ASP.NET Web PDF Document Viewer/Editor Control Library

Listing 1-17 shows how these methods are used The string result will contain the text "bazbarfoo" when the code shown in the listing has executed Notice that the item first pushed onto the stack appears last in the string LIFO Listing 1-17 Using a stack QStack<QString> stack; stackpush( "foo" ); stackpush( "bar" ); stackpush( "baz" ); QString result; while( !stackisEmpty() ) result += stackpop(); For the queue, the corresponding methods are enqueue for adding items, dequeue for pulling them out of the queue, and head for having a peek at the current item Just as for the stack, there is a method called isEmpty that indicates whether there is anything enqueued Listing 1-18 shows these methods in action The resulting string will contain the text "foobarbaz" when the code has executed That is, the item first enqueued appears first in the string FIFO Listing 1-18.

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In this case, the custom behavior was used to replace the base autocomplete behavior, as you ve seen in earlier chapters, where the results are rendered in a drop-down list that s attached to the control If you want to override this type of functionality (or any other behavior) with something different, then the object orientation that Atlas brings to JavaScript is an obvious candidate, and this is a great example Here, the requirement was to render the results in a separate <div> element, where you can add formatting, hyperlinks, and so on, to the results..

} } catch (InvalidOperationException iox) { throw new Exception("Some problem with the turtle...", iox); } catch (Exception ex) { // Log here Console.WriteLine("Log message: " + ex.Message); // Rethrow throw; }

Notice how we passed the exception to be wrapped as a parameter to the new exception when we constructed it. Let s make a quick modification to the exception handler in Main to take advantage of this new feature (see Example 6-19).

static void Main(string[] args) { Turtle arthurTheTurtle = new Turtle { PlatformWidth = 0.0, PlatformHeight = 10.0, MotorSpeed = 5.0 }; ShowPosition(arthurTheTurtle); try {

Using a queue QQueue<QString> queue; queueenqueue( "foo" ); queueenqueue( "bar" ); queueenqueue( "baz" ); QString result; while( !queueisEmpty() ) result += queuedequeue();.

// ... } catch (InvalidOperationException e) { Console.WriteLine("Error running turtle:"); Console.WriteLine(e.Message); } catch (Exception e1) { // Loop through the inner exceptions, printing their messages Exception current = e1; while (current != null) { Console.WriteLine(current.Message); current = current.InnerException; } } finally

{ }

Console.WriteLine("Waiting in the finally block"); Console.ReadKey();

Lists are good for keeping things, but sometimes it is interesting to associate things, this is where maps and hashes enter the picture Let s start by having a look at the QMap class, which enables you to keep items in key-value pairs For example, you can associate a value to a string, as shown in Listing 1-19 When you create a QMap, the template arguments are the type of key and then the type of values Listing 1-19 Creating a map associating strings with integers and filling it with information QMap<QString, int> map; map["foo"] = 42; map["bar"] = 13; map["baz"] = 9; To insert a new item in a map, all you have to do is assign it with the [] operator If the key already exists, the new item replaces the existing one If the key is new to the map, a new item is created.

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Another place in the application where asynchrony occurs, powered by Atlas-style Ajax, is in rendering the table of contents for the wiki. You can see this screen by selecting the Contents tab at the top of the page (see Figure 7-22).

If we compile and run again, we can see the following output, including the messages from both the outer and inner exceptions:

Arthur is at (0,0) and is pointing at angle 0.00 radians. Arthur is at (0,10) and is pointing at angle 0.00 radians. Some problem with the turtle has occurred The PlatformWidth must be initialized to a value > 0.0 Waiting in the finally block

You can see whether a key exists by using the contains function or you can get a list of all keys using the keys method Listing 1-20 shows you how to acquire the keys and iterate over all items in the map Listing 1-20 Showing all key-value pairs on the debugging console foreach( QString key, mapkeys() ) qDebug() << key << " = " << map[key]; Instead of iterating over a list of the keys, it is possible to use an iterator directly on the map, as shown in Listing 1-21 This gives instant access to both the key and the value through the iterator, and thus saves a lookup per loop iteration Listing 1-21 Iterating over all key-value pairs QMap<QString, int>::ConstIterator ii; for( ii = mapconstBegin(); ii != mapconstEnd(); ++ii ) qDebug() << iikey() << " = " << ii.