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  • implementation of text editor in shell programming

    - by Arka Ghosh
    i have made a text editor in C. when i am changing the extension of that file from .c to .sh and compiling the file in the terminal,some error is shown,like for the global variables an external error is shown,and for the functions i have declared errors are shown there also.please help me to solve this. I am sending my code.. include include include int i,j,ec,fg,ec2; char fn[20],e,c,d; FILE *fp1,*fp2,fp; void Create(); void Append(); void Delete(); void Display(); int main() { do { printf("\n\t\t** TEXT EDITOR *"); printf("\n\n\tMENU:\n\t..\n "); printf("\n\t1.CREATE\n\t2.DISPLAY\n\t3.APPEND\n\t4.DELETE\n\t5.EXIT\n"); printf("\n\tEnter your choice: "); scanf("%d",&ec); switch(ec) { case 1: Create(); break; case 2: Display(); break; case 3: Append(); break; case 4: Delete(); break; case 5: exit(1); } }while(1); } void Create() { fp1=fopen("temp.txt","w"); printf("\n\tEnter the text and press '.' to save\n\n\t"); while(1) { c=getchar(); fputc(c,fp1); if(c == '.') { fclose(fp1); printf("\n\tEnter then new filename: "); scanf("%s",fn); fp1=fopen("temp.txt","r"); fp2=fopen(fn,"w"); while(!feof(fp1)) { c=getc(fp1); putc(c,fp2); } fclose(fp2); break; }} } void Display() { printf("\n\tEnter the file name: "); scanf("%s",fn); fp1=fopen(fn,"r"); if(fp1==NULL) { printf("\n\tFile not found!"); goto end1; } while(!feof(fp1)) { c=getc(fp1); printf("%c",c); } end1: fclose(fp1); printf("\n\n\tPress any key to continue.."); } void Delete() { printf("\n\tEnter the file name: "); scanf("%s",fn); fp1=fopen(fn,"r"); if(fp1==NULL) { printf("\n\tFile not found!"); goto end2; } fclose(fp1); if(remove(fn)==0) { printf("\n\n\tFile has been deleted successfully!"); goto end2; } else printf("\n\tError!\n"); end2: printf("\n\n\tPress any key to continue.."); getchar(); } void Append() { printf("\n\tEnter the file name: "); scanf("%s",fn); fp1=fopen(fn,"r"); if(fp1==NULL) { printf("\n\tFile not found!"); goto end3; } while(!feof(fp1)) { c=getc(fp1); printf("%c",c); } fclose(fp1); printf("\n\tType the text and press 'Ctrl+s' to append.\n"); fp1=fopen(fn,"a"); while(1) { c=getchar(); if(c==19) goto end3; if(c==13) { d='\n'; fputc(d,fp1); } else { fputc(c,fp1); } } end3: fclose(fp1); }

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  • What is the correct way to use g_signal_connect() in C++ for dynamic unity quicklists?

    - by hakermania
    I want to make my application use dynamic unity quicklists. For building my application I am using C++ and the QtCreator IDE. When a menu action is triggered I want to be able to have access to a non-static function of my MainWindow class so as to be able to update the Graphical User Interface which can be accessed from inside 'normal' MainWindow's functions. So, I am building up my quicklist like this (mainwindow.cpp): void MainWindow::enable_unity_quicklist(){ Unity_Menu = dbusmenu_menuitem_new(); dbusmenu_menuitem_property_set_bool (Unity_Menu, DBUSMENU_MENUITEM_PROP_VISIBLE, FALSE); Unity_Stop = dbusmenu_menuitem_new(); dbusmenu_menuitem_property_set(Unity_Stop, DBUSMENU_MENUITEM_PROP_LABEL, "Stop"); dbusmenu_menuitem_child_append (Unity_Menu, Unity_Stop); g_signal_connect (Unity_Stop, DBUSMENU_MENUITEM_SIGNAL_ITEM_ACTIVATED, G_CALLBACK(&fake_callback), (gpointer)this); if(!unity_entry) unity_entry = unity_launcher_entry_get_for_desktop_id("myapp.desktop"); unity_launcher_entry_set_quicklist(unity_entry, Unity_Menu); dbusmenu_menuitem_property_set_bool(Unity_Menu, DBUSMENU_MENUITEM_PROP_VISIBLE, true); dbusmenu_menuitem_property_set_bool(Unity_Stop, DBUSMENU_MENUITEM_PROP_VISIBLE, true); } void MainWindow::fake_callback(gpointer data){ MainWindow* m = (MainWindow*)data; m->on_stopButton_clicked(); } void MainWindow::on_stopButton_clicked(){ //stopping the process... } mainwindow.h: private slots: void enable_unity_quicklist(); void on_stopButton_clicked(); public slots: static void fake_callback(gpointer data); This suggestion was taken from http://old.nabble.com/Using-g_signal_connect-in-class-td18461823.html The program crashes immediately after I choose the 'Stop' action from the Unity Quicklist. Debugging the program shows that I am not able to access anything MainWindow related inside the on_stopButton_clicked() without crashing. For example, it crashes when doing this check (which is the first 2 lines of code inside this function): if (!ui->stopButton->isEnabled()) return; I have also tested lots of other things that I found at the internet, but nothing of them worked. One interesting solution would be to use gtkmm (http://developer.gnome.org/gtkmm-tutorial/stable/sec-connecting-signal-handlers.html.en) but I am not used at all working on GTK applications (I work solely in Qt) and I don't know if this even suits to my occasion. A compilable example indicating what the problem is can be found at: http://ubuntuone.com/7iKA3wnPmWVp8YNNDLlVQI (3.2Kb) If you are not familiar with the QtCreator IDE, you can compile with the following commands, as long as you have all the needed libraries: cd dynamic_unity_quicklists_test; qmake -project; qmake; make

