Vi Cheatsheet

a -> Append cursor (After position)
i -> Insert cursor (At position)
esc -> Remove cursor if active
:wq -> Save and quit
:q -> Ask to save and quit
:q! -> Quit without saving
dd -> Cut the line
yy -> Copy the line
p -> Paste the line
:n -> Go to line n
/text -> Search for ‘text’
n -> Jump to next match when search is active
0 -> Go to the beginning of the line
$ -> Go to the end of the line
G -> Go to the end of the document
yn + arrow down -> Copy the current line with next n lines
yn + arrow up -> Copy the current line with previous n lines

Gamification: (Even though it’s for vi not vim there shouldn’t be any major differences as mentioned here.)

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Aligning SKPhysicsBody Correctly with SKShapeNode

When you want to create a circle in SpriteKit, SKShapeNode is the quickest and the simplest way for it. You don’t need to create images, you can manage the size, fill colour, stroke colours etc.

However, if you want this node to involve with collisions, you may get some trouble when creating an SKPhysicsBody for that node. The creating process is similar to SKSpriteNode but the alignment of it is different.

By default, SKShapeNode anchor points begin from (0, 0) and there isn’t any property to set it as we want. When we assign a SKPhysicsBody to this node, body’s anchor is its center point so the body doesn’t cover the node correctly.

Here’s how it looks when you want to implement for SKShapeNode as you do in SKSpriteNode:


There are plenty of people who were unable to solve this issue. Yet there is one answer on SO that helped me out with this.

To work around this situation, you can create an SKSpriteNode to implement the body and an SKShapeNode as the SKSpriteNode’s child to draw the shape.

First, create an SKSpriteNode and set the width and height same with the diameter of the circle

float radius = 30.0;
SKSpriteNode *aCircle = [SKSpriteNode spriteNodeWithColor:[UIColor clearColor] size:CGSizeMake(radius * 2, radius * 2)];

Then create a circular SKPhysicsBody for the SKSpriteNode (thankfully, this is possible)

SKPhysicsBody *circleBody = [SKPhysicsBody bodyWithCircleOfRadius:radius];
[circleBody setDynamic:NO];
[circleBody setUsesPreciseCollisionDetection:YES];
[aCircle circleBody];

Here is the key part. Create a CGPathRef as an ellipse in the rect with correct center values.

CGPathRef bodyPath = CGPathCreateWithEllipseInRect(CGRectMake(-[aCircle size].width / 2, -[aCircle size].height / 2, [aCircle size].width, [aCircle size].width), nil);
SKShapeNode *circleShape = [SKShapeNode node];
[circleShape setFillColor:[UIColor redColor]];
[circleShape setLineWidth:0];
[circleShape setPath:bodyPath];
[aCircle addChild:circleShape];

Don’t forget to add the child to scene then you are done. As you can see below, the physics body now matches with the node frame correctly.


Source link of the answer:
SKPhysicsBody not as expected

Other questions about similar issues:
How to align SKPhysicsBody and SKShapeNode?
Align SKPhysicsBody with SKShapeNode
SKPhysicsBody does not work on SKShapeNode
SKshapenode is not responding to Physicsbody
how to make collisions with skshapenode circles
Keeping an SKShapeNode within the bounds of an SKSpriteNode

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Sample Apple Push Notification PHP Script

This is an old script that I used to use for sending notifications. I don’t remember the source, on the other hand, it has been modified a couple of times already.

Even though I could manage to send notifications with this script, the Apple server was rejecting the connection after the amount reaches more than 50. It was usually getting cut off around 70. So it needs to get some management for not sending in a loop, like threading or whatever.


// set time limit to zero in order to avoid timeout

// charset header for output
header('content-type: text/html; charset: utf-8');

// this is the pass phrase you defined when creating the key
$passphrase = 'my_secret_pass';

// you can post a variable to this string or edit the message here
if (!isset($_POST['msg'])) {
$_POST['msg'] = "Notification message here!";

// tr_to_utf function needed to fix the Turkish characters
$message = tr_to_utf($_POST['msg']);

// load your device ids to an array
$deviceIds = array(

// this is where you can customize your notification
$payload = '{"aps":{"alert":"' . $message . '","sound":"default"}}';

$result = 'Start' . '<br />';

// start to create connection
$ctx = stream_context_create();
stream_context_set_option($ctx, 'ssl', 'local_cert', 'MyAppGenerated.pem');
stream_context_set_option($ctx, 'ssl', 'passphrase', $passphrase);

echo count($deviceIds) . ' devices will receive notifications.<br />';

foreach ($deviceIds as $item) {
	// wait for some time
	// Open a connection to the APNS server
	$fp = stream_socket_client('ssl://', $err, $errstr, 60, STREAM_CLIENT_CONNECT | STREAM_CLIENT_PERSISTENT, $ctx);

	if (!$fp) {
		exit("Failed to connect: $err $errstr" . '<br />');
	} else {
		echo 'Apple service is online. ' . '<br />';

	// Build the binary notification
	$msg = chr(0) . pack('n', 32) . pack('H*', $item) . pack('n', strlen($payload)) . $payload;
	// Send it to the server
	$result = fwrite($fp, $msg, strlen($msg));
	if (!$result) {
		echo 'Undelivered message count: ' . $item . '<br />';
	} else {
		echo 'Delivered message count: ' . $item . '<br />';

	if ($fp) {
		echo 'The connection has been closed by the client' . '<br />';

echo count($deviceIds) . ' devices have received notifications.<br />';

