66 lines
1.1 KiB
D
66 lines
1.1 KiB
D
import std.stdio: writeln;
|
|
|
|
// IObserver interface
|
|
interface IObserver {
|
|
void update(string msg);
|
|
}
|
|
// Person (observer)
|
|
class Person: IObserver {
|
|
string name;
|
|
|
|
this(string name) {
|
|
this.name = name;
|
|
}
|
|
|
|
void update(string msg) {
|
|
writeln(name, "\t: notified. [", msg, "]");
|
|
}
|
|
}
|
|
|
|
// WhatsApp (subject)
|
|
class WhatsApp {
|
|
private IObserver[] list;
|
|
|
|
this() {}
|
|
~this() {}
|
|
|
|
void addClient(IObserver o) {
|
|
list ~= o;
|
|
}
|
|
|
|
void removeClient(IObserver o) {
|
|
import std.algorithm: remove;
|
|
list = list.remove!(a => a is o);
|
|
}
|
|
|
|
void notify(string msg) {
|
|
foreach(client; list) {
|
|
client.update(msg);
|
|
}
|
|
}
|
|
}
|
|
|
|
void main() {
|
|
WhatsApp conversation = new WhatsApp();
|
|
|
|
Person anna = new Person("Anna");
|
|
Person john = new Person("John");
|
|
Person markus = new Person("Markus");
|
|
|
|
conversation.addClient(anna);
|
|
conversation.addClient(john);
|
|
conversation.addClient(markus);
|
|
|
|
conversation.notify("hello, world!");
|
|
|
|
conversation.removeClient(john);
|
|
|
|
conversation.notify("john left the conversation");
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|