f:convertNumber pattern="###.#" /> </ice:inputText> I've also tried adding in <f:convert convertId="javax.faces.Float" /> in there as well but that doesn't seem to work either! Neither does changing the value object types to Double. I'm sure I'm probably missing something really simple but I've been staring at this for a while now and no answers are immediately obvious!

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  • XmlSerialize a custom collection with an Attribute

    - by roomaroo
    I've got a simple class that inherits from Collection and adds a couple of properties. I need to serialize this class to XML, but the XMLSerializer ignores my additional properties. I assume this is because of the special treatment that XMLSerializer gives ICollection and IEnumerable objects. What's the best way around this? Here's some sample code: using System.Collections.ObjectModel; using System.IO; using System.Xml.Serialization; namespace SerialiseCollection { class Program { static void Main(string[] args) { var c = new MyCollection(); c.Add("Hello"); c.Add("Goodbye"); var serializer = new XmlSerializer(typeof(MyCollection)); using (var writer = new StreamWriter("test.xml")) serializer.Serialize(writer, c); } } [XmlRoot("MyCollection")] public class MyCollection : Collection<string> { [XmlAttribute()] public string MyAttribute { get; set; } public MyCollection() { this.MyAttribute = "SerializeThis"; } } } This outputs the following XML (note MyAttribute is missing in the MyCollection element): <?xml version="1.0" encoding="utf-8"?> <MyCollection xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <string>Hello</string> <string>Goodbye</string> </MyCollection> What I want is <MyCollection MyAttribute="SerializeThis" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <string>Hello</string> <string>Goodbye</string> </MyCollection> Any ideas? The simpler the better. Thanks.

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  • How to work threading with ConcurrentQueue<T>.

    - by dboarman
    I am trying to figure out what the best way of working with a queue will be. I have a process that returns a DataTable. Each DataTable, in turn, is merged with the previous DataTable. There is one problem, too many records to hold until the final BulkCopy (OutOfMemory). So, I have determined that I should process each incoming DataTable immediately. Thinking about the ConcurrentQueue<T>...but I don't see how the WriteQueuedData() method would know to dequeue a table and write it to the database. For instance: public class TableTransporter { private ConcurrentQueue<DataTable> tableQueue = new ConcurrentQueue<DataTable>(); public TableTransporter() { tableQueue.OnItemQueued += new EventHandler(WriteQueuedData); // no events available } public void ExtractData() { DataTable table; // perform data extraction tableQueue.Enqueue(table); } private void WriteQueuedData(object sender, EventArgs e) { BulkCopy(e.Table); } } My first question is, aside from the fact that I don't actually have any events to subscribe to, if I call ExtractData() asynchronously will this be all that I need? Second, is there something I'm missing about the way ConcurrentQueue<T> functions and needing some form of trigger to work asynchronously with the queued objects?

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  • GL_COLOR_MATERIAL with lighting on Android

    - by kostmo
    It appears that glColorMaterial() is absent from OpenGL ES. According to this post (for iPhone), you may still enable GL_COLOR_MATERIAL in OpenGL ES 1.x, but you're stuck with the default settings of GL_FRONT_AND_BACK and GL_AMBIENT_AND_DIFFUSE that you would otherwise set with glColorMaterial(). I would be OK with this, but the diffuse lighting is not working correctly. I set up my scene and tested it with one light, setting glMaterialfv() for GL_AMBIENT and GL_DIFFUSE once in the initialization. The normals have been set correctly, and lighting works the way it's supposed to. I see the Gourad shading. With GL_LIGHTING disabled, the flat colors I have set with glColor4f() appear on the various objects in the scene. This also functions as expected. However, when glEnable(GL_COLOR_MATERIAL) is called, the flat colors remain. I would expect to see the lighting effects. What might be missing? glColorMaterial() is also mentioned on anddev.org, but I'm not sure if the information there is accurate. I'm testing this on an Android 2.1 handset (Motorola Droid). Edit: It works properly on my 1.6 handset (ADP1).

