Reflection and Meta-programming¶
Since the Ring programming language is a dynamic language, we can get answers about the program code and we can modify our code during the runtime.
In this chapter we will learn about this and the available functions to use.
locals()
globals()
functions()
cfunctions()
islocal()
isglobal()
isfunction()
iscfunction()
packages()
ispackage()
classes()
isclass()
packageclasses()
ispackageclass()
classname()
objectid()
isobject()
attributes()
methods()
isattribute()
isprivateattribute()
ismethod()
isprivatemethod()
addattribute()
addmethod()
getattribute()
setattribute()
mergemethods()
packagename()
importpackage()
locals() Function¶
We can get a list of variables names in the current scope using the locals() function.
Syntax:
locals() --> a list contains the variables names in the current scope
Example:
test("hello")
func test cMsg
see cMsg + nl
x = 10
y = 20
z = 30
see locals()
Output:
hello
cmsg
x
y
z
globals() Function¶
We can get a list of variables names in the global scope using the globals() function.
Syntax:
globals() --> a list contains variables names in the global scope
Example:
x=10 y=20 z=30
test()
func test
see "message from test()" + nl +
"Global Variables:" + nl
see globals()
Output:
message from test()
Global Variables:
x
y
z
functions() Function¶
We can get a list of functions names written in the Ring language using the functions() function.
Syntax:
functions() --> a list contains functions names
Example:
see functions()
func f1
see "f1" + nl
func f2
see "f2" + nl
func f3
see "f3" + nl
Output:
f1
f2
f3
cfunctions() Function¶
We can get a list of functions names written in the C language using the cfunctions() function.
Syntax:
cfunctions() --> a list contains functions names
Example:
aList = cfunctions()
See "Count : " + len(aList) + nl
for x in aList
see x + "()" + nl
next
Output:
Count : 251
len()
add()
del()
get()
clock()
...
Note
The complete list is removed from the previous output.
islocal() Function¶
We can check if a variable is defined in the local scope or not using the islocal() function.
Syntax:
islocal(cVariableName) --> returns 1 if the variable is defined in the local scope
returns 0 if the variable is not defined in the local scope
Example:
test()
func test
x=10 y=20
see islocal("x") + nl +
islocal("y") + nl +
islocal("z") + nl
Output:
1
1
0
isglobal() Function¶
We can check if a variable is defined in the global scope or not using the isglobal() function.
Syntax:
isglobal(cVariableName) --> returns 1 if the variable is defined in the global scope
returns 0 if the variable is not defined in the global scope
Example:
x=10 y=20
test()
func test
see isglobal("x") + nl +
isglobal("y") + nl +
isglobal("z") + nl
Output:
1
1
0
isfunction() Function¶
We can check if a Ring function is defined or not using the isfunction() function.
Syntax:
isfunction(cFunctionName) --> returns 1 if the Ring function is defined
returns 0 if the Ring function is not defined
Example:
see isfunction("f1") + nl +
isfunction("f2") + nl +
isfunction("f3") + nl
func f1
see "message from f1()" + nl
func f2
see "message from f2()" + nl
Output:
1
1
0
iscfunction() Function¶
We can check if a C function is defined or not using the iscfunction() function.
Syntax:
iscfunction(cFunctionName) --> returns 1 if the C function is defined
returns 0 if the C function is not defined
Example:
see iscfunction("len") + nl +
iscfunction("add") + nl +
iscfunction("test") + nl
Output:
1
1
0
packages() Function¶
We can get a list of packages names using the packages() function.
Syntax:
packages() --> a list contains packages names
Example:
See packages()
Package Package1
Class class1
Func f1
Package Package2
Class class1
Func f1
Package Package3
Class class1
Func f1
Package Package4
Class class1
Func f1
Output:
package1
package2
package3
package4
ispackage() Function¶
We can check if a package is defined or not using the ispackage() function.
Syntax:
ispackage(cPackageName) --> returns 1 if the Package is defined
returns 0 if the Package is not defined
Example:
See ispackage("package1") + nl +
ispackage("package4") + nl +
ispackage("package5") + nl +
ispackage("package3") + nl
Package Package1
Class class1
Func f1
Package Package2
Class class1
Func f1
Package Package3
Class class1
Func f1
Package Package4
Class class1
Func f1
Output:
1
1
0
1
classes() Function¶
We can get a list of classes names using the classes() function.
Syntax:
classes() --> a list contains classes names
Example:
See classes()
Class class1
Func f1
Class class2
Func f1
Class class3
Func f1
Output:
class1
class2
class3
isclass() Function¶
We can check if a class is defined or not using the isclass() function.
Syntax:
isclass(cClassName) --> returns 1 if the Class is defined
returns 0 if the Class is not defined
Example:
see isclass("class4") + nl +
isclass("class3") + nl +
isclass("class2") + nl
Class class1
func f1
class class2
func f1
class class3
func f1
Output:
0
1
1
packageclasses() Function¶
We can get a list of classes names inside a package using the packageclasses() function.
