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  • Interface Casting vs. Class Casting

    - by Legatou
    I've been led to believe that casting can, in certain circumstances, become a measurable hindrance on performance. This may be moreso the case when we start dealing with incoherent webs of nasty exception throwing\catching. Given that I wish to create more correct heuristics when it comes to programming, I've been prompted to ask this question to the .NET gurus out there: Is interface casting faster than class casting? To give a code example, let's say this exists: public interface IEntity { IParent DaddyMommy { get; } } public interface IParent : IEntity { } public class Parent : Entity, IParent { } public class Entity : IEntity { public IParent DaddyMommy { get; protected set; } public IParent AdamEve_Interfaces { get { IEntity e = this; while (this.DaddyMommy != null) e = e.DaddyMommy as IEntity; return e as IParent; } } public Parent AdamEve_Classes { get { Entity e = this; while (this.DaddyMommy != null) e = e.DaddyMommy as Entity; return e as Parent; } } } So, is AdamEve_Interfaces faster than AdamEve_Classes? If so, by how much? And, if you know the answer, why?

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  • Alternatives to type casting in your domain

    - by Mr Happy
    In my Domain I have an entity Activity which has a list of ITasks. Each implementation of this task has it's own properties beside the implementation of ITask itself. Now each operation of the Activity entity (e.g. Execute()) only needs to loop over this list and call an ITask method (e.g. ExecuteTask()). Where I'm having trouble is when a specific tasks' properties need to be updated. How do I get an instance of that task? The options I see are: Get the Activity by Id and cast the task I need. This'll either sprinkle my code with: Tasks.OfType<SpecificTask>().Single(t => t.Id == taskId) or Tasks.Single(t => t.Id == taskId) as SpecificTask Make each task unique in the whole system (make each task an entity), and create a new repository for each ITask implementation I don't like either option, the first because I don't like casting: I'm using NHibernate and I'm sure this'll come back and bite me when I start using Lazy Loading (NHibernate currently uses proxies to implement this). I don't like the second option because there are/will be dozens of different kind of tasks. Which would mean I'd have to create as many repositories. Am I missing a third option here? Or are any of my objections to the two options not justified? How have you solved this problem in the past?

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  • 3D Ray Casting / Picking

    - by Chris
    Hi, I am not sure if I should post this link, but I feel this falls into game development just as much as it does math. I have a ray cast's far and near values and I am trying to calculate the end point of the ray so that I can either draw a line to show the ray, or render an object at the end of 3d mouse position. Here is my post on the stack overflow math site, if there is a problem with me doing this just close the thread. Thank you. http://math.stackexchange.com/questions/15918/help-with-matrix-mathematica

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  • Question about casting a class in Java with generics

    - by Florian F
    In Java 6 Class<? extends ArrayList<?>> a = ArrayList.class; gives and error, but Class<? extends ArrayList<?>> b = (Class<? extends ArrayList<?>>)ArrayList.class; gives a warning. Why is (a) an error? What is it, that Java needs to do in the assignment, if not the cast shown in (b)? And why isn't ArrayList compatible with ArrayList? I know one is "raw" and the other is "generic", but what is it you can do with an ArrayList and not with an ArrayList, or the other way around?

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  • Optimization ended up in casting an object at each method call

    - by Aybe
    I've been doing some optimization for the following piece of code : public void DrawLine(int x1, int y1, int x2, int y2, int color) { _bitmap.DrawLineBresenham(x1, y1, x2, y2, color); } After profiling it about 70% of the time spent was in getting a context for drawing and disposing it. I ended up sketching the following overload : public void DrawLine(int x1, int y1, int x2, int y2, int color, BitmapContext bitmapContext) { _bitmap.DrawLineBresenham(x1, y1, x2, y2, color, bitmapContext); } Until here no problems, all the user has to do is to pass a context and performance is really great as a context is created/disposed one time only (previously it was a thousand times per second). The next step was to make it generic in the sense it doesn't depend on a particular framework for rendering (besides .NET obvisouly). So I wrote this method : public void DrawLine(int x1, int y1, int x2, int y2, int color, IDisposable bitmapContext) { _bitmap.DrawLineBresenham(x1, y1, x2, y2, color, (BitmapContext)bitmapContext); } Now every time a line is drawn the generic context is casted, this was unexpected for me. Are there any approaches for fixing this design issue ? Note : _bitmap is a WriteableBitmap from WPF BitmapContext is from WriteableBitmapEx library DrawLineBresenham is an extension method from WriteableBitmapEx

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  • Type Casting variables in PHP: Is there a practical example?

