LiveBindings happen by binding any object with another object of interest based on some events. This happens by an observer pattern, when there is event trigger, the object inspector will be notified and the inspector will notify the already registered components to display the changes.

 Hope this helps. There is lot of documentation for this if you want to dig around.

I have a `TextView` in my layout which is `wrap_content` in `layout_width`. It is limited to maximum of 15 characters so I&#39;m using `maxLength`.

I need to end this `TextView` with 3 dots (...) and it happens only when I give the `layout_width` a fixed size in dp, something that I don&#39;t want to do.

I know it is possible programmatically by trimming the string after the 15th character and then adding the 3 dots, but I prefer to do that by XML.

Any idea how to end the text with 3 dots and leave it wrap_content?

```xml
&lt;TextView
    android:id=&quot;@+id/inbox_contactName&quot;
    android:layout_width=&quot;wrap_content&quot;
    android:layout_height=&quot;wrap_content&quot;
    android:lines=&quot;1&quot;
    android:maxLines=&quot;1&quot;
    android:ellipsize=&quot;end&quot;
    android:singleLine=&quot;true&quot;
    android:maxLength=&quot;15&quot;
    android:textColor=&quot;#0670b4&quot;
    android:textSize=&quot;16sp&quot; /&gt;
```

How to end TextView with 3 dots by using maxLength

I&#39;m calling a method of my WebAPI sending a JSON that I would like to match (or bind) with a model.

In the controller I have a method like:

    public Result Post([ModelBinder(typeof(CustomModelBinder))]MyClass model);

&#39;MyClass&#39;, which is given as a parameter is an abstract class. I would like that at, depending of the type of json passed, the correct inherited class is instantiated.

To achieve it, I&#39;m trying to implement a custom binder. The problem is that (I don&#39;t know if it&#39;s very basic but I can&#39;t find anything) I don&#39;t know how to retrieve the raw JSON (or better, some kind of serialization) that comes in the request.

I see:

 - actionContext.Request.Content

But all methods are exposed as async. I don&#39;t know who this fits with passing the generate model to the controller method...

Deserialising JSON to derived types in Asp.Net Web API

I am currently using Delphi XE2, and heard about their new Live Binding with Automatic updates in XE3 (no need to call Notify() as in XE2).

in C# or in Delphi XE2 we have to implement `INotifyPropertyChanged` (`Notify();` in Delphi), and this approach really makes sense as we have full control over the contents to be updated and when to update it so we can fine tune the performance and implement virtualization easily.

But I just want to know how does it works, what kind of mechanism they have done in order to implement it, and i have no clue how they have did it, following are the assumptions may have used to implement Automatic updates.

 1. Timer : A timer tick frequently and refreshes all the data 
&gt; *Very slow performance no virtualization*

 1. Compiler Level Feature : All the `notify() events` related codes implemented by the compiler auto-magically 
&gt; *Lots of over heads*

 1. Somme other Approach: 

Please help me to identified how they have implemented it.

I am currently using XE3 trial so i don&#39;t have access to the source code, **your answers will help me decide whether to switch to new features or not**. &lt;br&gt; I have a class(collection item) with 400 properties to bind(Not all of them all the time), so the performance really plays a major role in the stability of my application.  
  

Live Binding with Automatic updates in XE3 (no need to call Notify() as in XE2)

I am currently using Delphi XE2, and heard about their new Live Binding with Automatic updates in XE3 (no need to call Notify() as in XE2).
in C# or in Delphi XE2 we have to implement <code>INotifyPropertyChanged</code> (<code>Notify();</code> in Delphi), and this approach really makes sense as we have full control over the contents to be updated and when to update it so we can fine tune the performance and implement virtualization easily.
But I just want to know how does it works, what kind of mechanism they have done in order to implement it, and i have no clue how they have did it, following are the assumptions may have used to implement Automatic updates.
<ol>
<li>
Timer : A timer tick frequently and refreshes all the data
> Very slow performance no virtualization
</li>
<li>
Compiler Level Feature : All the <code>notify() events</code> related codes implemented by the compiler auto-magically
> Lots of over heads
</li>
<li>
Somme other Approach:
</li>
</ol>
Please help me to identified how they have implemented it.
I am currently using XE3 trial so i don't have access to the source code, your answers will help me decide whether to switch to new features or not. I have a class(collection item) with 400 properties to bind(Not all of them all the time), so the performance really plays a major role in the stability of my application.

