The Ring programming language version 1.5.3 book - Part 188 of 194

1. Ring Documentation, Release 1.5.3
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
96.34 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
96.34. Why this example use the GetChar() twice? 1745

2. Ring Documentation, Release 1.5.3
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 )
96.35 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
96.35. How to use NULL and ISNULL() function? 1746

3. Ring Documentation, Release 1.5.3
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
96.36 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
96.36. How to print lists that contains objects? 1747

4. Ring Documentation, Release 1.5.3
96.37 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
96.38 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
96.39 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.
96.37. How to insert an item to the first position in the list? 1748

5. Ring Documentation, Release 1.5.3
96.40 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()
}
96.41 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)
{
96.40. Why the window title bar is going outside the screen? 1749

6. Ring Documentation, Release 1.5.3
setgeometry(200,100,100,30)
settext("Button2")
}
button = [btn1, btn2]
show()
}
exec()
}
func click
button[1] { settext ("Button3") }
button[2] { settext ("Button4") }
96.42 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()
}
96.43 How to create a Modal Window?
This example demonstrates how to create a modal window
96.42. How to Close a window then displaying another one? 1750

7. Ring Documentation, Release 1.5.3
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
96.44 How can I disable maximize button and resize window?
Use the method setWindowFlags()
Load "guilib.ring"
app1 = new qapp {
win1 = new qwidget() {
96.44. How can I disable maximize button and resize window? 1751

8. Ring Documentation, Release 1.5.3
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()
}
96.45 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:
96.45. How to use SQLite using ODBC? 1752

9. Ring Documentation, Release 1.5.3
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”.
96.46 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
96.46. Can I connect to dbase/harbour database? 1753

10. Ring Documentation, Release 1.5.3
odbc_connect(pODBC,"Driver={Microsoft Visual FoxPro Driver};"+
"SourceType=DBC;SourceDB=C:PWCT19ssbuildPWCTDATACH1Datamydata.dbc;")
See "Select data" + nl
see odbc_execute(pODBC,"select * from t38") + nl
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)
96.47 Why setClickEvent() doesn’t see the object methods directly?
setClickEvent(cCode) take a string contains code. The code will be executed when the event happens.
Ring support Many Programming Paradigms like Procedural, OOP, Functional and others.
But when you support many paradigms at the language level you can’t know which paradigm will be used so you have
two options
1. Provide General Solutions that works with many programming paradigms.
2. Provide Many Specific solutions where each one match a specific paradigm.
setClickEvent() and others belong to (General Solutions that works with many programming paradigms).
You just pass a string of code that will be executed without any care about classes and objects.
This code could be anything like calling a function, calling a method and setting variable value.
Some other languages force you to use OOP and call methods for events. Also some other languages uses anonymous
functions that may get parameters like the current object.
Now we have the general solution (not restricted with any paradigm), In the future we may add specific solutions that
match specific paradigms (OOP, Functional, Declarative and Natural).
96.48 Why I get Calling Function without definition Error?
Each program follow the next order
1 - Loading Files 2 - Global Variables and Statements 3 - Functions 4 - Packages, Classes and Methods
So what does that mean ?
1. **** No Functions comes After Classes ****
2. **** No command is required to end functions/methods/classes/packages ****
Look at this example
See "Hello"
test()
func test
96.47. Why setClickEvent() doesn’t see the object methods directly? 1754