The Ring programming language version 1.6 book - Part 183 of 189
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Here are the key steps to connect to a dBASE or Harbour database using ODBC in Ring: 1. Install the appropriate ODBC driver for the database you want to connect to (e.g. Microsoft dBase Driver for dBASE files, Visual FoxPro ODBC driver for Visual FoxPro databases). 2. Initialize an ODBC connection handle using odbc_init(). 3. Connect to the database using odbc_connect(), passing the connection string with the driver name and data source. For example: odbc_connect(pODBC, "Driver={Microsoft dBase Driver (*.dbf)};datasource=c:\path\to\database.dbf") 4
![Ring Documentation, Release 1.6
Try
see x
Catch
See "Sorry, We can't use x!" + nl
Done
Output
Sorry, We can't use x!
Now we will talk about NULL and ISNULL()
Since we get error message when we deal with uninitialized variables
We can check these errors using Try/Catch/Done, So we uses NULL and ISNULL() for dealing with Strings.
NULL is a variable contains an empty string
ISNULL() is a function that returns true (1) if the input is an empty string or just a string contains “NULL”
This because we need to test these values (empty strings) and strings contains “NULL” that sometimes come from
external resource like DBMS.
Example
See IsNull(5) + nl + # print 0
IsNull("hello") + nl + # print 0
IsNull([1,3,5]) + nl + # print 0
IsNull("") + nl + # print 1
IsNull("NULL") # print 1
100.36 How to print lists that contains objects?
In this example we will see how we can print a list contains objects.
aList = [[1,2,3] , new point(1,2,3), new point(1,2,3)]
see "print the list" + nl
see alist
see "print the item (object)" + nl
see alist[2]
class point x y z
func init p1,p2,p3 x=p1 y=p2 z=p3
Output
print the list
1
2
3
x: 1.000000
y: 2.000000
z: 3.000000
x: 1.000000
y: 2.000000
z: 3.000000
print the item (object)
x: 1.000000
y: 2.000000
z: 3.000000
100.36. How to print lists that contains objects? 1796](https://image.slidesharecdn.com/1821pdfsamfayedringdoc1-180707235121/85/The-Ring-programming-language-version-1-6-book-Part-183-of-189-4-320.jpg)
![Ring Documentation, Release 1.6
setgeometry(200,100,100,30)
settext("Button2")
}
button = [btn1, btn2]
show()
}
exec()
}
func click
button[1] { settext ("Button3") }
button[2] { settext ("Button4") }
100.42 How to Close a window then displaying another one?
This example demonstrates how to close a window and show another one
Load "guilib.ring"
app=new qApp
{
frmBefore=new Qwidget()
{
setWindowTitle("before!")
resize(300,320)
move(200,200)
button=new qPushButton(frmBefore)
{
setText("Close")
setClickEvent("frmBefore.close() frmMain.show()")
}
show()
}
frmMain=new Qwidget()
{
setWindowTitle("After!")
resize(300,320)
move(200,200)
}
exec()
