Use Control Attribute ATTR_DATA_TYPE to decalre a variable

[foufy]

I everyone,

I want to write a piece of very generic code to automatically declare a variable according to the control Attribute ATTR DATA TYPE in order to read any type of Control value.

The pseudo code looks as follow

For All Control in a Panel

  If It's a numeric Control type

     |      get control data type (GetCtrlAttribute(panel, Ctrl, ATTR_DATA_TYPE, ...)

     |      declare variable according to the control data type (???)

     |     read control value and put it in the variable (GetCtrlVal)

Any idea?

Thank you.

[gdargaud]

C doesn't have dynamic typing.

There are two ways to go around this usually: with a void* or a union.

// Direct check
int dt, MyInt;
double MyDouble;
GetCtrlAttribute (, , ATTR_DATA_TYPE, &dt);
switch (dt) {
	case VAL_INTEGER:GetCtrlVal(,,&MyInt);    break;
	case VAL_DOUBLE: GetCtrlVal(,,&MyDouble); break;
}

// Using void*
void* MyData;
// ... get MyData somehow, for instance with fread
switch (dt) {
	case VAL_INTEGER:MyInt=*(int*)MyData;    break;
	case VAL_DOUBLE: MyDouble=*(double*)MyData; break;
}

// Using union
typedef struct sSomeType {
	int dt;
	union {
		int MyInt;
		double MyDouble;
	}
} tSomeType;
tSomeType SomeType;
switch (SomeType.dt) {
	case VAL_INTEGER:AnInt=SomeType.MyInt;    break;
	case VAL_DOUBLE: ADouble=SomeType.MyDouble; break;
}

[foufy]

Thank for answering and for these elegant solutions.

Best regards

[gdargaud]

There might be a more elegant solution using C11 generics, but I rarely use them and I don't even know if they are supported by the current versions of the CVI compiler.