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  • constructor function's object literal returns toString() method but no other method

    - by JohnMerlino
    I'm very confused with javascript methods defined in objects and the "this" keyword. In the below example, the toString() method is invoked when Mammal object instantiated: function Mammal(name){ this.name=name; this.toString = function(){ return '[Mammal "'+this.name+'"]'; } } var someAnimal = new Mammal('Mr. Biggles'); alert('someAnimal is '+someAnimal); Despite the fact that the toString() method is not invoked on the object someAnimal like this: alert('someAnimal is '+someAnimal.toString()); It still returns 'someAnimal is [Mammal "Mr. Biggles"]' . That doesn't make sense to me because the toString() function is not being called anywhere. Then to add even more confusion, if I change the toString() method to a method I make up such as random(): function Mammal(name){ this.name=name; this.random = function(){ return Math.floor(Math.random() * 15); } } var someAnimal = new Mammal('Mr. Biggles'); alert(someAnimal); It completely ignores the random method (despite the fact that it is defined the same way was the toString() method was) and returns: [object object] Another issue I'm having trouble understanding with inheritance is the value of "this". For example, in the below example function person(w,h){ width.width = w; width.height = h; } function man(w,h,s) { person.call(this, w, h); this.sex = s; } "this" keyword is being send to the person object clearly. However, does "this" refer to the subclass (man) or the super class (person) when the person object receives it? Thanks for clearing up any of the confusion I have with inheritance and object literals in javascript.

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  • Handling file uploads with JavaScript and Google Gears, is there a better solution?

    - by gnarf
    So - I've been using this method of file uploading for a bit, but it seems that Google Gears has poor support for the newer browsers that implement the HTML5 specs. I've heard the word deprecated floating around a few channels, so I'm looking for a replacement that can accomplish the following tasks, and support the new browsers. I can always fall back to gears / standard file POST's but these following items make my process much simpler: Users MUST to be able to select multiple files for uploading in the dialog. I MUST be able to receive status updates on the transmission of a file. (progress bars) I would like to be able to use PUT requests instead of POST I would like to be able to easily attach these events to existing HTML elements using JavaScript. I.E. the File Selection should be triggered on a <button> click. I would like to be able to control response/request parameters easily using JavaScript. I'm not sure if the new HTML5 browsers have support for the desktop/request objects gears uses, or if there is a flash uploader that has these features that I am missing in my google searches. An example of uploading code using gears: // select some files: var desktop = google.gears.factory.create('beta.desktop'); desktop.openFiles(selectFilesCallback); function selectFilesCallback(files) { $.each(files,function(k,file) { // this code actually goes through a queue, and creates some status bars // but it is unimportant to show here... sendFile(file); }); } function sendFile(file) { google.gears.factory.create('beta.httprequest'); request.open('PUT', upl.url); request.setRequestHeader('filename', file.name); request.upload.onprogress = function(e) { // gives me % status updates... allows e.loaded/e.total }; request.onreadystatechange = function() { if (request.readyState == 4) { // completed the upload! } }; request.send(file.blob); return request; } Edit: apparently flash isn't capable of using PUT requests, so I have changed it to a "like" instead of a "must".

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  • How can I create a SQL table using excel columns?

    - by Phsika
    I need to help to generate column name from excel automatically. I think that: we can do below codes: CREATE TABLE [dbo].[Addresses_Temp] ( [FirstName] VARCHAR(20), [LastName] VARCHAR(20), [Address] VARCHAR(50), [City] VARCHAR(30), [State] VARCHAR(2), [ZIP] VARCHAR(10) ) via C#. How can I learn column name from Excel? private void Form1_Load(object sender, EventArgs e) { ExcelToSql(); } void ExcelToSql() { string connectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Source\MPD.xlsm;Extended Properties=""Excel 12.0;HDR=YES;"""; // if you don't want to show the header row (first row) // use 'HDR=NO' in the string string strSQL = "SELECT * FROM [Sheet1$]"; OleDbConnection excelConnection = new OleDbConnection(connectionString); excelConnection.Open(); // This code will open excel file. OleDbCommand dbCommand = new OleDbCommand(strSQL, excelConnection); OleDbDataAdapter dataAdapter = new OleDbDataAdapter(dbCommand); // create data table DataTable dTable = new DataTable(); dataAdapter.Fill(dTable); // bind the datasource // dataBingingSrc.DataSource = dTable; // assign the dataBindingSrc to the DataGridView // dgvExcelList.DataSource = dataBingingSrc; // dispose used objects if (dTable.Rows.Count > 0) MessageBox.Show("Count:" + dTable.Rows.Count.ToString()); dTable.Dispose(); dataAdapter.Dispose(); dbCommand.Dispose(); excelConnection.Close(); excelConnection.Dispose(); }