}
100.43 How to create a Modal Window?
This example demonstrates how to create a modal window
100.42. How to Close a window then displaying another one? 1799](https://image.slidesharecdn.com/1821pdfsamfayedringdoc1-180707235121/85/The-Ring-programming-language-version-1-6-book-Part-183-of-189-7-320.jpg)
The Ring programming language version 1.6 book - Part 183 of 189
- 1. Ring Documentation, Release 1.6 nl = char(13) + char(10) # just a variable that you can change to anything ! The + is an operator string + string ---> new string string + number ---> new string number + number ---> new number number + string ---> new number list + item —> nothing new will be created but the item will be added to the same list Exception number + nl ?> New String This exception is added to easily print numbers then new line. No need for this with printing lists because after printing the last item we already get a new line. 100.32 Could you explain the output of the StrCmp() function? At first remember that you can check strings using ‘=’ operator directly. see strcmp("hello","hello") + nl + strcmp("abc","bcd") + nl + strcmp("bcd","abc") + nl if the two strings are the same then it returns 0 abc and bcd aren’t the same. in the second line it returns -1 and in the third line it returns 1 In the second line we compare between “abc” and “bcd” Not equal because the first letter in “abc” = “a” and the first letter in “bcd” = “b” So we have “a” != “b” and “a” < “b” So we get output = -1 In the third line we have “bcd” and “abc” the first letter in “bcd” is “b” and the first letter in “abc” is “a” So we have “b” != “a” and “b” > “a” So we get output = 1 Note: ASCII(“a”) = 97 and ASCII(“b”) = 98 So “a” < “b” because 97 < 98 100.33 How to use many source code files in the project? Example: I have the next folder C:LRing Contains the next files 100.32. Could you explain the output of the StrCmp() function? 1793
- 2. Ring Documentation, Release 1.6 C:LRingt1.ring C:LRingmylib.ring C:LRinglibsmylib2.ring The file t1.ring contains the next code load "mylib.ring" load "libsmylib2.ring" myfunc() test() The file mylib.ring contains the next code func myfunc see "message from myfunc"+nl The file libsmylib2.ring contains the next code func test see "message from test" + nl from the folder C:LRing If Ring is not added to the path you can add it or use the next command set path=%path%;c:ringbin; Where c:ring is the Ring folder Now run Ring t1.ring Output message from myfunc message from test 100.34 Why this example use the GetChar() twice? The GetChar() function accept one character from the keyboard buffer In this example While True See " Main Menu (1) Say Hello (2) Exit " Option = GetChar() GetChar() GetChar() # End of line # the previous two lines can be replaced with the next line # Give Option if Option = 1 see "Enter your name : " give cName see "Hello " + cName else 100.34. Why this example use the GetChar() twice? 1794
- 3. Ring Documentation, Release 1.6 bye ok End We uses GetChar() Three times The first time we get the user option Option = GetChar() But in the second and the third times (We accept the new line characters from the buffer) GetChar() GetChar() # End of line Example : when the user select the option number 1 then press ENTER We have Three Characters • The first character is : Number 1 • The second character is : CHAR(13) • The third character is : CHAR(10) Because Windows uses CHAR(13) and CHAR(10) for each new line ( i.e. CR+LF ) 100.35 How to use NULL and ISNULL() function? when we try to use uninitialized variable in the Ring programming language, we get a clear runtime error message Example See x Output Line 1 Error (R24) : Using uninitialized variable : x in file testsseeuninit.ring The same happens when you try to access uninitialized attributes Example o1 = new point see o1 see o1.x class point x y z Output x: NULL y: NULL z: NULL Line 3 Error (R24) : Using uninitialized variable : x in file testsseeuninit2.ring if you want to check for the error, just use Try/Catch/End 100.35. How to use NULL and ISNULL() function? 1795