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  • Installing PHP-GTK with PHP 5.3 on OS X

    - by Shabbyrobe
    I'm having trouble getting php-gtk installed with php 5.3 on os x. I'm currently using macports to do it and when I try to install php-gtk, it spews 'duplicate static' errors: Error: Target org.macports.build returned: shell command " cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_php_php5-gtk/work/php-gtk-2.0.1" && /usr/bin/make -j2 all " returned error 2 Command output: ext/gtk+/gen_pango.c:2951: error: duplicate 'static' ext/gtk+/gen_pango.c:2957: error: duplicate 'static' ext/gtk+/gen_pango.c:3097: error: duplicate 'static' ext/gtk+/gen_pango.c:3103: error: duplicate 'static' Is there a way to coerce it into building, or an alternative way to install it?

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  • Serving images from different domain

    - by Tom Gullen
    Google audit: Serve static content from a cookieless domain (15) 2.65KB of cookies were sent with the following static resources. Serve these static resources from a domain that does not set cookies: If my domain is widgets.com, should I set up a img.widgets.com that servers these resources? How beneficial is this? Edit I setup img.widgets.com to serve images from, and changed all images to this URL. But I still get that message?

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  • whats the name of this pattern?

    - by Wes
    I see this a lot in frameworks. You have a master class which other classes register with. The master class then decides which of the registered classes to delegate the request to. An example based passed in class may be something this. public interface Processor { public boolean canHandle(Object objectToHandle); public void handle(Object objectToHandle); } public class EvenNumberProcessor extends Processor { public boolean canHandle(Object objectToHandle) { if (!isNumeric(objectToHandle)){ return false } return isEven(objectToHandle); } public void handle(objectToHandle) { //Optionally call canHandleAgain to ensure the calling class is fufilling its contract doSomething(); } } public class OddNumberProcessor extends Processor { public boolean canHandle(Object objectToHandle) { if (!isNumeric(objectToHandle)){ return false } return isOdd(objectToHandle); } public void handle(objectToHandle) { //Optionally call canHandleAgain to ensure the calling class is fufilling its contract doSomething(); } } //Can optionally implement processor interface public class processorDelegator { private List processors; public void addProcessor(Processor processor) { processors.add(processor); } public void process(Object objectToProcess) { //Lookup relevant processor either by keeping a list of what they can process //Or query each one to see if it can process the object. chosenProcessor=chooseProcessor(objectToProcess); chosenProcessor.handle(objectToProcess); } } Note there are a few variations I see on this. In one variation the sub classes provide a list of things they can process which the ProcessorDelegator understands. The other variation which is listed above in fake code is where each is queried in turn. This is similar to chain of command but I don't think its the same as chain of command means that the processor needs to pass to other processors. The other variation is where the ProcessorDelegator itself implements the interface which means you can get trees of ProcessorDelegators which specialise further. In the above example you could have a numeric processor delegator which delegates to an even/odd processor and a string processordelegator which delegates to different strings. My question is does this pattern have a name.

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  • apt-get not working

    - by Dave Daniels
    Everything I try with apt-get fails. I am installing Ubuntu server for the first time. It is version 12.04 LTS. When I run: apt-get update I get failed to fetch http://gb.whatever goes here...... If I run apt-get install install build-essential I get "unable to locate package build-essential" I have looked at the sources.list but do not know what should and shouldn't be in there. This is the current content of sources.list: # See help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://gb.archive.ubuntu.com/ubuntu precise main restricted deb-src http://gb.archive.ubuntu.com/ubuntu precise main restricted ## Major bug fix updates produced after the final release of the ## distribution. deb http://gb.archive.ubuntu.com/ubuntu precise-updates main restricted deb-src http://gb.archive.ubuntu.com/ubuntu precise-updates main restricted

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  • Opposite Force to Apply to a Collided Rigid Body?

    - by Milo
    I'm working on the physics for my GTA2-like game so I can learn more about game physics. The collision detection and resolution are working great. I'm now just unsure how to compute the force to apply to a body after it collides with a wall. My rigid body looks like this: /our simulation object class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; private Vector2D v = new Vector2D(); //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; private Matrix mat = new Matrix(); private float[] Vector2Ds = new float[2]; private Vector2D tangent = new Vector2D(); private static Vector2D worldRelVec = new Vector2D(); private static Vector2D relWorldVec = new Vector2D(); private static Vector2D pointVelVec = new Vector2D(); private static Vector2D acceleration = new Vector2D(); public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; setLayer(LAYER_OBJECTS); } protected void rectChanged() { if(getWorld() != null) { getWorld().updateDynamic(this); } } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position.x,position.y, getWidth(), getHeight(), angle); rectChanged(); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { doUpdate(timeStep); } public void doUpdate(float timeStep) { //integrate physics //linear acceleration.x = forces.x / mass; acceleration.y = forces.y / mass; velocity.x += (acceleration.x * timeStep); velocity.y += (acceleration.y * timeStep); //velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); v.x = getRect().getCenter().getX() + (velocity.x * timeStep); v.y = getRect().getCenter().getY() + (velocity.y * timeStep); setCenter(v.x, v.y); forces.x = 0; //clear forces forces.y = 0; //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { mat.reset(); Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); relWorldVec.x = Vector2Ds[0]; relWorldVec.y = Vector2Ds[1]; return relWorldVec; } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { mat.reset(); Vector2Ds[0] = world.x; Vector2Ds[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vector2Ds); worldRelVec.x = Vector2Ds[0]; worldRelVec.y = Vector2Ds[1]; return worldRelVec; } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { tangent.x = -worldOffset.y; tangent.y = worldOffset.x; pointVelVec.x = (tangent.x * angularVelocity) + velocity.x; pointVelVec.y = (tangent.y * angularVelocity) + velocity.y; return pointVelVec; } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces.x += worldForce.x; forces.y += worldForce.y; //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } public Vector2D getVelocity() { return velocity; } public void setVelocity(Vector2D velocity) { this.velocity = velocity; } } The way it is given force is by the applyForce method, this method considers angular torque. I'm just not sure how to come up with the vectors in the case where: RigidBody hits static entity RigidBody hits other RigidBody that may or may not be in motion. Would anyone know a way (without too complex math) that I could figure out the opposite force I need to apply to the car? I know the normal it is colliding with and how deep it collided. My main goal is so that say I hit a building from the side, well the car should not just stay there, it should slowly rotate out of it if I'm more than 45 degrees. Right now when I hit a wall I only change the velocity directly which does not consider angular force. Thanks!