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  • Turning a JSON list into a POJO

    - by Josh L
    I'm having trouble getting this bit of JSON into a POJO. I'm using Jackson configured like this: protected ThreadLocal<ObjectMapper> jparser = new ThreadLocal<ObjectMapper>(); public void receive(Object object) { try { if (object instanceof String && ((String)object).length() != 0) { ObjectDefinition t = null ; if (parserChoice==0) { if (jparser.get()==null) { jparser.set(new ObjectMapper()); } t = jparser.get().readValue((String)object, ObjectDefinition.class); } Object key = t.getKey(); if (key == null) return; transaction.put(key,t); } } catch (Exception e) { e.printStackTrace(); } } Here's the JSON that needs to be turned into a POJO: { "id":"exampleID1", "entities":{ "tags":[ { "text":"textexample1", "indices":[ 2, 14 ] }, { "text":"textexample2", "indices":[ 31, 36 ] }, { "text":"textexample3", "indices":[ 37, 43 ] } ] } And lastly, here's what I currently have for the java class: protected Entities entities; @JsonIgnoreProperties(ignoreUnknown = true) protected class Entities { public Entities() {} protected Tags tags; @JsonIgnoreProperties(ignoreUnknown = true) protected class Tags { public Tags() {} protected String text; public String getText() { return text; } public void setText(String text) { this.text = text; } }; public Tags getTags() { return tags; } public void setTags(Tags tags) { this.tags = tags; } }; //Getters & Setters ... I've been able to translate the more simple objects into a POJO, but the list has me stumped. Any help is appreciated. Thanks!

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  • equality on the sender of an event

    - by Berryl
    I have an interface for a UI widget, two of which are attributes of a presenter. public IMatrixWidget NonProjectActivityMatrix { set { // validate the incoming value and set the field _nonProjectActivityMatrix = value; .... // configure & load non-project activities } public IMatrixWidget ProjectActivityMatrix { set { // validate the incoming value and set the field _projectActivityMatrix = value; .... // configure & load project activities } The widget has an event that both presenter objects subscribe to, and so there is an event handler in the presenter like so: public void OnActivityEntry(object sender, EntryChangedEventArgs e) { // calculate newTotal here .... if (ReferenceEquals(sender, _nonProjectActivityMatrix)) { _nonProjectActivityMatrix.UpdateTotalHours(feedback.ActivityTotal); } else if (ReferenceEquals(sender, _projectActivityMatrix)) { _projectActivityMatrix.UpdateTotalHours(feedback.ActivityTotal); } else { // ERROR - we should never be here } } The problem is that the ReferenceEquals on the sender fails, even though it is the implemented widget that is the sender - the same implemented widget that was set to the presenter attribute! Can anyone spot what the problem / fix is? Cheers, Berryl I didn't know you could edit nicely. Cool. Here is the event raising code: void OnGridViewNumericUpDownEditingControl_ValueChanged(object sender, EventArgs e) { // omitted to save sapce if (EntryChanged == null) return; var args = new EntryChangedEventArgs(activityID, dayID, Convert.ToDouble(amount)); EntryChanged(this, args); } Here is the debugger dump of the presenter attribute, sans namespace info: ?_nonProjectActivityMatrix {WinPresentation.Widgets.MatrixWidgetDgv} [WinPresentation.Widgets.MatrixWidgetDgv]: {WinPresentation.Widgets.MatrixWidgetDgv} Here is the debugger dump of the sender: ?sender {WinPresentation.Widgets.MatrixWidgetDgv} base {Core.GUI.Widgets.Lookup.MatrixWidgetBase<Core.GUI.Widgets.Lookup.DynamicDisplayDto>}: {WinPresentation.Widgets.MatrixWidgetDgv} _configuration: {Domain.Presentation.Timesheet.Matrix.WeeklyMatrixConfiguration} _wrappedWidget: {Win.Widgets.DataGridViewDynamicLookupWidget} AllowUserToAddRows: true ColumnCount: 11 Count: 4 EntryChanged: {Method = {Void OnActivityEntry(System.Object, Smack.ConstructionAdmin.Domain.Presentation.Timesheet.Matrix.EntryChangedEventArgs)}} SelectedCell: {DataGridViewNumericUpDownCell { ColumnIndex=3, RowIndex=3 }} SelectedCellValue: "0.00" SelectedColumn: {DataGridViewNumericUpDownColumn { Name=MONDAY, Index=3 }} SelectedItem: {'AdministrativeActivity: 130-04', , AdministrativeTime, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00} Berryl