Syntax:
packageclasses(cPackageName) --> a list contains classes names inside the package
Example:
see "classes in Package1" + nl
see packageclasses("Package1")
see "classes in Package2" + nl
see packageclasses("Package2")
Package Package1
Class class1
Func f1
Package Package2
Class class1
Func f1
Class class2
Func f1
Class class3
func f1
Output:
classes in Package1
class1
classes in Package2
class1
class2
class3
ispackageclass() Function¶
We can check if a class is defined inside package or not using the ispackageclass() function.
Syntax:
ispackageclass(cPackageName,cClassName) --> returns 1 if the Class is defined
returns 0 if the Class is not defined
Example:
see ispackageclass("package1","class1") + nl +
ispackageclass("package1","class2") + nl +
ispackageclass("package2","class1") + nl +
ispackageclass("package2","class2") + nl
Package Package1
Class class1
Func f1
Package Package2
Class class1
Func f1
Class class2
Func f1
Class class3
func f1
Output:
1
0
1
1
classname() Function¶
We can know the class name of an object using the classname() function
Syntax:
classname(object) --> Returns the object class name
Example:
o1 = new point
o2 = new rect
see classname(o1) + nl # print point
see classname(o2) + nl # print rect
class point
class rect
objectid() Function¶
We can know the object id using the objectid() function
Syntax:
objectid(object) --> Returns the object id
Example:
o1 = new point
see objectid(o1) + nl
test(o1)
func test v
see objectid(v) + nl
Class point x y z
Output:
021B5808
021B5808
isobject() Function¶
We can check the variable to know if it’s an object or not using the isobject() function
Syntax:
isobject(variable) --> Returns True if it's an object, False if it's not
attributes() Function¶
We can get the object attributes using the attributes() function
Syntax:
attributes(object) --> Returns a list contains the object attributes
Example:
o1 = new point
aList = attributes(o1) # we can use see attributes(o1)
for t in aList see t next # print xyz
Class Point x y z
methods() Function¶
We can get the object methods using the methods() function
Syntax:
methods(object) --> Returns a list contains the object methods
Example:
o1 = new test
aList = methods(o1)
for x in aList
cCode = "o1."+x+"()"
eval(cCode)
next
Class Test
func f1
see "hello from f1" + nl
func f2
see "hello from f2" + nl
func f3
see "hello from f3" + nl
func f4
see "hello from f4" + nl
Output:
hello from f1
hello from f2
hello from f3
hello from f4
isattribute() Function¶
We can test if the object contains an attribute or not using the isattribute() function
Syntax:
isattribute(object,cAttributeName) --> Returns True if the object contains the attribute
Example:
o1 = new point
see isattribute(o1,"x") + nl # print 1
see isattribute(o1,"t") + nl # print 0
see isattribute(o1,"y") + nl # print 1
see isattribute(o1,"z") + nl # print 1
class point x y z
isprivateattribute() Function¶
We can test if the object contains a private attribute or not using the isprivateattribute() function
Syntax:
isprivateattribute(object,cAttributeName) --> Returns True if the object
contains the private attribute
Example:
o1 = new person
see isprivateattribute(o1,"name") + nl +
isprivateattribute(o1,"address") + nl +
isprivateattribute(o1,"phone") + nl +
isprivateattribute(o1,"job") + nl +
isprivateattribute(o1,"salary")
Class Person
name address phone
private
job salary
Output:
0
0
0
1
1
ismethod() Function¶
We can test if the object class contains a method or not using the ismethod() function
Syntax:
ismethod(object,cMethodName) --> Returns True if the object class contains the method
Example:
o1 = new point
see ismethod(o1,"print") + nl # print 1
mylist = []
mylist + new point
see ismethod(mylist[1],"print") + nl # print 1
class point x y z
func print
see x + nl + y + nl + z + nl
isprivatemethod() Function¶
We can test if the object class contains a private method or not using the isprivatemethod() function
Syntax:
isprivatemethod(object,cMethodName) --> Returns True if the object class contains
the private method
Example:
o1 = new Test
see isprivatemethod(o1,"f1") + nl +
isprivatemethod(o1,"f2")
Class Test
func f1
see "message from f1()" + nl
private
func f2
see "message from f2()" + nl
Output:
0
1
addattribute() Function¶
We can add an attribute (or a group of attributes) to the object state (not the class) using the addattribute() function
Syntax:
AddAttribute(object,cAttributeName|aAttributesList)
Example(1):
see new point {x=10 y=20 z=30}
Class Point
AddAttribute(self,["x","y","z"])
Example(2):
o1 = new point
addattribute(o1,"x")
addattribute(o1,"y")
addattribute(o1,"z")
see o1 {x=10 y=20 z=30}
class point
Output:
x: 10.000000
y: 20.000000
z: 30.000000
addmethod() Function¶
We can add a method to the object class using the addmethod() function This method can be used with any object from the same class.