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  • Future Of F# At Jazoon 2011

    - by Alois Kraus
    I was at the Jazoon 2011 in Zurich (Switzerland). It was a really cool event and it had many top notch speaker not only from the Microsoft universe. One of the most interesting talks was from Don Syme with the title: F# Today/F# Tomorrow. He did show how to use F# scripting to browse through open databases/, OData Web Services, Sharepoint, …interactively. It looked really easy with the help of F# Type Providers which is the next big language feature in a future F# version. The object returned by a Type Provider is used to access the data like in usual strongly typed object model. No guessing how the property of an object is called. Intellisense will show it just as you expect. There exists a range of Type Providers for various data sources where the schema of the stored data can somehow be dynamically extracted. Lets use e.g. a free database it would be then let data = DbProvider(http://.....); data the object which contains all data from e.g. a chemical database. It has an elements collection which contains an element which has the properties: Name, AtomicMass, Picture, …. You can browse the object returned by the Type Provider with full Intellisense because the returned object is strongly typed which makes this happen. The same can be achieved of course with code generators that use an input the schema of the input data (OData Web Service, database, Sharepoint, JSON serialized data, …) and spit out the necessary strongly typed objects as an assembly. This does work but has the downside that if the schema of your data source is huge you will quickly run against a wall with traditional code generators since the generated “deserialization” assembly could easily become several hundred MB. *** The following part contains guessing how this exactly work by asking Don two questions **** Q: Can I use Type Providers within C#? D: No. Q: F# is after all a library. I can reference the F# assemblies and use the contained Type Providers? D: F# does annotate the generated types in a special way at runtime which is not a static type that C# could use. The F# type providers seem to use a hybrid approach. At compilation time the Type Provider is instantiated with the url of your input data. The obtained schema information is used by the compiler to generate static types as usual but only for a small subset (the top level classes up to certain nesting level would make sense to me). To make this work you need to access the actual data source at compile time which could be a problem if you want to keep the actual url in a config file. Ok so this explains why it does work at all. But in the demo we did see full intellisense support down to the deepest object level. It looks like if you navigate deeper into the object hierarchy the type provider is instantiated in the background and attach to a true static type the properties determined at run time while you were typing. So this type is not really static at all. It is static if you define as a static type that its properties shows up in intellisense. But since this type information is determined while you are typing and it is not used to generate a true static type and you cannot use these “intellistatic” types from C#. Nonetheless this is a very cool language feature. With the plotting libraries you can generate expressive charts from any datasource within seconds to get quickly an overview of any structured data storage. My favorite programming language C# will not get such features in the near future there is hope. If you restrict yourself to OData sources you can use LINQPad to query any OData enabled data source with LINQ with ease. There you can query Stackoverflow with The output is also nicely rendered which makes it a very good tool to explore OData sources today.

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  • Overriding component behavior

    - by deft_code
    I was thinking of how to implement overriding of behaviors in a component based entity system. A concrete example, an entity has a heath component that can be damaged, healed, killed etc. The entity also has an armor component that limits the amount of damage a character receives. Has anyone implemented behaviors like this in a component based system before? How did you do it? If no one has ever done this before why do you think that is. Is there anything particularly wrong headed about overriding component behaviors? Below is rough sketch up of how I imagine it would work. Components in an entity are ordered. Those at the front get a chance to service an interface first. I don't detail how that is done, just assume it uses evil dynamic_casts (it doesn't but the end effect is the same without the need for RTTI). class IHealth { public: float get_health( void ) const = 0; void do_damage( float amount ) = 0; }; class Health : public Component, public IHealth { public: void do_damage( float amount ) { m_damage -= amount; } private: float m_health; }; class Armor : public Component, public IHealth { public: float get_health( void ) const { return next<IHealth>().get_health(); } void do_damage( float amount ) { next<IHealth>().do_damage( amount / 2 ); } }; entity.add( new Health( 100 ) ); entity.add( new Armor() ); assert( entity.get<IHealth>().get_health() == 100 ); entity.get<IHealth>().do_damage( 10 ); assert( entity.get<IHealth>().get_health() == 95 ); Is there anything particularly naive about the way I'm proposing to do this?

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  • Installing latest Firefox beta, am I doing it wrong?

    - by xiaohouzi79
    I followed the instructions in this question to install the latest Firefox beta: sudo add-apt-repository ppa:mozillateam/firefox-next sudo apt-get update && sudo apt-get install firefox-4.0 This is the error I'm getting when running the second set of commands: Err http://ppa.launchpad.net maverick/main Sources 404 Not Found Err http://ppa.launchpad.net maverick/main i386 Packages 404 Not Found Fetched 24.8kB in 4s (5,279B/s) W: Failed to fetch http://ppa.launchpad.net/mozillateam/firefoxt-next/ubuntu/dists/maverick/main/source/Sources.gz 404 Not Found W: Failed to fetch http://ppa.launchpad.net/mozillateam/firefoxt-next/ubuntu/dists/maverick/main/binary-i386/Packages.gz 404 Not Found E: Some index files failed to download, they have been ignored, or old ones used instead.