- 4. Ring Documentation, Release 1.6 Try see x Catch See "Sorry, We can't use x!" + nl Done Output Sorry, We can't use x! Now we will talk about NULL and ISNULL() Since we get error message when we deal with uninitialized variables We can check these errors using Try/Catch/Done, So we uses NULL and ISNULL() for dealing with Strings. NULL is a variable contains an empty string ISNULL() is a function that returns true (1) if the input is an empty string or just a string contains “NULL” This because we need to test these values (empty strings) and strings contains “NULL” that sometimes come from external resource like DBMS. Example See IsNull(5) + nl + # print 0 IsNull("hello") + nl + # print 0 IsNull([1,3,5]) + nl + # print 0 IsNull("") + nl + # print 1 IsNull("NULL") # print 1 100.36 How to print lists that contains objects? In this example we will see how we can print a list contains objects. aList = [[1,2,3] , new point(1,2,3), new point(1,2,3)] see "print the list" + nl see alist see "print the item (object)" + nl see alist[2] class point x y z func init p1,p2,p3 x=p1 y=p2 z=p3 Output print the list 1 2 3 x: 1.000000 y: 2.000000 z: 3.000000 x: 1.000000 y: 2.000000 z: 3.000000 print the item (object) x: 1.000000 y: 2.000000 z: 3.000000 100.36. How to print lists that contains objects? 1796
- 5. Ring Documentation, Release 1.6 100.37 How to insert an item to the first position in the list? To insert an item we can use the insert(aList,nIndex,Value) function. aList = 1:5 insert(aList,0,0) See aList # print numbers from 0 to 5 100.38 How to print new lines and other characters? To print new line we can use the nl variable. See "Hello" + nl or we can use multi-line literal as in the next example See "Hello " if we want to print other characters we can use the char(nASCII) function See char(109) + nl + # print m char(77) # print M 100.39 Why we don’t use () after the qApp class name? When we use RingQt to create GUI application, we uses () after the class name when we create new objects for example. new qWidget() { setWindowTitle("Hello World") resize(400,400) show() } but before doing that we create an object from the qApp class and we don’t use () after that Load "guilib.ring" app = new qApp { win=new qWidget() { setwindowtitle(:test) show() } exec() } Using () after the class name means calling the init() method in the class and passing parameters to this method. If we used () while no init() method in the class we get the expected error message. The class qApp don’t have this method while the other classes have it because they need it to create an object using a function that return a pointer to that object and this pointer will be stored in an attribute called pObject, for more information see ring_qt.ring file which contains the classes. 100.37. How to insert an item to the first position in the list? 1797
- 6. Ring Documentation, Release 1.6 100.40 Why the window title bar is going outside the screen? When we write the next code Load "guilib.ring" app = new qApp { win=new qWidget() { setwindowtitle(:test) setGeometry(0,0,200,200) show() } exec() } I would expect that the window will run at the point (0,0) with (200,200) size but the actual result is that the window title bar is going outside the screen. This is related to the behavior of Qt framework. The next code will avoid the problem load "guilib.ring" new qApp { new qWidget() { move(0,0) resize(200,200) show() } exec() } 100.41 How to create an array of buttons in GUI applications? Check the next example: Load "guilib.ring" App1 = new qApp { win1 = new qWidget() { move(0,0) resize(500,500) new qPushButton(win1) { settext("OK") setclickevent("click()") } btn1 = new qPushButton(win1) { setgeometry(100,100,100,30) settext("Button1") } btn2 = new qPushButton(win1) { 100.40. Why the window title bar is going outside the screen? 1798
- 7. Ring Documentation, Release 1.6 setgeometry(200,100,100,30) settext("Button2") } button = [btn1, btn2] show() } exec() } func click button[1] { settext ("Button3") } button[2] { settext ("Button4") } 100.42 How to Close a window then displaying another one? This example demonstrates how to close a window and show another one Load "guilib.ring" app=new qApp { frmBefore=new Qwidget() { setWindowTitle("before!") resize(300,320) move(200,200) button=new qPushButton(frmBefore) { setText("Close") setClickEvent("frmBefore.close() frmMain.show()") } show() } frmMain=new Qwidget() { setWindowTitle("After!") resize(300,320) move(200,200) } exec() } 100.43 How to create a Modal Window? This example demonstrates how to create a modal window 100.42. How to Close a window then displaying another one? 1799