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  • C#/LINQ: How to define generically a keySelector for a templated class before calling OrderBy

    - by PierrOz
    Hi Folks, I have the following class defined in C# class myClass<T,U> { public T PropertyOne { get; set; } public U PropertyTwo { get; set; } } I need to write a function that reorder a list of myClass objects and takes two other parameters which define how I do this reorder: does my reordering depend on PropertyOne or PropertyTwo and is it ascending or descending. Let's say this two parameters are boolean. With my current knowledge in LINQ, I would write: public IList<myClass<T,U>> ReOrder(IList<myClass<T,U>> myList, bool usePropertyOne, bool ascending) { if (usePropertyOne) { if (ascending) { return myList.OrderBy(o => o.PropertyOne).ToList(); } else { return myList.OrderByDescending(o => o.PropertyOne).ToList(); } } else { if (ascending) { return myList.OrderBy(o => o.PropertyTwo).ToList(); } else { return myList.OrderByDescending(o => o.PropertyTwo).ToList(); } } } What could be a more efficient/elegant way to do that ? How can I declare the Func,TResult keySelector object to reuse when I call either OrderBy or OrderByDescending? I'm interesting in the answer since in my real life, I can have more than two properties.

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  • Return an empty collection when Linq where returns nothing

    - by ahsteele
    I am using the below statement with the intent of getting all of the machine objects from the MachineList collection (type IEnumerable) that have a MachineStatus of i. The MachineList collection will not always contain machines with a status of i. At times when no machines have a MachineStatus of i I'd like to return an empty collection. My call to ActiveMachines (which is used first) works but InactiveMachines does not. public IEnumerable<Machine> ActiveMachines { get { return Customer.MachineList .Where(m => m.MachineStatus == "a"); } } public IEnumerable<Machine> InactiveMachines { get { return Customer.MachineList .Where(m => m.MachineStatus == "i"); } } Edit Upon further examination it appears that any enumeration of MachineList will cause subsequent enumerations of MachineList to throw an exeception: Object reference not set to an instance of an object. Therefore, it doesn't matter if a call is made to ActiveMachines or InactiveMachines as its an issue with the MachineList collection. This is especially troubling because I can break calls to MachineList simply by enumerating it in a Watch before it is called in code. At its lowest level MachineList implements NHibernate.IQuery being returned as an IEnumerable. What's causing MachineList to lose its contents after an initial enumeration?

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  • What are the options for overriding Django's cascading delete behaviour?

    - by Tom
    Django models generally handle the ON DELETE CASCADE behaviour quite adequately (in a way that works on databases that don't support it natively.) However, I'm struggling to discover what is the best way to override this behaviour where it is not appropriate, in the following scenarios for example: ON DELETE RESTRICT (i.e. prevent deleting an object if it has child records) ON DELETE SET NULL (i.e. don't delete a child record, but set it's parent key to NULL instead to break the relationship) Update other related data when a record is deleted (e.g. deleting an uploaded image file) The following are the potential ways to achieve these that I am aware of: Override the model's delete() method. While this sort of works, it is sidestepped when the records are deleted via a QuerySet. Also, every model's delete() must be overridden to make sure Django's code is never called and super() can't be called as it may use a QuerySet to delete child objects. Use signals. This seems to be ideal as they are called when directly deleting the model or deleting via a QuerySet. However, there is no possibility to prevent a child object from being deleted so it is not usable to implement ON CASCADE RESTRICT or SET NULL. Use a database engine that handles this properly (what does Django do in this case?) Wait until Django supports it (and live with bugs until then...) It seems like the first option is the only viable one, but it's ugly, throws the baby out with the bath water, and risks missing something when a new model/relation is added. Am I missing something? Any recommendations?