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  • tumblr blog under subdomain blog.mysite.com - do i still get the benefit?

    - by sam
    ive got a tumblr blog for my main site, i use it more as a proper blog with articles and images, rather than just a tumblog. The blog is mapped to blog.mydomain.com Becuase of the ease of 'social' reposting in tumblr people often repost my articles (which is great - Backlinks !) But all these links go back to my blog and not my main site which is a mydomain.com does google see blog.mydomain and mydomain as the same / linked item and is my main site getting the benefit of these links ?

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  • GPG Invalid Signature

    - by user46421
    I am having problems with the following (in an attempt to remove hyperlinks, I have removed one of the "/" from the addresses): W: GPG error: http://archive.ubuntu.com oneiric Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <[email protected]> W: GPG error: http://ppa.launchpad.net oneiric Release: The following signatures were invalid: BADSIG B725097B3ACC3965 Launchpad lffl W: GPG error: http://ppa.launchpad.net oneiric Release: The following signatures were invalid: BADSIG 4874D3686E80C6B7 Launchpad PPA for Banshee Team W: GPG error: http://archive.getdeb.net jaunty-getdeb Release: The following signatures were invalid: BADSIG A8A515F046D7E7CF GetDeb Archive Automatic Signing Key <[email protected]> W: GPG error: http://badgerports.org lucid Release: The following signatures were invalid: BADSIG C90F9CB90E1FAD0C Jo Shields <[email protected]> W: GPG error: http://ppa.launchpad.net oneiric Release: The following signatures were invalid: BADSIG 976B5901365C5CA1 Launchpad PPA for transmissionbt W: Failed to fetch http://ppa.launchpad.net/dlecan/openjdk/ubuntu/dists/oneiric/main/source/Sources 404 Not Found W: Failed to fetch http://ppa.launchpad.net/dlecan/openjdk/ubuntu/dists/oneiric/main/binary-i386/Packages 404 Not Found W: Failed to fetch http://ppa.launchpad.net/sevenmachines/flash/ubuntu/dists/oneiric/main/binary-i386/Packages 404 Not Found W: Failed to fetch http://ppa.launchpad.net/sun-java-community-team/sun-java6/ubuntu/dists/oneiric/main/source/Sources 404 Not Found W: Failed to fetch http://ppa.launchpad.net/sun-java-community-team/sun-java6/ubuntu/dists/oneiric/main/binary-i386/Packages 404 Not Found I have tried the following solutions which were in a closed case titled "The following signatures were invalid": First of all try sudo apt-get clean sudo apt-get update && sudo apt-get upgrade Some ISPs cache the packages and errors like these are reported then. If the above commands don't work, try sudo apt-get update -o Acquire::http::No-Cache=True and again sudo apt-get update && sudo apt-get upgrade If it still doesn't work, sudo apt-get update -o Acquire::BrokenProxy=true sudo apt-get update && sudo apt-get upgrade

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  • What are the disadvantages of self-encapsulation?

    - by Dave Jarvis
    Background Tony Hoare's billion dollar mistake was the invention of null. Subsequently, a lot of code has become riddled with null pointer exceptions (segfaults) when software developers try to use (dereference) uninitialized variables. In 1989, Wirfs-Brock and Wikerson wrote: Direct references to variables severely limit the ability of programmers to re?ne existing classes. The programming conventions described here structure the use of variables to promote reusable designs. We encourage users of all object-oriented languages to follow these conventions. Additionally, we strongly urge designers of object-oriented languages to consider the effects of unrestricted variable references on reusability. Problem A lot of software, especially in Java, but likely in C# and C++, often uses the following pattern: public class SomeClass { private String someAttribute; public SomeClass() { this.someAttribute = "Some Value"; } public void someMethod() { if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { return this.someAttribute; } } Sometimes a band-aid solution is used by checking for null throughout the code base: public void someMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Value" ) ) { // do something... } } public void anotherMethod() { assert this.someAttribute != null; if( this.someAttribute.equals( "Some Default Value" ) ) { // do something... } } The band-aid does not always avoid the null pointer problem: a race condition exists. The race condition is mitigated using: public void anotherMethod() { String someAttribute = this.someAttribute; assert someAttribute != null; if( someAttribute.equals( "Some Default Value" ) ) { // do something... } } Yet that requires two statements (assignment to local copy and check for null) every time a class-scoped variable is used to ensure it is valid. Self-Encapsulation Ken Auer's Reusability Through Self-Encapsulation (Pattern Languages of Program Design, Addison Wesley, New York, pp. 505-516, 1994) advocated self-encapsulation combined with lazy initialization. The result, in Java, would resemble: public class SomeClass { private String someAttribute; public SomeClass() { setAttribute( "Some Value" ); } public void someMethod() { if( getAttribute().equals( "Some Value" ) ) { // do something... } } public void setAttribute( String s ) { this.someAttribute = s; } public String getAttribute() { String someAttribute = this.someAttribute; if( someAttribute == null ) { setAttribute( createDefaultValue() ); } return someAttribute; } protected String createDefaultValue() { return "Some Default Value"; } } All duplicate checks for null are superfluous: getAttribute() ensures the value is never null at a single location within the containing class. Efficiency arguments should be fairly moot -- modern compilers and virtual machines can inline the code when possible. As long as variables are never referenced directly, this also allows for proper application of the Open-Closed Principle. Question What are the disadvantages of self-encapsulation, if any? (Ideally, I would like to see references to studies that contrast the robustness of similarly complex systems that use and don't use self-encapsulation, as this strikes me as a fairly straightforward testable hypothesis.)

