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  • soft question - Which of these topics is likely to be relevant in the future?

    - by Fool
    I hear some topics in computer science, such as object-oriented programming, are relevant today but may become obsolete in the future. I'm picking courses for a minor in computer science, and I need one more elective. Could someone help me choose topic(s) from the following list that would grant timeless knowledge, relevant and applicable in the future? Why are such topics relevant? Artificial Intelligence Human-Computer Interaction Object-Oriented Programming Operating Systems Compilers Networking Databases Graphics Automata and Complexity Theory Logic and Automated Reasoning Algorithms If some of these titles are too vague, I'll provide more info.

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  • Syncing client and server CRUD operations using json and php

    - by Justin
    I'm working on some code to sync the state of models between client (being a javascript application) and server. Often I end up writing redundant code to track the client and server objects so I can map the client supplied data to the server models. Below is some code I am thinking about implementing to help. What I don't like about the below code is that this method won't handle nested relationships very well, I would have to create multiple object trackers. One work around is for each server model after creating or loading, simply do $model->clientId = $clientId; IMO this is a nasty hack and I want to avoid it. Adding a setCientId method to all my model object would be another way to make it less hacky, but this seems like overkill to me. Really clientIds are only good for inserting/updating data in some scenarios. I could go with a decorator pattern but auto generating a proxy class seems a bit involved. I could use a generic proxy class that uses a __call function to allow for original object data to be accessed, but this seems wrong too. Any thoughts or comments? $clientData = '[{name: "Bob", action: "update", id: 1, clientId: 200}, {name:"Susan", action:"create", clientId: 131} ]'; $jsonObjs = json_decode($clientData); $objectTracker = new ObjectTracker(); $objectTracker->trackClientObjs($jsonObjs); $query = $this->em->createQuery("SELECT x FROM Application_Model_User x WHERE x.id IN (:ids)"); $query->setParameters("ids",$objectTracker->getClientSpecifiedServerIds()); $models = $query->getResults(); //Apply client data to server model foreach ($models as $model) { $clientModel = $objectTracker->getClientJsonObj($model->getId()); ... } //Create new models and persist foreach($objectTracker->getNewClientObjs() as $newClientObj) { $model = new Application_Model_User(); .... $em->persist($model); $objectTracker->trackServerObj($model); } $em->flush(); $resourceResponse = $objectTracker->createResourceResponse(); //Id mappings will be an associtave array representing server id resources with client side // id. //This method Dosen't seem to flexible if we want to return additional data with each resource... //Would have to modify the returned data structure, seems like tight coupling... //Ex return value: //[{clientId: 200, id:1} , {clientId: 131, id: 33}];

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  • How can I test a parser for a bespoke XML schema?

    - by Greg B
    I'm parsing a bespoke XML format into an object graph using .NET 4.0. My parser is using the System.XML namespace internally, I'm then interrogating the relevant properties of XmlNodes to create my object graph. I've got a first cut of the parser working on a basic input file and I want to put some unit tests around this before I progress on to more complex input files. Is there a pattern for how to test a parser such as this? When I started looking at this, my first move was to new up and XmlDocument, XmlNamespaceManager and create an XmlElement. But it occurs to me that this is quite lengthy and prone to human error. My parser is quite recursive as you can imagine and this might lead to testing the full system rather than the individual units (methods) of the system. So a second question might be What refactoring might make a recursive parser more testable?