    - by Stephen
    PHP, as most of us know, has weak typing. For those who don't, PHP.net says: PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined by the context in which the variable is used. Love it or hate it, PHP re-casts variables on-the-fly. So, the following code is valid: $var = "10"; $value = 10 + $var; var_dump($value); // int(20) PHP also alows you to explicitly cast a variable, like so: $var = "10"; $value = 10 + $var; $value = (string)$value; var_dump($value); // string(2) "20" That's all cool... but, for the life of me, I cannot conceive of a practical reason for doing this. I don't have a problem with strong typing in languages that support it, like Java. That's fine, and I completely understand it. Also, I'm aware of—and fully understand the usefulness of—type hinting in function parameters. The problem I have with type casting is explained by the above quote. If PHP can swap types at-will, it can do so even after you force cast a type; and it can do so on-the-fly when you need a certain type in an operation. That makes the following valid: $var = "10"; $value = (int)$var; $value = $value . ' TaDa!'; var_dump($value); // string(8) "10 TaDa!" So what's the point? Can anyone show me a practical application or example of type casting—one that would fail if type casting were not involved? I ask this here instead of SO because I figure practicality is too subjective. Edit in response to Chris' comment Take this theoretical example of a world where user-defined type casting makes sense in PHP: You force cast variable $foo as int -- (int)$foo. You attempt to store a string value in the variable $foo. PHP throws an exception!! <--- That would make sense. Suddenly the reason for user defined type casting exists! The fact that PHP will switch things around as needed makes the point of user defined type casting vague. For example, the following two code samples are equivalent: // example 1 $foo = 0; $foo = (string)$foo; $foo = '# of Reasons for the programmer to type cast $foo as a string: ' . $foo; // example 2 $foo = 0; $foo = (int)$foo; $foo = '# of Reasons for the programmer to type cast $foo as a string: ' . $foo;

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  • Type Casting variables in PHP: Is there a practical example?

    - by Stephen
    PHP, as most of us know, has weak typing. For those who don't, PHP.net says: PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined by the context in which the variable is used. Love it or hate it, PHP re-casts variables on-the-fly. So, the following code is valid: $var = "10"; $value = 10 + $var; var_dump($value); // int(20) PHP also alows you to explicitly cast a variable, like so: $var = "10"; $value = 10 + $var; $value = (string)$value; var_dump($value); // string(2) "20" That's all cool... but, for the life of me, I cannot conceive of a practical reason for doing this. I don't have a problem with strong typing in languages that support it, like Java. That's fine, and I completely understand it. Also, I'm aware of—and fully understand the usefulness of—type hinting in function parameters. The problem I have with type casting is explained by the above quote. If PHP can swap types at-will, it can do so even after you force cast a type; and it can do so on-the-fly when you need a certain type in an operation. That makes the following valid: $var = "10"; $value = (int)$var; $value = $value . ' TaDa!'; var_dump($value); // string(8) "10 TaDa!" So what's the point? Can anyone show me a practical application or example of type casting—one that would fail if type casting were not involved? I ask this here instead of SO because I figure practicality is too subjective. Edit in response to Chris' comment Take this theoretical example of a world where user-defined type casting makes sense in PHP: You force cast variable $foo as int -- (int)$foo. You attempt to store a string value in the variable $foo. PHP throws an exception!! <--- That would make sense. Suddenly the reason for user defined type casting exists! The fact that PHP will switch things around as needed makes the point of user defined type casting vague. For example, the following two code samples are equivalent: // example 1 $foo = 0; $foo = (string)$foo; $foo = '# of Reasons for the programmer to type cast $foo as a string: ' . $foo; // example 2 $foo = 0; $foo = (int)$foo; $foo = '# of Reasons for the programmer to type cast $foo as a string: ' . $foo; UPDATE Guess who found himself using typecasting in a practical environment? Yours Truly. The requirement was to display money values on a website for a restaurant menu. The design of the site required that trailing zeros be trimmed, so that the display looked something like the following: Menu Item 1 .............. $ 4 Menu Item 2 .............. $ 7.5 Menu Item 3 .............. $ 3 The best way I found to do that wast to cast the variable as a float: $price = '7.50'; // a string from the database layer. echo 'Menu Item 2 .............. $ ' . (float)$price; PHP trims the float's trailing zeros, and then recasts the float as a string for concatenation.

