ASP.NET Web PDF Document Viewer/Editor Control Library

If we were to review this design with the customer, they might point out that while they have some systems that do indeed want the speed in miles per hour the people they liaise with in European air traffic control want the speed in kilometers per hour. To avoid confusion, we will add another property so that they can get or set the speed in the units with which they are familiar. Example 3-9 shows a suitable property.

public double SpeedInKilometersPerHour { get { return SpeedInMilesPerHour * 1.609344; } set { SpeedInMilesPerHour = value / 1.609344; } }

barcode excel 2013 download, how to make barcode in excel sheet, how to add barcode font to excel 2007, microsoft barcode control excel 2010, barcode in excel free download, barcode excel vba free, barcode in excel vba, how to convert number to barcode in excel 2010, excel barcodes not working, barcode add in for word and excel freeware,

This chapter intended to take you through many simple examples of using Atlas client-side controls and demonstrate how to implement and manipulate them using Atlas Script and JavaScript. It was intended to be very hands-on; in other words, you learned by doing. You went through 11 examples of different functionalities, using data binding, actions, behaviors, and more, to implement some complex GUI functionality. You ll get into more client controls and client functionality later in the book, particularly as you work through the full example in 12. However, now is a good time to put these new tools that you ve learned into your pencil box and move onto the other side the server side. In the next few chapters, you will start looking at implementing Atlas applications using the ASP .NET Atlas server-side controls.

We ve done something different here rather than just writing get; and set; we ve provided code for these accessors. This is another reason we have to declare the accessors explicitly the C# compiler needs to know whether we want to write a custom property implementation. We don t want to use an ordinary property in Example 3-9, because our SpeedInKilo metersPerHour is not really a property in its own right it s an alternative representation for the information stored in the SpeedInMilesPerHour property. If we used the normal property syntax for both, it would be possible to set the speed as being both 100 mph and 400 km/h, which would clearly be inconsistent. So instead we ve chosen to implement SpeedInKilometersPerHour as a wrapper around the SpeedInMilesPerHour property. If you look at the getter, you ll see that it returns a value of type double. It is equivalent to a function with this signature:

The second half of the change is to actually emit the signal, which is done using the Qt keyword emit followed by the signal s name and arguments..

public double get_SpeedInKilometersPerHour()

The setter seems to provide an invisible parameter called value, which is also of type double. So it is equivalent to a method with this signature:

public void set_SpeedInKilometersPerHour(double value)

Signals and slots are implemented by Qt using function pointers. When calling emit with the signal as argument, you actually call the signal. The signal is a function implemented in the source file generated by the moc. This function calls any slots connected to the signal using the meta-objects of the objects holding the connected slots. The meta-objects contain function pointers to the slots, along with their names and argument types. They also contain a list of the available signals and their names and argument types. When calling connect, you ask the meta-object to add the slot to the signal s calling list. If the arguments match, the connection is made. When matching arguments, the match is checked only for the arguments accepted by the slot. This means that a slot that does not take any arguments matches all signals. The arguments not accepted by the slot are simply dropped by the signal-emitting code.

This value parameter is a contextual keyword C# only considers it to be a keyword in property or event accessors. (Events are described in 5.) This means you re allowed to use value as an identifier in other contexts for example, you can write a method that takes a parameter called value. You can t do that with other keywords you can t have a parameter called class, for example.

This is a very flexible system indeed. You can provide properties that provide real storage in the class to store their data, or calculated properties that use any mechanism you like to get and/or set the values concerned. This choice is an implementation detail hidden from users of our class we can switch between one and the other without changing our class s public face. For example, we could switch the implementation of these speed properties around so that we stored the value in kilometers per hour, and calculated the miles per hour Example 3-10 shows how these two properties would look if the real value was in km/h.

public double SpeedInMilesPerHour { get { return SpeedInKilometersPerHour / 1.609344; } set { SpeedInKilometersPerHour = value * 1.609344; } } public double SpeedInKilometersPerHour { get; set; }