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  • Microeconomical simulation: coordination/planning between self-interested trading agents

    - by Milton Manfried
    In a typical perfect-information strategy game like Chess, an agent can calculate its best move by searching the state tree for the best possible move, while assuming that the opponent will also make the best possible move (i.e. Mini-max). I would like to use this approach in a "game" modeling economic activity, where the possible "moves" would be to buy or sell for a given price, and the goal, rather than a specific class of states (e.g. Checkmate), would be to maximize some function F of the agent's state (e.g. F(money, widget) = 10*money + widget). How to handle buy/sell actions that require coordination between both parties, at the very least agreement upon a price? The cheap way out would be to set the price beforehand, maybe based upon the current supply -- but the idea of this simulation is to examine how prices emerge when freely determined by "perfectly rational" agents. A great example of what I do not want is the trading algorithm in SugarScape -- paraphrasing from Growing Artificial Societies p101-102: when a pair of agents interact to trade, they each compute their internal valuations of the goods, then a bargaining process is conducted and a price is agreed to. If this price makes both agents better off, they complete the transaction The protocol itself is beautiful, but what it cannot capture (as far as I can tell) is the ability for an agent to pay more than it might otherwise for a good, because it knows that it can sell it for even more at a later date -- what appears to be called "strategic thinking" in this pape at Google Books Multi-Agent-Based Simulation III: 4th International Workshop, MABS 2003... to get realistic behavior like that, it seems one would either (1) have to build an outrageously-complex internal valuation system which could at best only cover situations that were planned for at compile-time, or otherwise (2) have some mechanism to search the state tree... which would require some way of planning future trades. Note: The chess analogy only works as far as the state-space search goes; the simulation isn't intended to be "zero sum", so a literal mini-max search wouldn't be appropriate -- and ideally, it should work with more than two agents.

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  • API always returns JSONObject or JSONArray Best practices

    - by Michael Laffargue
    I'm making an API that will return data in JSON. I also wanted on client side to make an utility class to call this API. Something like : JSONObject sendGetRequest(Url url); JSONObject sendPostRequest(Url url, HashMap postData); However sometimes the API send back array of object [{id:1},{id:2}] I now got two choices (): Make the method test for JSONArray or JSONObject and send back an Object that I will have to cast in the caller Make a method that returns JSONObject and one for JSONArray (like sendGetRequestAndReturnAsJSONArray) Make the server always send Arrays even for one element Make the server always send Objects wrapping my Array I going for the two last methods since I think it would be a good thing to force the API to send consistent type of data. But what would be the best practice (if one exist). Always send arrays? or always send objects?

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  • Generically correcting data before save with Entity Framework

    - by koevoeter
    Been working with Entity Framework (.NET 4.0) for a week now for a data migration job and needed some code that generically corrects string values in the database. You probably also have seen things like empty strings instead of NULL or non-trimmed texts ("United States       ") in "old" databases, and you don't want to apply a correcting function on every column you migrate. Here's how I've done this (extending the partial class of my ObjectContext):public partial class MyDatacontext{    partial void OnContextCreated()    {        SavingChanges += OnSavingChanges;    }     private void OnSavingChanges(object sender, EventArgs e)    {        foreach (var entity in GetPersistingEntities(sender))        {            foreach (var propertyInfo in GetStringProperties(entity))            {                var value = (string)propertyInfo.GetValue(entity, null);                 if (value == null)                {                    continue;                }                 if (value.Trim().Length == 0 && IsNullable(propertyInfo))                {                    propertyInfo.SetValue(entity, null, null);                }                else if (value != value.Trim())                {                    propertyInfo.SetValue(entity, value.Trim(), null);                }            }        }    }     private IEnumerable<object> GetPersistingEntities(object sender)    {        return ((ObjectContext)sender).ObjectStateManager            .GetObjectStateEntries(EntityState.Added | EntityState.Modified)             .Select(e => e.Entity);    }    private IEnumerable<PropertyInfo> GetStringProperties(object entity)    {        return entity.GetType().GetProperties()            .Where(pi => pi.PropertyType == typeof(string));    }    private bool IsNullable(PropertyInfo propertyInfo)    {        return ((EdmScalarPropertyAttribute)propertyInfo             .GetCustomAttributes(typeof(EdmScalarPropertyAttribute), false)            .Single()).IsNullable;    }}   Obviously you can use similar code for other generic corrections.

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  • "Imprinting" as a language feature?

