In this chapter, you’ll be introduced to the Web component through a relatively
simple example that accesses fnancial stock price information from a public API
made available by Yahoo Finance. The protocol for talking to this API is fairly simple,
and the data returned is in a list of values separated by commas (comma-separated
values , or CSV), so it serves as a nice introduction to API communication.
Unfortunately, most APIs have complicated permission schemes and APIs, and they
often return data in formats such as JavaScript Object Notation (JSON) or XML, which
require some advanced code to parse.
STOCK MARKET SAMPLE
The figure below shows the blocks for an app that displays Google stock information when
the app launches.
On Screen.Initialize, Web1.Url is set to the URL for communicating with Yahoo
Finance. When Web1.Get is called, the request is made, but no data is returned
immediately.
Instead, when Yahoo returns the requested data to your app, the Web1.GotText
event is triggered, and this is where you can process the returned data. The event
parameter responseContent holds the data. As just mentioned, the Yahoo Finance API
returns data in CSV format. If you build this app and run it, you’ll see that the current Google stock price and the change in the price for the day are displayed in
StockInfoLabel , separated by commas.
You can customize the Web.Url to get the information for a diferent company (or
companies), and to get various types of stock market information. The Yahoo Finance
API, at https://code.google.com/p/yahoo-fnance-managed/wiki/CSVAPI , specifes how
you can change the URL to customize your request, as well as the format of the data it
returns.
NOTE: I HAVE COPIED THIS FROM THIS WEBSITE . I DO NOT OWN THIS.
