For context, please keep in mind I am coming from a python
background, but am very much enjoying strong typing, although it
is taking some significant adjustment.
Suppose I have a struct (which is really a memory map of a data
file I am reading in) with too many data members to reasonably
code getters/setters for by hand. I wish to either retrieve
individual values or set individual values, which could be
numeric, boolean, or string, from the command line, à la:
$ prog -i inputfile.bin get field_name;
(prints "300" or "false" or "Welcome to the jungle")
$ prog -i inputfile.bin set some_field:9000
$ prog -i inputfile.bin set other_field:Whatever_String
Each field itself is strongly typed, for what that's worth.
Approaches I have considered and implemented in part are:
* templated getter (T get(T)(string field) {...}) but this
approach requires knowledge of field types which I cannot
reasonably expect to know at runtime(?)
* modification to the above whereby I could have an AA
holding type information for each field, generated by static
foreach {mixin ...}, although I cannot get this to work as my
struct's static constructor complains (rightly) that it cannot
work without knowing 'this' at compile time. Code:
`mixin("field_types[\"" ~ prop ~ "\"] = typeid(this." ~ prop ~
");");` Is there another __trait I am missing that will give me
the type of the struct member without requiring an instance of
the struct?
I did manage to use metaprogramming inside my templated get
function to handle numeric values, which was fascinating
(although this is probably ugly code and it required a large enum
array FIELDS):
```
GetterSwitch:
switch (field)
{
static foreach(prop; FIELDS ) {
mixin("case \"" ~ prop ~ "\": val = this." ~ prop
~ "; break GetterSwitch;");
}
default:
val = 0;
assert(0); // This is to prevent subtle bugs,
but I need a better error handler
}
```
Any pointers / design patterns on this particular type of problem
class would be greatly appreciated. (Sidenote, I realize I could
probably use the witchcraft library, but I am also using this as
exercise to learn D beyond the basics).
Thanks in advance
James