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  • Casting a object to a base class , return the extented object??

    - by CrazyJoe
    My Code: public class Contact { public string id{ get; set; } public string contact_type_id { get; set; } public string value{ get; set; } public string person_id { get; set; } public Contact() { } } public class Contact:Base.Contact { public ContactType ContactType { get; set; } public Person Person {get; set;} public Contact() { ContactType = new ContactType(); Person = new Person(); } } And: Contact c = new Contact(); Base.Contact cb = (Base.Contact)c; The Problem: The **cb** is set to **Contac** and not to **Base.Contact**. Have any trick to do that????

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  • Why is casting Derived** to Base*const* forbidden ?

    - by smerlin
    After reading this question, i saw the answer by Naveen containing a link to this page, which basically says, that casting from Derived** to Base** is forbidden since could change a pointer to an pointer to a Derived1 object point to a pointer to a Derived2 object (like: *derived1PtrPtr=derived2Ptr). OK, i understand this is evil ... But when casting Derived** to Base*const* this is not even possible, so whats the reason that this is not allowed anyway ?

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  • PHP Equivalent of Java Type-Casting Solution

    - by stjowa
    Since PHP has no custom-class type-casting, how would I go about doing the PHP equivalent of this Java code: CustomBaseObject cusBaseObject = cusBaseObjectDao.readCustomBaseObjectById(id); ((CustomChildObject) cusBaseObject).setChildAttribute1(value1); ((CustomChildObject) cusBaseObject).setChildAttribute2(value2); In my case, it would very nice if I could do this. However, trying this without type-casting support, it gives me an error that the methods do not exist for the object. Thanks, Steve

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  • Java - short and casting

    - by chr1s
    Hi all, I have the following code snippet. public static void main(String[] args) { short a = 4; short b = 5; short c = 5 + 4; short d = a; short e = a + b; // does not compile (expression treated as int) short z = 32767; short z_ = 32768; // does not compile (out of range) test(a); test(7); // does not compile (not applicable for arg int) } public static void test(short x) { } Is the following summary correct (with regard to only the example above using short)? direct initializations without casting is only possible using literals or single variables (as long as the value is in the range of the declared type) if the rhs of an assignment deals with expressions using variables, casting is necessary But why exactly do I need to cast the argument of the second method call taking into account the previous summary?

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  • Casting DataTypes with DirectCast, CType, TryCast

    - by Alex Essilfie
    Ever since I moved from VB6 to VB.NET somewhere in 2005, I've been using CType to do casting from one data type to another. I do this because it is simply faster, used to exist in VB6 and I do not know why I have to be using DirectCast if there is apparently no difference between them. I use TryCast once in a while because I understand that sometimes casting can fail. I however cannot get the difference between CType and DirectCast. Can anyone tell me the difference in plain simple English what the difference the two (CType and DirectCast)? Adding examples of where to use what as well would be helpful. Thanks.