I recently upgraded my version of PHPStorm IDE and it now warns me about inefficient jQuery usage.

For example:

    var property_single_location = $(&quot;#property [data-role=&#39;content&#39;] .container&quot;);

Prompts this warning:

&gt; Checks that jQuery selectors are used in an efficient way. It suggests
&gt; to split descendant selectors which are prefaced with ID selector and
&gt; warns about duplicated selectors which could be cached.

So my question is:

&gt; Why is this inefficient and what is the efficient way to do the above selector?

I&#39;d guess at:

    var property_single_location = $(&quot;#property&quot;).find(&quot;[data-role=&#39;content&#39;]&quot;).find(&quot;.container&quot;);

Is this the right way?

Inefficient jQuery usage warnings in PHPStorm IDE

Here is my Perl and Python script to do some simple text processing from about 21 log files, each about 300&amp;nbsp;KB to 1&amp;nbsp;MB (maximum) x 5 times repeated (total of 125 files, due to the *log* repeated 5 times).

**Python Code** (code modified to use compiled `re` and using `re.I`)

    #!/usr/bin/python

    import re
    import fileinput

    exists_re = re.compile(r&#39;^(.*?) INFO.*Such a record already exists&#39;, re.I)
    location_re = re.compile(r&#39;^AwbLocation (.*?) insert into&#39;, re.I)

    for line in fileinput.input():
        fn = fileinput.filename()
        currline = line.rstrip()

        mprev = exists_re.search(currline)

        if(mprev):
            xlogtime = mprev.group(1)

        mcurr = location_re.search(currline)

        if(mcurr):
            print fn, xlogtime, mcurr.group(1)

**Perl Code**

    #!/usr/bin/perl

    while (&lt;&gt;) {
        chomp;

        if (m/^(.*?) INFO.*Such a record already exists/i) {
            $xlogtime = $1;
        }

        if (m/^AwbLocation (.*?) insert into/i) {
            print &quot;$ARGV $xlogtime $1\n&quot;;
        }
    }

And, on my PC both code generates exactly the same result file of 10,790 lines. And, here is the timing done on Cygwin&#39;s Perl and Python implementations.

    User@UserHP /cygdrive/d/tmp/Clipboard
    # time /tmp/scripts/python/afs/process_file.py *log* *log* *log* *log* *log* &gt;
    summarypy.log

    real    0m8.185s
    user    0m8.018s
    sys     0m0.092s

    User@UserHP /cygdrive/d/tmp/Clipboard
    # time /tmp/scripts/python/afs/process_file.pl *log* *log* *log* *log* *log* &gt;
    summarypl.log

    real    0m1.481s
    user    0m1.294s
    sys     0m0.124s

Originally, it took 10.2 seconds using Python and only 1.9 secs using Perl for this simple text processing.

**(UPDATE) but, after the compiled `re` version of Python, it now takes 8.2 seconds in Python and 1.5 seconds in Perl. Still Perl is much faster.**

Is there a way to improve the speed of Python at all OR it is obvious that Perl will be the speedy one for simple text processing.

By the way this was not the only test I did for simple text processing... And, each different way I make the source code, always always Perl wins by a large margin. And, not once did Python performed better for simple `m/regex/` match and print stuff.

&gt; Please do not suggest to use C, C++, Assembly, other flavours of
&gt; Python, etc.
&gt;
&gt; I am looking for a solution using Standard Python with its built-in
&gt; modules compared against Standard Perl (not even using the modules).
&gt; Boy, I wish to use Python for all my tasks due to its readability, but
&gt; to give up speed, I don&#39;t think so.
&gt;
&gt; So, please suggest how can the code be improved to have comparable
&gt; results with Perl.

**UPDATE: 2012-10-18**

As other users suggested, Perl has its place and Python has its.

So, for this question, one can safely conclude that for simple regex match on each line for hundreds or thousands of text files and writing the results to a file (or printing to screen), **Perl will always, always WIN in performance for this job. It as simple as that.**

Please note that when I say Perl wins in performance... only standard Perl and Python is compared... not resorting to some obscure modules (obscure for a normal user like me) and also not calling C, C++, assembly libraries from Python or Perl. We don&#39;t have time to learn all these extra steps and installation for a simple text matching job.