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  • Passing Strings by Ref

    - by SGWellens
    Humbled yet again…DOH! No matter how much experience you acquire, no matter how smart you may be, no matter how hard you study, it is impossible to keep fully up to date on all the nuances of the technology we are exposed to. There will always be gaps in our knowledge: Little 'dead zones' of uncertainty. For me, this time, it was about passing string parameters to functions. I thought I knew this stuff cold. First, a little review... Value Types and Ref Integers and structs are value types (as opposed to reference types). When declared locally, their memory storage is on the stack; not on the heap. When passed to a function, the function gets a copy of the data and works on the copy. If a function needs to change a value type, you need to use the ref keyword.  Here's an example:     // ---- declaration -----------------     public struct MyStruct    {        public string StrTag;    }     // ---- functions -----------------------     void SetMyStruct(MyStruct myStruct)     // pass by value    {        myStruct.StrTag = "BBB";    }     void SetMyStruct(ref MyStruct myStruct)  // pass by ref    {        myStruct.StrTag = "CCC";    }     // ---- Usage -----------------------     protected void Button1_Click(object sender, EventArgs e)    {        MyStruct Data;        Data.StrTag = "AAA";         SetMyStruct(Data);        // Data.StrTag is still "AAA"         SetMyStruct(ref Data);        // Data.StrTag is now "CCC"    } No surprises here. All value types like ints, floats, datetimes, enums, structs, etc. work the same way. And now on to... Class Types and Ref     // ---- Declaration -----------------------------     public class MyClass    {        public string StrTag;    }     // ---- Functions ----------------------------     void SetMyClass(MyClass myClass)  // pass by 'value'    {        myClass.StrTag = "BBB";    }     void SetMyClass(ref MyClass myClass)   // pass by ref    {        myClass.StrTag = "CCC";    }     // ---- Usage ---------------------------------------     protected void Button2_Click(object sender, EventArgs e)    {        MyClass Data = new MyClass();        Data.StrTag = "AAA";         SetMyClass(Data);          // Data.StrTag is now "BBB"         SetMyClass(ref Data);        // Data.StrTag is now "CCC"    }  No surprises here either. Since Classes are reference types, you do not need the ref keyword to modify an object. What may seem a little strange is that with or without the ref keyword, the results are the same: The compiler knows what to do. So, why would you need to use the ref keyword when passing an object to a function? Because then you can change the reference itself…ie you can make it refer to a completely different object. Inside the function you can do: myClass = new MyClass() and the old object will be garbage collected and the new object will be returned to the caller. That ends the review. Now let's look at passing strings as parameters. The String Type and Ref Strings are reference types. So when you pass a String to a function, you do not need the ref keyword to change the string. Right? Wrong. Wrong, wrong, wrong. When I saw this, I was so surprised that I fell out of my chair. Getting up, I bumped my head on my desk (which really hurt). My bumping the desk caused a large speaker to fall off of a bookshelf and land squarely on my big toe. I was screaming in pain and hopping on one foot when I lost my balance and fell. I struck my head on the side of the desk (once again) and knocked myself out cold. When I woke up, I was in the hospital where due to a database error (thanks Oracle) the doctors had put casts on both my hands. I'm typing this ever so slowly with just my ton..tong ..tongu…tongue. But I digress. Okay, the only true part of that story is that I was a bit surprised. Here is what happens passing a String to a function.     // ---- Functions ----------------------------     void SetMyString(String myString)   // pass by 'value'    {        myString = "BBB";    }     void SetMyString(ref String myString)  // pass by ref    {        myString = "CCC";    }     // ---- Usage ---------------------------------     protected void Button3_Click(object sender, EventArgs e)    {        String MyString = "AAA";         SetMyString(MyString);        // MyString is still "AAA"  What!!!!         SetMyString(ref MyString);        // MyString is now "CCC"    } What the heck. We should not have to use the ref keyword when passing a String because Strings are reference types. Why didn't the string change? What is going on?   I spent hours unssuccessfully researching this anomaly until finally, I had a Eureka moment: This code: String MyString = "AAA"; Is semantically equivalent to this code (note this code doesn't actually compile): String MyString = new String(); MyString = "AAA"; Key Point: In the function, the copy of the reference is pointed to a new object and THAT object is modified. The original reference and what it points to is unchanged. You can simulate this behavior by modifying the class example code to look like this:      void SetMyClass(MyClass myClass)  // call by 'value'    {        //myClass.StrTag = "BBB";        myClass = new MyClass();        myClass.StrTag = "BBB";    } Now when you call the SetMyClass function without using ref, the parameter is unchanged...just like the string example.  I hope someone finds this useful. Steve Wellens

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  • Storing deb packages on local media

    - by Saeid87
    Is there a way to store deb packages (all or a specific version of package) on a local media (dvd, usb etc...) so later I would be able to install those packages on a PC which does not have Internet connection? For example, these are the packages that I want to install on a PC which doesn't have Internet connection: # TinyOS MSP430 GCC Compiler Repository # Version 4.6.3 deb http://tinyprod.net/repos/debian squeeze main deb http://tinyprod.net/repos/debian msp430-46 main # TinyOS version 2.1.2 deb http://tinyos.stanford.edu/tinyos/dists/ubuntu lucid main

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  • Draw order in XNA

    - by Petr Abdulin
    It is possible to set draw order of a DrawableGameComponent by setting DrawOrder property. But is it possible to set draw order of "main" Game class? I have 2 DrawableGameComponents, and Draw method of a main Game class is called first, while I want it to be the last. Should I just mode all "main" draw code to another component and set it DrawOrder? Answer: seems like I'm just confused myself a little. Black on black, that's why I didn't saw it. Main Draw is called last, as expected.