Syntax:
AddMethod(Object,cNewMethodName,cMethodName|AnonymousFunction)
Example:
o1 = new point { x=10 y=20 z=30 }
addmethod(o1,"print", func { see x + nl + y + nl + z + nl } )
o1.print()
Class point
x y z
Output:
10
20
30
Instead of using anonymous function to add new method to the class, we can use the function name
Example:
o1 = new point { x=10 y=20 z=30 }
myfunc = func { see x + nl + y + nl + z + nl }
addmethod(o1,"print", myfunc )
addmethod(o1,"display", myfunc )
addmethod(o1,"show", myfunc )
o1.print()
o1.display()
o1.show()
Class point
x y z
Output:
10
20
30
10
20
30
10
20
30
Since we add the method to the class, any object from that class can use this method
Example:
o1 = new point { x=10 y=20 z=30 }
o2 = new point { x=100 y=200 z=300 }
o3 = new point { x=50 y=150 z=250 }
addmethod(o1,"print", func { see x + nl + y + nl + z + nl } )
o1.print()
o2.print()
o3.print()
Class point
x y z
Output:
10
20
30
100
200
300
50
150
250
getattribute() function¶
We can get the object attribute value using the getattribute() function
Syntax:
GetAttribute(oObject,cAttributeName) ---> Attribute Value
Example:
o1 = new point
see getattribute(o1,"name") + nl +
getattribute(o1,"x") + nl +
getattribute(o1,"y") + nl +
getattribute(o1,"z") + nl
Class Point
x=10 y=20 z=30
name = "3D-Point"
Output:
3D-Point
10
20
30
Example:
We can Find a Class List Member using GetAttribute() using a function findclass() The Find uses the member name, rather than the column number
myList =
[new Company {position=3 name="Mahmoud" symbol="MHD"},
new Company {position=2 name="Bert" symbol="BRT"},
new Company {position=1 name="Ring" symbol="RNG"}
]
see myList
see nl +"=====================" + nl + nl
for i = 1 to len(myList)
see "Pos: "+ i +" | "+ myList[i].position +" | "+ myList[i].name +
" | "+ myList[i].symbol +" | "+ nl
next
See findclass(myList, "MHD", "symbol") +nl ### Specify Member class name
###---------------------------------------
func findclass classList, cValue, classMember
See nl + "FindClass: " +" "+ cValue + nl + nl
for i = 1 to len(classList)
result = getattribute( classList[i], classMember )
See "Result-Attr: " + i +" "+ result +nl
if result = cValue
j = i
ok
next
return j
###--------------------------------------
class company position name symbol
Output:
Pos: 1 | 3 | Mahmoud | MHD |
Pos: 2 | 2 | Bert | BRT |
Pos: 3 | 1 | Ring | RNG |
FindClass: MHD
Result-Attr: 1 MHD
Result-Attr: 2 BRT
Result-Attr: 3 RNG
1
setattribute() function¶
We can set the object attribute value using the setattribute() function
Syntax:
SetAttribute(oObject,cAttributeName,Value)
Example:
o1 = new person
setattribute(o1,"cName","Mahmoud")
setattribute(o1,"nSalary",1000000)
setattribute(o1,"aColors",["white","blue","yellow"])
see o1
see o1.aColors
Class Person
cName
nSalary
aColors
Output:
cname: Mahmoud
nsalary: 1000000.000000
acolors: List...
white
blue
yellow
mergemethods() Function¶
We can share methods between classes without inheritance using the MergeMethods() function
This function merge class methods to another class.
Syntax:
MergeMethods(cClassNameDestination,cClassNameSource)
Example:
mergemethods("count","share")
mergemethods("count2","share")
o1 = new count { test() }
o1 = new count2 { test() }
Class Share
func one
see "one" + nl
func two
see "two" + nl
func three
see "three" + nl
Class Display
Func printline
see copy("*",20) + nl
Class Count from Display
Func test
printline()
one()
two()
three()
printline()
Class Count2 from Display
Func test
three()
two()
one()
printline()
Output:
********************
one
two
three
********************
three
two
one
********************
packagename() Function¶
We can know the package name of the latest successful import command using the packagename() function
Syntax:
packagename() --> Returns the package name of the latest successful import
Example:
load "weblib.ring"
import System.web
see packagename() # system.web
importpackage() Function¶
Instead of using the import command we can use the importpackage() function
This function get the package name through a string or variable
This is useful if the package name will be known only during the runtime
Syntax:
importpackage(cPackageName)
Example:
importpackage(:mypackage)
new myclass { myfunction() }
package mypackage
class myclass
function myfunction
? "Hello, World!"