So, Perl rocks for text processing and regex.

Python has its place to rock in other places.

**Update 2013-05-29:** An excellent article that does similar comparison [is here][1]. Perl again wins for simple text matching... And for more details, read the article.

  [1]: https://stuffivelearned.org/doku.php?id=programming:general:phpvspythonvsperl



Text processing - Python vs Perl performance

How can I check Heap Size (and Used Memory) of a Java Application on Linux through the command line?

I have tried through jmap. But it gives info. about internal memory areas like Eden/ PermGen etc., which is not useful to me. 

I am looking for something like:

 - Max Memory: 1GB
 - Min Memory: 256 MB
 - Heap Memory: 700 MB
 - Used Memory: 460 MB

That&#39;s all. I know that I can see this in JConsole etc., but I need to do it via command-line. (can&#39;t enable JMX etc.)

How to find Java Heap Size and Memory Used (Linux)?

Is there any good way to get the remaining memory available to the JVM at run time? The use case of this would be to have web services which fail gracefully when they are nearing their memory limits by refusing new connections with a nice error message &quot;too many people using this, try again later&quot;, rather than dying abruptly with an OutOfMemory error.

Note this has nothing to do with calculating/estimating the cost of each object beforehand. In principle I could estimate how much memory my objects take and refuse new connections based on that estimate, but that seems kind of hacky/fragile.



Java get available memory

I have Symfony2 running on an Ubuntu Server 12.04 (64-bit) VM (VirtualBox).  The host is a MacBook pro.  For some reason I am getting really long request times in development mode (app_dev.php).  I know its slower in dev mode, but I&#39;m talking 5-7 seconds per request (sometimes even slower).  On my Mac I get request times of 200ms or so in development mode.

After looking at my timeline in the Symfony2 profiler, I noticed that ~95% of the request time is &quot;initialization time&quot;.  What is this?  What are some reasons it could be so slow?

This issue only applies to Symfony2 in dev mode, not any other sites I&#39;m running on the VM, and not even to Symfony2 in production mode.

I saw this (http://stackoverflow.com/questions/11162429/whats-included-in-the-initialization-time-in-the-symfony2-web-profiler), but it doesn&#39;t seem to answer my questions.

Symfony2 Slow Initialization Time

I am using the `XML Data Binding Wizard` in `Delphi XE2`.
The schema has required tags of this type:

    &lt;xs:element name=&quot;MyReport&quot; type=&quot;MyReportType&quot; /&gt;
    &lt;xs:complexType name=&quot;MyReportType&quot;&gt;
      &lt;xs:all&gt;
        &lt;xs:element name=&quot;Header&quot; type=&quot;HeaderType&quot; /&gt;
        &lt;xs:element name=&quot;Values&quot; type=&quot;ValuesType&quot; /&gt;
        &lt;xs:element name=&quot;Events&quot; type=&quot;EventsType&quot; /&gt;
      &lt;/xs:all&gt;
    &lt;/xs:complexType&gt;

The problem is that if I don&#39;t add any elements to e.g. the `Values`-group, there will be no `&lt;Values&gt;`-tag, and the XML-file will fail validation against the `XSD`. This probably would not be a problem if the interface was providing a method for &quot;adding&quot; the `Values`-tag.

Is there a standard way of handling this, or am I using the generated code in-correctly?

**Put simply**, is there *any* way, work-around or otherwise, using the code from the `Data Binding Wizard`, to produce the following `XML` (which is what is needed to validate using the above schema when there are no child nodes), given `HeaderType`, `ValuesType` and `EventsType` are of complexType:

    &lt;MyReport&gt;
      &lt;Header /&gt;
      &lt;Values /&gt;
      &lt;Events /&gt;
    &lt;/MyReport&gt; 

(I know there are other similar issues, like the code generated by `&lt;xs:sequence&gt;` not enforcing the correct order in the final `XML`-file, but at least for that one, there&#39;s a work-around by simply inserting the children in the right order. I still think it would be nice if `Embarcadero` would provide a complete interface, which takes more of these features into account.)

