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Advanced Programming Techniques in D

Delegate Properties, Lazy Parameters & Lazy Variadic Functions

You will learn about delegate properties, lazy parameters, and lazy variadic functions in this lesson.

We'll cover the following...

Delegate properties

The function and context pointers of a delegate can be accessed through its .funcptr and .ptr properties, respectively:

D
import std.stdio;



struct MyStruct {

    void func() {

    }

}



void main() {

    auto o = MyStruct();

    auto d = &o.func;

    writeln(d.funcptr == &MyStruct.func);

    writeln(d.ptr == &o); 

}

It is possible to make a delegate from scratch by setting those properties explicitly:

D
import std.stdio;





struct MyStruct {

    int i;

    

    void func() {

        writeln(i);

    }

}



void main() {

    auto o = MyStruct(42); 

    void delegate() d;

    

    // null to begin with

    assert(d is null); 

    

    d.funcptr = &MyStruct.func;

    d.ptr = &o;

    

    d(); 

}

Above, calling the delegate as d() is the equivalent of the expression o.func() (i.e., calling MyStruct.func on o).

Lazy

...