Re: best approach to code hierarchical classes ?
On Tuesday, 8 June 2021 at 02:37:44 UTC, someone wrote:
On Tuesday, 8 June 2021 at 02:05:27 UTC, Paul Backus wrote:
Your module and class are both named `classComputers`, with an
`s` at the end. You should change one of the to have a
different name so that there's no ambiguity.
Although I am still not being able to solve the import issue for
the child code on my nested-classes (low priority by the time
being), I have now a more pressing issue.
But first and foremost: almost sure you'll find my code style
noisy given the heavily-used attribue/function properties, but
this is solely to remind me how things work in a new language,
what will be obvious to an experienced D developer (default
attributes) it is not obvious to me right now ... spare me the
style, will you ?
I moved all the boilerplate code to manage the collection to
classCollectionItems which also has a nested child
classCollectionItem (since I'll be widely using them as the basis
for hierarchical class models) and from then on I inherit the
class on my final classComputers/classComputer code which is my
first test-bed app in D.
Before moving the code to the new generic abstract classes the
code below worked flawlessly, and still works albeit for a minor
detail:
I now **have an issue accessing the collection** (previously
defined in the base classCollectionItems) through my derived
classComputers class: please, look for the comment block marked
with +++ below.
The base classCollectionItems will always have a collection named
items, and each derived class I will make from it should have a
reference to it renamed accordingly; eg: computers in the case of
my classComputers class. Later I will plan to make an interface
to hide all the inner details and hide the items property of the
base class once and for all, leaving each new derived class' own
renamed property publicly accessible). So when the issue first
appeared on my new refactored code I **started playing with alias
to no avail** -and even making a new computers property
initialized with items (but then I figured it out that this will
be copying the array -not referencing it, so this will be a
no-go).
Some advice please ?
```d
#!/bin/dmd
module dmclassescomputers;
import std.string;
abstract private class classCollectionItems {
classCollectionItems lhs;
classCollectionItems rhs;
int opApply(int delegate(classCollectionItem) dg) { ///
boilerplate code to handle the class's default collection
int lintResult = 0; /// must find a better name
foreach (lobjItem; items) { /// looping over the computers
starting in current node
lintResult = dg(lobjItem); /// passing single object to the
loop body
if (lintResult != 0) { break; }
}
if (lintResult != 0 && lhs ! is null) { lintResult =
lhs.opApply(dg); } /// recursing child nodes
if (lintResult != 0 && rhs ! is null) { lintResult =
rhs.opApply(dg); } /// recursing child nodes
return lintResult;
}
public @property classCollectionItem[] items; alias items
this; /// ie: default property
final public @property const long count0() { return
this.items.empty ? 0L : this.items.length - 1L; }
final public @property const long count1() { return
this.items.empty ? 0L : this.items.length; }
final public @property const long count() { return
this.count1; }
final public @property const bool empty() { return
this.items.empty; }
abstract public bool add(in string lstrID) { return false; }
abstract public bool remove(in string lstrID) { return false; }
abstract public bool removeAll() { return false; }
abstract class classCollectionItem {
private ulong pintPosition0 = 0L; /// keep in mind that
array positions are zero-based
final public @property const ulong position0() { return
this.pintPosition0; }
final public @property const ulong position1() { return
this.pintPosition0 + 1L; }
final public @property const ulong countAbove() { return
this.outer.items.empty ? 0L : this.pintPosition0; }
final public @property const ulong countBelow() { return
this.outer.items.empty ? 0L : this.outer.length -
this.pintPosition0 - 1L; }
/// eg: for position0=0 → countAbove=0=(position0=0) &
countBelow=2=(length=3)-(position0=0)-1
/// eg: for position0=1 → countAbove=1=(position0=1) &
countBelow=1=(length=3)-(position0=1)-1
/// eg: for position0=2 → countAbove=2=(position0=2) &
countBelow=0=(length=3)-(position0=2)-1
final public @property classCollectionItem first() { return
this.outer.items.empty ? null : this.outer.items[0L]; }
final public @property classCollectionItem previous() {
return this.outer.items.empty || this.countAbove == 0L ? null :
this.outer.items[this.pintPosition0 - 1L]; }
final public @property classCollectionItem next() { return
this.outer.items.empty || this.countBelow == 0L ? null :
Re: best approach to code hierarchical classes ?
On Tuesday, 8 June 2021 at 02:05:27 UTC, Paul Backus wrote:
Your module and class are both named `classComputers`, with an
`s` at the end. You should change one of the to have a
different name so that there's no ambiguity.
dmd output:
./dm.d(49): Error: undefined identifier `classComputer` in module
`dmclassescomputers`, did you mean class `classComputers`?
./dm.d(50): Error: undefined identifier `classComputer` in module
`dmclassescomputers`, did you mean class `classComputers`?
./dm.d(51): Error: undefined identifier `classComputer` in module
`dmclassescomputers`, did you mean class `classComputers`?