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  • How do JVM's implicit memory barriers behave when chaining constructors

    - by Joonas Pulakka
    Referring to my earlier question on incompletely constructed objects, I have a second question. As Jon Skeet pointed out, there's an implicit memory barrier in the end of a constructor that makes sure that final fields are visible to all threads. But what if a constructor calls another constructor; is there such a memory barrier in the end of each of them, or only in one being called from outside? That is, when the "wrong" solution is: public class ThisEscape { public ThisEscape(EventSource source) { source.registerListener( new EventListener() { public void onEvent(Event e) { doSomething(e); } }); } } And the correct one would be a factory method version: public class SafeListener { private final EventListener listener; private SafeListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public static SafeListener newInstance(EventSource source) { SafeListener safe = new SafeListener(); source.registerListener(safe.listener); return safe; } } Would the following work too, or not? public class MyListener { private final EventListener Listener; private MyListener() { listener = new EventListener() { public void onEvent(Event e) { doSomething(e); } } } public MyListener(EventSource source) { this(); source.register(listener); } }

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  • Is there a tool I can use to generate interfaces and wrappers for object mocking in c#

    - by fostandy
    Given a class like System.Timers.Timer, or ANY managed class (whether user defined, from the .net framework, or some 3rd party library) is there some program I can use to (a) generate an interface based on this class and (b) generate a wrapper for the given class? for example if I have a public class Foo { public object MyProperty { get { ... } set { ... } } public int SomeMethod(object a) { ... } } it will create an interface interface IFoo { object MyProperty { get; set; } int SomeMethod(object a) { ... } } and maybe even a wrapper class FooWrap { // something for relay constructor here ... Foo _me; public object MyProperty { get { return _me.MyProperty; } set { _me.MyProperty = value; } } public int SomeMethod(object a) { return _me.SomeMethod(); } } Obviously there's stuff I haven't thought about like events, generics etc. I want a DWIMNWIS-PSICHTO(-Plus-Stuff-I-Clearly-Haven't-Thought-Of). I'm aware resharper can be used to extract an interface but I've only been able to use this on my own classes. Aside: Wow, it is amazing how simply becoming accustomed to a previously 'unacceptable' idea eventually gives it legitimacy. A year ago the idea of having to create interfaces for all objects I want to mock and adopting an injection framework would have seemed like the height of madness. It turns out that while it's not quite death and taxes, it is sparta. I am aware of and have used typemock. It certainly is the work of elvish wizards. One day when $800 does not seem like quite so much money I intend to buy it.

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  • Multiple calls to data service from SL3?

    - by Chris
    I have an SL3 that makes asynchronous calls to a data service. Basically, there is a treeview that is bound to a collection of objects. The idea is that as a user selects a specific treeviewitem, a call is made to the data service, with a parameter specific to the selected treeviewitem being passed to the corresponding web method in the data service. The data service returns data back to the SL3 client, and the client presents the data to the user. This works well. The problem is that when users start to navigate through the treeview using the arrow keys on their keyboard, they could press the down arrow key, for example, 10 times, and 10 calls will be made to the data service, and then each of the 10 items will be displayed to the user momentarily, until finishing with the data for the most recently selected treeview item. So - onto the question. How can I put in some form of delay, to allow someone to navigate quickly through a treeview, then, once then stop at a certain treeviewitem, a call is made to the data service? Thanks for any suggestions. Chris

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  • Get string value of class propery names in Objective-C

    - by Flash84x
    I have the following class definition. Contact.h #import <CoreData/CoreData.h> @interface Contact : NSManagedObject { } @property (nonatomic, retain) NSString * City; @property (nonatomic, retain) NSDate * LastUpdated; @property (nonatomic, retain) NSString * Country; @property (nonatomic, retain) NSString * Email; @property (nonatomic, retain) NSNumber * Id; @property (nonatomic, retain) NSString * ContactNotes; @property (nonatomic, retain) NSString * State; @property (nonatomic, retain) NSString * StreetAddress2; @property (nonatomic, retain) NSDate * DateCreated; @property (nonatomic, retain) NSString * FirstName; @property (nonatomic, retain) NSString * Phone1; @property (nonatomic, retain) NSString * PostalCode; @property (nonatomic, retain) NSString * Website; @property (nonatomic, retain) NSString * StreetAddress1; @property (nonatomic, retain) NSString * LastName; @end Is it possible to obtain an array of NSString objects with all of the properties by name? Array would look like this... [@"City", @"LastUpdated", @"Country", .... ]