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  • Thread.Interrupt Is Evil

    - by Alois Kraus
    Recently I have found an interesting issue with Thread.Interrupt during application shutdown. Some application was crashing once a week and we had not really a clue what was the issue. Since it happened not very often it was left as is until we have got some memory dumps during the crash. A memory dump usually means WindDbg which I really like to use (I know I am one of the very few fans of it).  After a quick analysis I did find that the main thread already had exited and the thread with the crash was stuck in a Monitor.Wait. Strange Indeed. Running the application a few thousand times under the debugger would potentially not have shown me what the reason was so I decided to what I call constructive debugging. I did create a simple Console application project and try to simulate the exact circumstances when the crash did happen from the information I have via memory dump and source code reading. The thread that was  crashing was actually MS code from an old version of the Microsoft Caching Application Block. From reading the code I could conclude that the main thread did call the Dispose method on the CacheManger class which did call Thread.Interrupt on the cache scavenger thread which was just waiting for work to do. My first version of the repro looked like this   static void Main(string[] args) { Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); } static void ThreadFunc() { while (true) { object value = Dequeue(); // block until unblocked or awaken via ThreadInterruptedException } } static object WaitObject = new object(); static object Dequeue() { object lret = "got value"; try { lock (WaitObject) { } } catch (ThreadInterruptedException) { Console.WriteLine("Got ThreadInterruptException"); lret = null; } return lret; } I do start a background thread and call Thread.Interrupt on it and then directly let the application terminate. The thread in the meantime does plenty of Monitor.Enter/Leave calls to simulate work on it. This first version did not crash. So I need to dig deeper. From the memory dump I did know that the finalizer thread was doing just some critical finalizers which were closing file handles. Ok lets add some long running finalizers to the sample. class FinalizableObject : CriticalFinalizerObject { ~FinalizableObject() { Console.WriteLine("Hi we are waiting to finalize now and block the finalizer thread for 5s."); Thread.Sleep(5000); } } class Program { static void Main(string[] args) { FinalizableObject fin = new FinalizableObject(); Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); GC.KeepAlive(fin); // prevent finalizing it too early // After leaving main the other thread is woken up via Thread.Abort // while we are finalizing. This causes a stackoverflow in the CLR ThreadAbortException handling at this time. } With this changed Main method and a blocking critical finalizer I did get my crash just like the real application. The funny thing is that this is actually a CLR bug. When the main method is left the CLR does suspend all threads except the finalizer thread and declares all objects as garbage. After the normal finalizers were called the critical finalizers are executed to e.g. free OS handles (usually). Remember that I did call Thread.Interrupt as one of the last methods in the Main method. The Interrupt method is actually asynchronous and does wake a thread up and throws a ThreadInterruptedException only once unlike Thread.Abort which does rethrow the exception when an exception handling clause is left. It seems that the CLR does not expect that a frozen thread does wake up again while the critical finalizers are executed. While trying to raise a ThreadInterrupedException the CLR goes down with an stack overflow. Ups not so nice. Why has this nobody noticed for years is my next question. As it turned out this error does only happen on the CLR for .NET 4.0 (x86 and x64). It does not show up in earlier or later versions of the CLR. I have reported this issue on connect here but so far it was not confirmed as a CLR bug. But I would be surprised if my console application was to blame for a stack overflow in my test thread in a Monitor.Wait call. What is the moral of this story? Thread.Abort is evil but Thread.Interrupt is too. It is so evil that even the CLR of .NET 4.0 contains a race condition during the CLR shutdown. When the CLR gurus can get it wrong the chances are high that you get it wrong too when you use this constructs. If you do not believe me see what Patrick Smacchia does blog about Thread.Abort and List.Sort. Not only the CLR creators can get it wrong. The BCL writers do sometimes have a hard time with correct exception handling as well. If you do tell me that you use Thread.Abort frequently and never had problems with it I do suspect that you do not have looked deep enough into your application to find such sporadic errors.

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  • As a tooling/automation developer, can I be making better use of OOP?

    - by Tom Pickles
    My time as a developer (~8 yrs) has been spent creating tooling/automation of one sort or another. The tools I develop usually interface with one or more API's. These API's could be win32, WMI, VMWare, a help-desk application, LDAP, you get the picture. The apps I develop could be just to pull back data and store/report. It could be to provision groups of VM's to create live like mock environments, update a trouble ticket etc. I've been developing in .Net and I'm currently reading into design patterns and trying to think about how I can improve my skills to make better use of and increase my understanding of OOP. For example, I've never used an interface of my own making in anger (which is probably not a good thing), because I honestly cannot identify where using one would benefit later on when modifying my code. My classes are usually very specific and I don't create similar classes with similar properties/methods which could use a common interface (like perhaps a car dealership or shop application might). I generally use an n-tier approach to my apps, having a presentation layer, a business logic/manager layer which interfaces with layer(s) that make calls to the API's I'm working with. My business entities are always just method-less container objects, which I populate with data and pass back and forth between my API interfacing layer using static methods to proxy/validate between the front and the back end. My code by nature of my work, has few common components, at least from what I can see. So I'm struggling to see how I can better make use of OOP design and perhaps reusable patterns. Am I right to be concerned that I could be being smarter about how I work, or is what I'm doing now right for my line of work? Or, am I missing something fundamental in OOP? EDIT: Here is some basic code to show how my mgr and api facing layers work. I use static classes as they do not persist any data, only facilitate moving it between layers. public static class MgrClass { public static bool PowerOnVM(string VMName) { // Perform logic to validate or apply biz logic // call APIClass to do the work return APIClass.PowerOnVM(VMName); } } public static class APIClass { public static bool PowerOnVM(string VMName) { // Calls to 3rd party API to power on a virtual machine // returns true or false if was successful for example } }