    - by MKO
    Idea I had this idea for a language feature that I think would be useful, does anyone know of a language that implements something like this? The idea is that besides inheritance a class can also use something called "imprinting" (for lack of better term). A class can imprint one or several (non-abstract) classes. When a class imprints another class it gets all it's properties and all it's methods. It's like the class storing an instance of the imprinted class and redirecting it's methods/properties to it. A class that imprints another class therefore by definition also implements all it's interfaces and it's abstract class. So what's the point? Well, inheritance and polymorphism is hard to get right. Often composition gives far more flexibility. Multiple inheritance offers a slew of different problems without much benefits (IMO). I often write adapter classes (in C#) by implementing some interface and passing along the actual methods/properties to an encapsulated object. The downside to that approach is that if the interface changes the class breaks. You also you have to put in a lot of code that does nothing but pass things along to the encapsulated object. A classic example is that you have some class that implements IEnumerable or IList and contains an internal class it uses. With this technique things would be much easier Example (c#) [imprint List<Person> as peopleList] public class People : PersonBase { public void SomeMethod() { DoSomething(this.Count); //Count is from List } } //Now People can be treated as an List<Person> People people = new People(); foreach(Person person in people) { ... } peopleList is an alias/variablename (of your choice)used internally to alias the instance but can be skipped if not needed. One thing that's useful is to override an imprinted method, that could be achieved with the ordinary override syntax public override void Add(Person person) { DoSomething(); personList.Add(person); } note that the above is functional equivalent (and could be rewritten by the compiler) to: public class People : PersonBase , IList<Person> { private List<Person> personList = new List<Person>(); public override void Add(object obj) { this.personList.Add(obj) } public override int IndexOf(object obj) { return personList.IndexOf(obj) } //etc etc for each signature in the interface } only if IList changes your class will break. IList won't change but an interface that you, someone in your team, or a thirdparty has designed might just change. Also this saves you writing a whole lot of code for some interfaces/abstract classes. Caveats There's a couple of gotchas. First we, syntax must be added to call the imprinted classes's constructors from the imprinting class constructor. Also, what happends if a class imprints two classes which have the same method? In that case the compiler would detect it and force the class to define an override of that method (where you could chose if you wanted to call either imprinted class or both) So what do you think, would it be useful, any caveats? It seems it would be pretty straightforward to implement something like that in the C# language but I might be missing something :) Sidenote - Why is this different from multiple inheritance Ok, so some people have asked about this. Why is this different from multiple inheritance and why not multiple inheritance. In C# methods are either virtual or not. Say that we have ClassB who inherits from ClassA. ClassA has the methods MethodA and MethodB. ClassB overrides MethodA but not MethodB. Now say that MethodB has a call to MethodA. if MethodA is virtual it will call the implementation that ClassB has, if not it will use the base class, ClassA's MethodA and you'll end up wondering why your class doesn't work as it should. By the terminology sofar you might already confused. So what happens if ClassB inherits both from ClassA and another ClassC. I bet both programmers and compilers will be scratching their heads. The benefit of this approach IMO is that the imprinting classes are totally encapsulated and need not be designed with multiple inheritance in mind. You can basically imprint anything.

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  • How to create realistic 2d lighting using colour temperature

    - by Truncheon
    I'm looking for a lighting algorithm that produces realistic lights expressed in kelvins, from about 2500k to 6500k. What I'm confused about is how to make the lights properly interact with the colors of game objects. If a whole level is fully lit (overcast daylight) then it would seem that I should use just the color of the object. But what if I'm in a closed room with no windows, and there is an incandescent bulb shining light in the room? How would that light properly light up the objects in the room? There does not seem to be an obvious solution to the problem. And simply mixing the color of the light with the colors of the object, seems an inaccurate approach.

