class DDELink example

This sample application uses a DDE link to send data to a DDE server and optionally receive notification updates. The server program, shown in the class DDETopic example, runs in a second instance of dBASE Plus. For a demonstration of multiple-client DDE interaction, create and run another form using this same code, but change the DDE topic from "TEST" to any other name. At the same time, try linking another DDE client to the dBASE Plus server program using some other Windows program, such as Microsoft Word (code for a Word 95 macro to do just that appears at the bottom of this topic).

** END HEADER -- do not remove this line

//

// Generated on 02/24/00

//

parameter bModal

local f

f = new stockclientForm()

if (bModal)

f.mdi = false // ensure not MDI 

f.readModal() 

else

f.open() 

endif

class stockclientForm of FORM

with (this) 

onOpen = class::FORM_ONOPEN 

onClose = class::FORM_ONCLOSE 

scaleFontBold = false 

height = 6 

left = 4 

top = 2 

width = 42 

text = "Stock Client 2000" 

autoCenter = true 

mdi = false 

endwith 

this.NOTIFYTEXT = new TEXT(this) 

with (this.NOTIFYTEXT) 

height = 1 

left = 2 

top = 2 

width = 38 

border = true 

colorNormal = "BtnText" 

fontSize = 8 

text = "Welcome to Stock Client 2000" 

borderStyle = 7 // Client 

endwith 

this.SHARES = new SPINBOX(this) 

with (this.SHARES) 

height = 1 

left = 2 

top = 4 

width = 12 

picture = "99999" 

step = 10 

rangeMax = 10000 

rangeMin = 1 

fontSize = 8 

value = 10 

rangeRequired = true 

borderStyle = 7 // Client 

endwith 

this.BUYBUTTON = new PUSHBUTTON(this) 

with (this.BUYBUTTON) 

onClick = class::BUYBUTTON_ONCLICK 

height = 1 

left = 18 

top = 4 

width = 10 

text = "&Buy" 

fontSize = 8 

group = true 

value = false 

endwith 

this.SELLBUTTON = new PUSHBUTTON(this) 

with (this.SELLBUTTON) 

onClick = class::SELLBUTTON_ONCLICK 

height = 1 

left = 30 

top = 4 

width = 10 

text = "&Sell" 

fontSize = 8 

group = true 

value = false 

endwith 

this.NOTIFYBUYCHECKBOX = new CHECKBOX(this) 

with (this.NOTIFYBUYCHECKBOX) 

onChange = class::NOTIFYBUYCHECKBOX_ONCHANGE 

height = 0.8636 

left = 2 

top = 1 

width = 16 

text = "Notify on Buy" 

colorNormal = "WindowText/BtnFace" 

fontSize = 8 

value = false 

group = true 

endwith 

this.NOTIFYSELLCHECKBOX = new CHECKBOX(this) 

with (this.NOTIFYSELLCHECKBOX) 

onChange = class::NOTIFYSELLCHECKBOX_ONCHANGE 

height = 0.8636 

left = 24 

top = 1 

width = 16 

text = "Notify on Sell" 

colorNormal = "WindowText/BtnFace" 

fontSize = 8 

value = false 

group = true 

endwith 

function BUYBUTTON_onClick 

form.ddeClientObj.poke("Buy", "" + form.shares.value) 

return 

function form_onClose 

form.ddeClientObj.terminate() 

form.ddeClientObj.release() // Destroys parent reference to form 

return 

function form_onOpen 

this.ddeClientObj = new StockDDELink() 

with this.ddeClientObj 

if initiate("STOCKSERVER", "TEST") 

parent = this 

timeout = 2000 

msgbox("Connecting to " + server ; 

+ ". Account holder: " + topic ; 

+ ". Current holdings: " + peek("Buy"),; 

"Stock Client 2000") 

else 

msgbox("Could not connect to StockServer", ; 

"Connection failed", 16) 

form.close() 

endif 

endwith 

function NOTIFYBUYCHECKBOX_onChange 

if this.value 

form.ddeClientObj.advise("Buy") 

else 

form.ddeClientObj.unAdvise( "Buy" ) 

endif 

return 

function NOTIFYSELLCHECKBOX_onChange 

if this.value 

form.ddeClientObj.advise("Sell") 

else 

form.ddeClientObj.unAdvise("Sell") 

endif 

return 

function SELLBUTTON_onClick 

form.ddeClientObj.poke("Sell", "" + form.shares.value) 

return 

endclass

class StockDDELink of DDELink

this.parent = null 

function onNewValue(item, value) 

this.parent.notifyText.text := "Notified of changes in: " + item + ; 

" now: " + value 

endclass

This Word for Windows 95 macro also lets you communicate with the dBASE Plus DDE stock server program described in the class DDETopic example. You can use this macro from within Word at the same time as you use the dBASE Plus DDE client application described above to communicate with the dBASE Plus server running in a separate instance.

‘Word 95 macro to communicate with dBASE Plus Stock Server dde sample

Sub MAIN

DDETerminateAll 

channel = DDEInitiate("STOCKSERVER", "TEST") 

DDEPoke channel, "sell", "150" 

DDETerminate channel 

End Sub