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  • reinitializing javascript object's properties

    - by Pino
    In my Javascript drag and drop build app, a variety of buildings can be built. The specific characteristics of these are all saved in one object, like var buildings = { house: ['#07DA21',12,12,0,20], bank: ['#E7DFF2',16,16,0,3], stadium: ['#000000',12,12,0,1], townhall: ['#2082A8',20,8,0,1], etcetera } So every building has a number of characteristics, like color, size, look which can be called as buildings[townhall][0] (referring to the color). The object changes as the user changes things. When clicking 'reset' however, the whole object should be reset to its initial settings again to start over, but I have no idea how to do that. For normal objects it is something like. function building() {} var building = new building(); delete building; var building2 = new building(); You can easily delete and remake it, so the properties are reset. But my object is automatically initialized. Is there a way to turn my object into something that can be deleted and newly created, without making it very complicating, or a better way to store this information?

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  • How to create extensible dynamic array in Java without using pre-made classes?

    - by AndrejaKo
    Yeah, it's a homework question, so givemetehkodezplsthx! :) Anyway, here's what I need to do: I need to have a class which will have among its attributes array of objects of another class. The proper way to do this in my opinion would be to use something like LinkedList, Vector or similar. Unfortunately, last time I did that, I got fire and brimstone from my professor, because according to his belief I was using advanced stuff without understanding basics. Now next obvious solution would be to create array with fixed number of elements and add checks to get and set which will see if the array is full. If it is full, they'd create new bigger array, copy older array's data to the new array and return the new array to the caller. If it's mostly empty, they'd create new smaller array and move data from old array to new. To me this looks a bit stupid. For my homework, there probably won't be more that 3 elements in an array, but I'd like to make a scalable solution without manually calculating statistics about how often is array filled, what is the average number of new elements added, then using results of calculation to calculate number of elements in new array and so on. By the way, there is no need to remove elements from the middle of the array. Any tips?

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  • What is the performance penalty of XML data type in SQL Server when compared to NVARCHAR(MAX)?

    - by Piotr Owsiak
    I have a DB that is going to keep log entries. One of the columns in the log table contains serialized (to XML) objects and a guy on my team proposed to go with XML data type rather than NVARCHAR(MAX). This table will have logs kept "forever" (archiving some very old entries may be considered in the future). I'm a little worried about the CPU overhead, but I'm even more worried that DB can grow faster (FoxyBOA from the referenced question got 70% bigger DB when using XML). I have read this question http://stackoverflow.com/questions/514827/microsoft-sql-server-2005-2008-xml-vs-text-varchar-data-type and it gave me some ideas but I am particulairly interrested in clarification on whether the DB size increases or decreases. Can you please share your insight/experiences in that matter. BTW. I don't currently have any need to depend on XML features within SQL Server (there's nearly zero advantage to me in the specific case). Ocasionally log entries will be extracted, but I prefer to handle the XML using .NET (either by writing a small client or using a function defined in a .NET assembly).

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  • What is the most efficient/elegant way to parse a flat table into a tree?