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  • When to use functional programming approach and when not? (in Java)

    - by john smith optional
    let's assume I have a task to create a Set of class names. To remove duplication of .getName() method calls for each class, I used org.apache.commons.collections.CollectionUtils and org.apache.commons.collections.Transformer as follows: Snippet 1: Set<String> myNames = new HashSet<String>(); CollectionUtils.collect( Arrays.<Class<?>>asList(My1.class, My2.class, My3.class, My4.class, My5.class), new Transformer() { public Object transform(Object o) { return ((Class<?>) o).getName(); } }, myNames); An alternative would be this code: Snippet 2: Collections.addAll(myNames, My1.class.getName(), My2.class.getName(), My3.class.getName(), My4.class.getName(), My5.class.getName()); So, when using functional programming approach is overhead and when it's not and why? Isn't my usage of functional programming approach in snippet 1 is an overhead and why?

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  • Should I forward the a call to .Equals onto .Equals<T>?

    - by Jaimal Chohan
    So, I've got you bog standard c# object, overriding Equalsand implementing IEquatable public override int GetHashCode() { return _name.GetHashCode(); } public override bool Equals(object obj) { return Equals(obj as Tag) } #region IEquatable<Tag> Members public bool Equals(Tag other) { if (other == null) return false; else return _name == other._name; } #endregion Now, for some reason, I used to think that forwarding the calls from Equals into Equals was bad, no idea why, perhaps I read it a long time ago, anyway I'd write separate (but logically same) code for each method. Now I think forwarding Equals to Equals is okay, for obvious reasons, but for the life me I can't remember why I thought it wasn't before. Any thoughts?

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  • Lookup Viewer

    - by Geertjan
    The Maven integrated view that I showed yesterday I was able to create because I happened to know that an implementation of SubprojectProvider and LogicalViewProvider are in the Lookup of Maven projects. With that knowledge, I was able to use and even delegate to those implementations. But what if you don't know that those implementations are in the Lookup of the Project object? In the case of the Maven Project implementation, you could look in the source code of the Maven Project implementation, at the "getLookup" method. However, any other module could be putting its own objects into that Lookup, dynamically, i.e., at runtime. So there's no way of knowing what's in the Lookup of any Project object or any other object with a Lookup. But now imagine that you have a Lookup Viewer, as a tool during development, which you would exclude when distributing the application. Whenever new objects are found in the Lookup, the viewer displays them. You could install the Lookup Viewer into NetBeans IDE, or any other NetBeans Platform application, and then get a quick impression of what's actually in the Lookup when you select a different item in the application during development. Here it is (though I vaguely remember someone else writing something similar): Above, a Maven Project is selected. The Lookup Window shows that, among many other classes, an implementation of SubprojectProvider and LogicalViewProvider are found in the Lookup when the Maven Project is selected. If an item in the Lookup Window has its own Lookup, the content of that Lookup is displayed as child nodes of the Lookup, etc, i.e., you can explore all the way down the Lookup of each item found within objects found within the current selection. (What's especially fun is seeing the SaveCookieImpl being added and removed from the Lookup Window when you make/save a change in a document.) Another example is below, showing the Lookup Window installed in a custom application created during a course at MIT in Boston: A small trick I had to apply is that I always show the previous Lookup, since the current Lookup, when you select one of the Nodes in the Lookup Window, would be the Lookup of the Lookup Window itself! If anyone is interested in this, I can publish the NetBeans module providing the above window to the NetBeans update center. 

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  • Developing Schema Compare for Oracle (Part 5): Query Snapshots