- 8. Ring Documentation, Release 1.6 load "guilib.ring" app=new qApp { frmStart=new Qwidget() { setWindowTitle("The First Window") resize(300,320) move(200,200) button=new qPushButton(frmStart) { setText("Show Modal Window") resize(200,30) setClickEvent("frmModal.show()") } new qPushButton(frmStart) { setText("Close Window") move(0,50) resize(200,30) setClickEvent("frmStart.Close()") } show() } frmModal =new Qwidget() { setWindowTitle("Modal Window") resize(300,320) move(200,200) setparent(frmStart) setwindowmodality(true) setwindowflags(Qt_Dialog) } exec() } Related Documents • http://doc.qt.io/qt-5/qtwidgets-widgets-windowflags-example.html • http://doc.qt.io/qt-5/qt.html#WindowType-enum • http://doc.qt.io/qt-5/qwindow.html#setParent • http://doc.qt.io/qt-5/qt.html#WindowModality-enum 100.44 How can I disable maximize button and resize window? Use the method setWindowFlags() Load "guilib.ring" app1 = new qapp { win1 = new qwidget() { 100.44. How can I disable maximize button and resize window? 1800
- 9. Ring Documentation, Release 1.6 setwindowtitle("First") setgeometry(100,100,500,500) new qpushbutton(win1) { setgeometry(100,100,100,30) settext("close") setclickevent("app1.quit()") } new qpushbutton(win1) { setgeometry(250,100,100,30) settext("Second") setclickevent("second()") } showmaximized() } exec() } func second win2 = new qwidget() { setwindowtitle("Second") setgeometry(100,100,500,500) setwindowflags(Qt_dialog) show() } 100.45 How to use SQLite using ODBC? In Ring 1.1 and later versions we have native support for SQLite, so you don’t need to use it through ODBC. Also we can access SQLite through RingQt. The answer to your question pODBC = odbc_init() odbc_connect(pODBC,"DRIVER=SQLite3 ODBC Driver;Database=mydb.db;LongNames=0;"+ "Timeout=1000;NoTXN=0;SyncPragma=NORMAL;StepAPI=0;") odbc_execute(pODBC,"create table 'tel' ('ID','NAME','PHONE');") odbc_execute(pODBC,"insert into 'tel' values ('1','Mahmoud','123456');") odbc_execute(pODBC,"insert into 'tel' values ('2','Ahmed','123456');") odbc_execute(pODBC,"insert into 'tel' values ('3','Ibrahim','123456');") odbc_execute(pODBC,"select * from tel") + nl nMax = odbc_colcount(pODBC) See "Columns Count : " + nMax + nl while odbc_fetch(pODBC) See nl for x = 1 to nMax see odbc_getdata(pODBC,x) if x != nMax see " - " ok next end odbc_disconnect(pODBC) odbc_close(pODBC) Output: 100.45. How to use SQLite using ODBC? 1801
- 10. Ring Documentation, Release 1.6 Columns Count : 3 1 - Mahmoud - 123456 2 - Ahmed - 123456 3 - Ibrahim - 123456 The program will create the file : mydb.db Note : when I print the odbc drivers I see the long list that includes SQLite3 ODBC Driver - UsageCount=1 SQLite ODBC Driver - UsageCount=1 SQLite ODBC (UTF-8) Driver - UsageCount=1 And I’m using “SQLite3 ODBC Driver”. 100.46 Can I connect to dbase/harbour database? You can connect to any database using ODBC To connect to xbase files (*.DBF) See "Using DBF Files using ODBC" + nl pODBC = odbc_init() See "Connect to database" + nl odbc_connect(pODBC,"Driver={Microsoft dBase Driver (*.dbf)};"+ "datasource=dBase Files;DriverID=277") See "Select data" + nl odbc_execute(pODBC,"select * from tel.dbf") nMax = odbc_colcount(pODBC) See "Columns Count : " + nMax + nl while odbc_fetch(pODBC) See "Row data:" + nl for x = 1 to nMax see odbc_getdata(pODBC,x) + " - " next end See "Close database..." + nl odbc_disconnect(pODBC) odbc_close(pODBC) Output Using DBF Files using ODBC Connect to database Select data Columns Count : 3 Row data: Ahmad - Egypt - 234567 - Row data: Fady - Egypt - 345678 - Row data: Shady - Egypt - 456789 - Row data: Mahmoud - Egypt - 123456 - Close database... Also you can connect to a Visual FoxPro database (requires installing Visual FoxPro driver) See "ODBC test 6" + nl pODBC = odbc_init() See "Connect to database" + nl 100.46. Can I connect to dbase/harbour database? 1802