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  • Smooth Camera Zoom Factor Change

    - by Siddharth
    I have game play scene in which user can zoom in and out. For which I used smooth camera in the following manner. public static final int CAMERA_WIDTH = 1024; public static final int CAMERA_HEIGHT = 600; public static final float MAXIMUM_VELOCITY_X = 400f; public static final float MAXIMUM_VELOCITY_Y = 400f; public static final float ZOOM_FACTOR_CHANGE = 1f; mSmoothCamera = new SmoothCamera(0, 0, Constants.CAMERA_WIDTH, Constants.CAMERA_HEIGHT, Constants.MAXIMUM_VELOCITY_X, Constants.MAXIMUM_VELOCITY_Y, Constants.ZOOM_FACTOR_CHANGE); mSmoothCamera.setBounds(0f, 0f, Constants.CAMERA_WIDTH, Constants.CAMERA_HEIGHT); But above thing create problem for me. When user perform zoom in and leave game play scene then other scene behaviour not look good. I already set zoom factor to 1 for this purpose. But now it show camera translation in other scene. Because scene switching time it so much small that player can easily saw translation of camera that I don't want to show. After camera reposition, everything works perfect but how to set camera its proper position. For example my loading text move from bottom to top or vice versa based on camera movement. Any more detail you want then I can able to give you.

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  • Hot swapping for Linux web/database servers

    - by Art
    Is there a way to perform the following under Linux: There are two web servers, main and backup There are two database servers (postgres), main and backup Web Servers are in sync with each other, ie. configuration/content/applications are the same Backup database is continuously synced up with main database. If either of main servers goes down, it's being replaced with backup one on the fly. When main database server goes back up, all the data from backup server is uploaded to it. Essentially, I need the hot swapping working automatically with no or minimal user intervention, if possible. Recovery procedure is preferably automatic but can include some manual steps.

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  • How to make an object move again after being stopped by collision in Unity?

    - by Matthew Underwood
    I have a player object which position is always centered on the main camera's viewport. This object has a Rigidbody 2D, a box and circle collider. The player moves around a level, the level has a polygon collider attached. I move the camera until the object hits against the collider, which stops the movement of the camera by setting its speed to 0. The problem happens when I want to move the camera / player object away from the collider. As the speed is already at 0, it cannot move away from the collider. The script attached to the player object, checks for collisions and applies the speed to 0 on the main camera's test script. using UnityEngine; using System.Collections; public class move : MonoBehaviour { public float speed; public test testing; // Use this for initialization void Start () { speed = 10F; testing = Camera.main.GetComponent<test>(); } // Update is called once per frame void FixedUpdate () { Vector3 p = Camera.main.ViewportToWorldPoint(new Vector3(0.5F, 0.5F, Camera.main.nearClipPlane)); transform.position = new Vector3(p.x, p.y, -1); } void OnCollisionEnter2D(Collision2D col) { testing.speed = 0; } void OnCollisionExit2D(Collision2D col) { testing.speed = 10F; } } This is the script attached to the main camera; just a simple script that changes the camera's position. using UnityEngine; using System.Collections; public class test : MonoBehaviour { public float speed; public float translationY; public float translationX; // Use this for initialization void Start () { speed = 10F; } void FixedUpdate () { translationY = Input.GetAxis("Vertical") * speed * Time.deltaTime; translationX = Input.GetAxis("Horizontal") * speed * Time.deltaTime; transform.Translate(translationX, translationY, 0); } } The player object isn't kinematic and is a fixed angle, the colliders aren't triggers and the polygon collider isn't a trigger either. The player is the red square, the collider is the pink area. -- EDIT -- From the latest change the collider set up for the player So if the X speed was disabled. It wouldnt move into the side of the polygon colider which is good, but yet you couldnt move away from it. And moving down would move inside the colider.

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  • Moving a Cube from a GUI texture on iOS [on hold]

    - by London2423
    I really hope someone can help me in this since I am working already two days but without any result. What I' am trying to achieve in this instance is to move a GameObject when a GUI Texture is touch on a Iphone. The GameObject to be moved is named Cube. The Cube has a Script named "Left" that supposedly when is "call it " from the GUITexture the Cube should move left. I hope is clear: I want to "activated" the script in the Game Object from the Guitexture. I try to use send message but without any joy as well so I am using GetComponent. This is the script "inside" the GUITexture using Unity and C# //script inside the gameobject cube so it can move left when call it from the GUItexture void Awake() { left = Cube.GetComponent<Left>().enable = true; } void Start() { Cube = GameObject.Find ("Cube"); } void Update () { //loop through all the touches on the screeen for(int i = 0 ; i < Input.touchCount; i++) { //execute this code for current touch (i) on the screen if(this.guiTexture.HitTest(Input.GetTouch(i).position)) { //if current hits our guiTecture, run this code if(Input.GetTouch (i).phase == TouchPhase.Began) //move the cube object Cube.GetComponent<Left> (); } if(Input.GetTouch (i).phase == TouchPhase.Ended) { return; } if(Input.GetTouch(i).phase == TouchPhase.Stationary); //if current finger is stationary run this code { Cube.GetComponent<Left> (); } } } } } This is the script inside the GameObject named "Cube" that is activated from the Gui Texture and when is activated from the GUITexture should allow the cube to move left public class Left : MonoBehaviour { // Use this for initialization void Start () { } // Update is called once per frame void OnMousedown () { transform.position += Vector3.left * Time.deltaTime; } } Before write here I search all documentation, tutorial videos, forums but I still don't understand where is my mistake. May please someone help me Thanks CL