Required tags not present when using Delphi XML Data Binding Wizard

In XCode by adding these methods to your NSView subclass can prevent the window from becoming active when clicking on it:

&lt;!-- language: objective-c --&gt;

    - (BOOL)shouldDelayWindowOrderingForEvent:(NSEvent )theEvent {
        return YES;
    }
    - (BOOL)acceptsFirstMouse:(NSEvent )theEvent {
        return YES; 
    }
    - (void)mouseDown:(NSEvent )theEvent {
        [[[NSApp]] preventWindowOrdering]; 
    }

In Windows platform It is done by this simple code:

&lt;!-- language: c++ --&gt;

    HWND hWnd = FindWindowW((String(&quot;FM&quot;) + fmxForm-&gt;ClassName()).c_str(), 
        fmxForm-&gt;Caption.c_str());
    
    SetWindowLong(hWnd, GWL_EXSTYLE,
        GetWindowLong(hWnd, GWL_EXSTYLE) | WS_EX_NOACTIVATE);

How can I subclass NSView to prevent my FMX TForm becoming active when clicking on it?

How can I create &quot;**No Activate**&quot; form in *firemonkey*?


How to create &quot;No Activate&quot; form in Firemonkey

I&#39;m coming from a background of using [MSC* MidiSequencer][1] for a Delphi XE2 project and have been playing with DelphiASIOVST this weekend on the off chance the MIDI may be stable enough to use as my core MIDI engine while also allowing me to support VST plug ins. I pulled the D16 trunk off the SVN and compiled effortlessly after a few path tweaks. 

I understand a great deal of what I&#39;m seeing but I&#39;m wondering if others have experienced issues with MIDI file playback in the the MiniHost example application. Specifically with a one track melodic performance it sounds like notes are getting skipped and/or playing back a bit later over other notes that are playing as they should. Basically it&#39;s just hit or miss if a note is even played at all.

I have numerous pro sequencers on my machine and the MIDI files are fine there. they also support VST with little to no problems. I also know the MIDI lowest level file format and know the file structure is sound.

Can the TMidiFile play direct to the standard MIDI synth in the computer? I&#39;m trying to rule out VST issues by getting a direct pipeline to the built in synth. Barring that, anyone seen these issues or know of some more/better examples of MIDI file to VST using the component set?

  [1]: http://sourceforge.net/projects/midisequencer/


Midi Timing Issues with Delphi ASIO VST and MiniHost

What&#39;s the difference between parameters declared with `var` and those declared with `out`? How does the compiler treat them differently (e.g., by generating different code, or by changing which diagnostics it issues)? Or do the different modifiers merely allow the programmer to document intended use of the parameters? What effect do the *types* of the parameters have on the matter?

What&#39;s the difference between &quot;var&quot; and &quot;out&quot; parameters?

I&#39;ve created a custom MSBuild `.targets` file that I&#39;ve included in a Delphi XE project via the IDE and enabled it from the Project Manager&#39;s context menu. Although the file validates, it always gets disabled after I re-save the project file.

Here&#39;s a simplified version of the targets file, named `Custom.targets`.

    &lt;Project xmlns=&quot;http://schemas.microsoft.com/developer/msbuild/2003&quot;&gt;
      &lt;Target Name=&quot;Hello&quot;&gt;
        &lt;Message Text=&quot;Hello from custom target&quot;/&gt;
      &lt;/Target&gt;
    &lt;/Project&gt;

As a stand alone file this works as expected: typing...

    MSBuild Custom.target /t:Hello

...at the command line gives the expected message.    

Adding `Custom.targets` to a Delphi project via the IDE displays the file in the Project Manager as expected, and the `.dproj` file now contains the line...

    &lt;TargetsFile Include=&quot;Custom.targets&quot;/&gt;

I right-clicked the file in the IDE&#39;s Project Manager and selected `Enable`. But when the project is built the `Build` message window displays:

&gt; [MSBuild Warning] Custom.targets(1): Ignoring disabled import: `PathToProjectSource\\Custom.targets`

Right-clicking again in Project Manager still shows the `Enable` option instead of the expected `Disable`.

At the command line `MSBuild ProjectName.dproj /t:Hello` also fails.

I&#39;ve tried hacking the `.dproj` file to add the line...