    - by Simon Cooper
    If you've emailed us about a bug you've encountered with the EAP or beta versions of Schema Compare for Oracle, we probably asked you to send us a query snapshot of your databases. Here, I explain what a query snapshot is, and how it helps us fix your bug. Problem 1: Debugging users' bug reports When we started the Schema Compare project, we knew we were going to get problems with users' databases - configurations we hadn't considered, features that weren't installed, unicode issues, wierd dependencies... With SQL Compare, users are generally happy to send us a database backup that we can restore using a single RESTORE DATABASE command on our test servers and immediately reproduce the problem. Oracle, on the other hand, would be a lot more tricky. As Oracle generally has a 1-to-1 mapping between instances and databases, any databases users sent would have to be restored to their own instance. Furthermore, the number of steps required to get a properly working database, and the size of most oracle databases, made it infeasible to ask every customer who came across a bug during our beta program to send us their databases. We also knew that there would be lots of issues with data security that would make it hard to get backups. So we needed an easier way to be able to debug customers issues and sort out what strange schema data Oracle was returning. Problem 2: Test execution time Another issue we knew we would have to solve was the execution time of the tests we would produce for the Schema Compare engine. Our initial prototype showed that querying the data dictionary for schema information was going to be slow (at least 15 seconds per database), and this is generally proportional to the size of the database. If you're running thousands of tests on the same databases, each one registering separate schemas, not only would the tests would take hours and hours to run, but the test servers would be hammered senseless. The solution To solve these, we needed to be able to populate the schema of a database without actually connecting to it. Well, the IDataReader interface is the primary way we read data from an Oracle server. The data dictionary queries we use return their data in terms of simple strings and numbers, which we then process and reconstruct into an object model, and the results of these queries are identical for identical schemas. So, we can record the raw results of the queries once, and then replay these results to construct the same object model as many times as required without needing to actually connect to the original database. This is what query snapshots do. They are binary files containing the raw unprocessed data we get back from the oracle server for all the queries we run on the data dictionary to get schema information. The core of the query snapshot generation takes the results of the IDataReader we get from running queries on Oracle, and passes the row data to a BinaryWriter that writes it straight to a file. The query snapshot can then be replayed to create the same object model; when the results of a specific query is needed by the population code, we can simply read the binary data stored in the file on disk and present it through an IDataReader wrapper. This is far faster than querying the server over the network, and allows us to run tests in a reasonable time. They also allow us to easily debug a customers problem; using a simple snapshot generation program, users can generate a query snapshot that could be sent along with a bug report that we can immediately replay on our machines to let us debug the issue, rather than having to obtain database backups and restore databases to test systems. There are also far fewer problems with data security; query snapshots only contain schema information, which is generally less sensitive than table data. Query snapshots implementation However, actually implementing such a feature did have a couple of 'gotchas' to it. My second blog post detailed the development of the dependencies algorithm we use to ensure we get all the dependencies in the database, and that algorithm uses data from both databases to find all the needed objects - what database you're comparing to affects what objects get populated from both databases. We get information on these additional objects using an appropriate WHERE clause on all the population queries. So, in order to accurately replay the results of querying the live database, the query snapshot needs to be a snapshot of a comparison of two databases, not just populating a single database. Furthermore, although the code population queries (eg querying all_tab_cols to get column information) can simply be passed straight from the IDataReader to the BinaryWriter, we need to hook into and run the live dependencies algorithm while we're creating the snapshot to ensure we get the same WHERE clauses, and the same query results, as if we were populating straight from a live system. We also need to store the results of the dependencies queries themselves, as the resulting dependency graph is stored within the OracleDatabase object that is produced, and is later used to help order actions in synchronization scripts. This is significantly helped by the dependencies algorithm being a deterministic algorithm - given the same input, it will always return the same output. Therefore, when we're replaying a query snapshot, and processing dependency information, we simply have to return the results of the queries in the order we got them from the live database, rather than trying to calculate the contents of all_dependencies on the fly. Query snapshots are a significant feature in Schema Compare that really helps us to debug problems with the tool, as well as making our testers happier. Although not really user-visible, they are very useful to the development team to help us fix bugs in the product much faster than we otherwise would be able to.

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  • vector collision on polygon in 3d space detection/testing?

    - by LRFLEW
    In the 3d fps in java I'm working on, I need a bullet to be fired and to tell if it hit someone. All visual objects in the game are defined through OpenGL, so the object it can be colliding with can be any drawable polygon (although they will most likely be triangles and rectangles anyways). The bullet is not an object, but will be treated as a vector that instantaneously moves all the way across the map (like the snipper riffle in Halo). What's the best way to detect/test collisions with the polygon and the vector. I have access to OpenCL, however I have absolutely no experience with it. I am very early in the developmental stage, so if you think there's a better way of going about this, feel free to tell me (I barley have a player model to collide with anyways, so I'm flexible with it). Thanks

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  • Proper response for a REST insert - full new record, or just the record id value?

