On Thursday, 21 December 2017 at 06:47:25 UTC, Ali Çehreli wrote:
On 12/20/2017 10:36 PM, Chris Katko wrote:
Is there any way to get a warning anytime an implicit super
constructor is called in a sub-class/child-class?
There can be a number of solutions but can you please
demonstrate the issue with compilable code? My attempt does not
agree with your description: super() is called *before* the
subclass constructor. (Compiled with DMD64 D Compiler
v2.077.1-384-gc6829a8)
import std.stdio;
// To get the code compile:
enum : int {
BMP_PLACEHOLDER,
BMP_BUILDING
}
alias bitmap_t = int;
class object_t
{
bitmap_t bmp;
float x,y;
this() {
writeln("super()");
bmp = BMP_PLACEHOLDER;
}
this(float _x, float _y)
{
writeln("super(float, float)");
bmp = BMP_PLACEHOLDER;
x = _x;
y = _y;
}
}
class building_t : object_t
{
this(float _x, float _y)
{
// super(_x, _y);
// ^^ If I forget this, it implicitly gets called AFTER
// this function is done. Which resets bmp to
BMP_PLACEHOLDER!
// AND, it'll call the DEFAULT constructor this() with
no arguments.
writeln("setting in building_t");
bmp = BMP_BUILDING;
}
}
void main() {
auto b = new building_t(10, 20);
assert(b.bmp != BMP_PLACEHOLDER);
}
Prints
super()
setting in building_t
Ali
This is what I would believe __IS__ and __SHOULD__ be the default
behavior too, because that's how it generally is in other
languages.
It doesn't make much sense to call a super constructer after and
it's very rare cases that you need too.
The only time you really call super constructors after is if the
parameters are different.
Ex.
class Foo
{
int baz;
int boo;
this() { ... }
this(int baz, int boo) { ... }
}
class Bar : Foo
{
this()
{
int baz =getBazFromSomewhere();
int boo = getBooFromSomewhere();
super(baz, boo);
}
}
In that case it makes sense to call super() after, but you rarely
end up in cases like that and thus you should generally be able
to omit the call.
If super() is ever called explicit after (if no call to a super
constructor has been done.) then I can only imagine A LOT of code
will break, because it's a general concept and known behavior
from most languages that base/super constructors are called
before.