    &lt;Import Project=&quot;Custom.targets&quot;/&gt;

Typing `MSBuild ProjectName.dproj /t:Hello` now works. But the next time I save the project file from the IDE the `&lt;Import&gt;` statement gets removed.

Anyone got any idea what&#39;s going wrong please?

Delphi XE custom build target is always disabled

I have read lots that Backbone doesn&#39;t do two way binding but I don&#39;t exactly understand this concept.

Could somebody give me an example of how two way binding works in an MVC codebase and how it does not with Backbone?

What is two way binding?

Is it correct to pass the &quot;current&quot; `$scope` to an AngularJS service?

I&#39;m in the situation where I&#39;ve a $service knowing it&#39;s consumed by only one controller, and I&#39;d like to have a reference to the controller&#39;s scope in the $service methods themselves.

Is this *philosophically* correct?

Or I&#39;d better to broadcast events to the $rootScope and then make my controller listen to them?

Passing current scope to an AngularJS Service

What is the difference between the **[Observer Pattern][1]**, **[Publish/Subscribe][2]**, and **[Data Binding][3]**?

I searched around a bit on Stack Overflow and did not find any good answers.

What I have come to believe is that data binding is a generic term and there are different ways of implementing it such as the Observer Pattern or the Pub/Sub pattern. With the Observer pattern, an Observable updates its Observers.  With Pub/Sub, 0-many publishers can publish messages of certain classes and 0-many subscribers can subscribe to messages of certain classes.

**Are there other patterns of implementing &quot;data binding&quot;?**

  [1]: http://en.wikipedia.org/wiki/Observer_pattern
  [2]: http://en.wikipedia.org/wiki/Publish%E2%80%93subscribe_pattern
  [3]: http://en.wikipedia.org/wiki/UI_data_binding

Difference between Observer, Pub/Sub, and Data Binding

I’m looking for the best practice of how to bind to a service property in AngularJS.

I have worked through multiple examples to understand how to bind to properties in a service that is created using AngularJS.  

Below I have two examples of how to bind to properties in a service; they both work.  The first example uses basic bindings and the second example used $scope.$watch to bind to the service properties

Are either of these example preferred when binding to properties in a service or is there another option that I’m not aware of that would be recommended?

The premise of these examples is that the service should updated its properties “lastUpdated” and “calls” every 5 seconds.  Once the service properties are updated the view should reflect these changes.  Both these example work successfully; I wonder if there is a better way of doing it.

**Basic Binding**

The following code can be view and ran here: http://plnkr.co/edit/d3c16z

    &lt;html&gt;
    &lt;body ng-app=&quot;ServiceNotification&quot; &gt;
          
        &lt;div ng-controller=&quot;TimerCtrl1&quot; style=&quot;border-style:dotted&quot;&gt; 
            TimerCtrl1 &lt;br/&gt;
            Last Updated: {{timerData.lastUpdated}}&lt;br/&gt;
            Last Updated: {{timerData.calls}}&lt;br/&gt;
        &lt;/div&gt;
        
        &lt;script src=&quot;https://ajax.googleapis.com/ajax/libs/angularjs/1.0.5/angular.js&quot;&gt;&lt;/script&gt;
        &lt;script type=&quot;text/javascript&quot;&gt;
            var app = angular.module(&quot;ServiceNotification&quot;, []);
    
            function TimerCtrl1($scope, Timer) {
                $scope.timerData = Timer.data;
            };
    
            app.factory(&quot;Timer&quot;, function ($timeout) {
                var data = { lastUpdated: new Date(), calls: 0 };
    
                var updateTimer = function () {
                    data.lastUpdated = new Date();
                    data.calls += 1;
                    console.log(&quot;updateTimer: &quot; + data.lastUpdated);
    
                    $timeout(updateTimer, 5000);
                };
                updateTimer();
    
                return {
                    data: data
                };
            });
        &lt;/script&gt;
    &lt;/body&gt;
    &lt;/html&gt;

The other way I solved binding to service properties is to use $scope.$watch in the controller.