./dm.d(53): Error: no property `outer` for type
`dmclassescomputer.classComputer`
file [dm.d] as following:
```d
import dmclassescomputers = dmclassescomputers;
///import dmclassescomputer = dmclassescomputer;
import std.string;
import std.stdio;
void main (
) {
auto lobjComputers = new
dmclassescomputers.classComputers(r"lab"c);
lobjComputers ~= lobjComputers.new
dmclassescomputers.classComputer(r"dell"c); /// <- line 49
lobjComputers ~= lobjComputers.new
dmclassescomputers.classComputer(r"ibm"c);
lobjComputers ~= lobjComputers.new
dmclassescomputers.classComputer(r"apple"c);
lobjComputers[1].name = r"lenovo"c;
foreach(lobjComputer; lobjComputers) { writeln(r"["c ~
lobjComputer.outer.network ~ r" network has "c ~
lobjComputer.name ~ r"]"c); }
}
```
file [dmclassescomputers.d] as following:
```d
module dmclassescomputers;
import std.string;
class classComputers {
classComputers lhs;
classComputers rhs;
int opApply(int delegate(dmclassescomputer.classComputer) dg)
{ /// boilerplate code to handle the class's default collection
int lintResult = 0; /// must find a better name
foreach (lobjComputer; computers) { /// looping over the
computers starting in current node
lintResult = dg(lobjComputer); /// passing single object to
the loop body
if (lintResult != 0) { break; }
}
if (lintResult != 0 && lhs ! is null) { lintResult =
lhs.opApply(dg); } /// recursing child nodes
if (lintResult != 0 && rhs ! is null) { lintResult =
rhs.opApply(dg); } /// recursing child nodes
return lintResult;
}
public dmclassescomputer.classComputer[] computers; alias
computers this; /// ie: default property
private string pstrNetwork;
final @property string network() { return this.pstrNetwork; }
final @property void network(in string lstrNetwork) {
this.pstrNetwork = lstrNetwork.strip(); }
this(
string lstrNetwork
) {
this.network = lstrNetwork;
}
import dmclassescomputer;
}
```
file [dmclassescomputer.d] as following:
```d
module dmclassescomputer;
import std.string;
class classComputer {
private string pstrName;
final @property string name() { return this.pstrName; }
final @property void name(in string lstrName) { this.pstrName
= lstrName.strip(); }
this(
string lstrName
) {
this.name = lstrName;
}
}
```
Re: best approach to code hierarchical classes ?
On Tuesday, 8 June 2021 at 01:17:05 UTC, someone wrote: On Tuesday, 8 June 2021 at 00:54:41 UTC, someone wrote: Are there alternatives to nested classes for such scenarios ? Self-reply: I created two files for classComputers and classComputer and I replaced the nested-classComputer code within classComputers with: import classComputers; But it won't go: Error: undefined identifier `classComputer` in module `classComputers`, did you mean class `classComputers`? Your module and class are both named `classComputers`, with an `s` at the end. You should change one of the to have a different name so that there's no ambiguity.
Re: best approach to code hierarchical classes ?
On Tuesday, 8 June 2021 at 00:54:41 UTC, someone wrote: Are there alternatives to nested classes for such scenarios ? Self-reply: I created two files for classComputers and classComputer and I replaced the nested-classComputer code within classComputers with: import classComputers; But it won't go: Error: undefined identifier `classComputer` in module `classComputers`, did you mean class `classComputers`?
best approach to code hierarchical classes ?
Consider the following code in what I used nested-classes for the
first time within D:
```d
import std.string;
import std.stdio;
class classComputers {
classComputers lhs;
classComputers rhs;
int opApply(int delegate(classComputer) dg) { /// boilerplate
code to handle the class's default collection
int lintResult = 0; /// must find a better name
foreach (lobjComputer; computers) { /// looping over the
computers starting in current node
lintResult = dg(lobjComputer); /// passing single object to
the loop body
if (lintResult != 0) { break; }
}
if (lintResult != 0 && lhs ! is null) { lintResult =
lhs.opApply(dg); } /// recursing child nodes
if (lintResult != 0 && rhs ! is null) { lintResult =
rhs.opApply(dg); } /// recursing child nodes
return lintResult;
}
public classComputer[] computers; alias computers this; ///
ie: default property
private string pstrNetwork;
final @property string network() { return this.pstrNetwork; }
final @property void network(in string lstrNetwork) {
this.pstrNetwork = lstrNetwork.strip(); }
this(
string lstrNetwork
) {
this.network = lstrNetwork;
}
class classComputer {
private string pstrName;
final @property string name() { return this.pstrName; }
final @property void name(in string lstrName) {
this.pstrName = lstrName.strip(); }
this(
string lstrName
) {
this.name = lstrName;
}
}
}
void main (
) {
classComputers lobjComputers = new classComputers(r"lab"c);
/// ie: the lab network
lobjComputers ~= lobjComputers.new classComputer(r"dell"c);
lobjComputers ~= lobjComputers.new classComputer(r"ibm"c);
lobjComputers ~= lobjComputers.new classComputer(r"apple"c);
lobjComputers[1].name = r"lenovo"c;
foreach(lobjComputer; lobjComputers) { writeln(r"["c ~
lobjComputer.outer.network ~ r" network has "c ~
lobjComputer.name ~ r"]"c); }
}
```
As expected, the above code produces:
[lab network has dell]
[lab network has lenovo]
[lab network has apple]
Now think of wider hierarchical structures, let's say 6~9 to
begin with or greater; eg: computers.computer.devices.firmware...
and so on.
Coding such scenario with nested classes will produce a huge code
base within the same module. My first approach, obviously, was to
put each class in its own module and in main() I instantiate the
primary one and the child objects/classes are instantiated either
directly in main or say, by each class' own add()/remove()
methods. This works as expected. However, I can't manage to
traverse the tree from main() like something.parent.somethingelse
(like I can do with outer for the nested classes example I gave
you) nor I am able to access parent members within the classes
own bodies.
Are there alternatives to nested classes for such scenarios ?
