Description
Once a class instance is declared in a program through the REF_CLASS instruction, a special syntax needs to be used to gain access to its attributes, for both reading and writing.
This syntax is based on the principle of Getters and Setters of object languages.
Getting the value of a class attribute
To retrieve the value of an attribute of a REF_CLASS type variable, the following syntax must be used:
MyVariableResult = MyInstance.getNameAttribute()
or
MyVariableResult = MyInstance.getNameAttributeArray()(index[,index2])
Example:
Adelia class CAR whose 4GL source is:
*attributes
{
ALPHA(15) Make;
ALPHA(250) Model;
NUM_BIN_2 NumHp;
DATE DatePurch;
ALPHA(50) Options(30)
}
Then in the Visual Adelia Batch program:
* Declaring a REF_CLASS variable:
REF_CLASS(CAR) iCar
NUM_BIN_2 MyBin2
DATE MyDate
ALPHA(50) TabOptions(30)
ALPHA(50) option;
* Getting the value of the attribute 'NumHp' of the iCar class:
MyBin2 = iCar.getNumHp()
* Getting the value of the attribute 'NumHp' of the iCar class:
MyDate = iCar.getDatePurch()
* Getting the value of the attribute 'Options' of the iCar class:
tabOptions = iCar.getOptions()
* Get the value of the first element of the attribute 'Options' from the iCar class:
Option = iCar.getOptions()(1)
Note:
It is assumed here that the iCar variable is already instantiated (e.g. it is one of the parameters of the input to the program or procedure), or that it has been instantiated in the program via the 4GL instruction NEW:
iCar = new CAR()
It is possible to test whether the iCar variable is instantiated with the reserved word *NULL:
If iCar = *NULL
Changing the value of a class attribute
To fix the value of an attribute of a REF_CLASS type variable, the following syntax must be used:
XXX.setYYY(ZZZ)
XXX being a variable of the REF_CLASS type
YYY being an attribute of this class
ZZZ being the value to be fixed to this attribute
When the attribute is a simple standard Adelia type (ALPHA, NUM_BIN_2, ..) or an overall array:
MyInstance.setNameAttribute(NewValue)
NewValue may be an alphanumeric or numeric constant, or a variable, with an Adelia type compatible with that of the attribute concerned.
Example:
REF_CLASS(PERSON) iFather
ALPHA(33) MyAlpha33
iFather.setFirstname('John')
iFather.setName(MyAlpha33)
When it is desired to update an element of an array attribute
MyInstance.setNameAttribute(NewValue, Index1[, Index2])
NewValue may be an alphanumeric or numeric constant, or a variable, with an Adelia type compatible with that of the attribute concerned.
Index1 and Index2 may be a numeric constant or numeric variable.
Example:
REF_CLASS(PERSON) iFather
REF_CLASS(CAR) iCar
NUM_BIN_4 MyBin4
NUM_BIN_2 Index1
NUM_BIN_2 Index2
Index = 5
iFather.setArray1DFirstnamesChildren('nicholas', Index1)
iFather.setArray1DFirstnamesChildren('virginia', 4)
iCar.setOptions('peugeot', 4)
iFather.setArrayBin4_2D (MyBin4, 6, 11)
iFather.setTArrayBin4_2D (444, Index1, Index2)
When the attribute is a class
REF_CLASS(PERSON) iFather
REF_CLASS(FAMILY) iFamily
Father = new PERSON()
iFamily.setFather(iFather)