**$scope.$watch**

The following code can be view and ran here: http://plnkr.co/edit/dSBlC9

    &lt;html&gt;
    &lt;body ng-app=&quot;ServiceNotification&quot;&gt;
        &lt;div style=&quot;border-style:dotted&quot; ng-controller=&quot;TimerCtrl1&quot;&gt;
            TimerCtrl1&lt;br/&gt;
            Last Updated: {{lastUpdated}}&lt;br/&gt;
            Last Updated: {{calls}}&lt;br/&gt;
        &lt;/div&gt;
        
        &lt;script src=&quot;https://ajax.googleapis.com/ajax/libs/angularjs/1.0.5/angular.js&quot;&gt;&lt;/script&gt;
        &lt;script type=&quot;text/javascript&quot;&gt;
            var app = angular.module(&quot;ServiceNotification&quot;, []);
    
            function TimerCtrl1($scope, Timer) {
                $scope.$watch(function () { return Timer.data.lastUpdated; },
                    function (value) {
                        console.log(&quot;In $watch - lastUpdated:&quot; + value);
                        $scope.lastUpdated = value;
                    }
                );
    
                $scope.$watch(function () { return Timer.data.calls; },
                    function (value) {
                        console.log(&quot;In $watch - calls:&quot; + value);
                        $scope.calls = value;
                    }
                );
            };
    
            app.factory(&quot;Timer&quot;, function ($timeout) {
                var data = { lastUpdated: new Date(), calls: 0 };
    
                var updateTimer = function () {
                    data.lastUpdated = new Date();
                    data.calls += 1;
                    console.log(&quot;updateTimer: &quot; + data.lastUpdated);
    
                    $timeout(updateTimer, 5000);
                };
                updateTimer();
    
                return {
                    data: data
                };
            });
        &lt;/script&gt;
    &lt;/body&gt;
    &lt;/html&gt;

I’m aware that I can use $rootscope.$broadcast in the service and $root.$on in the controller, but in other examples that I’ve created that use $broadcast/$on the first broadcast is not captured by the controller, but additional calls that are broadcasted are triggered in the controller.  If you are aware of a way to solve $rootscope.$broadcast problem, please provide an answer.

But to restate what I mentioned earlier, I would like to know the best practice of how to bind to a service properties.

&lt;hr&gt;
**Update**

This question was originally asked and answered in April 2013. In May 2014, Gil Birman provided a new answer, which I changed as the correct answer. Since Gil Birman answer has very few up-votes, my concern is that people reading this question will disregard his answer in favor of other answers with many more votes.  Before you make a decision on what&#39;s the best answer, I highly recommend Gil Birman&#39;s answer.



AngularJS : The correct way of binding to a service properties

Please treat this question as strictly educational. **I&#39;m still interested in hearing new answers and ideas to implement this**


### tl;dr

How would I implement bi-directional data-binding with JavaScript?

### Data Binding to the DOM

By data binding to the DOM I mean  for example, having a JavaScript object `a` with a property `b`. Then having an `&lt;input&gt;` DOM element (for example), when the DOM element changes, `a` changes and vice versa (that is, I mean bidirectional data binding). 

Here is a diagram from AngularJS on what this looks like:

![two way data binding][1]

So basically I have JavaScript similar to:

    var a = {b:3};

Then an input (or other form) element like:

    &lt;input type=&#39;text&#39; value=&#39;&#39;&gt;

I&#39;d like the input&#39;s value to be `a.b`&#39;s value (for example), and when the input text changes, I&#39;d like `a.b` to change too. When `a.b` changes in JavaScript, the input changes.


### The Question

What are some basic techniques to accomplish this in plain JavaScript?

In specific, I&#39;d like a good answer to refer to:

 - How would binding work for objects?
 - How listening to change in the form might work?
 - Is it possible in a simple way to only have the HTML modified on the template level? I&#39;d like to not keep track of the binding in the HTML document itself but only in JavaScript (with DOM events, and JavaScript keeping reference to the DOM elements used).

### What have I tried?

I&#39;m a big fan of Mustache so I tried using it for templating. However, I ran into issues when trying to perform the data binding itself since Mustache processes HTML as a string so after I get its result I have no reference to where the objects in my viewmodel are. The only workaround I could think for this was modifying the HTML string (or created DOM tree) itself with attributes. I don&#39;t mind using a different templating engine.

Basically, I got a strong feeling that I was complicating the issue at hand and there is a simple solution.