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  • Beginner Java Question about Integer.parseInt() and casting

    - by happysoul
    so when casting like in the statement below :- int randomNumber=(int) (Math.random()*5) it causes the random no. generated to get converted into an int.. Also there's this method I just came across Integer.parseInt() which does the same ! i.e return an integer Why two different ways to make a value an int ? Also I made a search and it says parseInt() takes string as an argument.. So does this mean that parseInt() is ONLY to convert String into integer ? What about this casting then (int) ?? Can we use this to convert a string to an int too ? sorry if it sounds like a dumb question..I am just confused and trying to understand Help ?

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  • Casting to derived type problem in C++

    - by GONeale
    Hey there everyone, I am quite new to C++, but have worked with C# for years, however it is not helping me here! :) My problem: I have an Actor class which Ball and Peg both derive from on an objective-c iphone game I am working on. As I am testing for collision, I wish to set an instance of Ball and Peg appropriately depending on the actual runtime type of actorA or actorB. My code that tests this as follows: // Actors that collided Actor *actorA = (Actor*) bodyA->GetUserData(); Actor *actorB = (Actor*) bodyB->GetUserData(); Ball* ball; Peg* peg; if (static_cast<Ball*> (actorA)) { // true ball = static_cast<Ball*> (actorA); } else if (static_cast<Ball*> (actorB)) { ball = static_cast<Ball*> (actorB); } if (static_cast<Peg*> (actorA)) { // also true?! peg = static_cast<Peg*> (actorA); } else if (static_cast<Peg*> (actorB)) { peg = static_cast<Peg*> (actorB); } if (peg != NULL) { [peg hitByBall]; } Once ball and peg are set, I then proceed to run the hitByBall method (objective c). Where my problem really lies is in the casting procedurel Ball casts fine from actorA; the first if (static_cast<>) statement steps in and sets the ball pointer appropriately. The second step is to assign the appropriate type to peg. I know peg should be a Peg type and I previously know it will be actorB, however at runtime, detecting the types, I was surprised to find actually the third if (static_cast<>) statement stepped in and set this, this if statement was to check if actorA was a Peg, which we already know actorA is a Ball! Why would it have stepped here and not in the fourth if statement? The only thing I can assume is how casting works differently from c# and that is it finds that actorA which is actually of type Ball derives from Actor and then it found when static_cast<Peg*> (actorA) is performed it found Peg derives from Actor too, so this is a valid test? This could all come down to how I have misunderstood the use of static_cast. How can I achieve what I need? :) I'm really uneasy about what feels to me like a long winded brute-casting attempt here with a ton of ridiculous if statements. I'm sure there is a more elegant way to achieve a simple cast to Peg and cast to Ball dependent on actual type held in actorA and actorB. Hope someone out there can help! :) Thanks a lot.

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  • Casting SelectedItem of WPF Combobox to Color causes exception

    - by Nick Udell
    I have a combobox databound to the available system colors. When the user selects a color the following code is fired: private void cboFontColour_SelectionChanged(object sender, SelectionChangedEventArgs e) { Color colour = (Color)(cboFontColour.SelectedItem); } This throws a Casting Exception with the following message: "Specified cast is not valid." When I hover over cboFontColour.SelectedItem in the debugger, it is always a Color object. I do not understand why the system seemingly cannot cast from Color to Color, any help would be much obliged.

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  • Casting functions -- Is it a code smell?

    - by Earlz
    I recently began to start using functions to make casting easier on my fingers for one instance I had something like this ((Dictionary<string,string>)value).Add(foo); and converted it to a tiny little helper function so I can do this ToDictionary(value).Add(foo); Is this a code smell? (also I've marked this language agnostic even though my example is C#)

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  • java casting confusion

    - by Stardust
    Could anyone please tell me why the following casting is resulting in compile time error: Long l = (Long)Math.pow(5,2); But why not the following: long l = (long)Math.pow(5,2);

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  • Casting and dynamic vs static type in Java

    - by XpdX
    I'm learning about static vs dynamic types, and I am to the point of understanding it for the most part, but this case still eludes me. If class B extends A, and I have: A x = new B(); Is the following allowed?: B y = x; Or is explicit casting required?: B y = (B)x; Thanks!

