On 01/17/2012 06:02 PM, Matej Nanut wrote:
On 17 January 2012 16:54, H. S. Teoh<hst...@quickfur.ath.cx> wrote:
This may be the cause of your trouble. If the nested class references
members in the outer class, then moving it outside will break it, since
it won't have an outer scope anymore.
T
--
Only boring people get bored. -- JM
That was my guess too — but I'm not referencing the outer class. The
outer class is just using instances of the inner one. Also, the line number
of the error points to ‘new’ statements in the static method. (The calls
which instantiate subclasses of the inner class.) If I do "return null" it
works as well, without complaining. So it's not a referencing issue I think.
As you all seem eager to help, I will copy the entire class, without
subclasses, to here. I will be grateful for any comments regarding the
current issue at hand or about the code in general.
The ‘new’-ed Nodes are defined like ‘class CostNode : Node { ... }’.
Another note, the outer class is an inner class of another class as well,
if that makes a difference. Also, the outer class isn't really a class, it's
a struct, but renaming that to ‘class’ doesn't change anything either.
---- code begin ----
class Node
{
static Node parse(ref string line)
{
string mnemonic = munch(line, "A-Z");
line = line.stripLeft();
auto op = mnemonic in mnemonics;
if (!op)
throw new Exception("Unknown mnemonic: `" ~ mnemonic ~"'");
final switch (*op)
{
case NodeType.COST:
return new CostNode(line);
case NodeType.PAUSE:
return new PauseNode(line);
case NodeType.COLDR:
return new ColDrNode(line);
case NodeType.COLRA:
return new ColRaNode(line);
case NodeType.DROP:
return new DropNode(line);
case NodeType.RAISE:
return new RaiseNode(line);
}
/* Doing something like `return new Node()' doesn't work
either.
* Only `return null' works here. */
}
enum NodeType : ubyte
{
COST,
PAUSE,
COLDR,
COLRA,
DROP,
RAISE
}
static immutable NodeType[string] mnemonics;
static this()
{
mnemonics = [
"COST" : NodeType.COST,
"PAUSE" : NodeType.PAUSE,
"COLDR" : NodeType.COLDR,
"COLRA" : NodeType.COLRA,
"DROP" : NodeType.DROP,
"RAISE" : NodeType.RAISE
];
}
}
---- code end ----
I'm quite sure that the error in your code occurs for the same reason as
in the following code snippet:
class C{
class D{}
static make(){return new D();} // error
}
You can fix it by making D static:
class C{
static class D{}
static make(){return new D();} // ok
}
The reason is that non-static inner classes have an implicit 'outer'
property that links to the class it was created with. Therefore, to
construct them inside a member function, the implicit 'this' pointer is
needed. If the 'outer' property is actually unwanted, it is best to
declare inner classes as static.
