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version 2.104.0

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Alias std.typecons.BlackHole

BlackHole!Base is a subclass of Base which automatically implements all abstract member functions in Base as do-nothing functions. Each auto-implemented function just returns the default value of the return type without doing anything.

alias BlackHole(Base) = AutoImplement!(Base,generateEmptyFunction,isAbstractFunction);

The name came from Class::BlackHole Perl module by Sean M. Burke.

Parameters

NameDescription
Base A non-final class for BlackHole to inherit from.

See Also

AutoImplement, generateEmptyFunction

Example

import std.math.traits : isNaN;

static abstract class C
{
    int m_value;
    this(int v) { m_value = v; }
    int value() @property { return m_value; }

    abstract real realValue() @property;
    abstract void doSomething();
}

auto c = new BlackHole!C(42);
writeln(c.value); // 42

// Returns real.init which is NaN
assert(c.realValue.isNaN);
// Abstract functions are implemented as do-nothing
c.doSomething();

Authors

Andrei Alexandrescu, Bartosz Milewski, Don Clugston, Shin Fujishiro, Kenji Hara

License

Boost License 1.0.