    - by Tomalak
    Assume you have a flat table that stores an ordered tree hierarchy: Id Name ParentId Order 1 'Node 1' 0 10 2 'Node 1.1' 1 10 3 'Node 2' 0 20 4 'Node 1.1.1' 2 10 5 'Node 2.1' 3 10 6 'Node 1.2' 1 20 What minimalistic approach would you use to output that to HTML (or text, for that matter) as a correctly ordered, correctly intended tree? Assume further you only have basic data structures (arrays and hashmaps), no fancy objects with parent/children references, no ORM, no framework, just your two hands. The table is represented as a result set, which can be accessed randomly. Pseudo code or plain English is okay, this is purely a conceptional question. Bonus question: Is there a fundamentally better way to store a tree structure like this in a RDBMS? EDITS AND ADDITIONS To answer one commenter's (Mark Bessey's) question: A root node is not necessary, because it is never going to be displayed anyway. ParentId = 0 is the convention to express "these are top level". The Order column defines how nodes with the same parent are going to be sorted. The "result set" I spoke of can be pictured as an array of hashmaps (to stay in that terminology). For my example was meant to be already there. Some answers go the extra mile and construct it first, but thats okay. The tree can be arbitrarily deep. Each node can have N children. I did not exactly have a "millions of entries" tree in mind, though. Don't mistake my choice of node naming ('Node 1.1.1') for something to rely on. The nodes could equally well be called 'Frank' or 'Bob', no naming structure is implied, this was merely to make it readable. I have posted my own solution so you guys can pull it to pieces.

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  • accepts_nested_attributes with Model.update for multiple models

    - by Ohad
    Hi, I'm trying to follow http://railscasts.com/episodes/198-edit-multiple-individually but I would like to save objects which are nested (accepts_nested_attributes_for). I've added the following in my controller: def edit_multiple @people = Person.find(params[:person_ids], :include => [:parameters]) end def update_multiple keys = params[:people].keys if keys.empty? flash[:error] = "Please select at least one person" redirect_to :back and return end values = keys.map {|k| params[:people][k]} @people = Person.update(keys,values).reject { |h| h.errors.empty? } if @people.empty? flash[:notice] = 'Updated people!' redirect_to person_path else redirect_to edit_multiple_path end end and in the view: <% form_tag update_multiple_people_path, :method => :post do %> <% for person in @people %> <% fields_for "people[]", host do |f| %> <%= f.error_messages :object_name => "person" %> <h3><%= h person.name %></h3> <% for parameter in person.parameters %> <% f.fields_for "person_parameters[]", parameter do |builder| -%> <%= render "common/parameters", :f => builder %> <% end -%> <% end -%> <p><%= link_to_add_fields "Add a parameter", f, :person_parameters, "common/parameters" %></p> <% end %> <% end %> <p><%= submit_tag "Edit these Parameter(s)" %></p> <% end %> but I'm always getting a mistmatch - e.g. ActiveRecord::AssociationTypeMismatch and Parameter(#70341811965140) expected, got Array(#70341874300460) Thanks!

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  • Simplifying Testing through design considerations while utilizing dependency injection

    - by Adam Driscoll
    We are a few months into a green-field project to rework the Logic and Business layers of our product. By utilizing MEF (dependency injection) we have achieved high levels of code coverage and I believe that we have a pretty solid product. As we have been working through some of the more complex logic I have found it increasingly difficult to unit test. We are utilizing the CompositionContainer to query for types required by these complex algorithms. My unit tests are sometimes difficult to follow due to the lengthy mock object setup process that must take place, just right, to allow for certain circumstances to be verified. My unit tests often take me longer to write than the code that I'm trying to test. I realize this is not only an issue with dependency injection but with design as a whole. Is poor method design or lack of composition to blame for my overly complex tests? I've tried base classing tests, creating commonly used mock objects and ensuring that I utilize the container as much as possible to ease this issue but my tests always end up quite complex and hard to debug. What are some tips that you've seen to keep such tests concise, readable, and effective?

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  • Java many to many association map

    - by Raphael Jolivet
    Hi, I have to classes, ClassA and ClassB and a "many to many" AssociationClass. I want to use a structure to hold the associations between A and B such as I can know, for each instance of A or B, which are their counterparts. I thought of using a Hashmap, with pair keys: Hasmap<Pair<ClassA, ClassB>, AssociationClass> associations; This way, I can add and remove an association between two instances of ClassA and ClassB, and I can query a relation for two given instances. However, I miss the feature of getting all associations defined for a given instance of ClassA or ClassB. I could do it by brute force and loop over all keys of the map to search for associations between a given instance, but this is inefficient and not elegant. Do you know of any data structure / free library that enables this ? I don't want to reinvent the wheel. Thanks in advance for your help, Raphael NB: This is not a "database" question. These objects are pure POJO used for live computation, I don't need persistence stuff.

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