I have the following small example(vala 0.18.1):
namespace Learning
{
public interface IExample<T>
{
public abstract void set_to(T val);
public abstract T get_to();
}
public class Example : Object, IExample<double>
{
private double to;
public void set_to(double val)
{
to = val;
}
public double get_to()
{
return to;
}
public string to_string()
{
return "Example: %.5f".printf(to);
}
}
public class Test
{
public static void main(string[] args)
{
stdout.printf("Start test\n");
Example ex = new Example();
stdout.printf("%s\n", ex.to_string());
ex.set_to(5.0);
stdout.printf("%s\n", ex.to_string());
stdout.printf("End test\n");
}
}
}
This throws the error:
/src/Test.vala.c: In function ‘learning_test_main’:
/src/Test.vala.c:253:2: error: incompatible type for argument 2 of ‘learning_iexample_set_to’
/src/Test.vala.c:117:6: note: expected ‘gconstpointer’ but argument is of type ‘double’
error: cc exited with status 256
Compilation failed: 1 error(s), 0 warning(s)
Now from what little documentation I have been able to find on generics interfaces in Vala, http://www.vala-project.org/doc/vala-draft/generics.html#genericsexamples, this should work. When I check the resulting C code, it shows the Example's set_to function as taking a double and the IExample's set_to function as taking a gconstpointer.
So why is the main function then using the gconstpointer version instead of the double version? Can some one explain to me why it does not work and a way to get around it?
Thank you for your help.
P.S. Yes I know the documentation found is a draft document.
ANSWER CODE: According to the selected answer below this is what I changed the code to.
namespace Learning
{
public interface IExample<T>
{
public abstract void set_to(T val);
public abstract T get_to();
}
public class Example : Object, IExample<double?>
{
private double? to;
public void set_to(double? val)
{
to = val;
}
public double? get_to()
{
return to;
}
public string to_string()
{
return (to == null) ? "NULL" : "Example: %.5f".printf(to);
}
}
public class Test
{
public static void main(string[] args)
{
stdout.printf("Start test\n");
Example ex = new Example();
stdout.printf("%s\n", ex.to_string());
ex.set_to(5.0);
stdout.printf("%s\n", ex.to_string());
stdout.printf("End test\n");
}
}
}