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  • Compare Two NameValueCollections Extension Method

    - by Jon Canning
    public static class NameValueCollectionExtension     {         public static bool CollectionEquals(this NameValueCollection nameValueCollection1, NameValueCollection nameValueCollection2)         {             return nameValueCollection1.ToKeyValue().SequenceEqual(nameValueCollection2.ToKeyValue());         }         private static IEnumerable<object> ToKeyValue(this NameValueCollection nameValueCollection)         {             return nameValueCollection.AllKeys.OrderBy(x => x).Select(x => new {Key = x, Value = nameValueCollection[x]});         }     }

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  • How to prevent a 404 Error when installing a subdomain using a wordpress multi-site installation

    - by Chris
    I have installed a multi-site instillation of WordPress onto my domain. I then added the necessary code to the wp-config.php file and .htaccess as instructed by WordPress. I also installed a plugin called Quick Page/Post Redirect Plugin which allowed me to place a 301 redirect onto the main domain as I only want to use the sub domain and not the main domain. Then I also added the following line of code to the wp-config.php file to redirect the main domain define( 'NOBLOGREDIRECT', 'URL Redirect Address' ); The site works fine with a redirect on the main domain and my subdomain runs fine when you type in subdomain.domain.com or http://subdomain.domain.com. However when I enter www.subdomain.domain.com or http://www.subdomain.domain.com the following error message is returned: Not Found The requested URL / was not found on this server. Apache/2.4.9 (Unix) Server at www.subdomain.domain.com Port 80 Any help with this would be much appreciated.

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  • Better way to load level content in XNA?

    - by user2002495
    Currently I loaded all my assets in XNA in the main Game class. What I want to achieve later is that I only load specific assets for specific levels (the game will consist of many levels). Here is how I load my main assets into the main class: protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); plane = new Player(Content.Load<Texture2D>(@"Player/playerSprite"), 6, 8); plane.animation = "down"; plane.pos = new Vector2(400, 500); plane.fps = 15; Global.currentPos = plane.pos; lvl1 = new Level1(Content.Load<Texture2D>(@"Levels/bgLvl1"), Content.Load<Texture2D>(@"Levels/bgLvl1-other"), new Vector2(0, 0), new Vector2(0, -600)); CommonBullet.LoadContent(Content); CommonEnemyBullet.LoadContent(Content); } protected override void UnloadContent() { } protected override void Update(GameTime gameTime) { if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) this.Exit(); plane.Update(gameTime); lvl1.Update(gameTime); foreach (CommonEnemy ce in cel) { if (ce.CollidesWith(plane)) { ce.hasSpawn = false; } foreach (CommonBullet b in plane.commonBulletList) { if (b.CollidesWith(ce)) { ce.hasSpawn = false; } } ce.Update(gameTime); } LoadCommonEnemy(); base.Update(gameTime); } private void LoadCommonEnemy() { int randY = rand.Next(-600, -10); int randX = rand.Next(0, 750); if (cel.Count < 3) { cel.Add(new CommonEnemy(Content.Load<Texture2D>(@"Enemy/Common/commonEnemySprite"), 7, 2, "left", randX, randY)); } for (int i = 0; i < cel.Count; i++) { if (!cel[i].hasSpawn) { cel.RemoveAt(i); i--; } } } protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.Black); spriteBatch.Begin(); lvl1.Draw(spriteBatch); plane.Draw(spriteBatch); foreach (CommonEnemy ce in cel) { ce.Draw(spriteBatch); } spriteBatch.End(); base.Draw(gameTime); } I wish to load my players, enemies, all in Level1 class. However, when I move my player & enemy code into the Level1 class, the gameTime returns null. Here is my Level1 class: using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Media; using Microsoft.Xna.Framework.Input; using SpaceShooter_Beta.Animation.PlayerCollection; using SpaceShooter_Beta.Animation.EnemyCollection.Common; namespace SpaceShooter_Beta.Levels { public class Level1 { public Texture2D bgTexture1, bgTexture2; public Vector2 bgPos1, bgPos2; public float speed = 5f; Player plane; public Level1(Texture2D texture1, Texture2D texture2, Vector2 pos1, Vector2 pos2) { this.bgTexture1 = texture1; this.bgTexture2 = texture2; this.bgPos1 = pos1; this.bgPos2 = pos2; } public void LoadContent(ContentManager cm) { plane = new Player(cm.Load<Texture2D>(@"Player/playerSprite"), 6, 8); plane.animation = "down"; plane.pos = new Vector2(400, 500); plane.fps = 15; Global.currentPos = plane.pos; } public void Draw(SpriteBatch sb) { sb.Draw(bgTexture1, bgPos1, Color.White); sb.Draw(bgTexture2, bgPos2, Color.White); plane.Draw(sb); } public void Update(GameTime gt) { bgPos1.Y += speed; bgPos2.Y += speed; if (bgPos1.Y >= 600) { bgPos1.Y = -600; } if (bgPos2.Y >= 600) { bgPos2.Y = -600; } plane.Update(gt); } } } Of course when I did this, I delete all my player's code in the main Game class. All of that works fine (no errors) except that the game cannot start. The debugger says that plane.Update(gt); in Level 1 class has null GameTime, same thing with the Draw method in the Level class. Please help, I appreciate for the time. [EDIT] I know that using switch in the main class can be a solution. But I prefer a cleaner solution than that, since using switch still means I need to load all the assets through the main class, the code will be A LOT later on for each levels

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