Mega Code Archive

WebSnap III use of Adapter instead of Html Transparent Tags

Title: WebSnap III: use of Adapter instead of Html-Transparent-Tags Question: On this article I will show you the use of adapters to manage content in your web pages Answer: So far in my 2 articles of websnap I showed you the way websnap "interacts" with the html WebSnapI: The unknown powerful WebSnap II: Interacting with the user that is using "html transparent tags", where you put in the html files, tags like: and so on... then on your websnap application pageproducer OnHTMLTag you replace those with the content you want... well, there are other ways to achieve the same thing, I'll show you how easy it is The AdapterFields are going to do this for us, look at them as... a replacement for the html transparent tags or an interface between our variables and the html jscript I'm not going to get into detail about how to create a websnap application this time, so here we go Create a new websnap application (Web App Debbuger executable), you get one form and another "form" (WebAppPageModule) with 5 components on it: PageProducer, WebAppComponents, ApplicationAdapter, PageDispatcher and AdapterDispatcher. Ok, this time we are going to make use of ApplicationAdapter, this component can hold variables and actions which we can use in our html code (using jscript), let's see how right click on the applicationadapter: click on fields editor, then a little window comes up right click on that box and select new component, then AdapterField, that new component gets added to the right side of that window, click on the AdapterField and let's see the properties Name: obviously the Delphi Name for that variable (I called TheTimeAF) FieldName: the name by which we will access this variable from our html script (I called it TheTime) that's all we need from here for now now let's see the events of this object OnGetValue is the one we are interested in right now doble click there and write this code: procedure Ttutorial2.TimeAFGetValue(Sender: TObject; var Value: Variant); begin Value:=FormatDateTime('mm/dd/yy HH:MM:SS', Now) end; you see where we are going? I will use this variable to show the server time in my webpage ok, let's add another AdapterField, repeat the same steps to add another AdapterField, I put these properties for this one Name: HitsAF FieldName: Hits we will use this variable to show the number of hits in our page since the page has been up (cool!) For this we will also need a variable (Integer or LongInt) to hold the number of hits the OnGetValue code looks like this: procedure Ttutorial2.HitsAFGetValue(Sender: TObject; var Value: Variant); begin Hits:=Hits+1; Value:=Hits end; looks pretty easy huh?... it is that easy let's see now how we would add a random image to our page! Add another AdapterField, properties: Name: RandomImageAF FieldName: RandomImage and on the OnGetValue we put something like this: procedure Ttutorial2.RandomImageAFGetValue(Sender: TObject; var Value: Variant); begin Value:=ImagesPath+Images[Random(Images.Count)] end; where did I get ImagesPath and Images? ImagesPath is a string variable and Images is a tstringlist which I created on the WebAppPageModule OnCreateEvent something like this: procedure Ttutorial2.WebAppPageModuleCreate(Sender: TObject); Var S:TSearchRec; begin Images:=TStringList.Create; ImagesPath:=ExtractFilePath(ParamStr(0))+'images\'; If (FindFirst(ImagesPath+'*.jpg', faAnyFile-faDirectory, S)=0) Then Repeat Images.Add(S.Name) Until (FindNext(S)0); FindClose(S) end; This code is pretty simple and self explanatory I think... anyway... just created the images variable and loaded it with the names of images found in the images folder, I also save the path Note that this would work only when using the Web App Debugger, because I'm saving an absolute path to the location of my .exe... to make it work for the actual web isapi you would change that to something like: ImagesPath:='/images/' where 'images' would be a virtual directory on your server don't forget to free the images stringlist on the OnDestroy of WebAppPageModule procedure Ttutorial2.WebAppPageModuleDestroy(Sender: TObject); begin Images.Free end; Now... that was the Delphi part... that's easy... what about the html part? well, is not that hard... it looks like this: Current time at server: Hits (since page has been up): A Random image: " pretty simple huh?? you can see how you can directly access the variables you just created ApplicationAdapter is the name of the component in the WebAppPageModule (one of the 5 default components) the TheTime, Hits and RandomImage are the variables we created... that easy Run The Web App Debugger (Delphi menu Tools, Web App Debugger), start your server run your application and look at your cool new page that shows the server time, the number of hits and show a random image every time you reload the page Final notes: I showed you 3 examples of the use of AdapterField and I only showed small data, but nothing should stop you from loading entire html files and puthing them on the value of your variables (html formatted) even something like: Value := MyPageProducer.Value; you get the picture? pretty much you can do with them the same thing as with the html transparent tags but this is maybe more organized, as you have each variable separated That's it for now... you can download the source code along with the images here: have fun salu2 EberSys