    - by Keith Palmer
    I'm building a REST API which allows inserts (POST, not idempotent) and updates (PUT, idempotent) requests to add/update database to our application. I'm wondering if there are any standards or best practices regarding what data we send back to the client in the response for a POST (insert) operation. We need to send back at least a record ID value (e.g. your new record is record #1234). Should we respond with the full object? (e.g. essentially the same response they'd get back from a "GET /object_type/1234" request) Should we respond with only the new ID value? (e.g. "{ id: 1234 }", which means that if they want to fetch the whole record they need to do an additional HTTP GET request to grab the full record) A redirect header pointing them to the URL for the full object? Something else entirely?

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  • PerlRegEx vs RegularExpressionsCore Delphi Units

    - by Jan Goyvaerts
    The RegularExpressionsCore unit that is part of Delphi XE is based on the latest class-based PerlRegEx unit that I developed. Embarcadero only made a few changes to the unit. These changes are insignificant enough that code written for earlier versions of Delphi using the class-based PerlRegEx unit will work just the same with Delphi XE. The unit was renamed from PerlRegEx to RegularExpressionsCore. When migrating your code to Delphi XE, you can choose whether you want to use the new RegularExpressionsCore unit or continue using the PerlRegEx unit in your application. All you need to change is which unit you add to the uses clause in your own units. Indentation and line breaks in the code were changed to match the style used in the Delphi RTL and VCL code. This does not change the code, but makes it harder to diff the two units. Literal strings in the unit were separated into their own unit called RegularExpressionsConsts. These strings are only used for error messages that indicate bugs in your code. If your code uses TPerlRegEx correctly then the user should not see any of these strings. My code uses assertions to check for out of bounds parameters, while Embarcadero uses exceptions. Again, if you use TPerlRegEx correctly, you should never get any assertions or exceptions. The Compile method raises an exception if the regular expression is invalid in both my original TPerlRegEx component and Embarcadero’s version. If your code allows the user to provide the regular expression, you should explicitly call Compile and catch any exceptions it raises so you can tell the user there is a problem with the regular expression. Even with user-provided regular expressions, you shouldn’t get any other assertions or exceptions if your code is correct. Note that Embarcadero owns all the rights to their RegularExpressionsCore unit. Like all the other RTL and VCL units, this unit cannot be distributed by myself or anyone other than Embarcadero. I do retain the rights to my original PerlRegEx unit which I will continue to make available for those using older versions of Delphi.

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  • Executing EXE with wildcard from psexec

    - by Danny
    I'm writing a few scripts that I am using to integrate with bamboo for some continuous integration improvements and I've run into a bit of a snag. I'm currently trying to run a psexec command that installs the latest build on the remote machine but I dont necessary know the revision number. For example, the remote exe file could be Installer-3.1.xxxxx.exe where the xxxxx changes. I tried running the command with Installer-3.1.*.exe but it takes it as literal in Windows. I'm not overly familiar with Windows command prompt and am more used to Linux at this moment.

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  • Making an efficient collision detection system

    - by Sri Harsha Chilakapati
    I'm very new to game development (just started 3 months ago) and I'm learning through creating a game engine. It's located here. In terms of collision, I know only brute-force detection, in which case, the game slows down if there are a number of objects. So my question is How should I program the collisions? I want them to happen automatically for every object and call the object's collision(GObject other) method on each collision. Are there any new algorithms which can make this fast? If so, can anybody shed some light on this topic?

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  • design practice for business layer when supporting API versioning

    - by user1186065
    Is there any design pattern or practice recommended for business layer when dealing with multiple API version. For example, I have something like this. http://site.com/blogs/v1/?count=10 which calls business object method GetAllBlogs(int count) to get information http://site.com/blogs/v2/?blog_count=20 which calls business object method GetAllBlogs_v2(int blogCounts) Since parameter name is changed, I created another business method for version 2. This is just one example but it could have other breaking changes for which it requires me to create another method to support both version. Is there any design pattern or best practice for business/data access layer I should follow when supporting API Versioning?