// function for fixing Turkish characters
function tr_to_utf($text) {
	$text = trim($text);
	$search = array('Ü', 'Þ', 'Ð', 'Ç', 'Ý', 'Ö', 'ü', 'þ', 'ð', 'ç', 'ý', 'ö');
	$replace = array('Ãœ', 'Åž', '&#286;ž', 'Ç', 'Ä°', 'Ö', 'ü', 'ÅŸ', 'ÄŸ', 'ç', 'ı', 'ö');
	$new_text = str_replace($search, $replace, $text);
	return $new_text;

// set time limit back to a normal value

Selecting Grouped Row Count When Using MySQL GROUP BY Column

You may have been using subqueries to get how many rows were grouped when using MySQL’s GROUP BY function. There’s a little trick that helps to get this number without using subqueries, more clean and faster (when the amount of rows get higher).

Let’s assume we have a table contain folks from different cities. Like this:

folk_name   |   city_name
evren       |   ohio
steve       |   ohio
cem         |   weston
don         |   sunderland
ritchie     |   weston
ian         |   hounslow
alican      |   ohio

When we want to get only city names (distinct) from this table, we may group the data by city_name column like this:

SELECT f.* FROM `folks` f GROUP BY f.`city_name`

And the result would be:

folk_name   |   city_name
ian         |   hounslow
evren       |   ohio
don         |   sunderland
cem         |   weston

The expected behaviour of GROUP BY is to select first rows so other folks from same cities do not appear. It also orders by the GROUP BY column (ascending).

Let’s say we want to get how many folks exist in each city by grouping by. First thing comes to mind could be using a subquery like this:

SELECT f1.*, (SELECT COUNT(f2.`folk_name`) FROM `folks` f2 WHERE f2.`city_name` = f1.`city_name`) AS `folk_count` FROM `folks` f1 GROUP BY `city_name`

And the result would be:

folk_name   |   city_name   |   folk_count
ian         |   hounslow    |   1
evren       |   ohio        |   3
don         |   sunderland  |   1
cem         |   weston      |   2

Let’s admit, subqueries are messy. They make the query more complicated to read and also are question marks on performance.

How about selecting number 1 (one) for each row and sum it up on grouping by?

Doing something like this:

SELECT f.*,SUM(1) AS `folk_count` FROM `folks` f GROUP BY f.`city_name`

Would return:

folk_name   |   city_name   |   folk_count
ian         |   hounslow    |   1
evren       |   ohio        |   3
don         |   sunderland  |   1
cem         |   weston      |   2

Nicely done.

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DateTime Ticks With Objective-C

If you need to generate unique strings for every case, the concept of DateTime.Ticks is probably the best solution for you. It represents the count of seconds since the oldest DateTime object available.

However, DateTime.Ticks usage comes from .NET platform and it is that easy in .NET, not in Objective-C.

To generate a ticks number in Objective-C, you need to do the following:

  1. Create an NSDate (01.01.0001), I know, rocking.
  2. Calculate the ticks between this oldest date and [NSDate date] (which means now).
  3. Turn that double variable to an integer. Well, long integer. Or… long long integer. (True story).

Here’s how I did it:

// Create the date formatter
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:@"yyyyMMdd"];

// Create the oldest day possible
NSDate *ticksDate = [dateFormat dateFromString:@"00010101"];

// Get ticks difference between now and 01.01.0001 in double    
double ticksDouble = [[NSDate date] timeIntervalSinceDate:ticksDate];

// Turn it to a long long int
long long int ticks = llround(ticksDouble);

// Test it
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Javascript: Export HTML Table to Excel With Custom File Name

Web browser wars hurt developers’ hearts. It is mostly about CSS, sometimes about JavaScript, HTML etc…

Thus I know how it feels when you expect something to get done easily appears a lot more harder than you expected.

Code below is tested only with Chrome (24+). It is making these processes:

  • Gets the HTML code of your table inside your div element.
  • Replaces the spaces in the code with correct syntax for Excel (otherwise spaces will be removed in your Excel sheet).
  • Generates a specific file name (for minutes) in order to avoid overriding old files and to supply archiving by date values.
  • And lastly and most importantly, saving the file with a custom file name.

Here’s my combination of codes (from different SO questions or tutorials) if you want to save HTML table to client computer using JavaScript code.

$(document).ready(function() {
	$("#btnExport").click(function(e) {
		//getting values of current time for generating the file name
		var dt = new Date();
		var day = dt.getDate();
		var month = dt.getMonth() + 1;
		var year = dt.getFullYear();
		var hour = dt.getHours();
		var mins = dt.getMinutes();
		var postfix = day + "." + month + "." + year + "_" + hour + "." + mins;
		//creating a temporary HTML link element (they support setting file names)
		var a = document.createElement('a');
		//getting data from our div that contains the HTML table
		var data_type = 'data:application/';
		var table_div = document.getElementById('dvData');
		var table_html = table_div.outerHTML.replace(/ /g, '%20');
		a.href = data_type + ', ' + table_html;
		//setting the file name = 'exported_table_' + postfix + '.xls';
		//triggering the function;
		//just in case, prevent default behaviour