d疊代構或類的示例

​​原文​​​ 如何實作疊代​

​構/類​

​?這樣:

foreach (k, v; T.init)
{
    ...
}      

​

​T.byKeyValue​

​沒用.

​​參考在此​​

你應該用​

​opApply​

​.示例:

struct A {
    static int[string] impl;
    static this() {
        impl = [
            "a": 1,
            "b": 2,
        ];
    }

    int opApply(scope int delegate(string a, int b) dg) {
        foreach (k, v; impl) {
            auto r = dg(k, v);
            if (r) return r;
        }
        return 0;
    }
}

void main() {
    import std;A a;
    foreach (k, v; a) {
        writefln("%s -> %s", k, v);
    }
}      

import std.typecons : tuple;
import std.conv : to;
import std.stdio : writeln;
import std.range : take;

struct S {
    size_t count;
    bool empty = false;

    auto front() {
        const key = count;
        const value = key.to!string;
        return tuple(key, value);// 在此
    }

    void popFront() {
        ++count;
    }
}

void main() {
    foreach (k, v; S.init.take(10))
    {
        writeln(k, ": ", v);
    }
}