Category: Tutorials

For nearly all problems there are probably a hundred different solutions. Recently one solution I have chosen for a few problems has been a Javascript bookmarklet. A bookmarklet is a regular bookmark that runs a bit of Javascript code instead of just going to a link. They are really useful for doing a small task on a website or webpage that you don’t have direct access to the backend or source of. So, today I am going to show you how to make a simple bookmarklet.

The bookmarklet today is going to grab a super high-res photo of Amazon Products. Ok, let me explain a little bit more. So, a designer co-worker uses super high-res product images for design mockups. Well, he typically would go scouring the internet for these images. However, he noticed that on Amazon product pages you can look at really large images of products using their Zoom viewer, but you could right-click and download the image from there. So I created a simple bookmarklet to grab the product id from the page url and then open up a link to the large image.

Okay, back to work. So a typical link which can be turned into a book looks like:

SOTC Tutorials

And the code looks like.

So if we were going to do something javascript we could do something like:

And the code would be:

Now, that just covers the basics of the syntax we are going to use for this. You can see above that to tell the browser to run our href as Javascript we need to start with javascript:. Ok so let’s jump to something a bit more complicated. The next piece of Javascript is going create an alert with the current time – I know we all love alerts.

Looking at the code we start by creating anonymous function and inside the function we create a new Date object, then use it to create a string of hours and minutes, and then show this (current time) in an alert.

So, now if you want to make this a Bookmarklet simply do one of two things.

1. Drag the link to your bookmark toolbar.
2. Create a bookmark. Copy the location of the link above and change location of the new bookmark you just created.

The final piece of code we are going to look a is the actual bookmarklet Javascript for the Amazon Image grabber.

The code starts with creating a regular expression that pulls the product id from a url. Next we run the expression on the current page url – it won’t work on this page – using the match to run the expression. Then the url for the large image is created. The last thing is to change the url of the page to go to the large image. Really, that is about it. For a link we wrap it with the aforementioned function and the javascript: starting. In link format this looks like:

And the link:

Well, I hope you learned something today about Javascript links and Bookmarklets. If you have any questions or comments feel free to leave a comment below or head on over to the forums.

For nearly all problems there are probably a hundred different solutions. Recently one solution I have chosen for a few problems has been a Javascript bookmarklet. A bookmarklet is a regular bookmark that runs a bit of Javascript code instead of just going to a link. They are really useful for doing a small task on a website or webpage that you don’t have direct access to the backend or source of. So, today I am going to show you how to make a simple bookmarklet.

The bookmarklet today is going to grab a super high-res photo of Amazon Products. Ok, let me explain a little bit more. So, a designer co-worker uses super high-res product images for design mockups. Well, he typically would go scouring the internet for these images. However, he noticed that on Amazon product pages you can look at really large images of products using their Zoom viewer, but you could right-click and download the image from there. So I created a simple bookmarklet to grab the product id from the page url and then open up a link to the large image.

Okay, back to work. So a typical link which can be turned into a book looks like:

SOTC Tutorials

And the code looks like.

So if we were going to do something javascript we could do something like:

And the code would be:

Now, that just covers the basics of the syntax we are going to use for this. You can see above that to tell the browser to run our href as Javascript we need to start with javascript:. Ok so let’s jump to something a bit more complicated. The next piece of Javascript is going create an alert with the current time – I know we all love alerts.

Looking at the code we start by creating anonymous function and inside the function we create a new Date object, then use it to create a string of hours and minutes, and then show this (current time) in an alert.

So, now if you want to make this a Bookmarklet simply do one of two things.

1. Drag the link to your bookmark toolbar.
2. Create a bookmark. Copy the location of the link above and change location of the new bookmark you just created.

The final piece of code we are going to look a is the actual bookmarklet Javascript for the Amazon Image grabber.

The code starts with creating a regular expression that pulls the product id from a url. Next we run the expression on the current page url – it won’t work on this page – using the match to run the expression. Then the url for the large image is created. The last thing is to change the url of the page to go to the large image. Really, that is about it. For a link we wrap it with the aforementioned function and the javascript: starting. In link format this looks like:

And the link:

Well, I hope you learned something today about Javascript links and Bookmarklets. If you have any questions or comments feel free to leave a comment below or head on over to the forums.

Building a Twitter client is nothing new to Switch On The Code. We’ve done it in WCF and Silverlight. To be honest though, using the Twitter API is a great way to exercise two very useful parts of a language and framework – making web requests and parsing XML. That’s what we’re going to do today. We’re going to build a very simple command line twitter client (read-only) using Python.

Today’s app will be very simple. It will request Switch On The Code’s Twitter feed and display them with their dates. Here’s what the first five tweets in the output will look like:

Python has a very large and powerful framework behind it, do doing simple things like making web requests and parsing XML are fairly straight forward and don’t require a lot of code. Let’s start by requesting the XML from Twitter’s API.