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  • Casting Between Data Types in C#

    - by Jimbo
    I have (for example) an object of type A that I want to be able to cast to type B (similar to how you can cast an int to a float) Data types A and B are my own. Is it possible to define the rules by which this casting occurs? Example int a = 1; float b = (float)a; int c = (int)b;

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  • Dynamically specify the type in C#

    - by Lirik
    I'm creating a custom DataSet and I'm under some constrains: I want the user to specify the type of the data which they want to store. I want to reduce type-casting because I think it will be VERY expensive. I will use the data VERY frequently in my application. I don't know what type of data will be stored in the DataSet, so my initial idea was to make it a List of objects, but I suspect that the frequent use of the data and the need to type-cast will be very expensive. The basic idea is this: class DataSet : IDataSet { private Dictionary<string, List<Object>> _data; /// <summary> /// Constructs the data set given the user-specified labels. /// </summary> /// <param name="labels"> /// The labels of each column in the data set. /// </param> public DataSet(List<string> labels) { _data = new Dictionary<string, List<object>>(); foreach (string label in labels) { _data.Add(label, new List<object>()); } } #region IDataSet Members public List<string> DataLabels { get { return _data.Keys.ToList(); } } public int Count { get { _data[_data.Keys[0]].Count; } } public List<object> GetValues(string label) { return _data[label]; } public object GetValue(string label, int index) { return _data[label][index]; } public void InsertValue(string label, object value) { _data[label].Insert(0, value); } public void AddValue(string label, object value) { _data[label].Add(value); } #endregion } A concrete example where the DataSet will be used is to store data obtained from a CSV file where the first column contains the labels. When the data is being loaded from the CSV file I'd like to specify the type rather than casting to object. The data could contain columns such as dates, numbers, strings, etc. Here is what it could look like: "Date","Song","Rating","AvgRating","User" "02/03/2010","Code Monkey",4.6,4.1,"joe" "05/27/2009","Code Monkey",1.2,4.5,"jill" The data will be used in a Machine Learning/Artificial Intelligence algorithm, so it is essential that I make the reading of data very fast. I want to eliminate type-casting as much as possible, since I can't afford to cast from 'object' to whatever data type is needed on every read. I've seen applications that allow the user to pick the specific data type for each item in the csv file, so I'm trying to make a similar solution where a different type can be specified for each column. I want to create a generic solution so I don't have to return a List<object> but a List<DateTime> (if it's a DateTime column) or List<double> (if it's a column of doubles). Is there any way that this can be achieved? Perhaps my approach is wrong, is there a better approach to this problem?

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  • Helper Casting Functions -- Is it a code smell?

    - by Earlz
    I recently began to start using functions to make casting easier on my fingers for one instance I had something like this ((Dictionary<string,string>)value).Add(foo); and converted it to a tiny little helper function so I can do this ToDictionary(value).Add(foo); Is this a code smell? Also, what about simpler examples? For example in my scripting engine I've considered making things like this ((StringVariable)arg).Value="foo"; be ToStringVar(arg).Value="foo"; I really just dislike how inorder to cast a value and instantly get a property from it you must enclose it in double parentheses. I have a feeling the last one is much worse than the first one though (also I've marked this language agnostic even though my example is C#)

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  • Explanation of casting/conversion int/double in C#

    - by cad
    I coded some calculation stuff (I copied below a really simplifed example of what I did) like CASE2 and got bad results. Refactored the code like CASE1 and worked fine. I know there is an implicit cast in CASE 2, but not sure of the full reason. Any one could explain me what´s exactly happening below? //CASE 1, result 5.5 double auxMedia = (5 + 6); auxMedia = auxMedia / 2; //CASE 2, result 5.0 double auxMedia1 = (5 + 6) / 2; //CASE 3, result 5.5 double auxMedia3 = (5.0 + 6.0) / 2.0; //CASE 4, result 5.5 double auxMedia4 = (5 + 6) / 2.0; My guess is that /2 in CASE2 is casting (5 + 6) to int and causing round of division to 5, then casted again to double and converted to 5.0. CASE3 and CASE 4 also fixes the problem.

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