The Ring programming language version 1.5.1 book - Part 175 of 180

1. Ring Documentation, Release 1.5.1
95.37 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
95.38 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
95.39 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.
95.37. How to insert an item to the first position in the list? 1715

2. Ring Documentation, Release 1.5.1
95.40 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()
}
95.41 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)
{
95.40. Why the window title bar is going outside the screen? 1716

3. Ring Documentation, Release 1.5.1
setgeometry(200,100,100,30)
settext("Button2")
}
button = [btn1, btn2]
show()
}
exec()
}
func click
button[1] { settext ("Button3") }
button[2] { settext ("Button4") }
95.42 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()
}
95.43 How to create a Modal Window?
This example demonstrates how to create a modal window
95.42. How to Close a window then displaying another one? 1717

4. Ring Documentation, Release 1.5.1
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
95.44 How can I disable maximize button and resize window?
Use the method setWindowFlags()
Load "guilib.ring"
app1 = new qapp {
win1 = new qwidget() {
95.44. How can I disable maximize button and resize window? 1718

5. Ring Documentation, Release 1.5.1
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()
}
95.45 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:
95.45. How to use SQLite using ODBC? 1719

6. Ring Documentation, Release 1.5.1
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”.
95.46 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
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7. Ring Documentation, Release 1.5.1
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)
95.47 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).
95.48 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
95.47. Why setClickEvent() doesn’t see the object methods directly? 1721

8. Ring Documentation, Release 1.5.1
see "message from the test function!" + nl
class test
In the previous example we have a function called test() so we can call it directly using test()
In the next example, test() will become a method
See"Hello"
test() # runtime error message
class test
func test # Test() now is a method (not a function)
see "message from the test method!" + nl
The errors comes when you define a method then try calling it directly as a function.
The previous program must be
See"Hello"
new test { test() } # now will call the method
class test
func test # Test() now is a method (not a function)
see "message from the test method!" + nl
95.49 Can Ring work on Windows XP?
Ring can work on Windows XP and load extensions without problems.
Just be sure that the extension can work on Windows XP and your compiler version support that (modern compilers
requires some flags to support XP)
Check this topic https://blogs.msdn.microsoft.com/vcblog/2012/10/08/windows-xp-targeting-with-c-in-visual-studio-
2012/
For example, We added
/link /SUBSYSTEM:CONSOLE,"5.01"
To the batch file to support Windows XP
See : https://github.com/ring-lang/ring/blob/master/src/buildvccomplete.bat
95.50 How to extend RingQt and add more classes?
You have many options
In general you can extend Ring using C or C++ code
Ring from Ring code you can call C Functions or use C++ Classes & Methods
This chapter in the documentation explains this part in the language http://ring-
lang.sourceforge.net/doc/extension.html
For example the next code in .c file can be compiled to a DLL file using the Ring library (.lib)
#include "ring.h"
RING_FUNC(ring_ringlib_dlfunc)
{
95.49. Can Ring work on Windows XP? 1722

9. Ring Documentation, Release 1.5.1
printf("Message from dlfunc");
}
RING_API void ringlib_init(RingState *pRingState)
{
ring_vm_funcregister("dlfunc",ring_ringlib_dlfunc);
}
Then from Ring you can load the DLL file using LoadLib() function then call the C function that called dlfunc() as
any Ring function.
See "Dynamic DLL" + NL
LoadLib("ringlib.dll")
dlfunc()
Output
Dynamic DLL
Message from dlfunc
When you read the documentation you will know about how to get parameters like (strings, numbers, lists and objects)
And how to return a value (any type) from you function.
From experience, when we support a C library or C++ Library
We discovered that a lot of functions share a lot of code
To save our time, and to quickly generate wrappers for C/C++ Libraries to be used in Ring
We have this code generator
https://github.com/ring-lang/ring/blob/master/extensions/codegen/parsec.ring
The code generator is just a Ring program < 1200 lines of Ring code
The generator take as input a configuration file contains the C/C++ library information
like Functions Prototype, Classes and Methods, Constants, Enum, Structures and members , etc.
Then the generator will generate
*.C File for C libraries (to be able to use the library functions)
*.CPP File for C++ libraries (to be able to use C++ classes and methods)
*.Ring File (to be able to use C++ classes as Ring classes)
*.RH file (Constants)
To understand how the generator work check this extension for the Allegro game programming library
https://github.com/ring-lang/ring/tree/master/extensions/ringallegro
At first we have the configuration file
https://github.com/ring-lang/ring/blob/master/extensions/ringallegro/allegro.cf
To write this file, i just used the Allegro documentation + the Ring code generator rules
Then after executing the generator using this batch file
https://github.com/ring-lang/ring/blob/master/extensions/ringallegro/gencode.bat
or using this script
https://github.com/ring-lang/ring/blob/master/extensions/ringallegro/gencode.sh
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10. Ring Documentation, Release 1.5.1
I get the generated source code file
https://github.com/ring-lang/ring/blob/master/extensions/ringallegro/ring_allegro.c
The generated source code file (ring_allegro.c) is around 12,000 Lines of code (12 KLOC)
While the configuration file is less than 1 KLOC
To build the library (create the DLL files)
https://github.com/ring-lang/ring/blob/master/extensions/ringallegro/buildvc.bat
Also you can check this extension for the LibSDL Library
https://github.com/ring-lang/ring/tree/master/extensions/ringsdl
After this know you should know about
1 - Writing the configuration file
2 - Using the Code Generator
3 - Building your library/extension
4 - Using your library/extension from Ring code
Let us move now to you question about Qt
We have RingQt which is just an extension to ring (ringqt.dll)
You don’t need to modify Ring.
1. You just need to modify RingQt
2. Or extend Ring with another extension based on Qt (but the same Qt version)
For the first option see the RingQt extension
https://github.com/ring-lang/ring/tree/master/extensions/ringqt
Configuration file
https://github.com/ring-lang/ring/blob/master/extensions/ringqt/qt.cf
To generate the source code
https://github.com/ring-lang/ring/blob/master/extensions/ringqt/gencode.bat
https://github.com/ring-lang/ring/blob/master/extensions/ringqt/gencode.sh
https://github.com/ring-lang/ring/blob/master/extensions/ringqt/gencodeandroid.bat
To build the DLL/so/Dylib files
https://github.com/ring-lang/ring/blob/master/extensions/ringqt/buildmingw32.bat
https://github.com/ring-lang/ring/blob/master/extensions/ringqt/buildgcc.sh
https://github.com/ring-lang/ring/blob/master/extensions/ringqt/buildclang.sh
Study RingQt
Learn about the options that you have
1. wrapping a Qt class directly
2. Creating a new class then wrapping your new class
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