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  • Sitecore Item Web API and Json.Net Test Drive (Part II –Strongly Typed)

    - by jonel
    In the earlier post I did related to this topic, I have talked about using Json.Net to consume the result of Sitecore Item Web API. In that post, I have used the keyword dynamic to express my intention of consuming the returned json of the API. In this article, I will create some useful classes to write our implementation of consuming the API using strongly-typed. We will start of with the Record class which will hold the top most elements the API will present us. Pretty straight forward class. It has 2 properties to hold the statuscode and the result elements. If you intend to use a different property name in your class from the json property, you can do so by passing a string literal of the json property name to the JsonProperty attribute and name your class property differently. If you look at the earlier post, you will notice that the API returns an array of items that contains all of the Sitecore content item or items and stores them under the result->items array element. To be able to map that array of items, we have to write a collection property and decorate that with the JsonProperty attribute. The JsonItem class is a simple class which will map to the corresponding item property contained in the array. If you notice, these properties are just the basic Sitecore fields. And here’s the main portion of this post that will binds them all together. And here’s the output of this code. In closing, the same result can be achieved using the dynamic keyword or defining classes to map the json propery returned by the Sitecore Item Web API. With a little bit more of coding, you can take advantage of power of strongly-typed solution. Have a good week ahead of you.

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  • Keypress Left is called twice in Update when key is pressed only once

    - by Simran kaur
    I have a piece of code that is changing the position of player when left key is pressed. It is inside of Update() function. I know, Update is called multiple times, but since I have an ifstatement to check if left arrow is pressed, it should update only once. I have tested using print statement that once pressed, it gets called twice. Problem: Position updated twice when key is pressed only once. Below given is the structure of my code: void Update() { if (Input.GetKeyDown (KeyCode.LeftArrow)) { print ("PRESSEEEEEEEEEEEEEEEEEEDDDDDDDDDDDDDD"); } } I looked up on web and what was suggested id this: if (Event.current.type == EventType.KeyDown && Event.current.keyCode == KeyCode.LeftArrow) { print("pressed"); } But, It gives me an error that says: Object reference not set to instance of an object How can I fix this?

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  • Using static in PHP

    - by nischayn22
    I have a few functions in PHP that read data from functions in a class readUsername(int userId){ $reader = getReader(); return $reader->getname(userId); } readUserAddress(){ $reader = getReader(); return $reader->getaddress(userId); } All these make a call to getReader() { require_once("Reader.php"); static $reader = new Reader(); return $reader; } An overview of Reader class Reader{ getname(int id) { //if in-memory cache exists for this id return that //else get from db and cache it } getaddress(int id) { $this->getname(int id); //get address from name here } /*Other stuff*/ } Why is class Reader needed The Reader class does some in-memory caching of user details. So, I need only one object of class Reader and it will cache the user details instead of making multiple db calls. I am using static so that it the object gets created only once. Is this the right approach or should I do something else?

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  • Delay command execution over sockets