The first thing we do is create an HTTPConnection object for twitter.com. We then tell it to request the timeline for the user SwitchOnTheCode. Next, we get the response as an HTTPResponse object. I do a quick check to make sure the request went ok, since we all know how often Twitter goes down. All that’s left to do is simply read the contents of the response, which will be our XML.

Now we need to parse the XML. There are a couple of available options, but I chose the DOM approach as I think it makes more logical sense.

Using Python’s minidom, we first parse the XML returned from Twitter using parseString (don’t forget to import parseString at the top of the file). Now things get a litte tricky. We need to rip through the DOM looking for the items we want to display. First off, every tweet is stored beneath a “status” tag, so we need to loop through every one of those. Underneath each status tag there’s the date (created_at) and the actual tweet (text), so we need to loop through every child of the status tag looking for those. Once we find one, we then need to find the text contained within it. Text is contained in TEXT_NODE type nodes, so we need to search through the children of our created_at and text tags looking for that specific type. Once we find it, we then print the nodeValue and we’re done.

Since tweets are Unicode, I needed to encode the text as utf-8 before printing it to the console.

And that’s it. With just a few lines of code, and some pretty complicated DOM traversing, we’ve got a very basic Twitter reader built in Python. If you’ve got any questions or comments, feel free to leave them below or head on over to our forums.

In many of the projects and applications I build with Flex I use a singleton for the Model – we’ve talked about Singletons in the past here. Whether this is the preferred method of handling a model is a matter of opinion so I won’t be discussing it. However, I do want to share the model class that I typically use. Actionscript lacks a real static constructor, used for creating a single instance of a class, which means creating a nice singleton takes a bit more work.

To create the singleton I take advantage of using a local class definition inside of my model Actionscript file. From my understanding the local class, it is only visible and valid inside of the file. Also I owe props to some blog for pointing this trick out but I can’t remember the blog – sorry. This means we can ensure that the only instance of the model is created inside of the class. Let’s take a look of the entire code below and we can make a little more sense of it.

Ok so above we have the ever so popular GetInstance method which is what all external files will use to get an instance of the model. This will check if the local static variable for the single instance is populated and if not calls the constructor which takes the aforementioned local class. Inside the constructor you can initialize whatever you need to and basically everything else in the class is going to a public variable or a convenience method.

To summarize, we have a local class that makes sure that the only instance is created inside the MainModel class. And, of course, use GetInstance to grab the instance. That is pretty much it. If you have any questions or want to simply comment on using this method feel free to leave a comment.

In many of the projects and applications I build with Flex I use a singleton for the Model – we’ve talked about Singletons in the past here. Whether this is the preferred method of handling a model is a matter of opinion so I won’t be discussing it. However, I do want to share the model class that I typically use. Actionscript lacks a real static constructor, used for creating a single instance of a class, which means creating a nice singleton takes a bit more work.

To create the singleton I take advantage of using a local class definition inside of my model Actionscript file. From my understanding the local class, it is only visible and valid inside of the file. Also I owe props to some blog for pointing this trick out but I can’t remember the blog – sorry. This means we can ensure that the only instance of the model is created inside of the class. Let’s take a look of the entire code below and we can make a little more sense of it.

Ok so above we have the ever so popular GetInstance method which is what all external files will use to get an instance of the model. This will check if the local static variable for the single instance is populated and if not calls the constructor which takes the aforementioned local class. Inside the constructor you can initialize whatever you need to and basically everything else in the class is going to a public variable or a convenience method.

To summarize, we have a local class that makes sure that the only instance is created inside the MainModel class. And, of course, use GetInstance to grab the instance. That is pretty much it. If you have any questions or want to simply comment on using this method feel free to leave a comment.

In nearly every programming language there is a way to delay a method call. Objective-C is no different. They have built in a few simple methods to achieve this. We are going take a look at one of these methods today, all which reside in NSObject. This means any class you create will have the ability to call these methods. The method we are going to take a gander at is - (void)performSelector:(SEL)aSelector withObject:(id)anArgument afterDelay:(NSTimeInterval)delay, got the love the Objective-C method names.

This method is pretty self explanatory thanks to the super long name. Basically, we are going to run a method and pass in the object as the parameter for the method after a certain amount of time (in seconds). Okay, imagine we have built an application which has a label that we want to change the text of after 5 seconds, why? I don’t know, if the label keeps the same text for more than 5 seconds it will self destruct, anyway I digress. So, we create a method to change the text to something like the following:

The new method is about as simple as it gets, it changes the label’s text to the passed in value. Now, in order to call this on a delay we need to use our aforementioned method, - (void)performSelector:(SEL)aSelector withObject:(id)anArgument afterDelay:(NSTimeInterval)delay. In order to call our change text method with this it would look something like below.

This pretty much covers it. One note is that say you have a method that doesn’t take a parameter like the one below.

Then if you want to call the method you pass in nil for the withObject argument, like the following:

Well that pretty much sums it up. You should now be able to call code after a delay. If you have any questions feel free to leave a comment or head on over to the forums.