**Note:** Please do not provide answers that use external libraries, especially ones that are thousands of lines of code. I&#39;ve used (and like!) AngularJS and KnockoutJS. I really don&#39;t want answers in the form &#39;use framework x&#39;. Optimally, I&#39;d like a future reader who doesn&#39;t know how to use many frameworks to grasp how to implement bi-directional data-binding herself. I do not expect a _complete_ answer, but one that gets the idea across.


  [1]: http://i.stack.imgur.com/hu1ps.png

How to Implement DOM Data Binding in JavaScript

When I ssh in to my vagrant vm, I can change permissions of files and folders above and outside the vagrant user folder, and for files within the vagrant user folder. But cannot change permissions for folders under the vagrant user folder. I have the same problem whether logged in as the vagrant user and root.

Is there some sort of restriction on changing permissions in the vagrant user&#39;s folder? The vagrant user folder is not shared with the host OS, but the capistrano deploy folder and the docRoot are. 

Guest is CentOS 6, Host is OS X 10.7. Vagrant is 1.0.5. Virtualbox is 4.2.1.

Cannot change permissions of folders within vagrant home folder

I tried to set up an virtual machine on Ubuntu 12.10.I installed Oracle Vm VirtualBox Manager.
Then, i followed the steps and i choose .iso file from settings&gt;storage.Then clicked live cd/dvd option.Then OK,when i clicked to start button i get such an error :

     Kernel driver not installed (rc=-1908)

     The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a                   
     permissionproblem with /dev/vboxdrv. Please reinstall the kernel module by 
     executing
 
     &#39;/etc/init.d/vboxdrv setup&#39;

     as root. If it is available in your distribution, you should install the DKMS package                               
     first. This package keeps track of Linux kernel changes and recompiles the vboxdrv  
     kernel module if necessary.

I reinstalled program and rebooted pc, but not worked.Also, updated kernel driver but not worked.What can be done to solve it ?

VirtualBox error : kernel driver not installed(rc=-1908)

How do I delete a VirtualBox machine in the GURU_MEDITATION error state?  Is it enough just to delete the directory while VirtualBox is not running?

EDIT: After posting, I deleted the entire directory that &quot;Show in File Manager&quot; navigates to.

It looks like:

![Screenshot of Virtualbox Guru Meditation][1]

Note that there is no power off, and even remove is greyed out.  I believe this is the exact same as it looked even before I deleted the directory.

EDIT 2: I tried the command line poweroff after deleting the files.  It hangs:

&gt; vboxmanage controlvm wmf-vagrant_1354733432 poweroff 0%...10%...20%...

EDIT 3: It also fails to unregister it from the command-line:

&gt; VBoxManage unregistervm wmf-vagrant_1354733432 --delete VBoxManage:
&gt; error: Cannot unregister the machine &#39;wmf-vagrant_1354733432&#39; while it
&gt; is locked VBoxManage: error: Details: code VBOX_E_INVALID_OBJECT_STATE
&gt; (0x80bb0007), component Machine, interface IMachine, callee
&gt; nsISupports Context: &quot;Unregister(fDelete ?
&gt; (CleanupMode_T)CleanupMode_DetachAllReturnHardDisksOnly :
&gt; (CleanupMode_T)CleanupMode_DetachAllReturnNone,
&gt; ComSafeArrayAsOutParam(aMedia))&quot; at line 160 of file
&gt; VBoxManageMisc.cpp


  [1]: http://i.stack.imgur.com/gU1mU.png

How do I delete a virtualbox machine in the GURU_MEDITATION error state?

I am often confused with the concept of virtualization in operating systems. Considering RAM as the physical memory, why do we need the virtual memory for executing a process?

Where does this virtual memory stand when the process (program) from the external hard drive is brought to the main memory (physical memory) for the execution.

Who takes care of the virtual memory and what is the size of the virtual memory?

Suppose if the size of the RAM is 4GB (i.e. 2^32-1 address spaces) what is the size of the virtual memory?

What are the differences between virtual memory and physical memory?

I am going through the topic of virtualization and i am totally sucked up understanding the basic concept, Wikipedia does provide some relevant information, but it is not good enough for me to understand the basic idea. The concept will be of 2 to 3 line, but neither I am able to find them on net, nor on the book. 

I will be pleased if someone gives me a basic understanding of these three types. I am well aware of virtualization and understand it well, but these 3 types... 

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