    - by David
    I've been trying to fix the game loop in a real time (tick delay) MUD. I realized using Thread.Sleep would seem clunky when the user spammed commands through their choice of client (Zmud, etc) e.g. east;south;southwest would wait three move ticks and then output everything from the past couple rooms. The game loop basically calls a Flush and Fill method for each socket during each tick (50ms) private void DoLoop() { Stopwatch stopWatch = new Stopwatch(); stopWatch.Start(); while (running) { // for each socket, flush and fill ConnectionMonitor.Update(); stopWatch.Stop(); WaitIfNeeded(stopWatch.ElapsedMilliseconds); stopWatch.Reset(); } } The Fill method fires the command events, but as mentioned before, they currently block using Thread.Sleep. I tried adding a "ready" flag to the state object that attempts to execute the command along with a queue of spammed commands, but it ends up executing one command and queuing up the rest i.e. each subsequent command executes something that got queued up that should've been executed before. I must be missing something about the timer. private readonly Queue<SpammedCommand> queuedCommands = new Queue<SpammedCommand>(); private bool ready = true; private void TryExecuteCommand(string input) { var commandContext = CommandContext.Create(input); var player = Server.Current.Database.Get<Player>(Session.Player.Key); var commandInfo = Server.Current.CommandLookup .FindCommand(commandContext.CommandName, player.IsAdmin); if (commandInfo != null) { if (!ready) { // queue command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo }); return; } if (queuedCommands.Count > 0) { // queue the incoming command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo, }); // dequeue and execute var command = queuedCommands.Dequeue(); command.Info.Command.Execute(Session, command.Context); setTimeout(command.Info.TickLength); return; } commandInfo.Command.Execute(Session, commandContext); setTimeout(commandInfo.TickLength); } else { Session.WriteLine("Command not recognized"); } } Finally, setTimeout was supposed to set the execution delay (TickLength) for that command, and makeReady just sets the ready flag on the state object to true. private void setTimeout(TickDelay tickDelay) { ready = false; var t = new System.Timers.Timer() { Interval = (long) tickDelay, AutoReset = false, }; t.Elapsed += makeReady; t.Start(); // fire this in tickDelay ms } // MAKE READYYYYY!!!! private void makeReady(object sender, System.Timers.ElapsedEventArgs e) { ready = true; } Am I missing something about the System.Timers.Timer created in setTimeout? How can I execute (and output) spammed commands per TickLength without using Thread.Sleep?

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  • Is passing the Model around in this way considered bad practice?

    - by Theomax
    If I have a view called, for example, ViewDetails that displays user information in labels and has a Model called ViewDetailsModel and if I want to allow the user to click a button to edit some of these details, is it considered bad practice is I pass the entire Model in the markup to a controller method which then assigns the values for another model, using the values stored in the Model that was passed in as a parameter to that action method? If so, should there instead be a service method that gets the data required for the edit view? For example: In the ViewDetails view, the user clicks the edit button which calls an action method in the controller (and passes in the Model object). The action method then uses the data in the Model object to populate another model which will be used for the EditDetails view that will be returned.

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  • How to get the Dash and HUD to appear. (and stop Unity spewing error messages.)

    - by Ubuntiac
    I just installed Ubuntu 12.04 on my wifes Dell Inspiron 1501, which uses an R300 ATI graphics chip. Neither the Dash or HUD appear when pushing the appropriate key. When I try unity --reset & in the terminal, I see that over and over it's spitting out: r300: CS space validation failed. (not enough memory?) Skipping rendering. This is just after starting Ubuntu with no apps open, so I find it hard to believe that just rendering the Dash / HUD is completely blowing out the VRAM. Any suggestions on getting this working? /usr/lib/nux/unity_support_test -p shows OpenGL vendor string: X.Org R300 Project OpenGL renderer string: Gallium 0.4 on ATI RS480 OpenGL version string: 2.1 Mesa 8.0.2 Not software rendered: yes Not blacklisted: yes GLX fbconfig: yes GLX texture from pixmap: yes GL npot or rect textures: yes GL vertex program: yes GL fragment program: yes GL vertex buffer object: yes GL framebuffer object: yes GL version is 1.4+: yes Unity 3D supported: yes All sections say "YES"

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  • The performance implications of IEnumerable vs. IQueryable

    It all started innocently enough. I was implementing a "Older Posts/Newer Posts" feature for my new web site and was writing code like this:IEnumerable<Post> FilterByCategory(IEnumerable<Post> posts, string category) {  if( !string.IsNullOrEmpty(category) ) { return posts.Where(p => p.Category.Contains(category)); }}...  var posts = FilterByCategory(db.Posts, category);  int count = posts.Count();... The "db" was an EF object context object, but it could just as...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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