Every once and a while I come across a simple task that deserves a script. Instead of using a language I know, this is often a great opportunity to pick up a new language or get a refresher on one I haven’t used in a long time. In this case, I needed to resize an entire directory of images. There are tons of free tools out there to do this, but where’s the fun in that? Also, I could have whipped this tool up very quickly in a language I know, like C#, however I haven’t used Python in several years and I decided it was time for a refresher.

For this tutorial, I’m using Python 2.6.5 and the Python Image Library (PIL). If you’re reading this tutorial, I’m sure you’ve got the first one installed and ready to go. The second one, PIL, is a free download.

I decided to create a simple command line application for this task. It will take three arguments: -d, -w, and -h. -d is the directory where your images are located. -w is the output image’s desired width. -h is the output image’s desired height. It will be used like this:

The first thing we’re going to have to do is parse the command line arguments. Fortunately Python comes with a function, getopt, that makes this very simple.

getopt requires two parameters. The first is the list of arguments passed into the script. We’re skipping the first argument because that’s just the name of the script being executed. The second is the shorthand notation for each command line option. Since each option requires extra information, like a directory path, we need to stick a colon after each one. If the option were just a flag, with no extra info, the colon would be omitted. This returns two things. The first is a collection of tuples containing the argument and the extra information. The second contains all the other arguments that didn’t match what we were looking for. getopt has an optional third parameter that lets you specify a long name for each argument, but it’s not necessary for this tutorial.

Now that we’ve got the command line arguments parsed, we need to read the values into some variables. And while we’re at it, we might as well stick in a little bit of validation.

All we’re doing here is iterating through every specified option and saving the value to some variables. The width and height will need to be converted to integers for later use.

We’re now ready to actually convert all the images.

This is actually the entire contents of the script. We first iterate through every file in the specified directory. We then open, resize, and save the image using PIL. There are several resizing techniques available, however I chose Bilinear because it yields perfectly satisfactory results. Every file will be saved to the same location it came from except with “resized” appended on the beginning.

And that’s it. Python has some great support for easily and quickly creating powerful command line applications. Thanks to the active community of developers there are libraries, like PIL, that will do pretty much anything you’ll need.

Every once and a while I come across a simple task that deserves a script. Instead of using a language I know, this is often a great opportunity to pick up a new language or get a refresher on one I haven’t used in a long time. In this case, I needed to resize an entire directory of images. There are tons of free tools out there to do this, but where’s the fun in that? Also, I could have whipped this tool up very quickly in a language I know, like C#, however I haven’t used Python in several years and I decided it was time for a refresher.

For this tutorial, I’m using Python 2.6.5 and the Python Image Library (PIL). If you’re reading this tutorial, I’m sure you’ve got the first one installed and ready to go. The second one, PIL, is a free download.

I decided to create a simple command line application for this task. It will take three arguments: -d, -w, and -h. -d is the directory where your images are located. -w is the output image’s desired width. -h is the output image’s desired height. It will be used like this:

The first thing we’re going to have to do is parse the command line arguments. Fortunately Python comes with a function, getopt, that makes this very simple.

getopt requires two parameters. The first is the list of arguments passed into the script. We’re skipping the first argument because that’s just the name of the script being executed. The second is the shorthand notation for each command line option. Since each option requires extra information, like a directory path, we need to stick a colon after each one. If the option were just a flag, with no extra info, the colon would be omitted. This returns two things. The first is a collection of tuples containing the argument and the extra information. The second contains all the other arguments that didn’t match what we were looking for. getopt has an optional third parameter that lets you specify a long name for each argument, but it’s not necessary for this tutorial.

Now that we’ve got the command line arguments parsed, we need to read the values into some variables. And while we’re at it, we might as well stick in a little bit of validation.

All we’re doing here is iterating through every specified option and saving the value to some variables. The width and height will need to be converted to integers for later use.

We’re now ready to actually convert all the images.

This is actually the entire contents of the script. We first iterate through every file in the specified directory. We then open, resize, and save the image using PIL. There are several resizing techniques available, however I chose Bilinear because it yields perfectly satisfactory results. Every file will be saved to the same location it came from except with “resized” appended on the beginning.

And that’s it. Python has some great support for easily and quickly creating powerful command line applications. Thanks to the active community of developers there are libraries, like PIL, that will do pretty much anything you’ll need.

XNA is quite possibly one of the most robust game programming frameworks out there. You can do nearly anything with it, and one of the reasons it is so flexible is its “Content Pipeline”. But sometimes it can be a bit tricky to use this feature, requiring us to do bit more work. But in the end, it helps to use the Content Pipeline. Luckily today we are going over how to use it to load in some XML.

A quick google search will reveal that loading in XML with C# and XNA can be a bit more complicated that it seems. There are several ways to accomplish XML integration, all dependent on your needs. Today we are going to go over the simplest way to load XML in XNA using the fancy Content Pipeline.

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